Put a system-wide lock on the build directory.

So that two qbs instances can't overwrite each other's
build graphs. In practice, this is probably most relevant
for IDEs, as these hold a build graph for potentially long
periods of time.
Facilitates QLockFile that was introduced in Qt 5.1. For older
Qt versions, no locking happens.

Task-number: QBS-162
Change-Id: Ib598617fb1742eb57b6a017f40b9631d1d54e627
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>

10 files changed, 215 insertions, 3 deletions

diff --git a/src/lib/corelib/api/internaljobs.cpp b/src/lib/corelib/api/internaljobs.cpp
index 840d7cc1c..ededa3279 100644
--- a/src/lib/corelib/api/internaljobs.cpp
+++ b/src/lib/corelib/api/internaljobs.cpp
@@ -42,6 +42,7 @@
 #include <language/loader.h>
 #include <logging/logger.h>
 #include <logging/translator.h>
+#include <tools/buildgraphlocker.h>
 #include <tools/error.h>
 #include <tools/progressobserver.h>
 #include <tools/preferences.h>
@@ -228,14 +229,23 @@ TopLevelProjectPtr InternalSetupProjectJob::project() const
 
 void InternalSetupProjectJob::start()
 {
+    BuildGraphLocker *bgLocker = 0;
     try {
         const ErrorInfo err = m_parameters.expandBuildConfiguration();
         if (err.hasError())
             throw err;
+        const QString projectId = TopLevelProject::deriveId(m_parameters.topLevelProfile(),
+                m_parameters.finalBuildConfigurationTree());
+        const QString buildDir
+                = TopLevelProject::deriveBuildDirectory(m_parameters.buildRoot(), projectId);
+        bgLocker = new BuildGraphLocker(ProjectBuildData::deriveBuildGraphFilePath(buildDir,
+                                                                                   projectId));
         execute();
+        m_project->bgLocker = bgLocker;
     } catch (const ErrorInfo &error) {
         m_project.clear();
         setError(error);
+        delete bgLocker;
     }
     emit finished(this);
 }
diff --git a/src/lib/corelib/corelib.qbs b/src/lib/corelib/corelib.qbs
index 45dfa2079..ac121783b 100644
--- a/src/lib/corelib/corelib.qbs
+++ b/src/lib/corelib/corelib.qbs
@@ -278,6 +278,8 @@ QbsLibrary {
         name: "tools"
         prefix: name + '/'
         files: [
+            "buildgraphlocker.cpp",
+            "buildgraphlocker.h",
             "buildoptions.cpp",
             "cleanoptions.cpp",
             "codelocation.cpp",
diff --git a/src/lib/corelib/language/language.cpp b/src/lib/corelib/language/language.cpp
index cc9d02180..d7815938e 100644
--- a/src/lib/corelib/language/language.cpp
+++ b/src/lib/corelib/language/language.cpp
@@ -39,6 +39,7 @@
 #include <buildgraph/transformer.h>
 #include <jsextensions/jsextensions.h>
 #include <logging/translator.h>
+#include <tools/buildgraphlocker.h>
 #include <tools/hostosinfo.h>
 #include <tools/error.h>
 #include <tools/propertyfinder.h>
@@ -937,12 +938,14 @@ void ResolvedProject::store(PersistentPool &pool) const
 }
 
 
-TopLevelProject::TopLevelProject() : locked(false), lastResolveTime(FileTime::oldestTime())
+TopLevelProject::TopLevelProject()
+    : bgLocker(0), locked(false), lastResolveTime(FileTime::oldestTime())
 {
 }
 
 TopLevelProject::~TopLevelProject()
 {
+    delete bgLocker;
 }
 
 QString TopLevelProject::deriveId(const QString &profile, const QVariantMap &config)
diff --git a/src/lib/corelib/language/language.h b/src/lib/corelib/language/language.h
index ed1b37320..e7df3232e 100644
--- a/src/lib/corelib/language/language.h
+++ b/src/lib/corelib/language/language.h
@@ -61,6 +61,7 @@ QT_END_NAMESPACE
 
 namespace qbs {
 namespace Internal {
+class BuildGraphLocker;
 class BuildGraphLoader;
 class BuildGraphVisitor;
 
@@ -460,7 +461,8 @@ public:
     QHash<QString, bool> fileExistsResults; // Results of calls to "File.exists()".
     QHash<QString, FileTime> fileLastModifiedResults; // Results of calls to "File.lastModified()".
     QScopedPointer<ProjectBuildData> buildData;
-    bool locked;
+    BuildGraphLocker *bgLocker; // This holds the system-wide build graph file lock.
+    bool locked; // This is the API-level lock for the project instance.
 
     QSet<QString> buildSystemFiles;
     FileTime lastResolveTime;
diff --git a/src/lib/corelib/tools/buildgraphlocker.cpp b/src/lib/corelib/tools/buildgraphlocker.cpp
new file mode 100644
index 000000000..f49686c8a
--- /dev/null
+++ b/src/lib/corelib/tools/buildgraphlocker.cpp
@@ -0,0 +1,96 @@
+/****************************************************************************
+**
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the Qt Build Suite.
+**
+** 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 Digia.  For licensing terms and
+** conditions see http://qt.digia.com/licensing.  For further information
+** use the contact form at http://qt.digia.com/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 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Digia gives you certain additional
+** rights.  These rights are described in the Digia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+****************************************************************************/
+
+#include "buildgraphlocker.h"
+
+#include "error.h"
+
+#include <logging/translator.h>
+
+#include <QDir>
+#include <QFileInfo>
+#include <QString>
+
+namespace qbs {
+namespace Internal {
+
+BuildGraphLocker::BuildGraphLocker(const QString &buildGraphFilePath)
+#if HAS_QLOCKFILE
+    : m_lockFile(buildGraphFilePath + QLatin1String(".lock"))
+#endif
+{
+#if HAS_QLOCKFILE
+    const QString buildDir = QFileInfo(buildGraphFilePath).absolutePath();
+    if (!QDir::root().mkpath(buildDir))
+        throw ErrorInfo(Tr::tr("Cannot lock build graph file '%1': Failed to create directory."));
+    m_lockFile.setStaleLockTime(0);
+    int attemptsToGetInfo = 0;
+    do {
+        if (m_lockFile.tryLock(250))
+            return;
+        switch (m_lockFile.error()) {
+        case QLockFile::LockFailedError: {
+            qint64 pid;
+            QString hostName;
+            QString appName;
+            if (m_lockFile.getLockInfo(&pid, &hostName, &appName)) {
+                throw ErrorInfo(Tr::tr("Cannot lock build graph file '%1': "
+                        "Already locked by '%2' (PID %3).")
+                                .arg(buildGraphFilePath, appName).arg(pid));
+            }
+            break;
+        }
+        case QLockFile::PermissionError:
+            throw ErrorInfo(Tr::tr("Cannot lock build graph file '%1': Permission denied.")
+                            .arg(buildGraphFilePath));
+        case QLockFile::UnknownError:
+        case QLockFile::NoError:
+            throw ErrorInfo(Tr::tr("Cannot lock build graph file '%1' (reason unknown).")
+                            .arg(buildGraphFilePath));
+        }
+    } while (++attemptsToGetInfo < 10);
+
+    // This very unlikely case arises if tryLock() repeatedly returns LockFailedError
+    // with the subsequent getLockInfo() failing as well.
+    throw ErrorInfo(Tr::tr("Cannot lock build graph file '%1' (reason unknown).")
+                    .arg(buildGraphFilePath));
+#else
+    Q_UNUSED(buildGraphFilePath);
+#endif
+}
+
+BuildGraphLocker::~BuildGraphLocker()
+{
+#if HAS_QLOCKFILE
+    m_lockFile.unlock();
+#endif
+}
+
+} // namespace Internal
+} // namespace qbs
diff --git a/src/lib/corelib/tools/buildgraphlocker.h b/src/lib/corelib/tools/buildgraphlocker.h
new file mode 100644
index 000000000..d4b067789
--- /dev/null
+++ b/src/lib/corelib/tools/buildgraphlocker.h
@@ -0,0 +1,63 @@
+/****************************************************************************
+**
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the Qt Build Suite.
+**
+** 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 Digia.  For licensing terms and
+** conditions see http://qt.digia.com/licensing.  For further information
+** use the contact form at http://qt.digia.com/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 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Digia gives you certain additional
+** rights.  These rights are described in the Digia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+****************************************************************************/
+
+#ifndef QBS_BUILDGRAPHLOCKER_H
+#define QBS_BUILDGRAPHLOCKER_H
+
+#include <QtGlobal>
+
+#define HAS_QLOCKFILE (QT_VERSION >= QT_VERSION_CHECK(5, 1, 0))
+
+#if HAS_QLOCKFILE
+#include <QLockFile>
+#endif
+
+QT_BEGIN_NAMESPACE
+class QString;
+QT_END_NAMESPACE
+
+namespace qbs {
+namespace Internal {
+
+class BuildGraphLocker
+{
+public:
+    explicit BuildGraphLocker(const QString &buildGraphFilePath);
+    ~BuildGraphLocker();
+
+private:
+#if HAS_QLOCKFILE
+    QLockFile m_lockFile;
+#endif
+};
+
+} // namespace Internal
+} // namespace qbs
+
+#endif // Include guard.
diff --git a/src/lib/corelib/tools/tools.pri b/src/lib/corelib/tools/tools.pri
index fca3d8f4b..38f8eb63d 100644
--- a/src/lib/corelib/tools/tools.pri
+++ b/src/lib/corelib/tools/tools.pri
@@ -1,6 +1,7 @@
 INCLUDEPATH += $$PWD/../.. # for plugins
 
 HEADERS += \
+    $$PWD/buildgraphlocker.h \
     $$PWD/codelocation.h \
     $$PWD/error.h \
     $$PWD/fileinfo.h \
@@ -28,6 +29,7 @@ HEADERS += \
     $$PWD/qttools.h
 
 SOURCES += \
+    $$PWD/buildgraphlocker.cpp \
     $$PWD/codelocation.cpp \
     $$PWD/error.cpp \
     $$PWD/fileinfo.cpp \
diff --git a/tests/auto/api/testdata/buildgraph-locking/project.qbs b/tests/auto/api/testdata/buildgraph-locking/project.qbs
new file mode 100644
index 000000000..e08b008bc
--- /dev/null
+++ b/tests/auto/api/testdata/buildgraph-locking/project.qbs
@@ -0,0 +1,4 @@
+import qbs
+
+Project {
+}
diff --git a/tests/auto/api/tst_api.cpp b/tests/auto/api/tst_api.cpp
index 73e9bb1b6..db0fc4d41 100644
--- a/tests/auto/api/tst_api.cpp
+++ b/tests/auto/api/tst_api.cpp
@@ -120,6 +120,25 @@ void printProjectData(const qbs::ProjectData &project)
     }
 }
 
+
+void TestApi::buildGraphLocking()
+{
+    qbs::SetupProjectParameters setupParams = defaultSetupParameters();
+    const QString projectDirPath = QDir::cleanPath(m_workingDataDir + "/buildgraph-locking");
+    setupParams.setProjectFilePath(projectDirPath + "/project.qbs");
+    QScopedPointer<qbs::SetupProjectJob> setupJob(qbs::Project::setupProject(setupParams,
+                                                                        m_logSink, 0));
+    waitForFinished(setupJob.data());
+    QVERIFY2(!setupJob->error().hasError(), qPrintable(setupJob->error().toString()));
+    const qbs::Project project = setupJob->project();
+    Q_UNUSED(project);
+    setupJob.reset(qbs::Project::setupProject(setupParams, m_logSink, 0));
+    waitForFinished(setupJob.data());
+    QVERIFY(setupJob->error().hasError());
+    QVERIFY2(setupJob->error().toString().contains("lock"),
+             qPrintable(setupJob->error().toString()));
+}
+
 void TestApi::buildSingleFile()
 {
     qbs::SetupProjectParameters setupParams = defaultSetupParameters();
@@ -330,6 +349,8 @@ void TestApi::changeContent()
 
     // Now check whether the data updates were done correctly.
     projectData = project.projectData();
+    buildJob.reset(0);
+    project = qbs::Project();
     job.reset(qbs::Project::setupProject(setupParams, m_logSink, 0));
     waitForFinished(job.data());
     QVERIFY2(!job->error().hasError(), qPrintable(job->error().toString()));
@@ -373,6 +394,9 @@ void TestApi::changeContent()
     // Add a file to the top level of a product that does not have a "files" binding yet.
     setupParams.setProjectFilePath(QDir::cleanPath(m_workingDataDir +
         "/project-editing/project-with-no-files.qbs"));
+
+    buildJob.reset(0);
+    project = qbs::Project();
     job.reset(qbs::Project::setupProject(setupParams, m_logSink, 0));
     waitForFinished(job.data());
     QVERIFY2(!job->error().hasError(), qPrintable(job->error().toString()));
@@ -390,6 +414,8 @@ void TestApi::changeContent()
     waitForFinished(buildJob.data());
     QVERIFY2(!buildJob->error().hasError(), qPrintable(buildJob->error().toString()));
     QVERIFY(rcvr.descriptions.contains("compiling main.cpp"));
+    buildJob.reset(0);
+    project = qbs::Project();
     job.reset(qbs::Project::setupProject(setupParams, m_logSink, 0));
     waitForFinished(job.data());
     QVERIFY2(!job->error().hasError(), qPrintable(job->error().toString()));
@@ -532,6 +558,7 @@ void TestApi::installableFiles()
 
     setupParams.setProjectFilePath(QDir::cleanPath(QLatin1String(SRCDIR "/../blackbox/testdata"
         "/recursive_wildcards/recursive_wildcards.qbs")));
+    project = qbs::Project();
     job.reset(qbs::Project::setupProject(setupParams, m_logSink, 0));
     waitForFinished(job.data());
     QVERIFY2(!job->error().hasError(), qPrintable(job->error().toString()));
@@ -611,7 +638,7 @@ void TestApi::multiArch()
                                                                         m_logSink, 0));
     waitForFinished(setupJob.data());
     QVERIFY2(!setupJob->error().hasError(), qPrintable(setupJob->error().toString()));
-    const qbs::Project &project = setupJob->project();
+    qbs::Project project = setupJob->project();
     QCOMPARE(project.profile(), QLatin1String("qbs_autotests"));
     const QList<qbs::ProductData> &products = project.projectData().products();
     QCOMPARE(products.count(), 3);
@@ -653,6 +680,8 @@ void TestApi::multiArch()
     // Error check: Try to build for the same profile twice.
     overriddenValues.insert("project.targetProfile", hostProfile.name());
     setupParams.setOverriddenValues(overriddenValues);
+    project = qbs::Project();
+    buildJob.reset(0);
     setupJob.reset(qbs::Project::setupProject(setupParams, m_logSink, 0));
     waitForFinished(setupJob.data());
     QVERIFY(setupJob->error().hasError());
diff --git a/tests/auto/api/tst_api.h b/tests/auto/api/tst_api.h
index 7d1157512..5e75218ba 100644
--- a/tests/auto/api/tst_api.h
+++ b/tests/auto/api/tst_api.h
@@ -47,6 +47,7 @@ public:
 private slots:
     void initTestCase();
 
+    void buildGraphLocking();
     void buildSingleFile();
     void changeContent();
     void disabledInstallGroup();