Clang: Process distinct documents concurrently

Speed ups the typical use cases that can profit from this:
 * Change a header file and switch then to source file
 * Open documents one after the other (Follow Symbol)
 * Change documents visible in splits (e.g. by refactoring action)
 * Restore a session with multiple splits

Fixes the test ClangIpcServer.GetCodeCompletionDependingOnArgumets.

Change-Id: Ia575bd59780df14146dfc091a4d48794e4a0543d
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/tools/clangbackend/ipcsource/clangcompletecodejob.cpp

@@ -0,0 +1,95 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+****************************************************************************/
+
+#include "clangcompletecodejob.h"
+
+#include <clangbackendipc/clangbackendipcdebugutils.h>
+#include <clangbackendipc/clangcodemodelclientinterface.h>
+#include <clangbackendipc/cmbcodecompletedmessage.h>
+
+#include <utils/qtcassert.h>
+
+namespace ClangBackEnd {
+
+static CompleteCodeJob::AsyncResult runAsyncHelper(const TranslationUnitCore &translationUnitCore,
+                                                   UnsavedFiles unsavedFiles,
+                                                   quint32 line,
+                                                   quint32 column)
+{
+    TIME_SCOPE_DURATION("CompleteCodeJobRunner");
+
+    CompleteCodeJob::AsyncResult asyncResult;
+
+    try {
+        const TranslationUnitCore::CodeCompletionResult results
+                = translationUnitCore.complete(unsavedFiles, line, column);
+
+        asyncResult.completions = results.completions;
+        asyncResult.correction = results.correction;
+    } catch (const std::exception &exception) {
+        qWarning() << "Error in CompleteCodeJobRunner:" << exception.what();
+    }
+
+    return asyncResult;
+}
+
+bool CompleteCodeJob::prepareAsyncRun()
+{
+    const JobRequest jobRequest = context().jobRequest;
+    QTC_ASSERT(jobRequest.type == JobRequest::Type::CompleteCode, return false);
+
+    try {
+        m_pinnedTranslationUnit = context().translationUnitForJobRequest();
+
+        const TranslationUnitCore translationUnitCore = m_pinnedTranslationUnit.translationUnitCore();
+        const UnsavedFiles unsavedFiles = *context().unsavedFiles;
+        const quint32 line = jobRequest.line;
+        const quint32 column = jobRequest.column;
+        setRunner([translationUnitCore, unsavedFiles, line, column]() {
+            return runAsyncHelper(translationUnitCore, unsavedFiles, line, column);
+        });
+
+
+    } catch (const std::exception &exception) {
+        qWarning() << "Error in CompleteCodeJob::prepareAsyncRun:" << exception.what();
+        return false;
+    }
+
+    return true;
+}
+
+void CompleteCodeJob::finalizeAsyncRun()
+{
+    if (context().isDocumentOpen()) {
+        const AsyncResult result = asyncResult();
+
+        const CodeCompletedMessage message(result.completions,
+                                           result.correction,
+                                           context().jobRequest.ticketNumber);
+        context().client->codeCompleted(message);
+    }
+}
+
+} // namespace ClangBackEnd