Clang: fix completion after forward-declared class

Do not complete -> and . with global completions if
foo is a ptr/ref to forward-declared class.

Change-Id: I41e6745ffb07be1d973fe6a8132824f1b3bf7fb1
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/tools/clangbackend/ipcsource/clangcodecompleteresults.cpp

@@ -61,6 +61,12 @@ bool ClangCodeCompleteResults::hasNoResultsForDotCompletion() const
     return !hasResults() && isDotCompletion();
 }
 
+bool ClangCodeCompleteResults::hasUnknownContext() const
+{
+    const unsigned long long contexts = clang_codeCompleteGetContexts(cxCodeCompleteResults);
+    return contexts == CXCompletionContext_Unknown;
+}
+
 bool ClangCodeCompleteResults::isDotCompletion() const
 {
     const unsigned long long contexts = clang_codeCompleteGetContexts(cxCodeCompleteResults);

src/tools/clangbackend/ipcsource/clangcodecompleteresults.h

@@ -51,6 +51,7 @@ public:
     bool hasResults() const;
     bool hasNoResultsForDotCompletion() const;
 
+    bool hasUnknownContext() const;
     bool isDotCompletion() const;
 
     CXCodeCompleteResults *data() const;

src/tools/clangbackend/ipcsource/codecompleter.cpp

@@ -56,6 +56,22 @@ CodeCompletions toCodeCompletions(const ClangCodeCompleteResults &results)
     return codeCompletions;
 }
 
+void filterUnknownContextResults(ClangCodeCompleteResults &results,
+                                 const UnsavedFile &theUnsavedFile,
+                                 uint line,
+                                 uint column)
+{
+    if (results.hasUnknownContext()) {
+        bool positionIsOk = false;
+        const uint position = theUnsavedFile.toUtf8Position(line, column - 1, &positionIsOk);
+        if (positionIsOk && (theUnsavedFile.hasCharacterAt(position, '.')
+                             || (theUnsavedFile.hasCharacterAt(position - 1, '-')
+                                 && theUnsavedFile.hasCharacterAt(position, '>')))) {
+            results = {};
+        }
+    }
+}
+
 } // anonymous namespace
 
 CodeCompleter::CodeCompleter(const TranslationUnit &translationUnit,
@@ -70,7 +86,7 @@ CodeCompletions CodeCompleter::complete(uint line, uint column)
     neededCorrection_ = CompletionCorrection::NoCorrection;
 
     ClangCodeCompleteResults results = completeHelper(line, column);
-
+    filterUnknownContextResults(results, unsavedFile(), line, column);
     tryDotArrowCorrectionIfNoResults(results, line, column);
 
     return toCodeCompletions(results);
@@ -139,6 +155,7 @@ ClangCodeCompleteResults CodeCompleter::completeWithArrowInsteadOfDot(uint line,
         results = completeHelper(line, column + 1);
         if (results.hasResults())
             neededCorrection_ = CompletionCorrection::DotToArrowCorrection;
+        filterUnknownContextResults(results, unsavedFile(), line, column+1);
     }
 
     return results;

tests/unit/unittest/codecompleter-test.cpp

@@ -176,6 +176,18 @@ protected:
         readFileContent(QStringLiteral("/complete_withNoDotArrowCorrectionForColonColon.cpp")),
         true
     };
+    ClangBackEnd::FileContainer dotArrowCorrectionForForwardDeclaredClassPointer{
+        Utf8StringLiteral(TESTDATA_DIR"/complete_withDotArrowCorrectionForForwardDeclaredClassPointer.cpp"),
+        projectPart.projectPartId(),
+        readFileContent(QStringLiteral("/complete_withDotArrowCorrectionForForwardDeclaredClassPointer.cpp")),
+        true
+    };
+    ClangBackEnd::FileContainer globalCompletionAfterForwardDeclaredClassPointer{
+        Utf8StringLiteral(TESTDATA_DIR"/complete_withGlobalCompletionAfterForwardDeclaredClassPointer.cpp"),
+        projectPart.projectPartId(),
+        readFileContent(QStringLiteral("/complete_withGlobalCompletionAfterForwardDeclaredClassPointer.cpp")),
+        true
+    };
 };
 
 using CodeCompleterSlowTest = CodeCompleter;
@@ -425,10 +437,18 @@ TEST_F(CodeCompleterSlowTest, NoDotArrowCorrectionForOnlyDot)
 
     const ClangBackEnd::CodeCompletions completions = myCompleter.complete(5, 6);
 
+    ASSERT_TRUE(completions.isEmpty());
+    ASSERT_THAT(myCompleter.neededCorrection(), ClangBackEnd::CompletionCorrection::NoCorrection);
+}
+
+TEST_F(CodeCompleterSlowTest, GlobalCompletionForSpaceAfterOnlyDot)
+{
+    auto myCompleter = setupCompleter(noDotArrowCorrectionForOnlyDotFileContainer);
+
+    const ClangBackEnd::CodeCompletions completions = myCompleter.complete(5, 7);
     ASSERT_THAT(completions,
                 Contains(IsCodeCompletion(Utf8StringLiteral("Foo"),
                                           CodeCompletion::ClassCompletionKind)));
-    ASSERT_THAT(myCompleter.neededCorrection(), ClangBackEnd::CompletionCorrection::NoCorrection);
 }
 
 TEST_F(CodeCompleterSlowTest, NoDotArrowCorrectionForColonColon)
@@ -439,6 +459,33 @@ TEST_F(CodeCompleterSlowTest, NoDotArrowCorrectionForColonColon)
     ASSERT_THAT(myCompleter.neededCorrection(), ClangBackEnd::CompletionCorrection::NoCorrection);
 }
 
+TEST_F(CodeCompleterSlowTest, DotArrowCorrectionForForwardDeclaredClassPointer)
+{
+    auto myCompleter = setupCompleter(dotArrowCorrectionForForwardDeclaredClassPointer);
+    const ClangBackEnd::CodeCompletions completions = myCompleter.complete(5, 9);
+
+    ASSERT_TRUE(completions.isEmpty());
+    ASSERT_THAT(myCompleter.neededCorrection(), ClangBackEnd::CompletionCorrection::DotToArrowCorrection);
+}
+
+TEST_F(CodeCompleterSlowTest, NoGlobalCompletionAfterForwardDeclaredClassPointer)
+{
+    auto myCompleter = setupCompleter(globalCompletionAfterForwardDeclaredClassPointer);
+    const ClangBackEnd::CodeCompletions completions = myCompleter.complete(5, 10);
+
+    ASSERT_TRUE(completions.isEmpty());
+    ASSERT_THAT(myCompleter.neededCorrection(), ClangBackEnd::CompletionCorrection::NoCorrection);
+}
+
+TEST_F(CodeCompleterSlowTest, GlobalCompletionAfterForwardDeclaredClassPointer)
+{
+    auto myCompleter = setupCompleter(globalCompletionAfterForwardDeclaredClassPointer);
+    const ClangBackEnd::CodeCompletions completions = myCompleter.complete(6, 4);
+
+    ASSERT_TRUE(!completions.isEmpty());
+    ASSERT_THAT(myCompleter.neededCorrection(), ClangBackEnd::CompletionCorrection::NoCorrection);
+}
+
 ClangBackEnd::CodeCompleter CodeCompleter::setupCompleter(
         const ClangBackEnd::FileContainer &fileContainer)
 {

tests/unit/unittest/data/complete_withDotArrowCorrectionForForwardDeclaredClassPointer.cpp

@@ -0,0 +1,6 @@
+struct Bar;
+
+void g(Bar *bar)
+{
+    bar.
+}

tests/unit/unittest/data/complete_withGlobalCompletionAfterForwardDeclaredClassPointer.cpp

@@ -0,0 +1,7 @@
+struct Bar;
+
+void g(Bar *bar)
+{
+    bar->
+    // white space preserver
+}

tests/unit/unittest/data/complete_withNoDotArrowCorrectionForOnlyDot.cpp

@@ -2,6 +2,6 @@ struct Foo { int member; };
 
 void g(Foo *foo)
 {
-    .
+    . // white space preserver
 }