Clang: Avoid duplicate jobs without changes in-between

This could happen, e.g. with this message order:

  >>> updateTranslationUnitsForEditor()
  add job<1>
  run job<1>
  >>> updateVisibleTranslationUnits(Utf8String(), {})
  >>> updateVisibleTranslationUnits(path, {path})
  add job<2>
  finish job<1>
  run job<2> -- Ops, nothing is changed but job<2> is started

This led to an outdated translation unit (e.g. wrong highlighting).

Now JobQueue checks for duplicates in the queue and checks all the
currently running jobs.

Change-Id: I05843fddcbd21ce0489681c283227c0027ded428
Reviewed-by: David Schulz <david.schulz@qt.io>

src/tools/clangbackend/ipcsource/clangjobqueue.cpp

@@ -41,11 +41,22 @@ JobQueue::JobQueue(Documents &documents, ProjectParts &projectParts)
 {
 }
 
-void JobQueue::add(const JobRequest &job)
+bool JobQueue::add(const JobRequest &job)
 {
-    qCDebug(jobsLog) << "Adding" << job;
+    if (m_queue.contains(job)) {
+        qCDebug(jobsLog) << "Not adding duplicate request" << job;
+        return false;
+    }
 
+    if (isJobRunningForJobRequest(job)) {
+        qCDebug(jobsLog) << "Not adding duplicate request for already running job" << job;
+        return false;
+    }
+
+    qCDebug(jobsLog) << "Adding" << job;
     m_queue.append(job);
+
+    return true;
 }
 
 int JobQueue::size() const
@@ -200,15 +211,30 @@ JobRequests JobQueue::takeJobRequestsToRunNow()
 
 bool JobQueue::isJobRunningForTranslationUnit(const Utf8String &translationUnitId)
 {
-    if (m_isJobRunningHandler)
-        return m_isJobRunningHandler(translationUnitId);
+    if (m_isJobRunningForTranslationUnitHandler)
+        return m_isJobRunningForTranslationUnitHandler(translationUnitId);
 
     return false;
 }
 
-void JobQueue::setIsJobRunningHandler(const IsJobRunningHandler &isJobRunningHandler)
+bool JobQueue::isJobRunningForJobRequest(const JobRequest &jobRequest)
 {
-    m_isJobRunningHandler = isJobRunningHandler;
+    if (m_isJobRunningForJobRequestHandler)
+        return m_isJobRunningForJobRequestHandler(jobRequest);
+
+    return false;
+}
+
+void JobQueue::setIsJobRunningForTranslationUnitHandler(
+        const IsJobRunningForTranslationUnitHandler &isJobRunningHandler)
+{
+    m_isJobRunningForTranslationUnitHandler = isJobRunningHandler;
+}
+
+void JobQueue::setIsJobRunningForJobRequestHandler(
+        const JobQueue::IsJobRunningForJobRequestHandler &isJobRunningHandler)
+{
+    m_isJobRunningForJobRequestHandler = isJobRunningHandler;
 }
 
 JobRequests JobQueue::queue() const