CMake: Avoid needless cmake runs after kit changes

Do not run cmake if the kit has changed in ways that
do not effect cmake. Do clean rebuilds for changes to the generator
or cmake tool, etc. which do not work without that.

Change-Id: I4e9d43c5161246c3ded7f784cb0d44c3bd4b04e9
Reviewed-by: Alexander Drozdov <adrozdoff@gmail.com>
Reviewed-by: Tim Jenssen <tim.jenssen@theqtcompany.com>

src/plugins/cmakeprojectmanager/builddirmanager.cpp

@@ -595,5 +595,58 @@ CMakeConfig BuildDirManager::parseConfiguration(const Utils::FileName &cacheFile
     return result;
 }
 
+void BuildDirManager::maybeForceReparse()
+{
+    const QByteArray GENERATOR_KEY = "CMAKE_GENERATOR";
+    const QByteArray EXTRA_GENERATOR_KEY = "CMAKE_EXTRA_GENERATOR";
+    const QByteArray CMAKE_COMMAND_KEY = "CMAKE_COMMAND";
+
+    if (!m_hasData)
+        return;
+
+    const CMakeConfig currentConfig = parsedConfiguration();
+
+    const QString kitGenerator = CMakeGeneratorKitInformation::generator(kit());
+    int pos = kitGenerator.lastIndexOf(QLatin1String(" - "));
+    const QString extraKitGenerator = (pos > 0) ? kitGenerator.left(pos) : QString();
+    const QString mainKitGenerator = (pos > 0) ? kitGenerator.mid(pos + 3) : kitGenerator;
+    CMakeConfig targetConfig = m_buildConfiguration->cmakeConfiguration();
+    targetConfig.append(CMakeConfigItem(GENERATOR_KEY, CMakeConfigItem::INTERNAL,
+                                     QByteArray(), mainKitGenerator.toUtf8()));
+    if (!extraKitGenerator.isEmpty())
+        targetConfig.append(CMakeConfigItem(EXTRA_GENERATOR_KEY, CMakeConfigItem::INTERNAL,
+                                         QByteArray(), extraKitGenerator.toUtf8()));
+    const CMakeTool *tool = CMakeKitInformation::cmakeTool(kit());
+    if (tool)
+        targetConfig.append(CMakeConfigItem(CMAKE_COMMAND_KEY, CMakeConfigItem::INTERNAL,
+                                         QByteArray(), tool->cmakeExecutable().toUserOutput().toUtf8()));
+    Utils::sort(targetConfig, CMakeConfigItem::sortOperator());
+
+    auto ccit = currentConfig.constBegin();
+    auto kcit = targetConfig.constBegin();
+    while (ccit != currentConfig.constEnd() && kcit != targetConfig.constEnd()) {
+        if (ccit->key == kcit->key) {
+            if (ccit->value != kcit->value)
+                break;
+            ++ccit;
+            ++kcit;
+        } else {
+            if (ccit->key < kcit->key)
+                ++ccit;
+            else
+                break;
+        }
+    }
+
+    if (kcit != targetConfig.end()) {
+        if (kcit->key == GENERATOR_KEY
+                || kcit->key == EXTRA_GENERATOR_KEY
+                || kcit->key == CMAKE_COMMAND_KEY)
+            clearCache();
+        else
+            forceReparse();
+    }
+}
+
 } // namespace Internal
 } // namespace CMakeProjectManager

src/plugins/cmakeprojectmanager/builddirmanager.h

@@ -77,6 +77,7 @@ public:
     void parse();
     void clearCache();
     void forceReparse();
+    void maybeForceReparse(); // Only reparse if the configuration has changed...
     void resetData();
     bool persistCMakeState();
 

src/plugins/cmakeprojectmanager/cmakebuildconfiguration.cpp

@@ -80,7 +80,13 @@ CMakeBuildConfiguration::CMakeBuildConfiguration(ProjectExplorer::Target *parent
             m_buildDirManager, &BuildDirManager::forceReparse);
     connect(this, &CMakeBuildConfiguration::buildDirectoryChanged,
             m_buildDirManager, &BuildDirManager::forceReparse);
-    connect(target(), &Target::kitChanged, m_buildDirManager, &BuildDirManager::forceReparse);
+    connect(target(), &Target::kitChanged, this, [this]() {
+        ProjectExplorer::Kit *k = target()->kit();
+        CMakeConfig config = cmakeConfiguration();
+        config.append(CMakeConfigurationKitInformation::configuration(k));  // last value wins...
+        setCMakeConfiguration(config);
+        m_buildDirManager->maybeForceReparse();
+    });
 
     connect(this, &CMakeBuildConfiguration::parsingStarted, project, &CMakeProject::handleParsingStarted);
     connect(this, &CMakeBuildConfiguration::dataAvailable, project, &CMakeProject::parseCMakeOutput);