ClangCodeModel: Fix shadow document handling

Our approach was not fully thought through: When we got informed of a
file getting created by an ExtraCompiler, we would make it known to the
first client that came along and then forget about it. This means that
e.g. a source file including a UI header would parse fine with the first
client that opened it, but after switching the build configuration or
possibly even just touching the project file, the UI header would not be
found anymore.
Fix this by keeping the information about generated files around and
attaching them to every newly initialized client.
Note that this state should probably be kept somewhere more central.

Change-Id: Ib1d8cca9258d1962513d8d463f5d16f9ff91a048
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/clangcodemodel/clangmodelmanagersupport.cpp

@@ -553,17 +553,15 @@ void ClangModelManagerSupport::updateLanguageClient(Project *project)
                 hasDocuments = true;
             }
 
-            for (auto it = m_queuedShadowDocuments.begin(); it != m_queuedShadowDocuments.end();) {
+            for (auto it = m_potentialShadowDocuments.begin();
-                if (fileIsProjectBuildArtifact(client, it.key())) {
+                 it != m_potentialShadowDocuments.end(); ++it) {
+                if (!fileIsProjectBuildArtifact(client, it.key()))
+                    continue;
                 if (it.value().isEmpty())
                     client->removeShadowDocument(it.key());
                 else
                     client->setShadowDocument(it.key(), it.value());
                 ClangdClient::handleUiHeaderChange(it.key().fileName());
-                    it = m_queuedShadowDocuments.erase(it);
-                } else {
-                    ++it;
-                }
             }
 
             updateParserConfig(client);
@@ -799,10 +797,8 @@ void ClangModelManagerSupport::onAbstractEditorSupportContentsUpdated(const QStr
     if (Client * const client = clientForGeneratedFile(fp)) {
         client->setShadowDocument(fp, stringContent);
         ClangdClient::handleUiHeaderChange(fp.fileName());
-        QTC_CHECK(m_queuedShadowDocuments.remove(fp) == 0);
-    } else  {
-        m_queuedShadowDocuments.insert(fp, stringContent);
     }
+    m_potentialShadowDocuments.insert(fp, stringContent);
 }
 
 void ClangModelManagerSupport::onAbstractEditorSupportRemoved(const QString &filePath)
@@ -813,10 +809,8 @@ void ClangModelManagerSupport::onAbstractEditorSupportRemoved(const QString &fil
     if (Client * const client = clientForGeneratedFile(fp)) {
         client->removeShadowDocument(fp);
         ClangdClient::handleUiHeaderChange(fp.fileName());
-        QTC_CHECK(m_queuedShadowDocuments.remove(fp) == 0);
-    } else {
-        m_queuedShadowDocuments.insert(fp, {});
     }
+    m_potentialShadowDocuments.remove(fp);
 }
 
 void addFixItsActionsToMenu(QMenu *menu, const TextEditor::QuickFixOperations &fixItOperations)

src/plugins/clangcodemodel/clangmodelmanagersupport.h

@@ -96,7 +96,7 @@ private:
     Utils::FutureSynchronizer m_generatorSynchronizer;
     QList<QPointer<ClangdClient>> m_clientsToRestart;
     QTimer * const m_clientRestartTimer;
-    QHash<Utils::FilePath, QString> m_queuedShadowDocuments;
+    QHash<Utils::FilePath, QString> m_potentialShadowDocuments;
 };
 
 } // namespace Internal

src/plugins/languageclient/client.cpp

@@ -1058,6 +1058,8 @@ void Client::setShadowDocument(const Utils::FilePath &filePath, const QString &c
     if (shadowIt == d->m_shadowDocuments.end()) {
         shadowIt = d->m_shadowDocuments.insert(filePath, {content, {}});
     } else  {
+        if (shadowIt.value().first == content)
+            return;
         shadowIt.value().first = content;
         if (!shadowIt.value().second.isEmpty()) {
             VersionedTextDocumentIdentifier docId(hostPathToServerUri(filePath));