Move transformer change tracking out of the build graph loader

The checks that determine whether to re-run prepare scripts and/or
commands due to property or environment changes do not belong into the
build graph loader. Instead, we now do them on demand during the build
process. Advantages:
- The code is at its "natural" place, making it easier to understand
  and less fragile.
- There are a lot fewer unnecessary build data invalidations, speeding
  up both re-resolving and rebuilding in case only some rules/commands
  have changed.
- Re-running commands due to property or environment changes no longer
  implies re-running prepare scripts.
- We now catch property changes on generated artifacts, which was not
  possible before, because the build graph loader only had access to
  the source artifacts of the re-resolved project.

Change-Id: I36b022cf631fa9e8293feec4d6f416c2686539c1
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

25 files changed, 344 insertions, 216 deletions

diff --git a/src/lib/corelib/buildgraph/abstractcommandexecutor.cpp b/src/lib/corelib/buildgraph/abstractcommandexecutor.cpp
index 94597e6d3..3790da9c8 100644
--- a/src/lib/corelib/buildgraph/abstractcommandexecutor.cpp
+++ b/src/lib/corelib/buildgraph/abstractcommandexecutor.cpp
@@ -58,7 +58,7 @@ AbstractCommandExecutor::AbstractCommandExecutor(const Logger &logger, QObject *
 {
 }
 
-void AbstractCommandExecutor::start(Transformer *transformer, const AbstractCommand *cmd)
+void AbstractCommandExecutor::start(Transformer *transformer, AbstractCommand *cmd)
 {
     m_transformer = transformer;
     m_command = cmd;
diff --git a/src/lib/corelib/buildgraph/abstractcommandexecutor.h b/src/lib/corelib/buildgraph/abstractcommandexecutor.h
index 505fd8da0..94ac15afc 100644
--- a/src/lib/corelib/buildgraph/abstractcommandexecutor.h
+++ b/src/lib/corelib/buildgraph/abstractcommandexecutor.h
@@ -66,7 +66,7 @@ public:
 
     virtual void cancel() = 0;
 
-    void start(Transformer *transformer, const AbstractCommand *cmd);
+    void start(Transformer *transformer, AbstractCommand *cmd);
 
 signals:
     void reportCommandDescription(const QString &highlight, const QString &message);
@@ -74,7 +74,7 @@ signals:
 
 protected:
     virtual void doReportCommandDescription();
-    const AbstractCommand *command() const { return m_command; }
+    AbstractCommand *command() const { return m_command; }
     Transformer *transformer() const { return m_transformer; }
     ScriptEngine *scriptEngine() const { return m_mainThreadScriptEngine; }
     bool dryRun() const { return m_dryRun; }
@@ -86,7 +86,7 @@ private:
     virtual void doStart() = 0;
 
 private:
-    const AbstractCommand *m_command;
+    AbstractCommand *m_command;
     Transformer *m_transformer;
     ScriptEngine *m_mainThreadScriptEngine;
     bool m_dryRun;
diff --git a/src/lib/corelib/buildgraph/buildgraphloader.cpp b/src/lib/corelib/buildgraph/buildgraphloader.cpp
index 4b1c6588d..933d0cb34 100644
--- a/src/lib/corelib/buildgraph/buildgraphloader.cpp
+++ b/src/lib/corelib/buildgraph/buildgraphloader.cpp
@@ -47,7 +47,6 @@
 #include "rulecommands.h"
 #include "rulesevaluationcontext.h"
 #include "transformer.h"
-#include "transformerchangetracking.h"
 
 #include <language/artifactproperties.h>
 #include <language/language.h>
@@ -333,6 +332,7 @@ void BuildGraphLoader::trackProjectChanges()
     }
 
     restoredProject->buildData->isDirty = true;
+    markTransformersForChangeTracking(allRestoredProducts);
     if (!m_parameters.overrideBuildGraphData())
         m_parameters.setEnvironment(restoredProject->environment);
     Loader ldr(m_evalContext->engine(), m_logger);
@@ -348,16 +348,11 @@ void BuildGraphLoader::trackProjectChanges()
         ldr.setStoredProfiles(restoredProject->profileConfigs);
     m_result.newlyResolvedProject = ldr.loadProject(m_parameters);
 
-    m_freshProjectsByName.insert(m_result.newlyResolvedProject->name,
-                                 m_result.newlyResolvedProject.get());
-    for (const ResolvedProjectConstPtr &p : m_result.newlyResolvedProject->allSubProjects())
-        m_freshProjectsByName.insert(p->name, p.get());
     QList<ResolvedProductPtr> allNewlyResolvedProducts
             = m_result.newlyResolvedProject->allProducts();
     for (const ResolvedProductPtr &cp : qAsConst(allNewlyResolvedProducts))
         m_freshProductsByName.insert(cp->uniqueName(), cp);
 
-    m_envChange = restoredProject->environment != m_result.newlyResolvedProject->environment;
     checkAllProductsForChanges(allRestoredProducts, changedProducts);
 
     std::shared_ptr<ProjectBuildData> oldBuildData;
@@ -625,6 +620,21 @@ bool BuildGraphLoader::hasBuildSystemFileChanged(const Set<QString> &buildSystem
     return false;
 }
 
+void BuildGraphLoader::markTransformersForChangeTracking(
+        const QList<ResolvedProductPtr> &restoredProducts)
+{
+    for (const ResolvedProductPtr &product : restoredProducts) {
+        if (!product->buildData)
+            continue;
+        for (Artifact * const artifact : filterByType<Artifact>(product->buildData->allNodes())) {
+            if (artifact->transformer) {
+                artifact->transformer->prepareScriptNeedsChangeTracking = true;
+                artifact->transformer->commandsNeedChangeTracking = true;
+            }
+        }
+    }
+}
+
 void BuildGraphLoader::checkAllProductsForChanges(const QList<ResolvedProductPtr> &restoredProducts,
         QList<ResolvedProductPtr> &changedProducts)
 {
@@ -718,10 +728,6 @@ bool BuildGraphLoader::checkForPropertyChanges(const ResolvedProductPtr &restore
     if (!restoredProduct->buildData)
         return false;
 
-    // This check must come first, as it can prevent build data rescuing.
-    if (checkTransformersForChanges(restoredProduct, newlyResolvedProduct))
-        return true;
-
     if (restoredProduct->fileTags != newlyResolvedProduct->fileTags) {
         qCDebug(lcBuildGraph) << "Product type changed from" << restoredProduct->fileTags
                               << "to" << newlyResolvedProduct->fileTags;
@@ -737,27 +743,6 @@ bool BuildGraphLoader::checkForPropertyChanges(const ResolvedProductPtr &restore
     return false;
 }
 
-bool BuildGraphLoader::checkTransformersForChanges(const ResolvedProductPtr &restoredProduct,
-        const ResolvedProductPtr &newlyResolvedProduct)
-{
-    bool transformerChanges = false;
-    Set<TransformerConstPtr> seenTransformers;
-    for (Artifact *artifact : filterByType<Artifact>(restoredProduct->buildData->allNodes())) {
-        const TransformerPtr transformer = artifact->transformer;
-        if (!transformer || !seenTransformers.insert(transformer).second)
-            continue;
-        if (qbs::Internal::checkForPropertyChanges(transformer, newlyResolvedProduct,
-                                                   m_freshProductsByName, m_freshProjectsByName)
-                || checkForEnvChanges(transformer, newlyResolvedProduct))
-            transformerChanges = true;
-    }
-    if (transformerChanges) {
-        qCDebug(lcBuildGraph) << "Property or environment changes in product"
-                              << newlyResolvedProduct->uniqueName();
-    }
-    return transformerChanges;
-}
-
 void BuildGraphLoader::onProductRemoved(const ResolvedProductPtr &product,
         ProjectBuildData *projectBuildData, bool removeArtifactsFromDisk)
 {
@@ -784,15 +769,6 @@ void BuildGraphLoader::onProductRemoved(const ResolvedProductPtr &product,
     }
 }
 
-bool BuildGraphLoader::checkForEnvChanges(const TransformerPtr &restoredTrafo,
-                                          const ResolvedProductPtr &freshProduct)
-{
-    if (!m_envChange)
-        return false;
-    return checkForEnvironmentChanges(restoredTrafo, freshProduct,
-                                      m_freshProductsByName, m_freshProjectsByName);
-}
-
 void BuildGraphLoader::replaceFileDependencyWithArtifact(const ResolvedProductPtr &fileDepProduct,
         FileDependency *filedep, Artifact *artifact)
 {
@@ -894,6 +870,9 @@ void BuildGraphLoader::rescueOldBuildData(const ResolvedProductConstPtr &restore
             rad.depsRequestedInPrepareScript
                     = oldArtifact->transformer->depsRequestedInPrepareScript;
             rad.depsRequestedInCommands = oldArtifact->transformer->depsRequestedInCommands;
+            rad.lastCommandExecutionTime = oldArtifact->transformer->lastCommandExecutionTime;
+            rad.lastPrepareScriptExecutionTime
+                    = oldArtifact->transformer->lastPrepareScriptExecutionTime;
             const ChildrenInfo &childrenInfo = childLists.value(oldArtifact);
             for (Artifact * const child : qAsConst(childrenInfo.children)) {
                 rad.children << RescuableArtifactData::ChildData(child->product->name,
diff --git a/src/lib/corelib/buildgraph/buildgraphloader.h b/src/lib/corelib/buildgraph/buildgraphloader.h
index a37af78cb..cc29a49cf 100644
--- a/src/lib/corelib/buildgraph/buildgraphloader.h
+++ b/src/lib/corelib/buildgraph/buildgraphloader.h
@@ -96,6 +96,7 @@ private:
                                QList<ResolvedProductPtr> &productsWithChangedFiles);
     bool hasBuildSystemFileChanged(const Set<QString> &buildSystemFiles,
                                    const FileTime &referenceTime);
+    void markTransformersForChangeTracking(const QList<ResolvedProductPtr> &restoredProducts);
     void checkAllProductsForChanges(const QList<ResolvedProductPtr> &restoredProducts,
             QList<ResolvedProductPtr> &changedProducts);
     bool checkProductForChanges(const ResolvedProductPtr &restoredProduct,
@@ -104,15 +105,11 @@ private:
                                            const ResolvedProductPtr &newlyResolvedProduct);
     bool checkForPropertyChanges(const ResolvedProductPtr &restoredProduct,
                                  const ResolvedProductPtr &newlyResolvedProduct);
-    bool checkTransformersForChanges(const ResolvedProductPtr &restoredProduct,
-                                             const ResolvedProductPtr &newlyResolvedProduct);
     QVariantMap propertyMapByKind(const ResolvedProductConstPtr &product, const Property &property);
     void onProductRemoved(const ResolvedProductPtr &product, ProjectBuildData *projectBuildData,
                           bool removeArtifactsFromDisk = true);
     bool checkForPropertyChanges(const TransformerPtr &restoredTrafo,
             const ResolvedProductPtr &freshProduct);
-    bool checkForEnvChanges(const TransformerPtr &restoredTrafo,
-                            const ResolvedProductPtr &freshProduct);
     bool checkForPropertyChange(const Property &restoredProperty,
                                 const QVariantMap &newProperties);
     void replaceFileDependencyWithArtifact(const ResolvedProductPtr &fileDepProduct,
@@ -133,7 +130,6 @@ private:
                             const AllRescuableArtifactData &existingRad);
 
     QMap<QString, ResolvedProductPtr> m_freshProductsByName;
-    QMap<QString, const ResolvedProject *> m_freshProjectsByName;
     RulesEvaluationContextPtr m_evalContext;
     SetupProjectParameters m_parameters;
     BuildGraphLoadResult m_result;
@@ -144,8 +140,6 @@ private:
 
     // These must only be deleted at the end so we can still peek into the old look-up table.
     QList<FileResourceBase *> m_objectsToDelete;
-
-    bool m_envChange = false;
 };
 
 } // namespace Internal
diff --git a/src/lib/corelib/buildgraph/executor.cpp b/src/lib/corelib/buildgraph/executor.cpp
index 24f077f65..be6efc1c4 100644
--- a/src/lib/corelib/buildgraph/executor.cpp
+++ b/src/lib/corelib/buildgraph/executor.cpp
@@ -51,6 +51,7 @@
 #include "rulecommands.h"
 #include "rulenode.h"
 #include "rulesevaluationcontext.h"
+#include "transformerchangetracking.h"
 
 #include <buildgraph/transformer.h>
 #include <language/language.h>
@@ -160,11 +161,18 @@ void Executor::setProject(const TopLevelProjectPtr &project)
 {
     m_project = project;
     m_allProducts = project->allProducts();
+    m_projectsByName.clear();
+    m_projectsByName.insert(std::make_pair(project->name, project.get()));
+    for (const ResolvedProjectPtr &p : project->allSubProjects())
+        m_projectsByName.insert(std::make_pair(p->name, p.get()));
 }
 
 void Executor::setProducts(const QList<ResolvedProductPtr> &productsToBuild)
 {
     m_productsToBuild = productsToBuild;
+    m_productsByName.clear();
+    for (const ResolvedProductPtr &p : productsToBuild)
+        m_productsByName.insert(std::make_pair(p->uniqueName(), p.get()));
 }
 
 class ProductPrioritySetter
@@ -424,6 +432,11 @@ bool Executor::mustExecuteTransformer(const TransformerPtr &transformer) const
             return true;
     }
 
+    if (commandsNeedRerun(transformer.get(), transformer->product().get(), m_productsByName,
+                          m_projectsByName)) {
+        return true;
+    }
+
     // If all artifacts in a transformer have "alwaysUpdated" set to false, that transformer
     // is always run.
     return !hasAlwaysUpdatedArtifacts;
@@ -493,7 +506,7 @@ void Executor::executeRuleNode(RuleNode *ruleNode)
     }
 
     RuleNode::ApplicationResult result;
-    ruleNode->apply(m_logger, changedInputArtifacts, &result);
+    ruleNode->apply(m_logger, changedInputArtifacts, m_productsByName, m_projectsByName, &result);
 
     if (result.upToDate) {
         qCDebug(lcExec) << ruleNode->toString() << "is up to date. Skipping.";
@@ -823,6 +836,9 @@ void Executor::rescueOldBuildData(Artifact *artifact, bool *childrenAdded = 0)
         artifact->transformer->importedFilesUsedInCommands = rad.importedFilesUsedInCommands;
         artifact->transformer->depsRequestedInPrepareScript = rad.depsRequestedInPrepareScript;
         artifact->transformer->depsRequestedInCommands = rad.depsRequestedInCommands;
+        artifact->transformer->lastCommandExecutionTime = rad.lastCommandExecutionTime;
+        artifact->transformer->lastPrepareScriptExecutionTime = rad.lastPrepareScriptExecutionTime;
+        artifact->transformer->commandsNeedChangeTracking = true;
         artifact->setTimestamp(rad.timeStamp);
         if (childrenAdded && !childrenToConnect.empty())
             *childrenAdded = true;
diff --git a/src/lib/corelib/buildgraph/executor.h b/src/lib/corelib/buildgraph/executor.h
index 64ea62cb8..4127e3563 100644
--- a/src/lib/corelib/buildgraph/executor.h
+++ b/src/lib/corelib/buildgraph/executor.h
@@ -48,9 +48,12 @@
 #include <logging/logger.h>
 #include <tools/buildoptions.h>
 #include <tools/error.h>
+#include <tools/qttools.h>
 
 #include <QtCore/qobject.h>
+
 #include <queue>
+#include <unordered_map>
 
 QT_BEGIN_NAMESPACE
 class QTimer;
@@ -164,6 +167,8 @@ private:
     TopLevelProjectPtr m_project;
     QList<ResolvedProductPtr> m_productsToBuild;
     QList<ResolvedProductPtr> m_allProducts;
+    std::unordered_map<QString, const ResolvedProduct *> m_productsByName;
+    std::unordered_map<QString, const ResolvedProject *> m_projectsByName;
     NodeSet m_roots;
     Leaves m_leaves;
     QList<Artifact *> m_changedSourceArtifacts;
diff --git a/src/lib/corelib/buildgraph/executorjob.cpp b/src/lib/corelib/buildgraph/executorjob.cpp
index 88dbda59f..639a17fe3 100644
--- a/src/lib/corelib/buildgraph/executorjob.cpp
+++ b/src/lib/corelib/buildgraph/executorjob.cpp
@@ -106,6 +106,7 @@ void ExecutorJob::run(Transformer *t)
     t->propertiesRequestedFromArtifactInCommands.clear();
     t->importedFilesUsedInCommands.clear();
     t->depsRequestedInCommands.clear();
+    t->lastCommandExecutionTime = FileTime::currentTime();
     QBS_CHECK(!t->outputs.empty());
     m_processCommandExecutor->setProcessEnvironment(
                 (*t->outputs.cbegin())->product->buildEnvironment);
diff --git a/src/lib/corelib/buildgraph/processcommandexecutor.cpp b/src/lib/corelib/buildgraph/processcommandexecutor.cpp
index ac4d266aa..2442f7a70 100644
--- a/src/lib/corelib/buildgraph/processcommandexecutor.cpp
+++ b/src/lib/corelib/buildgraph/processcommandexecutor.cpp
@@ -103,10 +103,13 @@ static QProcessEnvironment mergeEnvironments(const QProcessEnvironment &baseEnv,
 
 void ProcessCommandExecutor::doSetup()
 {
-    const ProcessCommand * const cmd = processCommand();
+    ProcessCommand * const cmd = processCommand();
     const QString program = ExecutableFinder(transformer()->product(),
                                              transformer()->product()->buildEnvironment)
             .findExecutable(cmd->program(), cmd->workingDir());
+    cmd->clearRelevantEnvValues();
+    for (const QString &key : cmd->relevantEnvVars())
+        cmd->addRelevantEnvValue(key, transformer()->product()->buildEnvironment.value(key));
 
     m_commandEnvironment = mergeEnvironments(m_buildEnvironment, cmd->environment());
     m_program = program;
@@ -399,9 +402,9 @@ void ProcessCommandExecutor::removeResponseFile()
     m_responseFileName.clear();
 }
 
-const ProcessCommand *ProcessCommandExecutor::processCommand() const
+ProcessCommand *ProcessCommandExecutor::processCommand() const
 {
-    return static_cast<const ProcessCommand *>(command());
+    return static_cast<ProcessCommand *>(command());
 }
 
 } // namespace Internal
diff --git a/src/lib/corelib/buildgraph/processcommandexecutor.h b/src/lib/corelib/buildgraph/processcommandexecutor.h
index 877c0bffb..1e4b18777 100644
--- a/src/lib/corelib/buildgraph/processcommandexecutor.h
+++ b/src/lib/corelib/buildgraph/processcommandexecutor.h
@@ -80,7 +80,7 @@ private:
 
     void sendProcessOutput();
     void removeResponseFile();
-    const ProcessCommand *processCommand() const;
+    ProcessCommand *processCommand() const;
 
 private:
     QString m_program;
diff --git a/src/lib/corelib/buildgraph/rescuableartifactdata.cpp b/src/lib/corelib/buildgraph/rescuableartifactdata.cpp
index 2f83283fc..37c05c5f4 100644
--- a/src/lib/corelib/buildgraph/rescuableartifactdata.cpp
+++ b/src/lib/corelib/buildgraph/rescuableartifactdata.cpp
@@ -64,6 +64,8 @@ void RescuableArtifactData::load(PersistentPool &pool)
     pool.load(depsRequestedInPrepareScript);
     pool.load(depsRequestedInCommands);
     pool.load(commands);
+    pool.load(lastPrepareScriptExecutionTime);
+    pool.load(lastCommandExecutionTime);
     pool.load(fileTags);
     pool.load(properties);
 }
@@ -82,6 +84,8 @@ void RescuableArtifactData::store(PersistentPool &pool) const
     pool.store(depsRequestedInPrepareScript);
     pool.store(depsRequestedInCommands);
     pool.store(commands);
+    pool.store(lastPrepareScriptExecutionTime);
+    pool.store(lastCommandExecutionTime);
     pool.store(fileTags);
     pool.store(properties);
 }
diff --git a/src/lib/corelib/buildgraph/rescuableartifactdata.h b/src/lib/corelib/buildgraph/rescuableartifactdata.h
index 119bcc317..87e18c2f7 100644
--- a/src/lib/corelib/buildgraph/rescuableartifactdata.h
+++ b/src/lib/corelib/buildgraph/rescuableartifactdata.h
@@ -111,6 +111,8 @@ public:
     std::vector<QString> importedFilesUsedInCommands;
     RequestedDependencies depsRequestedInPrepareScript;
     RequestedDependencies depsRequestedInCommands;
+    FileTime lastPrepareScriptExecutionTime;
+    FileTime lastCommandExecutionTime;
 
     // Only needed for API purposes
     FileTags fileTags;
diff --git a/src/lib/corelib/buildgraph/rulecommands.cpp b/src/lib/corelib/buildgraph/rulecommands.cpp
index f235280a4..d45a246cd 100644
--- a/src/lib/corelib/buildgraph/rulecommands.cpp
+++ b/src/lib/corelib/buildgraph/rulecommands.cpp
@@ -276,6 +276,7 @@ bool ProcessCommand::equals(const AbstractCommand *otherAbstractCommand) const
             && m_stdoutFilePath == other->m_stdoutFilePath
             && m_stderrFilePath == other->m_stderrFilePath
             && m_relevantEnvVars == other->m_relevantEnvVars
+            && m_relevantEnvValues == other->m_relevantEnvValues
             && m_environment == other->m_environment;
 }
 
@@ -336,6 +337,11 @@ QStringList ProcessCommand::relevantEnvVars() const
     return vars;
 }
 
+void ProcessCommand::addRelevantEnvValue(const QString &key, const QString &value)
+{
+    m_relevantEnvValues.insert(key, value);
+}
+
 void ProcessCommand::load(PersistentPool &pool)
 {
     AbstractCommand::load(pool);
@@ -350,6 +356,7 @@ void ProcessCommand::load(PersistentPool &pool)
     pool.load(m_responseFileThreshold);
     pool.load(m_responseFileArgumentIndex);
     pool.load(m_relevantEnvVars);
+    pool.load(m_relevantEnvValues);
     pool.load(m_stdoutFilePath);
     pool.load(m_stderrFilePath);
 }
@@ -368,6 +375,7 @@ void ProcessCommand::store(PersistentPool &pool) const
     pool.store(m_responseFileThreshold);
     pool.store(m_responseFileArgumentIndex);
     pool.store(m_relevantEnvVars);
+    pool.store(m_relevantEnvValues);
     pool.store(m_stdoutFilePath);
     pool.store(m_stderrFilePath);
 }
diff --git a/src/lib/corelib/buildgraph/rulecommands.h b/src/lib/corelib/buildgraph/rulecommands.h
index 2fae81e99..1472611b9 100644
--- a/src/lib/corelib/buildgraph/rulecommands.h
+++ b/src/lib/corelib/buildgraph/rulecommands.h
@@ -122,6 +122,9 @@ public:
     QString responseFileUsagePrefix() const { return m_responseFileUsagePrefix; }
     QProcessEnvironment environment() const { return m_environment; }
     QStringList relevantEnvVars() const;
+    void clearRelevantEnvValues() { m_relevantEnvValues.clear(); }
+    void addRelevantEnvValue(const QString &key, const QString &value);
+    QString relevantEnvValue(const QString &key) const { return m_relevantEnvValues.value(key); }
     QString stdoutFilePath() const { return m_stdoutFilePath; }
     QString stderrFilePath() const { return m_stderrFilePath; }
 
@@ -146,6 +149,7 @@ private:
     QString m_responseFileUsagePrefix;
     QProcessEnvironment m_environment;
     QStringList m_relevantEnvVars;
+    QProcessEnvironment m_relevantEnvValues;
     QString m_stdoutFilePath;
     QString m_stderrFilePath;
 };
@@ -191,6 +195,7 @@ private:
     QList<AbstractCommandPtr> m_commands;
 };
 bool operator==(const CommandList &cl1, const CommandList &cl2);
+inline bool operator!=(const CommandList &cl1, const CommandList &cl2) { return !(cl1 == cl2); }
 
 } // namespace Internal
 } // namespace qbs
diff --git a/src/lib/corelib/buildgraph/rulenode.cpp b/src/lib/corelib/buildgraph/rulenode.cpp
index ca4b06a20..ece35fcf7 100644
--- a/src/lib/corelib/buildgraph/rulenode.cpp
+++ b/src/lib/corelib/buildgraph/rulenode.cpp
@@ -45,6 +45,7 @@
 #include "projectbuilddata.h"
 #include "rulesapplicator.h"
 #include "transformer.h"
+#include "transformerchangetracking.h"
 
 #include <language/language.h>
 #include <logging/categories.h>
@@ -78,7 +79,9 @@ QString RuleNode::toString() const
 }
 
 void RuleNode::apply(const Logger &logger, const ArtifactSet &changedInputs,
-        ApplicationResult *result)
+                     const std::unordered_map<QString, const ResolvedProduct *> &productsByName,
+                     const std::unordered_map<QString, const ResolvedProject *> &projectsByName,
+                     ApplicationResult *result)
 {
     ArtifactSet allCompatibleInputs = currentInputArtifacts();
     const ArtifactSet addedInputs = allCompatibleInputs - m_oldInputArtifacts;
@@ -108,6 +111,22 @@ void RuleNode::apply(const Logger &logger, const ArtifactSet &changedInputs,
     else
         inputs += addedInputs;
 
+    for (Artifact * const input : allCompatibleInputs) {
+        for (const Artifact * const output : input->parentArtifacts()) {
+            if (output->transformer->rule != m_rule)
+                continue;
+            if (prepareScriptNeedsRerun(output->transformer.get(),
+                                        output->transformer->product().get(),
+                                        productsByName, projectsByName)) {
+                result->upToDate = false;
+                inputs += input;
+            }
+            break;
+        }
+        if (m_rule->multiplex)
+            break;
+    }
+
     if (result->upToDate)
         return;
     if (!removedInputs.empty()) {
@@ -132,7 +151,7 @@ void RuleNode::apply(const Logger &logger, const ArtifactSet &changedInputs,
         RulesApplicator::handleRemovedRuleOutputs(inputs, outputArtifactsToRemove, logger);
     }
     if (!inputs.empty() || !m_rule->declaresInputs() || !m_rule->requiresInputs) {
-        RulesApplicator applicator(product.lock(), logger);
+        RulesApplicator applicator(product.lock(), productsByName, projectsByName, logger);
         applicator.applyRule(m_rule, inputs);
         result->createdNodes = applicator.createdArtifacts();
         result->invalidatedNodes = applicator.invalidatedArtifacts();
diff --git a/src/lib/corelib/buildgraph/rulenode.h b/src/lib/corelib/buildgraph/rulenode.h
index b10447c00..50c625799 100644
--- a/src/lib/corelib/buildgraph/rulenode.h
+++ b/src/lib/corelib/buildgraph/rulenode.h
@@ -46,6 +46,8 @@
 #include <language/forward_decls.h>
 #include <tools/dynamictypecheck.h>
 
+#include <unordered_map>
+
 namespace qbs {
 namespace Internal {
 
@@ -71,7 +73,10 @@ public:
         NodeSet invalidatedNodes;
     };
 
-    void apply(const Logger &logger, const ArtifactSet &changedInputs, ApplicationResult *result);
+    void apply(const Logger &logger, const ArtifactSet &changedInputs,
+               const std::unordered_map<QString, const ResolvedProduct *> &productsByName,
+               const std::unordered_map<QString, const ResolvedProject *> &projectsByName,
+               ApplicationResult *result);
     void removeOldInputArtifact(Artifact *artifact) { m_oldInputArtifacts.remove(artifact); }
 
     void load(PersistentPool &pool);
diff --git a/src/lib/corelib/buildgraph/rulesapplicator.cpp b/src/lib/corelib/buildgraph/rulesapplicator.cpp
index e07194bf6..3ad01a008 100644
--- a/src/lib/corelib/buildgraph/rulesapplicator.cpp
+++ b/src/lib/corelib/buildgraph/rulesapplicator.cpp
@@ -43,8 +43,10 @@
 #include "productbuilddata.h"
 #include "projectbuilddata.h"
 #include "qtmocscanner.h"
+#include "rulecommands.h"
 #include "rulesevaluationcontext.h"
 #include "transformer.h"
+#include "transformerchangetracking.h"
 
 #include <jsextensions/moduleproperties.h>
 #include <language/artifactproperties.h>
@@ -72,8 +74,14 @@
 namespace qbs {
 namespace Internal {
 
-RulesApplicator::RulesApplicator(const ResolvedProductPtr &product, const Logger &logger)
+RulesApplicator::RulesApplicator(
+        const ResolvedProductPtr &product,
+        const std::unordered_map<QString, const ResolvedProduct *> &productsByName,
+        const std::unordered_map<QString, const ResolvedProject *> &projectsByName,
+        const Logger &logger)
     : m_product(product)
+    , m_productsByName(productsByName)
+    , m_projectsByName(projectsByName)
     , m_mocScanner(nullptr)
     , m_logger(logger)
 {
@@ -174,6 +182,7 @@ void RulesApplicator::doApply(const ArtifactSet &inputArtifacts, QScriptValue &p
     m_transformer->inputs = inputArtifacts;
     m_transformer->explicitlyDependsOn = collectExplicitlyDependsOn();
     m_transformer->alwaysRun = m_rule->alwaysRun;
+    m_oldTransformer.reset();
 
     engine()->clearRequestedProperties();
 
@@ -257,6 +266,16 @@ void RulesApplicator::doApply(const ArtifactSet &inputArtifacts, QScriptValue &p
     if (Q_UNLIKELY(m_transformer->commands.empty()))
         throw ErrorInfo(Tr::tr("There is a rule without commands: %1.")
                         .arg(m_rule->toString()), m_rule->prepareScript.location());
+    if (!m_oldTransformer || m_oldTransformer->outputs != m_transformer->outputs
+            || m_oldTransformer->commands != m_transformer->commands
+            || commandsNeedRerun(m_transformer.get(), m_product.get(), m_productsByName,
+                                 m_projectsByName)) {
+        for (Artifact * const output : outputArtifacts) {
+            output->clearTimestamp();
+            m_invalidatedArtifacts += output;
+        }
+    }
+    m_transformer->commandsNeedChangeTracking = false;
 }
 
 ArtifactSet RulesApplicator::collectOldOutputArtifacts(const ArtifactSet &inputArtifacts) const
@@ -353,10 +372,8 @@ Artifact *RulesApplicator::createOutputArtifact(const QString &filePath, const F
                               (*inputArtifacts.cbegin())->filePath()));
             throw error;
         }
-        if (m_rule->declaresInputs() && m_rule->requiresInputs)
-            outputArtifact->clearTimestamp();
-        m_invalidatedArtifacts += outputArtifact;
         m_transformer->rescueChangeTrackingData(outputArtifact->transformer);
+        m_oldTransformer = outputArtifact->transformer;
     } else {
         std::unique_ptr<Artifact> newArtifact(new Artifact);
         newArtifact->artifactType = Artifact::Generated;
diff --git a/src/lib/corelib/buildgraph/rulesapplicator.h b/src/lib/corelib/buildgraph/rulesapplicator.h
index ee26caebd..bc3bd2bcc 100644
--- a/src/lib/corelib/buildgraph/rulesapplicator.h
+++ b/src/lib/corelib/buildgraph/rulesapplicator.h
@@ -48,9 +48,10 @@
 
 #include <QtCore/qhash.h>
 #include <QtCore/qstring.h>
-
 #include <QtScript/qscriptvalue.h>
 
+#include <unordered_map>
+
 namespace qbs {
 namespace Internal {
 class BuildGraphNode;
@@ -60,7 +61,10 @@ class ScriptEngine;
 class RulesApplicator
 {
 public:
-    RulesApplicator(const ResolvedProductPtr &product, const Logger &logger);
+    RulesApplicator(const ResolvedProductPtr &product,
+                    const std::unordered_map<QString, const ResolvedProduct *> &productsByName,
+                    const std::unordered_map<QString, const ResolvedProject *> &projectsByName,
+                    const Logger &logger);
     ~RulesApplicator();
 
     const NodeSet &createdArtifacts() const { return m_createdArtifacts; }
@@ -88,11 +92,14 @@ private:
     QScriptValue scope() const;
 
     const ResolvedProductPtr m_product;
+    const std::unordered_map<QString, const ResolvedProduct *> &m_productsByName;
+    const std::unordered_map<QString, const ResolvedProject *> &m_projectsByName;
     NodeSet m_createdArtifacts;
     NodeSet m_invalidatedArtifacts;
     RuleConstPtr m_rule;
     ArtifactSet m_completeInputSet;
     TransformerPtr m_transformer;
+    TransformerConstPtr m_oldTransformer;
     QtMocScanner *m_mocScanner;
     Logger m_logger;
 };
diff --git a/src/lib/corelib/buildgraph/transformer.cpp b/src/lib/corelib/buildgraph/transformer.cpp
index 92853d9da..e09e779d8 100644
--- a/src/lib/corelib/buildgraph/transformer.cpp
+++ b/src/lib/corelib/buildgraph/transformer.cpp
@@ -210,8 +210,8 @@ void Transformer::setupExplicitlyDependsOn(QScriptValue targetScriptValue)
     targetScriptValue.setProperty(StringConstants::explicitlyDependsOnVar(), scriptValue);
 }
 
-static AbstractCommandPtr createCommandFromScriptValue(const QScriptValue &scriptValue,
-                                                       const CodeLocation &codeLocation)
+AbstractCommandPtr Transformer::createCommandFromScriptValue(const QScriptValue &scriptValue,
+                                                             const CodeLocation &codeLocation)
 {
     AbstractCommandPtr cmdBase;
     if (scriptValue.isUndefined() || !scriptValue.isValid())
@@ -223,6 +223,12 @@ static AbstractCommandPtr createCommandFromScriptValue(const QScriptValue &scrip
         cmdBase = JavaScriptCommand::create();
     if (cmdBase)
         cmdBase->fillFromScriptValue(&scriptValue, codeLocation);
+    if (className == StringConstants::commandType()) {
+        ProcessCommand *procCmd = static_cast<ProcessCommand *>(cmdBase.get());
+        procCmd->clearRelevantEnvValues();
+        for (const QString &key : procCmd->relevantEnvVars())
+            procCmd->addRelevantEnvValue(key, product()->buildEnvironment.value(key));
+    }
     return cmdBase;
 }
 
@@ -243,6 +249,7 @@ void Transformer::createCommands(ScriptEngine *engine, const PrivateScriptFuncti
     propertiesRequestedFromArtifactInPrepareScript = engine->propertiesRequestedFromArtifact();
     importedFilesUsedInPrepareScript = engine->importedFilesUsedInScript();
     depsRequestedInPrepareScript = engine->requestedDependencies();
+    lastPrepareScriptExecutionTime = FileTime::currentTime();
     engine->clearRequestedProperties();
     if (Q_UNLIKELY(engine->hasErrorOrException(scriptValue)))
         throw engine->lastError(scriptValue, script.location());
@@ -279,6 +286,10 @@ void Transformer::rescueChangeTrackingData(const TransformerConstPtr &other)
     importedFilesUsedInCommands = other->importedFilesUsedInCommands;
     depsRequestedInPrepareScript = other->depsRequestedInPrepareScript;
     depsRequestedInCommands = other->depsRequestedInCommands;
+    lastCommandExecutionTime = other->lastCommandExecutionTime;
+    lastPrepareScriptExecutionTime = other->lastPrepareScriptExecutionTime;
+    prepareScriptNeedsChangeTracking = other->prepareScriptNeedsChangeTracking;
+    commandsNeedChangeTracking = other->commandsNeedChangeTracking;
 }
 
 void Transformer::load(PersistentPool &pool)
@@ -296,7 +307,11 @@ void Transformer::load(PersistentPool &pool)
     pool.load(depsRequestedInPrepareScript);
     pool.load(depsRequestedInCommands);
     pool.load(commands);
+    pool.load(lastPrepareScriptExecutionTime);
+    pool.load(lastCommandExecutionTime);
     pool.load(alwaysRun);
+    pool.load(prepareScriptNeedsChangeTracking);
+    pool.load(commandsNeedChangeTracking);
 }
 
 void Transformer::store(PersistentPool &pool) const
@@ -314,7 +329,11 @@ void Transformer::store(PersistentPool &pool) const
     pool.store(depsRequestedInPrepareScript);
     pool.store(depsRequestedInCommands);
     pool.store(commands);
+    pool.store(lastPrepareScriptExecutionTime);
+    pool.store(lastCommandExecutionTime);
     pool.store(alwaysRun);
+    pool.store(prepareScriptNeedsChangeTracking);
+    pool.store(commandsNeedChangeTracking);
 }
 
 } // namespace Internal
diff --git a/src/lib/corelib/buildgraph/transformer.h b/src/lib/corelib/buildgraph/transformer.h
index f1ef01ae7..180bc8d49 100644
--- a/src/lib/corelib/buildgraph/transformer.h
+++ b/src/lib/corelib/buildgraph/transformer.h
@@ -47,6 +47,7 @@
 #include <language/forward_decls.h>
 #include <language/property.h>
 #include <language/scriptengine.h>
+#include <tools/filetime.h>
 
 #include <QtCore/qhash.h>
 
@@ -76,7 +77,11 @@ public:
     std::vector<QString> importedFilesUsedInCommands;
     RequestedDependencies depsRequestedInPrepareScript;
     RequestedDependencies depsRequestedInCommands;
+    FileTime lastPrepareScriptExecutionTime;
+    FileTime lastCommandExecutionTime;
     bool alwaysRun;
+    bool prepareScriptNeedsChangeTracking = false;
+    bool commandsNeedChangeTracking = false;
 
     static QScriptValue translateFileConfig(ScriptEngine *scriptEngine,
                                             const Artifact *artifact,
@@ -94,6 +99,8 @@ public:
 
 private:
     Transformer();
+    AbstractCommandPtr createCommandFromScriptValue(const QScriptValue &scriptValue,
+                                                    const CodeLocation &codeLocation);
 
     static void setupInputs(QScriptValue targetScriptValue, const ArtifactSet &inputs,
             const QString &defaultModuleName);
diff --git a/src/lib/corelib/buildgraph/transformerchangetracking.cpp b/src/lib/corelib/buildgraph/transformerchangetracking.cpp
index 07300b25b..96a612b70 100644
--- a/src/lib/corelib/buildgraph/transformerchangetracking.cpp
+++ b/src/lib/corelib/buildgraph/transformerchangetracking.cpp
@@ -27,6 +27,7 @@
 ****************************************************************************/
 #include "transformerchangetracking.h"
 
+#include "projectbuilddata.h"
 #include "requesteddependencies.h"
 #include "rulecommands.h"
 #include "transformer.h"
@@ -47,10 +48,10 @@ namespace Internal {
 class TrafoChangeTracker
 {
 public:
-    TrafoChangeTracker(const TransformerPtr &transformer,
-                       const ResolvedProductPtr &product,
-                       const QMap<QString, ResolvedProductPtr> &productsByName,
-                       const QMap<QString, const ResolvedProject *> projectsByName)
+    TrafoChangeTracker(const Transformer *transformer,
+                       const ResolvedProduct *product,
+                       const std::unordered_map<QString, const ResolvedProduct *> &productsByName,
+                       const std::unordered_map<QString, const ResolvedProject *> &projectsByName)
         : m_transformer(transformer),
           m_product(product),
           m_productsByName(productsByName),
@@ -58,59 +59,27 @@ public:
     {
     }
 
-    bool propertyChangeFound();
-    bool environmentChangeFound();
+    bool prepareScriptNeedsRerun() const;
+    bool commandsNeedRerun() const;
 
 private:
-    SourceArtifactConstPtr findSourceArtifact(const QString &artifactFilePath,
-                                              QMap<QString, SourceArtifactConstPtr> &artifactMap);
     QVariantMap propertyMapByKind(const Property &property) const;
-    void invalidateTransformer();
     bool checkForPropertyChange(const Property &restoredProperty,
                                 const QVariantMap &newProperties) const;
     bool checkForImportFileChange(const std::vector<QString> &importedFiles,
                                   const FileTime &referenceTime,
                                   const char *context) const;
+    const Artifact *getArtifact(const QString &filePath, const QString &productName) const;
+    const ResolvedProduct *getProduct(const QString &name) const;
 
-    const TransformerPtr &m_transformer;
-    const ResolvedProductPtr &m_product;
-    const QMap<QString, ResolvedProductPtr> &m_productsByName;
-    const QMap<QString, const ResolvedProject *> m_projectsByName;
+    const Transformer * const m_transformer;
+    const ResolvedProduct * const m_product;
+    const std::unordered_map<QString, const ResolvedProduct *> &m_productsByName;
+    const std::unordered_map<QString, const ResolvedProject *> &m_projectsByName;
+    mutable const ResolvedProduct * m_lastProduct = nullptr;
+    mutable const Artifact *m_lastArtifact = nullptr;
 };
 
-bool checkForPropertyChanges(const TransformerPtr &transformer,
-                             const ResolvedProductPtr &product,
-                             const QMap<QString, ResolvedProductPtr> &productsByName,
-                             const QMap<QString, const ResolvedProject *> projectsByName)
-{
-    return TrafoChangeTracker(transformer, product, productsByName, projectsByName)
-            .propertyChangeFound();
-}
-
-bool checkForEnvironmentChanges(const TransformerPtr &transformer,
-                                const ResolvedProductPtr &product,
-                                const QMap<QString, ResolvedProductPtr> &productsByName,
-                                const QMap<QString, const ResolvedProject *> projectsByName)
-{
-    return TrafoChangeTracker(transformer, product, productsByName, projectsByName)
-            .environmentChangeFound();
-}
-
-SourceArtifactConstPtr TrafoChangeTracker::findSourceArtifact(const QString &artifactFilePath,
-        QMap<QString, SourceArtifactConstPtr> &artifactMap)
-{
-    SourceArtifactConstPtr &artifact = artifactMap[artifactFilePath];
-    if (!artifact) {
-        for (const SourceArtifactConstPtr &a : m_product->allFiles()) {
-            if (a->absoluteFilePath == artifactFilePath) {
-                artifact = a;
-                break;
-            }
-        }
-    }
-    return artifact;
-}
-
 template<typename T> static QVariantMap getParameterValue(
         const QHash<T, QVariantMap> &parameters,
         const QString &depName)
@@ -124,28 +93,27 @@ template<typename T> static QVariantMap getParameterValue(
 
 QVariantMap TrafoChangeTracker::propertyMapByKind(const Property &property) const
 {
-    const auto getProduct = [&property, this]() {
-        return property.productName == m_product->uniqueName()
-                ? m_product : m_productsByName.value(property.productName);
-    };
     switch (property.kind) {
     case Property::PropertyInModule: {
-        const ResolvedProductConstPtr &p = getProduct();
+        const ResolvedProduct * const p = getProduct(property.productName);
         return p ? p->moduleProperties->value() : QVariantMap();
     }
     case Property::PropertyInProduct: {
-        const ResolvedProductConstPtr &p = getProduct();
+        const ResolvedProduct * const p = getProduct(property.productName);
         return p ? p->productProperties : QVariantMap();
     }
     case Property::PropertyInProject: {
-        const ResolvedProject *project = property.productName == m_product->project->name
-                ? m_product->project.get() : m_projectsByName.value(property.productName);
-        return project ? project->projectProperties() : QVariantMap();
+        if (property.productName == m_product->project->name)
+            return m_product->project->projectProperties();
+        const auto it = m_projectsByName.find(property.productName);
+        if (it != m_projectsByName.cend())
+            return it->second->projectProperties();
+        return QVariantMap();
     }
     case Property::PropertyInParameters: {
         const int sepIndex = property.moduleName.indexOf(QLatin1Char(':'));
         const QString depName = property.moduleName.left(sepIndex);
-        const ResolvedProductConstPtr &p = getProduct();
+        const ResolvedProduct * const p = getProduct(property.productName);
         if (!p)
             return QVariantMap();
         QVariantMap v = getParameterValue(p->dependencyParameters, depName);
@@ -159,78 +127,6 @@ QVariantMap TrafoChangeTracker::propertyMapByKind(const Property &property) cons
     return QVariantMap();
 }
 
-void TrafoChangeTracker::invalidateTransformer()
-{
-    const JavaScriptCommandPtr &pseudoCommand = JavaScriptCommand::create();
-    pseudoCommand->setSourceCode(QStringLiteral("random stuff that will cause "
-                                                "commandsEqual() to fail"));
-    m_transformer->commands.addCommand(pseudoCommand);
-}
-
-bool TrafoChangeTracker::propertyChangeFound()
-{
-    // This check must come first, as it can prevent build data rescuing.
-    for (const Property &property : qAsConst(m_transformer->propertiesRequestedInCommands)) {
-        if (checkForPropertyChange(property, propertyMapByKind(property))) {
-            invalidateTransformer();
-            return true;
-        }
-    }
-
-    QMap<QString, SourceArtifactConstPtr> artifactMap;
-    for (auto it = m_transformer->propertiesRequestedFromArtifactInCommands.cbegin();
-         it != m_transformer->propertiesRequestedFromArtifactInCommands.cend(); ++it) {
-        const SourceArtifactConstPtr artifact
-                = findSourceArtifact(it.key(), artifactMap);
-        if (!artifact)
-            continue;
-        for (const Property &property : qAsConst(it.value())) {
-            if (checkForPropertyChange(property, artifact->properties->value())) {
-                invalidateTransformer();
-                return true;
-            }
-        }
-    }
-
-    const FileTime referenceTime = m_transformer->product()->topLevelProject()->lastResolveTime; // TODO: This will need to be a transformer-specific timestamp
-    if (checkForImportFileChange(m_transformer->importedFilesUsedInCommands, referenceTime,
-                                 "command")) {
-        invalidateTransformer();
-        return true;
-    }
-
-    if (!m_transformer->depsRequestedInCommands.isUpToDate(m_product->topLevelProject())) {
-        invalidateTransformer();
-        return true;
-    }
-
-    for (const Property &property : qAsConst(m_transformer->propertiesRequestedInPrepareScript)) {
-        if (checkForPropertyChange(property, propertyMapByKind(property)))
-            return true;
-    }
-
-    if (checkForImportFileChange(m_transformer->importedFilesUsedInPrepareScript, referenceTime,
-                                 "prepare script")) {
-        return true;
-    }
-
-    for (auto it = m_transformer->propertiesRequestedFromArtifactInPrepareScript.constBegin();
-         it != m_transformer->propertiesRequestedFromArtifactInPrepareScript.constEnd(); ++it) {
-        const SourceArtifactConstPtr &artifact = findSourceArtifact(it.key(), artifactMap); // TODO: This can use the actual artifact data later
-        if (!artifact)
-            continue;
-        for (const Property &property : qAsConst(it.value())) {
-            if (checkForPropertyChange(property, artifact->properties->value()))
-                return true;
-        }
-    }
-
-    if (!m_transformer->depsRequestedInPrepareScript.isUpToDate(m_product->topLevelProject()))
-        return true;
-
-    return false;
-}
-
 bool TrafoChangeTracker::checkForPropertyChange(const Property &restoredProperty,
                                                 const QVariantMap &newProperties) const
 {
@@ -278,29 +174,154 @@ bool TrafoChangeTracker::checkForImportFileChange(const std::vector<QString> &im
         }
         if (fi.lastModified() > referenceTime) {
             qCDebug(lcBuildGraph) << context << "imported file" << importedFile
-                                  << "has been updated, need to re-run";
+                                  << "has been updated, need to re-run"
+                                  << fi.lastModified() << referenceTime;
             return true;
         }
     }
     return false;
 }
 
-bool TrafoChangeTracker::environmentChangeFound()
+const Artifact *TrafoChangeTracker::getArtifact(const QString &filePath,
+                                                const QString &productName) const
 {
-    // TODO: Also check results of getEnv() from commands here; we currently do not track them
+    if (m_lastArtifact && m_lastArtifact->filePath() == filePath
+            && m_lastArtifact->product.get()->uniqueName() == productName) {
+        return m_lastArtifact;
+    }
+    const ResolvedProduct * const product = getProduct(productName);
+    if (!product)
+        return nullptr;
+    const QList<FileResourceBase *> &candidates
+            = product->topLevelProject()->buildData->lookupFiles(filePath);
+    const Artifact *artifact = nullptr;
+    for (const FileResourceBase * const candidate : candidates) {
+        if (candidate->fileType() == FileResourceBase::FileTypeArtifact) {
+            const Artifact * const a = static_cast<const Artifact *>(candidate);
+            if (a->product.get() == product) {
+                m_lastArtifact = artifact = a;
+                break;
+            }
+        }
+    }
+    return artifact;
+}
+
+const ResolvedProduct *TrafoChangeTracker::getProduct(const QString &name) const
+{
+    if (m_lastProduct && name == m_lastProduct->uniqueName())
+        return m_lastProduct;
+    if (name == m_product->uniqueName()) {
+        m_lastProduct = m_product;
+        return m_product;
+    }
+    const auto it = m_productsByName.find(name);
+    if (it != m_productsByName.cend()) {
+        m_lastProduct = it->second;
+        return it->second;
+    }
+    return nullptr;
+}
+
+bool TrafoChangeTracker::prepareScriptNeedsRerun() const
+{
+    for (const Property &property : qAsConst(m_transformer->propertiesRequestedInPrepareScript)) {
+        if (checkForPropertyChange(property, propertyMapByKind(property)))
+            return true;
+    }
+
+    if (checkForImportFileChange(m_transformer->importedFilesUsedInPrepareScript,
+                                 m_transformer->lastPrepareScriptExecutionTime, "prepare script")) {
+        return true;
+    }
+
+    for (auto it = m_transformer->propertiesRequestedFromArtifactInPrepareScript.constBegin();
+         it != m_transformer->propertiesRequestedFromArtifactInPrepareScript.constEnd(); ++it) {
+        for (const Property &property : qAsConst(it.value())) {
+            const Artifact * const artifact = getArtifact(it.key(), property.productName);
+            if (!artifact)
+                return true;
+            if (checkForPropertyChange(property, artifact->properties->value()))
+                return true;
+        }
+    }
+
+    if (!m_transformer->depsRequestedInPrepareScript.isUpToDate(m_product->topLevelProject()))
+        return true;
+
+    return false;
+}
+
+bool TrafoChangeTracker::commandsNeedRerun() const
+{
+    for (const Property &property : qAsConst(m_transformer->propertiesRequestedInCommands)) {
+        if (checkForPropertyChange(property, propertyMapByKind(property)))
+            return true;
+    }
+
+    QMap<QString, SourceArtifactConstPtr> artifactMap;
+    for (auto it = m_transformer->propertiesRequestedFromArtifactInCommands.cbegin();
+         it != m_transformer->propertiesRequestedFromArtifactInCommands.cend(); ++it) {
+        for (const Property &property : qAsConst(it.value())) {
+            const Artifact * const artifact = getArtifact(it.key(), property.productName);
+            if (!artifact)
+                return true;
+            if (checkForPropertyChange(property, artifact->properties->value()))
+                return true;
+        }
+    }
+
+    if (checkForImportFileChange(m_transformer->importedFilesUsedInCommands,
+                                 m_transformer->lastCommandExecutionTime, "command")) {
+        return true;
+    }
+
+    if (!m_transformer->depsRequestedInCommands.isUpToDate(m_product->topLevelProject()))
+        return true;
+
+    // TODO: Also track env access in JS commands and prepare scripts
     for (const AbstractCommandPtr &c : qAsConst(m_transformer->commands.commands())) {
         if (c->type() != AbstractCommand::ProcessCommandType)
             continue;
-        for (const QString &var : std::static_pointer_cast<ProcessCommand>(c)->relevantEnvVars()) {
-            if (m_transformer->product()->topLevelProject()->environment.value(var) // TODO: These will need to get stored per transformer
-                    != m_product->topLevelProject()->environment.value(var)) {
-                invalidateTransformer();
+        const ProcessCommandPtr &processCmd = std::static_pointer_cast<ProcessCommand>(c);
+        for (const QString &var : processCmd->relevantEnvVars()) {
+            const QString &oldValue = processCmd->relevantEnvValue(var);
+            const QString &newValue = m_product->buildEnvironment.value(var);
+            if (oldValue != newValue) {
+                qCDebug(lcBuildGraph) << "need to re-run command: value of environment variable"
+                                      << var << "changed from" << oldValue << "to" << newValue
+                                      << "for command" << processCmd->program() << "in rule"
+                                      << m_transformer->rule->toString();
                 return true;
             }
         }
     }
+
     return false;
 }
 
+bool prepareScriptNeedsRerun(
+        Transformer *transformer, const ResolvedProduct *product,
+        const std::unordered_map<QString, const ResolvedProduct *> &productsByName,
+        const std::unordered_map<QString, const ResolvedProject *> &projectsByName)
+{
+    if (!transformer->prepareScriptNeedsChangeTracking)
+        return false;
+    transformer->prepareScriptNeedsChangeTracking = false;
+    return TrafoChangeTracker(transformer, product, productsByName, projectsByName)
+            .prepareScriptNeedsRerun();
+}
+
+bool commandsNeedRerun(Transformer *transformer, const ResolvedProduct *product,
+                       const std::unordered_map<QString, const ResolvedProduct *> &productsByName,
+                       const std::unordered_map<QString, const ResolvedProject *> &projectsByName)
+{
+    if (!transformer->commandsNeedChangeTracking)
+        return false;
+    transformer->commandsNeedChangeTracking = false;
+    return TrafoChangeTracker(transformer, product, productsByName, projectsByName)
+            .commandsNeedRerun();
+}
+
 } // namespace Internal
 } // namespace qbs
diff --git a/src/lib/corelib/buildgraph/transformerchangetracking.h b/src/lib/corelib/buildgraph/transformerchangetracking.h
index 4d20ffc9c..56efa458b 100644
--- a/src/lib/corelib/buildgraph/transformerchangetracking.h
+++ b/src/lib/corelib/buildgraph/transformerchangetracking.h
@@ -31,20 +31,21 @@
 #include "forward_decls.h"
 #include <language/forward_decls.h>
 
-#include <QtCore/qmap.h>
+#include <unordered_map>
 
 namespace qbs {
 namespace Internal {
 
-bool checkForPropertyChanges(const TransformerPtr &transformer,
-                             const ResolvedProductPtr &product,
-                             const QMap<QString, ResolvedProductPtr> &productsByName,
-                             const QMap<QString, const ResolvedProject *> projectsByName);
+bool prepareScriptNeedsRerun(
+        Transformer *transformer,
+        const ResolvedProduct *product,
+        const std::unordered_map<QString, const ResolvedProduct *> &productsByName,
+        const std::unordered_map<QString, const ResolvedProject *> &projectsByName);
 
-bool checkForEnvironmentChanges(const TransformerPtr &transformer,
-                                const ResolvedProductPtr &product,
-                                const QMap<QString, ResolvedProductPtr> &productsByName,
-                                const QMap<QString, const ResolvedProject *> projectsByName);
+bool commandsNeedRerun(Transformer *transformer,
+                       const ResolvedProduct *product,
+                       const std::unordered_map<QString, const ResolvedProduct *> &productsByName,
+                       const std::unordered_map<QString, const ResolvedProject *> &projectsByName);
 
 } // namespace Internal
 } // namespace qbs
diff --git a/src/lib/corelib/tools/persistence.cpp b/src/lib/corelib/tools/persistence.cpp
index 88f6555f8..8ec6c03f1 100644
--- a/src/lib/corelib/tools/persistence.cpp
+++ b/src/lib/corelib/tools/persistence.cpp
@@ -49,7 +49,7 @@
 namespace qbs {
 namespace Internal {
 
-static const char QBS_PERSISTENCE_MAGIC[] = "QBSPERSISTENCE_112";
+static const char QBS_PERSISTENCE_MAGIC[] = "QBSPERSISTENCE-113";
 
 NoBuildGraphError::NoBuildGraphError(const QString &filePath)
     : ErrorInfo(Tr::tr("Build graph not found for configuration '%1'. Expected location was '%2'.")
diff --git a/src/lib/corelib/tools/qttools.h b/src/lib/corelib/tools/qttools.h
index 083a1ae03..94d1ccb0d 100644
--- a/src/lib/corelib/tools/qttools.h
+++ b/src/lib/corelib/tools/qttools.h
@@ -43,6 +43,14 @@
 #include <QtCore/qhash.h>
 #include <QtCore/qstringlist.h>
 
+#include <functional>
+
+namespace std {
+template<> struct hash<QString> {
+    std::size_t operator()(const QString &s) const { return qHash(s); }
+};
+}
+
 QT_BEGIN_NAMESPACE
 uint qHash(const QStringList &list);
 
diff --git a/tests/auto/blackbox/testdata/dependenciesProperty/dependenciesProperty.qbs b/tests/auto/blackbox/testdata/dependenciesProperty/dependenciesProperty.qbs
index 3d861f17c..ea32bbb52 100644
--- a/tests/auto/blackbox/testdata/dependenciesProperty/dependenciesProperty.qbs
+++ b/tests/auto/blackbox/testdata/dependenciesProperty/dependenciesProperty.qbs
@@ -12,6 +12,7 @@ Project {
         // Depends { name: 'newDependency' }
         Rule {
             multiplex: true
+            inputsFromDependencies: "application"
             Artifact {
                 fileTags: ["deps"]
                 filePath: product.name + '.deps'
diff --git a/tests/auto/blackbox/tst_blackbox.cpp b/tests/auto/blackbox/tst_blackbox.cpp
index aa14cae17..85aa07678 100644
--- a/tests/auto/blackbox/tst_blackbox.cpp
+++ b/tests/auto/blackbox/tst_blackbox.cpp
@@ -1258,16 +1258,15 @@ void TestBlackbox::wholeArchive()
     QFETCH(bool, ruleInvalidationExpected);
     QFETCH(bool, dllLinkingExpected);
     const QbsRunParameters resolveParams("resolve",
-            QStringList("-vv") << "products.dynamiclib.linkWholeArchive:" + wholeArchiveString);
+            QStringList("products.dynamiclib.linkWholeArchive:" + wholeArchiveString));
     QCOMPARE(runQbs(QbsRunParameters(resolveParams)), 0);
-    const QByteArray resolveStderr = m_qbsStderr;
-    QCOMPARE(runQbs(QbsRunParameters(QStringList({ "-p", "dynamiclib" }))), 0);
+    QCOMPARE(runQbs(QbsRunParameters(QStringList({ "-vvp", "dynamiclib" }))), 0);
     const bool wholeArchive = !wholeArchiveString.isEmpty();
     const bool outdatedVisualStudio = wholeArchive && m_qbsStderr.contains("upgrade");
     const QByteArray invalidationOutput
             = "Value for property 'staticlib 1:cpp.linkWholeArchive' has changed.";
     if (!outdatedVisualStudio)
-        QCOMPARE(resolveStderr.contains(invalidationOutput), ruleInvalidationExpected);
+        QCOMPARE(m_qbsStderr.contains(invalidationOutput), ruleInvalidationExpected);
     QCOMPARE(m_qbsStdout.contains("linking"), dllLinkingExpected && !outdatedVisualStudio);
     QbsRunParameters buildParams(QStringList("-p"));
     buildParams.expectFailure = !wholeArchive || outdatedVisualStudio;
@@ -5649,6 +5648,7 @@ void TestBlackbox::importChangeTracking()
     QVERIFY2(!m_qbsStdout.contains("running probe1 "), m_qbsStdout.constData());
     QVERIFY2(!m_qbsStdout.contains("running probe2"), m_qbsStdout.constData());
     QVERIFY2(m_qbsStdout.contains("running custom1 prepare script"), m_qbsStdout.constData());
+    QVERIFY2(!m_qbsStdout.contains("running custom2 prepare script"), m_qbsStdout.constData());
     QVERIFY2(!m_qbsStdout.contains("running custom1 command"), m_qbsStdout.constData());
     QVERIFY2(!m_qbsStdout.contains("running custom2 command"), m_qbsStdout.constData());
 
@@ -5660,6 +5660,7 @@ void TestBlackbox::importChangeTracking()
     QVERIFY2(!m_qbsStdout.contains("running probe1 "), m_qbsStdout.constData());
     QVERIFY2(!m_qbsStdout.contains("running probe2"), m_qbsStdout.constData());
     QVERIFY2(m_qbsStdout.contains("running custom1 prepare script"), m_qbsStdout.constData());
+    QVERIFY2(!m_qbsStdout.contains("running custom2 prepare script"), m_qbsStdout.constData());
     QVERIFY2(!m_qbsStdout.contains("running custom1 command"), m_qbsStdout.constData());
     QVERIFY2(!m_qbsStdout.contains("running custom2 command"), m_qbsStdout.constData());
 
@@ -5670,6 +5671,8 @@ void TestBlackbox::importChangeTracking()
     QVERIFY2(m_qbsStdout.contains("Resolving"), m_qbsStdout.constData());
     QVERIFY2(!m_qbsStdout.contains("running probe1 "), m_qbsStdout.constData());
     QVERIFY2(!m_qbsStdout.contains("running probe2"), m_qbsStdout.constData());
+    QVERIFY2(!m_qbsStdout.contains("running custom1 prepare script"), m_qbsStdout.constData());
+    QVERIFY2(!m_qbsStdout.contains("running custom2 prepare script"), m_qbsStdout.constData());
     QVERIFY2(m_qbsStdout.contains("running custom1 command"), m_qbsStdout.constData());
     QVERIFY2(!m_qbsStdout.contains("running custom2 command"), m_qbsStdout.constData());
 
@@ -5680,6 +5683,7 @@ void TestBlackbox::importChangeTracking()
     QVERIFY2(m_qbsStdout.contains("Resolving"), m_qbsStdout.constData());
     QVERIFY2(!m_qbsStdout.contains("running probe1 "), m_qbsStdout.constData());
     QVERIFY2(!m_qbsStdout.contains("running probe2"), m_qbsStdout.constData());
+    QVERIFY2(!m_qbsStdout.contains("running custom1 prepare script"), m_qbsStdout.constData());
     QVERIFY2(m_qbsStdout.contains("running custom2 prepare script"), m_qbsStdout.constData());
     QVERIFY2(!m_qbsStdout.contains("running custom1 command"), m_qbsStdout.constData());
     QVERIFY2(!m_qbsStdout.contains("running custom2 command"), m_qbsStdout.constData());
@@ -5691,6 +5695,8 @@ void TestBlackbox::importChangeTracking()
     QVERIFY2(m_qbsStdout.contains("Resolving"), m_qbsStdout.constData());
     QVERIFY2(!m_qbsStdout.contains("running probe1 "), m_qbsStdout.constData());
     QVERIFY2(!m_qbsStdout.contains("running probe2"), m_qbsStdout.constData());
+    QVERIFY2(!m_qbsStdout.contains("running custom1 prepare script"), m_qbsStdout.constData());
+    QVERIFY2(!m_qbsStdout.contains("running custom2 prepare script"), m_qbsStdout.constData());
     QVERIFY2(!m_qbsStdout.contains("running custom1 command"), m_qbsStdout.constData());
     QVERIFY2(m_qbsStdout.contains("running custom2 command"), m_qbsStdout.constData());