C++: Fix completion for doxygen tags I

There are three cases that must be handled:

 1. Completion in C++ style comment
 2. Completion in first line of a C style comment
 3. Completion in non-first line of a C style comment

This change fixes case 1 + 2. Case 3 will be addressed in a follow-up
change, same goes for the duplication.

Task-number: QTCREATORBUG-15143
Change-Id: I449711f965ddcbbe6158870a8a5ae33218e0d238
Reviewed-by: David Schulz <david.schulz@theqtcompany.com>

src/plugins/cpptools/cppcompletion_test.cpp

@@ -24,6 +24,7 @@
 ****************************************************************************/
 
 #include "cppcompletionassist.h"
+#include "cppdoxygen.h"
 #include "cppmodelmanager.h"
 #include "cpptoolsplugin.h"
 #include "cpptoolstestcase.h"
@@ -171,6 +172,17 @@ bool isProbablyGlobalCompletion(const QStringList &list)
         && list.contains(QLatin1String("bool"));
 }
 
+bool isDoxygenTagCompletion(const QStringList &list)
+{
+    for (int i = 1; i < T_DOXY_LAST_TAG; ++i) {
+        const QString doxygenTag = QString::fromLatin1(doxygenTagSpell(i));
+        if (!list.contains(doxygenTag))
+            return false;
+    }
+
+    return true;
+}
+
 } // anonymous namespace
 
 void CppToolsPlugin::test_completion_basic_1()
@@ -384,6 +396,29 @@ void CppToolsPlugin::test_global_completion()
     QVERIFY(completions.toSet().contains(requiredCompletionItems.toSet()));
 }
 
+void CppToolsPlugin::test_doxygen_tag_completion_data()
+{
+    QTest::addColumn<QByteArray>("code");
+
+    QTest::newRow("C++ comment")
+         << _("/// @");
+
+    QTest::newRow("C comment single line")
+         << _("/*! @ */");
+}
+
+void CppToolsPlugin::test_doxygen_tag_completion()
+{
+    QFETCH(QByteArray, code);
+
+    const QByteArray prefix = "\\";
+
+    CompletionTestCase test(code, prefix);
+    QVERIFY(test.succeededSoFar());
+    const QStringList completions = test.getCompletions();
+    QVERIFY(isDoxygenTagCompletion(completions));
+}
+
 static void enumTestCase(const QByteArray &tag, const QByteArray &source,
                          const QByteArray &prefix = QByteArray())
 {