Introduce module providers

If a dependency is not found, we now search for a matching module
provider that can generate one for us.
We also provide a generic fall-back provider which uses pkg-config to
locate the dependency (but could be extended to incorporate other
methods in the future). This is the most important part of this change
for practical purposes, as it makes hundreds of popular libraries
available for use in qbs projects without users having to write any
boilerplate code.
In a future patch, a module provider could also be used to implement the
functionality of the qtprofilesetup library, relieving users of the need
to create a profile for building Qt applications.

[ChangeLog] The Depends item now falls back to pkg-config to locate
dependencies whose names do not correspond to a qbs module.

Fixes: QBS-1107
Change-Id: Ifd4f05c237cf58cd9fe707c3da648d3dbb33e82b
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

27 files changed, 460 insertions, 24 deletions

diff --git a/src/app/qbs/commandlinefrontend.cpp b/src/app/qbs/commandlinefrontend.cpp
index 978fdbb7a..c848b24d0 100644
--- a/src/app/qbs/commandlinefrontend.cpp
+++ b/src/app/qbs/commandlinefrontend.cpp
@@ -146,6 +146,7 @@ void CommandLineFrontend::start()
         params.setDryRun(m_parser.dryRun());
         params.setForceProbeExecution(m_parser.forceProbesExecution());
         params.setWaitLockBuildGraph(m_parser.waitLockBuildGraph());
+        params.setFallbackProviderEnabled(!m_parser.disableFallbackProvider());
         params.setLogElapsedTime(m_parser.logTime());
         params.setSettingsDirectory(m_settings->baseDirectory());
         params.setOverrideBuildGraphData(m_parser.command() == ResolveCommandType);
diff --git a/src/app/qbs/parser/commandlineoption.cpp b/src/app/qbs/parser/commandlineoption.cpp
index e18658751..dc5b4e440 100644
--- a/src/app/qbs/parser/commandlineoption.cpp
+++ b/src/app/qbs/parser/commandlineoption.cpp
@@ -681,6 +681,17 @@ QString WaitLockOption::longRepresentation() const
     return QLatin1String("--wait-lock");
 }
 
+QString DisableFallbackProviderOption::description(CommandType) const
+{
+    return Tr::tr("%1\n\tDo not fall back to pkg-config if a dependency is not found.\n")
+            .arg(longRepresentation());
+}
+
+QString DisableFallbackProviderOption::longRepresentation() const
+{
+    return QLatin1String("--no-fallback-module-provider");
+}
+
 QString RunEnvConfigOption::description(CommandType command) const
 {
     Q_UNUSED(command);
diff --git a/src/app/qbs/parser/commandlineoption.h b/src/app/qbs/parser/commandlineoption.h
index d57ec76b7..414f90489 100644
--- a/src/app/qbs/parser/commandlineoption.h
+++ b/src/app/qbs/parser/commandlineoption.h
@@ -75,6 +75,7 @@ public:
         GeneratorOptionType,
         WaitLockOptionType,
         RunEnvConfigOptionType,
+        DisableFallbackProviderType,
     };
 
     virtual ~CommandLineOption();
@@ -414,6 +415,14 @@ public:
     QString longRepresentation() const override;
 };
 
+class DisableFallbackProviderOption : public OnOffOption
+{
+public:
+    QString description(CommandType command) const override;
+    QString shortRepresentation() const override { return QString(); }
+    QString longRepresentation() const override;
+};
+
 } // namespace qbs
 
 #endif // QBS_COMMANDLINEOPTION_H
diff --git a/src/app/qbs/parser/commandlineoptionpool.cpp b/src/app/qbs/parser/commandlineoptionpool.cpp
index 9964f051a..63711f623 100644
--- a/src/app/qbs/parser/commandlineoptionpool.cpp
+++ b/src/app/qbs/parser/commandlineoptionpool.cpp
@@ -128,6 +128,9 @@ CommandLineOption *CommandLineOptionPool::getOption(CommandLineOption::Type type
         case CommandLineOption::WaitLockOptionType:
             option = new WaitLockOption;
             break;
+        case CommandLineOption::DisableFallbackProviderType:
+            option = new DisableFallbackProviderOption;
+            break;
         case CommandLineOption::RunEnvConfigOptionType:
             option = new RunEnvConfigOption;
             break;
@@ -273,6 +276,12 @@ WaitLockOption *CommandLineOptionPool::waitLockOption() const
     return static_cast<WaitLockOption *>(getOption(CommandLineOption::WaitLockOptionType));
 }
 
+DisableFallbackProviderOption *CommandLineOptionPool::disableFallbackProviderOption() const
+{
+    return static_cast<DisableFallbackProviderOption *>(
+                getOption(CommandLineOption::DisableFallbackProviderType));
+}
+
 RunEnvConfigOption *CommandLineOptionPool::runEnvConfigOption() const
 {
     return static_cast<RunEnvConfigOption *>(getOption(CommandLineOption::RunEnvConfigOptionType));
diff --git a/src/app/qbs/parser/commandlineoptionpool.h b/src/app/qbs/parser/commandlineoptionpool.h
index 6a4669165..c7ac263e1 100644
--- a/src/app/qbs/parser/commandlineoptionpool.h
+++ b/src/app/qbs/parser/commandlineoptionpool.h
@@ -77,6 +77,7 @@ public:
     RespectProjectJobLimitsOption *respectProjectJobLimitsOption() const;
     GeneratorOption *generatorOption() const;
     WaitLockOption *waitLockOption() const;
+    DisableFallbackProviderOption *disableFallbackProviderOption() const;
     RunEnvConfigOption *runEnvConfigOption() const;
 
 private:
diff --git a/src/app/qbs/parser/commandlineparser.cpp b/src/app/qbs/parser/commandlineparser.cpp
index c2e265336..2ec0df1df 100644
--- a/src/app/qbs/parser/commandlineparser.cpp
+++ b/src/app/qbs/parser/commandlineparser.cpp
@@ -231,6 +231,11 @@ bool CommandLineParser::waitLockBuildGraph() const
     return d->optionPool.waitLockOption()->enabled();
 }
 
+bool CommandLineParser::disableFallbackProvider() const
+{
+    return d->optionPool.disableFallbackProviderOption()->enabled();
+}
+
 bool CommandLineParser::logTime() const
 {
     return d->logTime;
diff --git a/src/app/qbs/parser/commandlineparser.h b/src/app/qbs/parser/commandlineparser.h
index e2ef8ad77..d47657b16 100644
--- a/src/app/qbs/parser/commandlineparser.h
+++ b/src/app/qbs/parser/commandlineparser.h
@@ -76,6 +76,7 @@ public:
     bool dryRun() const;
     bool forceProbesExecution() const;
     bool waitLockBuildGraph() const;
+    bool disableFallbackProvider() const;
     bool logTime() const;
     bool withNonDefaultProducts() const;
     bool buildBeforeInstalling() const;
diff --git a/src/app/qbs/parser/parsercommand.cpp b/src/app/qbs/parser/parsercommand.cpp
index 33f93ce53..79636ff0a 100644
--- a/src/app/qbs/parser/parsercommand.cpp
+++ b/src/app/qbs/parser/parsercommand.cpp
@@ -210,7 +210,8 @@ static QList<CommandLineOption::Type> resolveOptions()
             << CommandLineOption::ShowProgressOptionType
             << CommandLineOption::DryRunOptionType
             << CommandLineOption::ForceProbesOptionType
-            << CommandLineOption::LogTimeOptionType;
+            << CommandLineOption::LogTimeOptionType
+            << CommandLineOption::DisableFallbackProviderType;
 }
 
 QList<CommandLineOption::Type> ResolveCommand::supportedOptions() const
diff --git a/src/lib/corelib/buildgraph/buildgraphloader.cpp b/src/lib/corelib/buildgraph/buildgraphloader.cpp
index a1ca7afdb..e6d1cb75a 100644
--- a/src/lib/corelib/buildgraph/buildgraphloader.cpp
+++ b/src/lib/corelib/buildgraph/buildgraphloader.cpp
@@ -340,6 +340,8 @@ void BuildGraphLoader::trackProjectChanges()
     ldr.setSearchPaths(m_parameters.searchPaths());
     ldr.setProgressObserver(m_evalContext->observer());
     ldr.setOldProjectProbes(restoredProject->probes);
+    if (!m_parameters.forceProbeExecution())
+        ldr.setStoredModuleProviderInfo(restoredProject->moduleProviderInfo);
     ldr.setLastResolveTime(restoredProject->lastResolveTime);
     QHash<QString, std::vector<ProbeConstPtr>> restoredProbes;
     for (const auto &restoredProduct : qAsConst(allRestoredProducts))
diff --git a/src/lib/corelib/corelib.qbs b/src/lib/corelib/corelib.qbs
index c947cb484..db00a7005 100644
--- a/src/lib/corelib/corelib.qbs
+++ b/src/lib/corelib/corelib.qbs
@@ -299,6 +299,7 @@ QbsLibrary {
             "moduleloader.h",
             "modulemerger.cpp",
             "modulemerger.h",
+            "moduleproviderinfo.h",
             "preparescriptobserver.cpp",
             "preparescriptobserver.h",
             "projectresolver.cpp",
diff --git a/src/lib/corelib/language/builtindeclarations.cpp b/src/lib/corelib/language/builtindeclarations.cpp
index bfdfab51e..3ca0608d4 100644
--- a/src/lib/corelib/language/builtindeclarations.cpp
+++ b/src/lib/corelib/language/builtindeclarations.cpp
@@ -69,6 +69,7 @@ BuiltinDeclarations::BuiltinDeclarations()
         { QLatin1String("Group"), ItemType::Group },
         { QLatin1String("JobLimit"), ItemType::JobLimit },
         { QLatin1String("Module"), ItemType::Module },
+        { QLatin1String("ModuleProvider"), ItemType::ModuleProvider },
         { QLatin1String("Parameter"), ItemType::Parameter },
         { QLatin1String("Parameters"), ItemType::Parameters },
         { QLatin1String("Probe"), ItemType::Probe },
@@ -90,6 +91,7 @@ BuiltinDeclarations::BuiltinDeclarations()
     addGroupItem();
     addJobLimitItem();
     addModuleItem();
+    addModuleProviderItem();
     addProbeItem();
     addProductItem();
     addProfileItem();
@@ -244,6 +246,8 @@ void BuiltinDeclarations::addDependsItem()
     item << PropertyDeclaration(StringConstants::multiplexConfigurationIdsProperty(),
                                 PropertyDeclaration::StringList, QString(),
                                 PropertyDeclaration::ReadOnlyFlag);
+    item << PropertyDeclaration(StringConstants::enableFallbackProperty(),
+                                PropertyDeclaration::Boolean, StringConstants::trueValue());
     insert(item);
 }
 
@@ -316,6 +320,16 @@ void BuiltinDeclarations::addModuleItem()
     insert(item);
 }
 
+void BuiltinDeclarations::addModuleProviderItem()
+{
+    ItemDeclaration item(ItemType::ModuleProvider);
+    item << nameProperty()
+         << PropertyDeclaration(QStringLiteral("outputBaseDir"), PropertyDeclaration::String)
+         << PropertyDeclaration(QStringLiteral("relativeSearchPaths"),
+                                PropertyDeclaration::StringList);
+    insert(item);
+}
+
 ItemDeclaration BuiltinDeclarations::moduleLikeItem(ItemType type)
 {
     ItemDeclaration item(type);
diff --git a/src/lib/corelib/language/builtindeclarations.h b/src/lib/corelib/language/builtindeclarations.h
index ff16b395a..988f9ab81 100644
--- a/src/lib/corelib/language/builtindeclarations.h
+++ b/src/lib/corelib/language/builtindeclarations.h
@@ -78,6 +78,7 @@ private:
     void addGroupItem();
     void addJobLimitItem();
     void addModuleItem();
+    void addModuleProviderItem();
     static ItemDeclaration moduleLikeItem(ItemType type);
     void addProbeItem();
     void addProductItem();
diff --git a/src/lib/corelib/language/evaluatorscriptclass.cpp b/src/lib/corelib/language/evaluatorscriptclass.cpp
index a5e23a131..829cb7494 100644
--- a/src/lib/corelib/language/evaluatorscriptclass.cpp
+++ b/src/lib/corelib/language/evaluatorscriptclass.cpp
@@ -621,7 +621,8 @@ public:
                     || itemOfProperty->type() == ItemType::Export)) {
             const VariantValueConstPtr varValue
                     = itemOfProperty->variantProperty(StringConstants::nameProperty());
-            QBS_ASSERT(varValue, return);
+            if (!varValue)
+                return;
             m_stackUpdate = true;
             const QualifiedId fullPropName
                     = QualifiedId::fromString(varValue->value().toString()) << name.toString();
diff --git a/src/lib/corelib/language/itemtype.h b/src/lib/corelib/language/itemtype.h
index 324a1fb87..724666cb4 100644
--- a/src/lib/corelib/language/itemtype.h
+++ b/src/lib/corelib/language/itemtype.h
@@ -55,6 +55,7 @@ enum class ItemType {
     Group,
     JobLimit,
     Module,
+    ModuleProvider,
     Parameter,
     Parameters,
     Probe,
diff --git a/src/lib/corelib/language/language.cpp b/src/lib/corelib/language/language.cpp
index d8a5d9162..2a9eb5b0e 100644
--- a/src/lib/corelib/language/language.cpp
+++ b/src/lib/corelib/language/language.cpp
@@ -594,6 +594,7 @@ TopLevelProject::TopLevelProject()
 
 TopLevelProject::~TopLevelProject()
 {
+    cleanupModuleProviderOutput();
     delete bgLocker;
 }
 
@@ -636,6 +637,8 @@ void TopLevelProject::store(Logger logger)
         qCDebug(lcBuildGraph) << "build graph is unchanged in project" << id();
         return;
     }
+    for (ModuleProviderInfo &m : moduleProviderInfo)
+        m.transientOutput = false;
     const QString fileName = buildGraphFilePath();
     qCDebug(lcBuildGraph) << "storing:" << fileName;
     PersistentPool pool(logger);
@@ -661,6 +664,23 @@ void TopLevelProject::store(PersistentPool &pool)
     serializationOp<PersistentPool::Store>(pool);
 }
 
+void TopLevelProject::cleanupModuleProviderOutput()
+{
+    QString error;
+    for (const ModuleProviderInfo &m : moduleProviderInfo) {
+        if (m.transientOutput) {
+            if (!removeDirectoryWithContents(m.outputDirPath(buildDirectory), &error))
+                qCWarning(lcBuildGraph) << "Error removing module provider output:" << error;
+        }
+    }
+    QDir moduleProviderBaseDir(buildDirectory + QLatin1Char('/')
+                               + ModuleProviderInfo::outputBaseDirName());
+    if (moduleProviderBaseDir.exists() && moduleProviderBaseDir.isEmpty()
+            && !removeDirectoryWithContents(moduleProviderBaseDir.path(), &error)) {
+        qCWarning(lcBuildGraph) << "Error removing module provider output:" << error;
+    }
+}
+
 /*!
  * \class SourceWildCards
  * \brief Objects of the \c SourceWildCards class result from giving wildcards in a
diff --git a/src/lib/corelib/language/language.h b/src/lib/corelib/language/language.h
index f9d69efff..994ad6c55 100644
--- a/src/lib/corelib/language/language.h
+++ b/src/lib/corelib/language/language.h
@@ -43,6 +43,7 @@
 #include "filetags.h"
 #include "forward_decls.h"
 #include "jsimports.h"
+#include "moduleproviderinfo.h"
 #include "propertydeclaration.h"
 #include "resolvedfilecontext.h"
 
@@ -691,6 +692,7 @@ public:
     QString buildDirectory; // Not saved
     QProcessEnvironment environment;
     std::vector<ProbeConstPtr> probes;
+    ModuleProviderInfoList moduleProviderInfo;
 
     QHash<QString, QString> canonicalFilePathResults; // Results of calls to "File.canonicalFilePath()."
     QHash<QString, bool> fileExistsResults; // Results of calls to "File.exists()".
@@ -722,11 +724,14 @@ private:
         pool.serializationOp<opType>(m_id, canonicalFilePathResults, fileExistsResults,
                                      directoryEntriesResults, fileLastModifiedResults, environment,
                                      probes, profileConfigs, overriddenValues, buildSystemFiles,
-                                     lastResolveTime, warningsEncountered, buildData);
+                                     lastResolveTime, warningsEncountered, buildData,
+                                     moduleProviderInfo);
     }
     void load(PersistentPool &pool) override;
     void store(PersistentPool &pool) override;
 
+    void cleanupModuleProviderOutput();
+
     QString m_id;
     QVariantMap m_buildConfiguration;
 };
diff --git a/src/lib/corelib/language/language.pri b/src/lib/corelib/language/language.pri
index 6d68f9643..e07a671b9 100644
--- a/src/lib/corelib/language/language.pri
+++ b/src/lib/corelib/language/language.pri
@@ -28,6 +28,7 @@ HEADERS += \
     $$PWD/loader.h \
     $$PWD/moduleloader.h \
     $$PWD/modulemerger.h \
+    $$PWD/moduleproviderinfo.h \
     $$PWD/preparescriptobserver.h \
     $$PWD/projectresolver.h \
     $$PWD/property.h \
diff --git a/src/lib/corelib/language/loader.cpp b/src/lib/corelib/language/loader.cpp
index 98a90e221..4d2eef983 100644
--- a/src/lib/corelib/language/loader.cpp
+++ b/src/lib/corelib/language/loader.cpp
@@ -104,6 +104,11 @@ void Loader::setStoredProfiles(const QVariantMap &profiles)
     m_storedProfiles = profiles;
 }
 
+void Loader::setStoredModuleProviderInfo(const ModuleProviderInfoList &providerInfo)
+{
+    m_storedModuleProviderInfo = providerInfo;
+}
+
 TopLevelProjectPtr Loader::loadProject(const SetupProjectParameters &_parameters)
 {
     SetupProjectParameters parameters = _parameters;
@@ -160,6 +165,7 @@ TopLevelProjectPtr Loader::loadProject(const SetupProjectParameters &_parameters
     moduleLoader.setOldProductProbes(m_oldProductProbes);
     moduleLoader.setLastResolveTime(m_lastResolveTime);
     moduleLoader.setStoredProfiles(m_storedProfiles);
+    moduleLoader.setStoredModuleProviderInfo(m_storedModuleProviderInfo);
     const ModuleLoaderResult loadResult = moduleLoader.load(parameters);
     ProjectResolver resolver(&evaluator, loadResult, parameters, m_logger);
     resolver.setProgressObserver(m_progressObserver);
diff --git a/src/lib/corelib/language/loader.h b/src/lib/corelib/language/loader.h
index 9883d5b66..48a0b6065 100644
--- a/src/lib/corelib/language/loader.h
+++ b/src/lib/corelib/language/loader.h
@@ -40,6 +40,7 @@
 #define  QBS_LOADER_H
 
 #include "forward_decls.h"
+#include "moduleproviderinfo.h"
 #include <logging/logger.h>
 #include <tools/filetime.h>
 
@@ -64,6 +65,7 @@ public:
     void setOldProductProbes(const QHash<QString, std::vector<ProbeConstPtr>> &oldProbes);
     void setLastResolveTime(const FileTime &time) { m_lastResolveTime = time; }
     void setStoredProfiles(const QVariantMap &profiles);
+    void setStoredModuleProviderInfo(const ModuleProviderInfoList &providerInfo);
     TopLevelProjectPtr loadProject(const SetupProjectParameters &parameters);
 
     static void setupProjectFilePath(SetupProjectParameters &parameters);
@@ -75,6 +77,7 @@ private:
     QStringList m_searchPaths;
     std::vector<ProbeConstPtr> m_oldProjectProbes;
     QHash<QString, std::vector<ProbeConstPtr>> m_oldProductProbes;
+    ModuleProviderInfoList m_storedModuleProviderInfo;
     QVariantMap m_storedProfiles;
     FileTime m_lastResolveTime;
 };
diff --git a/src/lib/corelib/language/moduleloader.cpp b/src/lib/corelib/language/moduleloader.cpp
index b34cfd6a9..c4d77ba40 100644
--- a/src/lib/corelib/language/moduleloader.cpp
+++ b/src/lib/corelib/language/moduleloader.cpp
@@ -57,6 +57,7 @@
 #include <logging/translator.h>
 #include <tools/error.h>
 #include <tools/fileinfo.h>
+#include <tools/jsliterals.h>
 #include <tools/preferences.h>
 #include <tools/profile.h>
 #include <tools/profiling.h>
@@ -73,6 +74,8 @@
 #include <QtCore/qdiriterator.h>
 #include <QtCore/qjsondocument.h>
 #include <QtCore/qjsonobject.h>
+#include <QtCore/qtemporaryfile.h>
+#include <QtCore/qtextstream.h>
 #include <QtScript/qscriptvalueiterator.h>
 
 #include <algorithm>
@@ -267,6 +270,11 @@ void ModuleLoader::setStoredProfiles(const QVariantMap &profiles)
     m_storedProfiles = profiles;
 }
 
+void ModuleLoader::setStoredModuleProviderInfo(const ModuleProviderInfoList &moduleProviderInfo)
+{
+    m_moduleProviderInfo = moduleProviderInfo;
+}
+
 ModuleLoaderResult ModuleLoader::load(const SetupProjectParameters &parameters)
 {
     TimedActivityLogger moduleLoaderTimer(m_logger, Tr::tr("ModuleLoader"),
@@ -290,6 +298,7 @@ ModuleLoaderResult ModuleLoader::load(const SetupProjectParameters &parameters)
         static const QStringList prefixes({ StringConstants::projectPrefix(),
                                             QLatin1String("projects"),
                                             QLatin1String("products"), QLatin1String("modules"),
+                                            StringConstants::moduleProviders(),
                                             StringConstants::qbsModule()});
         bool ok = false;
         for (const auto &prefix : prefixes) {
@@ -309,6 +318,8 @@ ModuleLoaderResult ModuleLoader::load(const SetupProjectParameters &parameters)
         e.append(QLatin1Char('\t') + Tr::tr("modules.<module-name>.<property-name>:value"));
         e.append(QLatin1Char('\t') + Tr::tr("products.<product-name>.<module-name>."
                                             "<property-name>:value"));
+        e.append(QLatin1Char('\t') + Tr::tr("moduleProviders.<provider-name>."
+                                            "<property-name>:value"));
         handlePropertyError(e, m_parameters, m_logger);
     }
 
@@ -456,6 +467,9 @@ private:
         m_parentItems.push_back(item);
         for (Item::PropertyMap::const_iterator it = item->properties().constBegin();
                 it != item->properties().constEnd(); ++it) {
+            if (item->type() == ItemType::Product && it.key() == StringConstants::moduleProviders()
+                    && it.value()->type() == Value::ItemValueType)
+                continue;
             const PropertyDeclaration decl = item->propertyDeclaration(it.key());
             if (decl.isValid()) {
                 if (!decl.isDeprecated())
@@ -547,6 +561,9 @@ void ModuleLoader::handleTopLevelProject(ModuleLoaderResult *loadResult, Item *p
                     throw err;
                 handleProductError(err, &productContext);
             }
+            for (std::size_t i = 0; i < productContext.newlyAddedModuleProviderSearchPaths.size(); ++i)
+                m_reader->popExtraSearchPaths();
+            productContext.newlyAddedModuleProviderSearchPaths.clear();
         }
     }
     if (!m_productsWithDeferredDependsItems.empty() || !m_exportsWithDeferredDependsItems.empty()) {
@@ -585,6 +602,7 @@ void ModuleLoader::handleTopLevelProject(ModuleLoaderResult *loadResult, Item *p
     }
 
     loadResult->projectProbes = tlp.probes;
+    loadResult->moduleProviderInfo = m_moduleProviderInfo;
 
     m_reader->clearExtraSearchPathsStack();
     AccumulatingTimer timer(m_parameters.logElapsedTime()
@@ -2111,6 +2129,18 @@ void ModuleLoader::setSearchPathsForProduct(ModuleLoader::ProductContext *produc
         if (!currentSearchPaths.contains(p) && FileInfo(p).exists())
             product->searchPaths << p;
     }
+
+    // Existing module provider search paths are re-used if and only if the provider configuration
+    // at setup time was the same as the current one for the respective module provider.
+    if (!m_moduleProviderInfo.empty()) {
+        const QVariantMap configForProduct = moduleProviderConfig(*product);
+        for (const ModuleProviderInfo &c : m_moduleProviderInfo) {
+            if (configForProduct.value(c.name.toString()) == c.config) {
+                product->knownModuleProviders.insert(c.name);
+                product->searchPaths << c.searchPaths;
+            }
+        }
+    }
 }
 
 ModuleLoader::ShadowProductInfo ModuleLoader::getShadowProductInfo(
@@ -2498,6 +2528,9 @@ void ModuleLoader::resolveDependsItem(DependsContext *dependsContext, Item *pare
         QString msg = Tr::tr("A Depends item with more than one module cannot have an id.");
         throw ErrorInfo(msg, dependsItem->location());
     }
+    const FallbackMode fallbackMode = m_parameters.fallbackProviderEnabled()
+            && m_evaluator->boolValue(dependsItem, StringConstants::enableFallbackProperty())
+            ? FallbackMode::Enabled : FallbackMode::Disabled;
 
     QList<QualifiedId> moduleNames;
     const QualifiedId nameParts = QualifiedId::fromString(name);
@@ -2554,8 +2587,8 @@ void ModuleLoader::resolveDependsItem(DependsContext *dependsContext, Item *pare
         QVariantMap defaultParameters;
         Item *moduleItem = loadModule(dependsContext->product, dependsContext->exportingProductItem,
                                       parentItem, dependsItem->location(), dependsItem->id(),
-                                      moduleName, multiplexConfigurationIds.first(), isRequired,
-                                      &result.isProduct, &defaultParameters);
+                                      moduleName, multiplexConfigurationIds.first(), fallbackMode,
+                                      isRequired, &result.isProduct, &defaultParameters);
         if (!moduleItem) {
             const QString productName = ResolvedProduct::fullDisplayName(
                         dependsContext->product->name,
@@ -2746,11 +2779,12 @@ Item *ModuleLoader::moduleInstanceItem(Item *containerItem, const QualifiedId &m
     return instance;
 }
 
-ModuleLoader::ProductModuleInfo *ModuleLoader::productModule(
-        ProductContext *productContext, const QString &name, const QString &multiplexId)
+ModuleLoader::ProductModuleInfo *ModuleLoader::productModule(ProductContext *productContext,
+        const QString &name, const QString &multiplexId, bool &productNameMatch)
 {
     auto &exportsData = productContext->project->topLevelProject->productModules;
     const auto firstIt = exportsData.find(name);
+    productNameMatch = firstIt != exportsData.end();
     for (auto it = firstIt; it != exportsData.end() && it.key() == name; ++it) {
         if (it.value().multiplexId == multiplexId)
             return &it.value();
@@ -2861,8 +2895,9 @@ private:
 Item *ModuleLoader::loadModule(ProductContext *productContext, Item *exportingProductItem,
                                Item *item, const CodeLocation &dependsItemLocation,
                                const QString &moduleId, const QualifiedId &moduleName,
-                               const QString &multiplexId, bool isRequired,
-                               bool *isProductDependency, QVariantMap *defaultParameters)
+                               const QString &multiplexId, FallbackMode fallbackMode,
+                               bool isRequired, bool *isProductDependency,
+                               QVariantMap *defaultParameters)
 {
     qCDebug(lcModuleLoader) << "loadModule name:" << moduleName.toString() << "id:" << moduleId;
 
@@ -2900,17 +2935,15 @@ Item *ModuleLoader::loadModule(ProductContext *productContext, Item *exportingPr
 
     Item *modulePrototype = nullptr;
     ProductModuleInfo * const pmi = productModule(productContext, moduleName.toString(),
-                                                  multiplexId);
+                                                  multiplexId, *isProductDependency);
     if (pmi) {
-        *isProductDependency = true;
         m_dependsChain.back().isProduct = true;
         modulePrototype = pmi->exportItem;
         if (defaultParameters)
             *defaultParameters = pmi->defaultParameters;
-    } else {
-        *isProductDependency = false;
+    } else if (!*isProductDependency) {
         modulePrototype = searchAndLoadModuleFile(productContext, dependsItemLocation,
-                moduleName, isRequired, moduleInstance);
+                moduleName, fallbackMode, isRequired, moduleInstance);
     }
     delayedPropertyChanger.applyNow();
     if (!modulePrototype)
@@ -2968,17 +3001,19 @@ static Item *chooseModuleCandidate(const std::vector<PrioritizedItem> &candidate
 
 Item *ModuleLoader::searchAndLoadModuleFile(ProductContext *productContext,
         const CodeLocation &dependsItemLocation, const QualifiedId &moduleName,
-        bool isRequired, Item *moduleInstance)
+        FallbackMode fallbackMode, bool isRequired, Item *moduleInstance)
 {
     bool triedToLoadModule = false;
     const QString fullName = moduleName.toString();
     std::vector<PrioritizedItem> candidates;
     const QStringList &searchPaths = m_reader->allSearchPaths();
+    bool matchingDirectoryFound = false;
     for (int i = 0; i < searchPaths.size(); ++i) {
         const QString &path = searchPaths.at(i);
         const QString dirPath = findExistingModulePath(path, moduleName);
         if (dirPath.isEmpty())
             continue;
+        matchingDirectoryFound = true;
         QStringList moduleFileNames = m_moduleDirListCache.value(dirPath);
         if (moduleFileNames.empty()) {
             QDirIterator dirIter(dirPath, StringConstants::qbsFileWildcards());
@@ -2999,6 +3034,36 @@ Item *ModuleLoader::searchAndLoadModuleFile(ProductContext *productContext,
     }
 
     if (candidates.empty()) {
+        if (!matchingDirectoryFound) {
+            bool moduleAlreadyKnown = false;
+            ModuleProviderResult result;
+            for (QualifiedId providerName = moduleName; !providerName.empty();
+                 providerName.pop_back()) {
+                if (!productContext->knownModuleProviders.insert(providerName).second) {
+                    moduleAlreadyKnown = true;
+                    break;
+                }
+                qCDebug(lcModuleLoader) << "Module" << moduleName.toString()
+                                        << "not found, checking for module providers";
+                result = findModuleProvider(providerName, *productContext,
+                                            ModuleProviderLookup::Regular, dependsItemLocation);
+                if (result.providerFound)
+                    break;
+            }
+            if (fallbackMode == FallbackMode::Enabled && !result.providerFound
+                    && !moduleAlreadyKnown) {
+                qCDebug(lcModuleLoader) << "Specific module provider not found for"
+                                        << moduleName.toString()  << ", setting up fallback.";
+                result = findModuleProvider(moduleName, *productContext,
+                                            ModuleProviderLookup::Fallback, dependsItemLocation);
+            }
+            if (result.providerAddedSearchPaths) {
+                qCDebug(lcModuleLoader) << "Re-checking for module" << moduleName.toString()
+                                        << "with newly added search paths from module provider";
+                return searchAndLoadModuleFile(productContext, dependsItemLocation, moduleName,
+                                               fallbackMode, isRequired, moduleInstance);
+            }
+        }
         if (!isRequired)
             return createNonPresentModule(fullName, QLatin1String("not found"), nullptr);
         if (Q_UNLIKELY(triedToLoadModule))
@@ -3177,8 +3242,8 @@ Item::Module ModuleLoader::loadBaseModule(ProductContext *productContext, Item *
     Item::Module baseModuleDesc;
     baseModuleDesc.name = baseModuleName;
     baseModuleDesc.item = loadModule(productContext, nullptr, item, CodeLocation(), QString(),
-                                     baseModuleName, QString(), true, &baseModuleDesc.isProduct,
-                                     nullptr);
+                                     baseModuleName, QString(), FallbackMode::Disabled, true,
+                                     &baseModuleDesc.isProduct, nullptr);
     if (productContext->item) {
         const Item * const qbsInstanceItem
                 = moduleInstanceItem(productContext->item, baseModuleName);
@@ -3599,6 +3664,145 @@ QString ModuleLoader::findExistingModulePath(const QString &searchPath,
     return dirPath;
 }
 
+QVariantMap ModuleLoader::moduleProviderConfig(ModuleLoader::ProductContext &product)
+{
+    if (product.moduleProviderConfigRetrieved)
+        return product.theModuleProviderConfig;
+    const ItemValueConstPtr configItemValue
+            = product.item->itemProperty(StringConstants::moduleProviders());
+    if (configItemValue) {
+        const std::function<void(const Item *, QualifiedId)> collectMap
+                = [this, &product, &collectMap](const Item *item, QualifiedId name) {
+            const Item::PropertyMap &props = item->properties();
+            for (auto it = props.begin(); it != props.end(); ++it) {
+                QVariant value;
+                switch (it.value()->type()) {
+                case Value::ItemValueType:
+                    collectMap(static_cast<ItemValue *>(it.value().get())->item(),
+                               QualifiedId(name += it.key()));
+                    return;
+                case Value::JSSourceValueType:
+                    value = m_evaluator->value(item, it.key()).toVariant();
+                    break;
+                case Value::VariantValueType:
+                    value = static_cast<VariantValue *>(it.value().get())->value();
+                    break;
+                }
+                QVariantMap m = product.theModuleProviderConfig.value(name.toString()).toMap();
+                m.insert(it.key(), value);
+                product.theModuleProviderConfig.insert(name.toString(), m);
+            }
+        };
+        collectMap(configItemValue->item(), QualifiedId());
+    }
+    for (auto it = product.moduleProperties.begin(); it != product.moduleProperties.end(); ++it) {
+        if (!it.key().startsWith(QStringLiteral("moduleProviders.")))
+            continue;
+        const QString provider = it.key().mid(QStringLiteral("moduleProviders.").size());
+        const QVariantMap providerConfigFromBuildConfig = it.value().toMap();
+        if (providerConfigFromBuildConfig.empty())
+            continue;
+        QVariantMap currentMapForProvider = product.theModuleProviderConfig.value(provider).toMap();
+        for (auto propIt = providerConfigFromBuildConfig.begin();
+             propIt != providerConfigFromBuildConfig.end(); ++propIt) {
+            currentMapForProvider.insert(propIt.key(), propIt.value());
+        }
+        product.theModuleProviderConfig.insert(provider, currentMapForProvider);
+    }
+    product.moduleProviderConfigRetrieved = true;
+    return product.theModuleProviderConfig;
+}
+
+ModuleLoader::ModuleProviderResult ModuleLoader::findModuleProvider(const QualifiedId &name,
+        ModuleLoader::ProductContext &product, ModuleProviderLookup lookupType,
+        const CodeLocation &dependsItemLocation)
+{
+    for (const QString &path : m_reader->allSearchPaths()) {
+        QString fullPath = FileInfo::resolvePath(path, QStringLiteral("module-providers"));
+        switch (lookupType) {
+        case ModuleProviderLookup::Regular:
+            for (const QString &component : name)
+                fullPath = FileInfo::resolvePath(fullPath, component);
+            break;
+        case ModuleProviderLookup::Fallback:
+            fullPath = FileInfo::resolvePath(fullPath, QStringLiteral("__fallback"));
+            break;
+        }
+        const QString providerFile = FileInfo::resolvePath(fullPath,
+                                                           QStringLiteral("provider.qbs"));
+        if (!FileInfo::exists(providerFile)) {
+            qCDebug(lcModuleLoader) << "No module provider found at" << providerFile;
+            continue;
+        }
+        QTemporaryFile dummyItemFile;
+        if (!dummyItemFile.open()) {
+            throw ErrorInfo(Tr::tr("Failed to create temporary file for running module provider "
+                                   "for dependency '%1': %2").arg(name.toString(),
+                                                                  dummyItemFile.errorString()));
+        }
+        qCDebug(lcModuleLoader) << "Instantiating module provider at" << providerFile;
+        const QString projectBuildDir = product.project->item->variantProperty(
+                    StringConstants::buildDirectoryProperty())->value().toString();
+        const QString searchPathBaseDir = ModuleProviderInfo::outputDirPath(projectBuildDir, name);
+        const QVariant moduleConfig = moduleProviderConfig(product).value(name.toString());
+        QTextStream stream(&dummyItemFile);
+        stream.setCodec("UTF-8");
+        stream << "import qbs.FileInfo" << endl;
+        stream << "import qbs.Utilities" << endl;
+        stream << "import '" << providerFile << "' as Provider" << endl;
+        stream << "Provider {" << endl;
+        stream << "    name: " << toJSLiteral(name.toString()) << endl;
+        stream << "    property var config: (" << toJSLiteral(moduleConfig) << ')' << endl;
+        stream << "    outputBaseDir: FileInfo.joinPaths(baseDirPrefix, "
+                  "        Utilities.getHash(JSON.stringify(config)))" << endl;
+        stream << "    property string baseDirPrefix: " << toJSLiteral(searchPathBaseDir) << endl;
+        stream << "    property stringList searchPaths: (relativeSearchPaths || [])"
+                  "        .map(function(p) { return FileInfo.joinPaths(outputBaseDir, p); })"
+               << endl;
+        stream << "}" << endl;
+        stream.flush();
+        Item * const providerItem = loadItemFromFile(dummyItemFile.fileName(), dependsItemLocation);
+        if (providerItem->type() != ItemType::ModuleProvider) {
+            throw ErrorInfo(Tr::tr("File '%1' declares an item of type '%2', "
+                                   "but '%3' was expected.")
+                .arg(providerFile, providerItem->typeName(),
+                     BuiltinDeclarations::instance().nameForType(ItemType::ModuleProvider)));
+        }
+        const QVariantMap configMap = moduleConfig.toMap();
+        for (auto it = configMap.begin(); it != configMap.end(); ++it) {
+            const PropertyDeclaration decl = providerItem->propertyDeclaration(it.key());
+            if (!decl.isValid()) {
+                throw ErrorInfo(Tr::tr("No such property '%1' in module provider '%2'.")
+                                .arg(it.key(), name.toString()));
+            }
+            providerItem->setProperty(it.key(), VariantValue::create(it.value()));
+        }
+        EvalContextSwitcher contextSwitcher(m_evaluator->engine(), EvalContext::ProbeExecution);
+        const QStringList searchPaths
+                = m_evaluator->stringListValue(providerItem, QStringLiteral("searchPaths"));
+        if (searchPaths.empty()) {
+            qCDebug(lcModuleLoader) << "Module provider did run, but did not set up "
+                                       "any modules.";
+            return ModuleProviderResult(true, false);
+        }
+        qCDebug(lcModuleLoader) << "Module provider added" << searchPaths.size()
+                                << "new search path(s)";
+
+        // (1) is needed so the immediate new look-up works.
+        // (2) is needed so the next use of SearchPathManager considers the new paths.
+        // (3) is needed for the code that removes the product-specific search paths when
+        //     product handling is done.
+        // (4) is needed for possible re-use in subsequent products and builds.
+        m_reader->pushExtraSearchPaths(searchPaths); // (1)
+        product.searchPaths << searchPaths; // (2)
+        product.newlyAddedModuleProviderSearchPaths.push_back(searchPaths); // (3)
+        m_moduleProviderInfo.emplace_back(ModuleProviderInfo(name, moduleConfig.toMap(), // (4)
+                                                     searchPaths, m_parameters.dryRun()));
+        return ModuleProviderResult(true, true);
+    }
+    return ModuleProviderResult();
+}
+
 void ModuleLoader::setScopeForDescendants(Item *item, Item *scope)
 {
     for (Item * const child : item->children()) {
@@ -3755,8 +3959,8 @@ void ModuleLoader::addTransitiveDependencies(ProductContext *ctx)
         } else {
             Item::Module dep;
             dep.item = loadModule(ctx, nullptr, ctx->item, ctx->item->location(), QString(),
-                                  module.name, QString(), module.required, &dep.isProduct,
-                                  &dep.parameters);
+                                  module.name, QString(), FallbackMode::Disabled,
+                                  module.required, &dep.isProduct, &dep.parameters);
             if (!dep.item) {
                 throw ErrorInfo(Tr::tr("Module '%1' not found when setting up transitive "
                                        "dependencies for product '%2'.").arg(module.name.toString(),
diff --git a/src/lib/corelib/language/moduleloader.h b/src/lib/corelib/language/moduleloader.h
index 7b9e0bede..9e45908c3 100644
--- a/src/lib/corelib/language/moduleloader.h
+++ b/src/lib/corelib/language/moduleloader.h
@@ -44,6 +44,7 @@
 #include "forward_decls.h"
 #include "item.h"
 #include "itempool.h"
+#include "moduleproviderinfo.h"
 #include <logging/logger.h>
 #include <tools/filetime.h>
 #include <tools/qttools.h>
@@ -106,6 +107,7 @@ struct ModuleLoaderResult
     Item *root;
     QHash<Item *, ProductInfo> productInfos;
     std::vector<ProbeConstPtr> projectProbes;
+    ModuleProviderInfoList moduleProviderInfo;
     Set<QString> qbsFiles;
     QVariantMap profileConfigs;
 };
@@ -128,6 +130,7 @@ public:
     void setOldProductProbes(const QHash<QString, std::vector<ProbeConstPtr>> &oldProbes);
     void setLastResolveTime(const FileTime &time) { m_lastResolveTime = time; }
     void setStoredProfiles(const QVariantMap &profiles);
+    void setStoredModuleProviderInfo(const ModuleProviderInfoList &moduleProviderInfo);
     Evaluator *evaluator() const { return m_evaluator; }
 
     ModuleLoaderResult load(const SetupProjectParameters &parameters);
@@ -181,6 +184,11 @@ private:
         std::unordered_map<const Item *, std::vector<ErrorInfo>> unknownProfilePropertyErrors;
         QStringList searchPaths;
 
+        std::vector<QStringList> newlyAddedModuleProviderSearchPaths;
+        Set<QualifiedId> knownModuleProviders;
+        QVariantMap theModuleProviderConfig;
+        bool moduleProviderConfigRetrieved = false;
+
         // The key corresponds to DeferredDependsContext.exportingProductItem, which is the
         // only value from that data structure that we still need here.
         std::unordered_map<Item *, std::vector<Item *>> deferredDependsItems;
@@ -297,16 +305,18 @@ private:
     QVariantMap extractParameters(Item *dependsItem) const;
     Item *moduleInstanceItem(Item *containerItem, const QualifiedId &moduleName);
     static ProductModuleInfo *productModule(ProductContext *productContext, const QString &name,
-                                            const QString &multiplexId);
+                                            const QString &multiplexId, bool &productNameMatch);
     static ProductContext *product(ProjectContext *projectContext, const QString &name);
     static ProductContext *product(TopLevelProjectContext *tlpContext, const QString &name);
+
+    enum class FallbackMode { Enabled, Disabled };
     Item *loadModule(ProductContext *productContext, Item *exportingProductItem, Item *item,
             const CodeLocation &dependsItemLocation, const QString &moduleId,
-            const QualifiedId &moduleName, const QString &multiplexId, bool isRequired,
-                     bool *isProductDependency, QVariantMap *defaultParameters);
+            const QualifiedId &moduleName, const QString &multiplexId, FallbackMode fallbackMode,
+            bool isRequired, bool *isProductDependency, QVariantMap *defaultParameters);
     Item *searchAndLoadModuleFile(ProductContext *productContext,
             const CodeLocation &dependsItemLocation, const QualifiedId &moduleName,
-            bool isRequired, Item *moduleInstance);
+            FallbackMode fallbackMode, bool isRequired, Item *moduleInstance);
     Item *loadModuleFile(ProductContext *productContext, const QString &fullModuleName,
             bool isBaseModule, const QString &filePath, bool *triedToLoad, Item *moduleInstance);
     Item *getModulePrototype(ProductContext *productContext, const QString &fullModuleName,
@@ -329,6 +339,20 @@ private:
     Item *wrapInProjectIfNecessary(Item *item);
     static QString findExistingModulePath(const QString &searchPath,
             const QualifiedId &moduleName);
+
+    enum class ModuleProviderLookup { Regular, Fallback };
+    struct ModuleProviderResult
+    {
+        ModuleProviderResult() = default;
+        ModuleProviderResult(bool ran, bool added)
+            : providerFound(ran), providerAddedSearchPaths(added) {}
+        bool providerFound = false;
+        bool providerAddedSearchPaths = false;
+    };
+    ModuleProviderResult findModuleProvider(const QualifiedId &name, ProductContext &product,
+            ModuleProviderLookup lookupType, const CodeLocation &dependsItemLocation);
+    QVariantMap moduleProviderConfig(ProductContext &product);
+
     static void setScopeForDescendants(Item *item, Item *scope);
     void overrideItemProperties(Item *item, const QString &buildConfigKey,
                                 const QVariantMap &buildConfig);
@@ -425,6 +449,8 @@ private:
     std::unordered_map<ProductContext *, Set<DeferredDependsContext>> m_productsWithDeferredDependsItems;
     Set<Item *> m_exportsWithDeferredDependsItems;
 
+    ModuleProviderInfoList m_moduleProviderInfo;
+
     SetupProjectParameters m_parameters;
     std::unique_ptr<Settings> m_settings;
     Version m_qbsVersion;
diff --git a/src/lib/corelib/language/moduleproviderinfo.h b/src/lib/corelib/language/moduleproviderinfo.h
new file mode 100644
index 000000000..fef9d9765
--- /dev/null
+++ b/src/lib/corelib/language/moduleproviderinfo.h
@@ -0,0 +1,90 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qbs.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QBS_MODULEPROVIDERINFO_H
+#define QBS_MODULEPROVIDERINFO_H
+
+#include "qualifiedid.h"
+#include <tools/persistence.h>
+
+#include <QtCore/qstringlist.h>
+#include <QtCore/qvariant.h>
+
+#include <vector>
+
+namespace qbs {
+namespace Internal {
+
+class ModuleProviderInfo
+{
+public:
+    ModuleProviderInfo() = default;
+    ModuleProviderInfo(const QualifiedId &name, const QVariantMap &config,
+                   const QStringList &searchPaths, bool transientOutput)
+        : name(name), config(config), searchPaths(searchPaths), transientOutput(transientOutput)
+    {}
+
+    static QString outputBaseDirName() { return QStringLiteral("genmodules"); }
+    static QString outputDirPath(const QString &baseDir, const QualifiedId &name)
+    {
+        return baseDir + QLatin1Char('/') + outputBaseDirName() + QLatin1Char('/')
+                + name.toString();
+    }
+    QString outputDirPath(const QString &baseDir) const
+    {
+        return outputDirPath(baseDir, name);
+    }
+
+    template<PersistentPool::OpType opType> void completeSerializationOp(PersistentPool &pool)
+    {
+        pool.serializationOp<opType>(reinterpret_cast<QStringList &>(name), config, searchPaths);
+    }
+
+    QualifiedId name;
+    QVariantMap config;
+    QStringList searchPaths;
+    bool transientOutput = false; // Not to be serialized.
+};
+
+using ModuleProviderInfoList = std::vector<ModuleProviderInfo>;
+
+} // namespace Internal
+} // namespace qbs
+
+#endif // Include guard
diff --git a/src/lib/corelib/language/projectresolver.cpp b/src/lib/corelib/language/projectresolver.cpp
index 7deb964b3..d0af0b7ed 100644
--- a/src/lib/corelib/language/projectresolver.cpp
+++ b/src/lib/corelib/language/projectresolver.cpp
@@ -240,6 +240,7 @@ TopLevelProjectPtr ProjectResolver::resolveTopLevelProject()
     project->buildSystemFiles = m_loadResult.qbsFiles;
     project->profileConfigs = m_loadResult.profileConfigs;
     project->probes = m_loadResult.projectProbes;
+    project->moduleProviderInfo = m_loadResult.moduleProviderInfo;
     ProjectContext projectContext;
     projectContext.project = project;
 
diff --git a/src/lib/corelib/tools/persistence.cpp b/src/lib/corelib/tools/persistence.cpp
index ec412cf3b..b50084702 100644
--- a/src/lib/corelib/tools/persistence.cpp
+++ b/src/lib/corelib/tools/persistence.cpp
@@ -48,7 +48,7 @@
 namespace qbs {
 namespace Internal {
 
-static const char QBS_PERSISTENCE_MAGIC[] = "QBSPERSISTENCE-124";
+static const char QBS_PERSISTENCE_MAGIC[] = "QBSPERSISTENCE-125";
 
 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/setupprojectparameters.cpp b/src/lib/corelib/tools/setupprojectparameters.cpp
index 39304d4c9..5600d9b0b 100644
--- a/src/lib/corelib/tools/setupprojectparameters.cpp
+++ b/src/lib/corelib/tools/setupprojectparameters.cpp
@@ -92,6 +92,7 @@ public:
     bool logElapsedTime;
     bool forceProbeExecution;
     bool waitLockBuildGraph;
+    bool fallbackProviderEnabled = true;
     SetupProjectParameters::RestoreBehavior restoreBehavior;
     ErrorHandlingMode propertyCheckingMode;
     ErrorHandlingMode productErrorMode;
@@ -505,6 +506,22 @@ void SetupProjectParameters::setWaitLockBuildGraph(bool wait)
 }
 
 /*!
+ * \brief Returns true if qbs should fall back to pkg-config if a dependency is not found.
+ */
+bool SetupProjectParameters::fallbackProviderEnabled() const
+{
+    return d->fallbackProviderEnabled;
+}
+
+/*!
+ * Controls whether to fall back to pkg-config if a dependency is not found.
+ */
+void SetupProjectParameters::setFallbackProviderEnabled(bool enable)
+{
+    d->fallbackProviderEnabled = enable;
+}
+
+/*!
  * \brief Gets the environment used while resolving the project.
  */
 QProcessEnvironment SetupProjectParameters::environment() const
diff --git a/src/lib/corelib/tools/setupprojectparameters.h b/src/lib/corelib/tools/setupprojectparameters.h
index fe7e3d487..10e4310cd 100644
--- a/src/lib/corelib/tools/setupprojectparameters.h
+++ b/src/lib/corelib/tools/setupprojectparameters.h
@@ -123,6 +123,9 @@ public:
     bool waitLockBuildGraph() const;
     void setWaitLockBuildGraph(bool wait);
 
+    bool fallbackProviderEnabled() const;
+    void setFallbackProviderEnabled(bool enable);
+
     QProcessEnvironment environment() const;
     void setEnvironment(const QProcessEnvironment &env);
     QProcessEnvironment adjustedEnvironment() const;
diff --git a/src/lib/corelib/tools/stringconstants.h b/src/lib/corelib/tools/stringconstants.h
index 1a9356e49..cd41f3768 100644
--- a/src/lib/corelib/tools/stringconstants.h
+++ b/src/lib/corelib/tools/stringconstants.h
@@ -86,6 +86,7 @@ public:
     static const QString &explicitlyDependsOnFromDependenciesProperty() {
         return explicitlyDependsOnFromDependencies();
     }
+    QBS_STRING_CONSTANT(enableFallbackProperty, "enableFallback")
     static const QString &fileNameProperty() { return fileName(); }
     static const QString &filePathProperty() { return filePath(); }
     static const QString &filePathVar() { return filePath(); }
@@ -111,6 +112,7 @@ public:
     QBS_STRING_CONSTANT(limitToSubProjectProperty, "limitToSubProject")
     QBS_STRING_CONSTANT(minimumQbsVersionProperty, "minimumQbsVersion")
     QBS_STRING_CONSTANT(moduleNameProperty, "moduleName")
+    QBS_STRING_CONSTANT(moduleProviders, "moduleProviders")
     QBS_STRING_CONSTANT(multiplexByQbsPropertiesProperty, "multiplexByQbsProperties")
     QBS_STRING_CONSTANT(multiplexConfigurationIdProperty, "multiplexConfigurationId")
     QBS_STRING_CONSTANT(multiplexConfigurationIdsProperty, "multiplexConfigurationIds")