ClangCodeModel: Clear existing libclang diagnostics

... when clangd takes over a document.
This fixes the problem that temporary diagnostics persisted after opening
a session.

Change-Id: Ic781f83747cabb4d15c2c1f8181e36f4343e0394
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/clangcodemodel/clangdiagnosticmanager.h

@@ -65,11 +65,11 @@ public:
 
     static void clearTaskHubIssues();
     void generateTaskHubIssues();
+    void cleanMarks();
 
     static void addTask(const ClangBackEnd::DiagnosticContainer &diagnostic, bool isChild = false);
 
 private:
-    void cleanMarks();
     QString filePath() const;
     void filterDiagnostics(const QVector<ClangBackEnd::DiagnosticContainer> &diagnostics);
     void generateEditorSelections();

src/plugins/clangcodemodel/clangeditordocumentprocessor.cpp

@@ -251,6 +251,14 @@ void ClangEditorDocumentProcessor::generateTaskHubIssues()
     m_diagnosticManager.generateTaskHubIssues();
 }
 
+void ClangEditorDocumentProcessor::clearTextMarks(const Utils::FilePath &filePath)
+{
+    if (ClangEditorDocumentProcessor * const proc = get(filePath.toString())) {
+        proc->m_diagnosticManager.cleanMarks();
+        emit proc->codeWarningsUpdated(proc->revision(), {}, {}, {});
+    }
+}
+
 void ClangEditorDocumentProcessor::updateHighlighting(
         const QVector<ClangBackEnd::TokenInfoContainer> &tokenInfos,
         const QVector<ClangBackEnd::SourceRangeContainer> &skippedPreprocessorRanges,

src/plugins/clangcodemodel/clangeditordocumentprocessor.h

@@ -108,6 +108,8 @@ public:
     static void clearTaskHubIssues();
     void generateTaskHubIssues();
 
+    static void clearTextMarks(const Utils::FilePath &filePath);
+
 public:
     static ClangEditorDocumentProcessor *get(const QString &filePath);
 

src/plugins/clangcodemodel/clangmodelmanagersupport.cpp

@@ -316,6 +316,7 @@ void ClangModelManagerSupport::updateLanguageClient(ProjectExplorer::Project *pr
                 if (!project->isKnownFile(entry->fileName()))
                     continue;
                 client->openDocument(textDocument);
+                ClangEditorDocumentProcessor::clearTextMarks(textDocument->filePath());
                 hasDocuments = true;
             }