CompilationDatabaseProjectManager: Fix unexpected double emit of signal

Do not rely on QFutureWatcher::isFinished(), which triggers a crash in
the plugin unit test with Qt 6 (race condition?).

Change-Id: I379d894ebd4a28a64b1e70e0cee6eef9ab720a14
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/compilationdatabaseprojectmanager/compilationdbparser.cpp

@@ -59,8 +59,7 @@ CompilationDbParser::CompilationDbParser(const QString &projectName,
 {
     connect(&m_parserWatcher, &QFutureWatcher<void>::finished, this, [this] {
         m_dbContents = m_parserWatcher.result();
-        if (!m_treeScanner || m_treeScanner->isFinished())
-            finish(ParseResult::Success);
+        parserJobFinished();
     });
 }
 
@@ -80,6 +79,7 @@ void CompilationDbParser::start()
         return;
     }
     m_projectFileHash = newHash;
+    m_runningParserJobs = 0;
 
     // Thread 1: Scan disk.
     if (!m_rootPath.isEmpty()) {
@@ -109,10 +109,9 @@ void CompilationDbParser::start()
         Core::ProgressManager::addTask(m_treeScanner->future(),
                                        tr("Scan \"%1\" project tree").arg(m_projectName),
                                        "CompilationDatabase.Scan.Tree");
-        connect(m_treeScanner, &TreeScanner::finished, this, [this] {
-            if (m_parserWatcher.isFinished())
-                finish(ParseResult::Success);
-        });
+        ++m_runningParserJobs;
+        connect(m_treeScanner, &TreeScanner::finished,
+                this, &CompilationDbParser::parserJobFinished);
     }
 
     // Thread 2: Parse the project file.
@@ -120,6 +119,7 @@ void CompilationDbParser::start()
     Core::ProgressManager::addTask(future,
                                    tr("Parse \"%1\" project").arg(m_projectName),
                                    "CompilationDatabase.Parse");
+    ++m_runningParserJobs;
     m_parserWatcher.setFuture(future);
 }
 
@@ -143,6 +143,12 @@ QList<FileNode *> CompilationDbParser::scannedFiles() const
                                                                   : QList<FileNode *>();
 }
 
+void CompilationDbParser::parserJobFinished()
+{
+    if (--m_runningParserJobs == 0)
+        finish(ParseResult::Success);
+}
+
 void CompilationDbParser::finish(ParseResult result)
 {
     emit finished(result);

src/plugins/compilationdatabaseprojectmanager/compilationdbparser.h

@@ -77,6 +77,7 @@ signals:
     void finished(ParseResult result);
 
 private:
+    void parserJobFinished();
     void finish(ParseResult result);
     DbContents parseProject();
     std::vector<DbEntry> readJsonObjects() const;
@@ -90,6 +91,7 @@ private:
     DbContents m_dbContents;
     QByteArray m_projectFileContents;
     QByteArray m_projectFileHash;
+    int m_runningParserJobs = 0;
 
     ProjectExplorer::BuildSystem::ParseGuard m_guard;
 };