CppTools: Provide hints about chosen project part for editor document

Parse issues can have multiple reasons (invalid kit, not a project file,
actual parse issue) and we should be able to tell them apart. With this
change, we can distinguish between the fallback project part and a
ambiguous project part.

Follow up changes will use this to display more accurate diagnostics.

Change-Id: Icc8767607cc17dc14d6227b07f34e81ba5525a96
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/clangcodemodel/clangeditordocumentparser.cpp

@@ -39,12 +39,13 @@ void ClangEditorDocumentParser::updateImpl(const QFutureInterface<void> &,
                                            const UpdateParams &updateParams)
 {
     State state_ = state();
-    state_.projectPart = determineProjectPart(filePath(),
+    state_.projectPartInfo = determineProjectPart(filePath(),
                                                   configuration(),
                                                   state_,
                                                   updateParams.activeProject,
                                                   updateParams.languagePreference,
                                                   updateParams.hasActiveProjectChanged);
+    emit projectPartInfoUpdated(state_.projectPartInfo);
     setState(state_);
 }
 

src/plugins/clangcodemodel/clangeditordocumentprocessor.cpp

@@ -80,6 +80,9 @@ ClangEditorDocumentProcessor::ClangEditorDocumentProcessor(
     connect(&m_updateTranslationUnitTimer, &QTimer::timeout,
             this, &ClangEditorDocumentProcessor::updateTranslationUnitIfProjectPartExists);
 
+    connect(m_parser.data(), &ClangEditorDocumentParser::projectPartInfoUpdated,
+            this, &BaseEditorDocumentProcessor::projectPartInfoUpdated);
+
     // Forwarding the semantic info from the builtin processor enables us to provide all
     // editor (widget) related features that are not yet implemented by the clang plugin.
     connect(&m_builtinProcessor, &CppTools::BuiltinEditorDocumentProcessor::cppDocumentUpdated,
@@ -302,7 +305,7 @@ static bool isProjectPartLoadedOrIsFallback(CppTools::ProjectPart::Ptr projectPa
 
 void ClangEditorDocumentProcessor::updateProjectPartAndTranslationUnitForEditor()
 {
-    const CppTools::ProjectPart::Ptr projectPart = m_parser->projectPart();
+    const CppTools::ProjectPart::Ptr projectPart = m_parser->projectPartInfo().projectPart;
 
     if (isProjectPartLoadedOrIsFallback(projectPart)) {
         registerTranslationUnitForEditor(projectPart.data());

src/plugins/clangcodemodel/clangutils.cpp

@@ -131,7 +131,7 @@ QStringList createClangOptions(const ProjectPart::Ptr &pPart, ProjectFile::Kind
 ProjectPart::Ptr projectPartForFile(const QString &filePath)
 {
     if (const auto parser = CppTools::BaseEditorDocumentParser::get(filePath))
-        return parser->projectPart();
+        return parser->projectPartInfo().projectPart;
     return ProjectPart::Ptr();
 }
 

src/plugins/cppeditor/cppcodemodelinspectordialog.cpp

@@ -1580,7 +1580,7 @@ void CppCodeModelInspectorDialog::refresh()
 
     // Project Parts
     const ProjectPart::Ptr editorsProjectPart = cppEditorDocument
-        ? cppEditorDocument->processor()->parser()->projectPart()
+        ? cppEditorDocument->processor()->parser()->projectPartInfo().projectPart
         : ProjectPart::Ptr();
 
     const QList<ProjectInfo> projectInfos = cmmi->projectInfos();

src/plugins/cppeditor/cppeditordocument.cpp

@@ -274,7 +274,8 @@ void CppEditorDocument::setPreprocessorSettings(const CppTools::ProjectPart::Ptr
 {
     const auto parser = processor()->parser();
     QTC_ASSERT(parser, return);
-    if (parser->projectPart() != projectPart || parser->configuration().editorDefines != defines) {
+    if (parser->projectPartInfo().projectPart != projectPart
+            || parser->configuration().editorDefines != defines) {
         CppTools::BaseEditorDocumentParser::Configuration config = parser->configuration();
         config.manuallySetProjectPart = projectPart;
         config.editorDefines = defines;

src/plugins/cpptools/baseeditordocumentparser.cpp

@@ -54,6 +54,8 @@ namespace CppTools {
 BaseEditorDocumentParser::BaseEditorDocumentParser(const QString &filePath)
     : m_filePath(filePath)
 {
+    static int meta = qRegisterMetaType<ProjectPartInfo>("CppTools::ProjectPartInfo");
+    Q_UNUSED(meta);
 }
 
 BaseEditorDocumentParser::~BaseEditorDocumentParser()
@@ -102,9 +104,9 @@ void BaseEditorDocumentParser::setState(const State &state)
     m_state = state;
 }
 
-ProjectPart::Ptr BaseEditorDocumentParser::projectPart() const
+ProjectPartInfo BaseEditorDocumentParser::projectPartInfo() const
 {
-    return state().projectPart;
+    return state().projectPartInfo;
 }
 
 BaseEditorDocumentParser::Ptr BaseEditorDocumentParser::get(const QString &filePath)
@@ -117,7 +119,7 @@ BaseEditorDocumentParser::Ptr BaseEditorDocumentParser::get(const QString &fileP
     return BaseEditorDocumentParser::Ptr();
 }
 
-ProjectPart::Ptr BaseEditorDocumentParser::determineProjectPart(
+ProjectPartInfo BaseEditorDocumentParser::determineProjectPart(
         const QString &filePath,
         const Configuration &config,
         const State &state,
@@ -125,7 +127,9 @@ ProjectPart::Ptr BaseEditorDocumentParser::determineProjectPart(
         Language languagePreference,
         bool hasActiveProjectChanged)
 {
-    Internal::ProjectPartChooser chooser;
+    using Internal::ProjectPartChooser;
+
+    ProjectPartChooser chooser;
     chooser.setFallbackProjectPart([](){
         return CppModelManager::instance()->fallbackProjectPart();
     });
@@ -137,13 +141,16 @@ ProjectPart::Ptr BaseEditorDocumentParser::determineProjectPart(
         return CppModelManager::instance()->projectPartFromDependencies(fileName);
     });
 
-    return chooser.choose(filePath,
+    const ProjectPartInfo chooserResult
-                          state.projectPart,
+            = chooser.choose(filePath,
+                             state.projectPartInfo.projectPart,
                              config.manuallySetProjectPart,
                              config.stickToPreviousProjectPart,
                              activeProject,
                              languagePreference,
                              hasActiveProjectChanged);
+
+    return chooserResult;
 }
 
 } // namespace CppTools

src/plugins/cpptools/baseeditordocumentparser.h

@@ -25,8 +25,8 @@
 
 #pragma once
 
-#include "cpplanguage.h"
 #include "cpptools_global.h"
+#include "cpptools_utils.h"
 #include "cppworkingcopy.h"
 #include "projectpart.h"
 
@@ -82,17 +82,21 @@ public:
     void update(const UpdateParams &updateParams);
     void update(const QFutureInterface<void> &future, const UpdateParams &updateParams);
 
-    ProjectPart::Ptr projectPart() const;
+    ProjectPartInfo projectPartInfo() const;
+
+signals:
+    void projectPartInfoUpdated(const CppTools::ProjectPartInfo &projectPartInfo);
 
 protected:
     struct State {
         QByteArray editorDefines;
-        ProjectPart::Ptr projectPart;
+        ProjectPartInfo projectPartInfo;
     };
     State state() const;
     void setState(const State &state);
 
-    static ProjectPart::Ptr determineProjectPart(const QString &filePath,
+    static ProjectPartInfo determineProjectPart(
+            const QString &filePath,
             const Configuration &config,
             const State &state,
             const ProjectExplorer::Project *activeProject,

src/plugins/cpptools/baseeditordocumentprocessor.cpp

@@ -26,10 +26,10 @@
 #include "baseeditordocumentprocessor.h"
 
 #include "cppcodemodelsettings.h"
-#include "cpplanguage.h"
 #include "cppmodelmanager.h"
 #include "cpptoolsbridge.h"
 #include "cpptoolsreuse.h"
+#include "cpptools_utils.h"
 #include "editordocumenthandle.h"
 
 #include <projectexplorer/session.h>

src/plugins/cpptools/baseeditordocumentprocessor.h

@@ -74,8 +74,9 @@ public:
     using HeaderErrorDiagnosticWidgetCreator = std::function<QWidget*()>;
 
 signals:
-
     // Signal interface to implement
+    void projectPartInfoUpdated(const CppTools::ProjectPartInfo &projectPartInfo);
+
     void codeWarningsUpdated(unsigned revision,
                              const QList<QTextEdit::ExtraSelection> selections,
                              const HeaderErrorDiagnosticWidgetCreator &creator,

src/plugins/cpptools/builtineditordocumentparser.cpp

@@ -77,19 +77,20 @@ void BuiltinEditorDocumentParser::updateImpl(const QFutureInterface<void> &futur
     QString projectConfigFile;
     LanguageFeatures features = LanguageFeatures::defaultFeatures();
 
-    baseState.projectPart = determineProjectPart(filePath(),
+    baseState.projectPartInfo = determineProjectPart(filePath(),
                                                     baseConfig,
                                                     baseState,
                                                     updateParams.activeProject,
                                                     updateParams.languagePreference,
                                                     updateParams.hasActiveProjectChanged);
+    emit projectPartInfoUpdated(baseState.projectPartInfo);
 
     if (state.forceSnapshotInvalidation) {
         invalidateSnapshot = true;
         state.forceSnapshotInvalidation = false;
     }
 
-    if (const ProjectPart::Ptr part = baseState.projectPart) {
+    if (const ProjectPart::Ptr part = baseState.projectPartInfo.projectPart) {
         configFile += part->toolchainDefines;
         configFile += overwrittenToolchainDefines(*part.data());
         configFile += part->projectDefines;

src/plugins/cpptools/builtineditordocumentprocessor.cpp

@@ -190,6 +190,8 @@ BuiltinEditorDocumentProcessor::BuiltinEditorDocumentProcessor(
             });
     }
 
+    connect(m_parser.data(), &BuiltinEditorDocumentParser::projectPartInfoUpdated,
+            this, &BaseEditorDocumentProcessor::projectPartInfoUpdated);
     connect(m_parser.data(), &BuiltinEditorDocumentParser::finished,
             this, &BuiltinEditorDocumentProcessor::onParserFinished);
     connect(&m_semanticInfoUpdater, &SemanticInfoUpdater::updated,

src/plugins/cpptools/cppmodelmanager_test.cpp

@@ -167,7 +167,7 @@ ProjectPart::Ptr projectPartOfEditorDocument(const QString &filePath)
 {
     auto *editorDocument = CppModelManager::instance()->cppEditorDocument(filePath);
     QTC_ASSERT(editorDocument, return ProjectPart::Ptr());
-    return editorDocument->processor()->parser()->projectPart();
+    return editorDocument->processor()->parser()->projectPartInfo().projectPart;
 }
 
 } // anonymous namespace

src/plugins/cpptools/cppprojectpartchooser.cpp

@@ -31,46 +31,99 @@
 namespace CppTools {
 namespace Internal {
 
-static bool isPreferredLanguage(const ProjectPart &projectPart, Language preference)
+class ProjectPartPrioritizer
 {
-    const bool isCProjectPart = projectPart.languageVersion <= ProjectPart::LatestCVersion;
+public:
-    return (preference == Language::C && isCProjectPart)
+    struct PrioritizedProjectPart
-        || (preference == Language::Cxx && !isCProjectPart);
+    {
-}
+        PrioritizedProjectPart(const ProjectPart::Ptr &projectPart, int priority)
+            : projectPart(projectPart) , priority(priority) {}
 
-static int priority(const ProjectPart &projectPart,
+        ProjectPart::Ptr projectPart;
+        int priority = 0;
+    };
+
+    ProjectPartPrioritizer(const QList<ProjectPart::Ptr> &projectParts,
                            const ProjectExplorer::Project *activeProject,
                            Language languagePreference)
-{
+        : m_projectParts(projectParts)
+        , m_activeProject(activeProject)
+        , m_languagePreference(languagePreference)
+    {
+        // Determine best project part
+        const QList<PrioritizedProjectPart> prioritized = prioritize();
+        m_projectPart = prioritized.first().projectPart;
+
+        // Determine ambiguity
+        m_isAmbiguous = prioritized.size() > 1
+                ? prioritized[0].priority == prioritized[1].priority
+                : false;
+    }
+
+    ProjectPart::Ptr projectPart()
+    {
+        return m_projectPart;
+    }
+
+    bool isAmbiguous() const
+    {
+        return m_isAmbiguous;
+    }
+
+private:
+    QList<PrioritizedProjectPart> prioritize()
+    {
+        // Prioritize
+        QList<PrioritizedProjectPart> prioritized = Utils::transform(m_projectParts,
+                [&](const ProjectPart::Ptr &projectPart) {
+            return PrioritizedProjectPart{projectPart, priority(*projectPart)};
+        });
+
+        // Sort according to priority
+        const auto lessThan = [&] (const PrioritizedProjectPart &p1,
+                                   const PrioritizedProjectPart &p2) {
+            return p1.priority > p2.priority;
+        };
+        std::stable_sort(prioritized.begin(), prioritized.end(), lessThan);
+
+        return prioritized;
+    }
+
+    int priority(const ProjectPart &projectPart) const
+    {
         int thePriority = 0;
 
-    if (projectPart.project == activeProject)
+        if (projectPart.project == m_activeProject)
             thePriority += 100;
 
         if (projectPart.selectedForBuilding)
             thePriority += 10;
 
-    if (isPreferredLanguage(projectPart, languagePreference))
+        if (isPreferredLanguage(projectPart))
             thePriority += 1;
 
         return thePriority;
-}
+    }
 
-static ProjectPart::Ptr chooseFromMultiple(const QList<ProjectPart::Ptr> &projectParts,
+    bool isPreferredLanguage(const ProjectPart &projectPart) const
-                                           const ProjectExplorer::Project *activeProject,
+    {
-                                           Language languagePreference)
+        const bool isCProjectPart = projectPart.languageVersion <= ProjectPart::LatestCVersion;
-{
+        return (m_languagePreference == Language::C && isCProjectPart)
-    QList<ProjectPart::Ptr> projectPartsPrioritized = projectParts;
+            || (m_languagePreference == Language::Cxx && !isCProjectPart);
-    const auto lessThan = [&] (const ProjectPart::Ptr &p1, const ProjectPart::Ptr &p2) {
+    }
-        return priority(*p1, activeProject, languagePreference)
-             > priority(*p2, activeProject, languagePreference);
-    };
-    std::stable_sort(projectPartsPrioritized.begin(), projectPartsPrioritized.end(), lessThan);
 
-    return projectPartsPrioritized.first();
+private:
-}
+    const QList<ProjectPart::Ptr> m_projectParts;
+    const ProjectExplorer::Project *m_activeProject = nullptr;
+    Language m_languagePreference = Language::Cxx;
 
-ProjectPart::Ptr ProjectPartChooser::choose(const QString &filePath,
+    // Results
+    ProjectPart::Ptr m_projectPart;
+    bool m_isAmbiguous = false;
+};
+
+ProjectPartInfo ProjectPartChooser::choose(
+        const QString &filePath,
         const ProjectPart::Ptr &currentProjectPart,
         const ProjectPart::Ptr &manuallySetProjectPart,
         bool stickToPreviousProjectPart,
@@ -83,30 +136,39 @@ ProjectPart::Ptr ProjectPartChooser::choose(const QString &filePath,
     QTC_CHECK(m_fallbackProjectPart);
 
     if (manuallySetProjectPart)
-        return manuallySetProjectPart;
+        return {manuallySetProjectPart, ProjectPartInfo::NoHint};
 
     ProjectPart::Ptr projectPart = currentProjectPart;
+    ProjectPartInfo::Hint hint = ProjectPartInfo::NoHint;
 
     QList<ProjectPart::Ptr> projectParts = m_projectPartsForFile(filePath);
     if (projectParts.isEmpty()) {
         if (projectPart && stickToPreviousProjectPart)
             // File is not directly part of any project, but we got one before. We will re-use it,
             // because re-calculating this can be expensive when the dependency table is big.
-            return projectPart;
+            return {projectPart, ProjectPartInfo::NoHint};
 
         // Fall-back step 1: Get some parts through the dependency table:
         projectParts = m_projectPartsFromDependenciesForFile(filePath);
-        if (projectParts.isEmpty())
+        if (projectParts.isEmpty()) {
             // Fall-back step 2: Use fall-back part from the model manager:
             projectPart = m_fallbackProjectPart();
-        else
+            hint = ProjectPartInfo::IsFallbackMatch;
-            projectPart = chooseFromMultiple(projectParts, activeProject, languagePreference);
         } else {
-        if (projectHasChanged || !projectParts.contains(projectPart))
+            ProjectPartPrioritizer prioritizer(projectParts, activeProject, languagePreference);
-            projectPart = chooseFromMultiple(projectParts, activeProject, languagePreference);
+            projectPart = prioritizer.projectPart();
+        }
+    } else {
+        if (projectHasChanged || !projectParts.contains(projectPart)) {
+            ProjectPartPrioritizer prioritizer(projectParts, activeProject, languagePreference);
+            projectPart = prioritizer.projectPart();
+            hint = prioritizer.isAmbiguous()
+                    ? ProjectPartInfo::IsAmbiguousMatch
+                    : ProjectPartInfo::NoHint;
+        }
     }
 
-    return projectPart;
+    return {projectPart, hint};
 }
 
 void ProjectPartChooser::setFallbackProjectPart(const FallBackProjectPart &getter)

src/plugins/cpptools/cppprojectpartchooser.h

@@ -25,7 +25,7 @@
 
 #pragma once
 
-#include "cpplanguage.h"
+#include "cpptools_utils.h"
 #include "projectpart.h"
 
 #include <functional>
@@ -48,7 +48,8 @@ public:
     void setProjectPartsForFile(const ProjectPartsForFile &getter);
     void setProjectPartsFromDependenciesForFile(const ProjectPartsFromDependenciesForFile &getter);
 
-    ProjectPart::Ptr choose(const QString &filePath,
+    ProjectPartInfo choose(
+            const QString &filePath,
             const ProjectPart::Ptr &currentProjectPart,
             const ProjectPart::Ptr &manuallySetProjectPart,
             bool stickToPreviousProjectPart,

src/plugins/cpptools/cpptools.pro

@@ -34,7 +34,6 @@ HEADERS += \
     cppfunctionsfilter.h \
     cppincludesfilter.h \
     cppindexingsupport.h \
-    cpplanguage.h \
     cpplocalsymbols.h \
     cpplocatordata.h \
     cpplocatorfilter.h \
@@ -50,6 +49,7 @@ HEADERS += \
     cppsemanticinfoupdater.h \
     cppsourceprocessor.h \
     cpptools_global.h \
+    cpptools_utils.h \
     cpptoolsconstants.h \
     cpptoolsjsextension.h \
     cpptoolsplugin.h \

src/plugins/cpptools/cpptools.qbs

@@ -61,7 +61,6 @@ Project {
             "cppfunctionsfilter.cpp", "cppfunctionsfilter.h",
             "cppincludesfilter.cpp", "cppincludesfilter.h",
             "cppindexingsupport.cpp", "cppindexingsupport.h",
-            "cpplanguage.h",
             "cpplocalsymbols.cpp", "cpplocalsymbols.h",
             "cpplocatordata.cpp", "cpplocatordata.h",
             "cpplocatorfilter.cpp", "cpplocatorfilter.h",
@@ -81,6 +80,7 @@ Project {
             "cpptoolsbridgeqtcreatorimplementation.cpp", "cpptoolsbridgeqtcreatorimplementation.h",
             "cpptools.qrc",
             "cpptools_global.h",
+            "cpptools_utils.h",
             "cpptoolsconstants.h",
             "cpptoolsjsextension.cpp", "cpptoolsjsextension.h",
             "cpptoolsplugin.cpp", "cpptoolsplugin.h",

src/plugins/cpptools/cpptools_utils.h

@@ -25,8 +25,23 @@
 
 #pragma once
 
+#include "projectpart.h"
+
 namespace CppTools {
 
 enum class Language { C, Cxx };
 
+class ProjectPartInfo {
+public:
+    enum Hint {
+        NoHint,
+        IsFallbackMatch,
+        IsAmbiguousMatch
+    };
+
+public:
+    ProjectPart::Ptr projectPart;
+    Hint hint;
+};
+
 } // namespace CppTools

src/plugins/cpptools/cpptoolsbridgeqtcreatorimplementation.cpp

@@ -47,7 +47,7 @@ namespace {
 CppTools::ProjectPart::Ptr projectPartForFile(const QString &filePath)
 {
     if (const auto parser = BaseEditorDocumentParser::get(filePath))
-        return parser->projectPart();
+        return parser->projectPartInfo().projectPart;
 
     return CppTools::ProjectPart::Ptr();
 }

tests/unit/unittest/cppprojectpartchooser-test.cpp

@@ -25,12 +25,13 @@
 
 #include "googletest.h"
 
-#include <cpptools/cpplanguage.h>
 #include <cpptools/cppprojectpartchooser.h>
+#include <cpptools/cpptools_utils.h>
 #include <cpptools/projectpart.h>
 
 using CppTools::Internal::ProjectPartChooser;
 using CppTools::ProjectPart;
+using CppTools::ProjectPartInfo;
 using CppTools::Language;
 
 using testing::Eq;
@@ -41,7 +42,7 @@ class ProjectPartChooser : public ::testing::Test
 {
 protected:
     void SetUp() override;
-    const ProjectPart::Ptr choose() const;
+    const ProjectPartInfo choose() const;
 
     static QList<ProjectPart::Ptr> createProjectPartsWithDifferentProjects();
     static QList<ProjectPart::Ptr> createCAndCxxProjectParts();
@@ -65,7 +66,7 @@ TEST_F(ProjectPartChooser, ChooseManuallySet)
 {
     manuallySetProjectPart.reset(new ProjectPart);
 
-    const ProjectPart::Ptr chosen = choose();
+    const ProjectPart::Ptr chosen = choose().projectPart;
 
     ASSERT_THAT(chosen, Eq(manuallySetProjectPart));
 }
@@ -76,7 +77,7 @@ TEST_F(ProjectPartChooser, ForMultipleChoosePrevious)
     projectPartsForFile += otherProjectPart;
     projectPartsForFile += currentProjectPart;
 
-    const ProjectPart::Ptr chosen = choose();
+    const ProjectPart::Ptr chosen = choose().projectPart;
 
     ASSERT_THAT(chosen, Eq(currentProjectPart));
 }
@@ -88,7 +89,7 @@ TEST_F(ProjectPartChooser, ForMultipleChooseFromActiveProject)
     projectPartsForFile += projectParts;
     activeProject = secondProjectPart->project;
 
-    const ProjectPart::Ptr chosen = choose();
+    const ProjectPart::Ptr chosen = choose().projectPart;
 
     ASSERT_THAT(chosen, Eq(secondProjectPart));
 }
@@ -102,7 +103,7 @@ TEST_F(ProjectPartChooser, ForMultiplePreferSelectedForBuilding)
     projectPartsForFile += firstProjectPart;
     projectPartsForFile += secondProjectPart;
 
-    const ProjectPart::Ptr chosen = choose();
+    const ProjectPart::Ptr chosen = choose().projectPart;
 
     ASSERT_THAT(chosen, Eq(secondProjectPart));
 }
@@ -114,7 +115,7 @@ TEST_F(ProjectPartChooser, ForMultipleFromDependenciesChooseFromActiveProject)
     projectPartsFromDependenciesForFile += projectParts;
     activeProject = secondProjectPart->project;
 
-    const ProjectPart::Ptr chosen = choose();
+    const ProjectPart::Ptr chosen = choose().projectPart;
 
     ASSERT_THAT(chosen, Eq(secondProjectPart));
 }
@@ -129,7 +130,7 @@ TEST_F(ProjectPartChooser, ForMultipleCheckIfActiveProjectChanged)
     activeProject = secondProjectPart->project;
     projectHasChanged = true;
 
-    const ProjectPart::Ptr chosen = choose();
+    const ProjectPart::Ptr chosen = choose().projectPart;
 
     ASSERT_THAT(chosen, Eq(secondProjectPart));
 }
@@ -140,7 +141,7 @@ TEST_F(ProjectPartChooser, ForMultipleAndAmbigiousHeaderPreferCProjectPart)
     projectPartsForFile = createCAndCxxProjectParts();
     const ProjectPart::Ptr cProjectPart = projectPartsForFile.at(0);
 
-    const ProjectPart::Ptr chosen = choose();
+    const ProjectPart::Ptr chosen = choose().projectPart;
 
     ASSERT_THAT(chosen, Eq(cProjectPart));
 }
@@ -151,16 +152,27 @@ TEST_F(ProjectPartChooser, ForMultipleAndAmbigiousHeaderPreferCxxProjectPart)
     projectPartsForFile = createCAndCxxProjectParts();
     const ProjectPart::Ptr cxxProjectPart = projectPartsForFile.at(1);
 
-    const ProjectPart::Ptr chosen = choose();
+    const ProjectPart::Ptr chosen = choose().projectPart;
 
     ASSERT_THAT(chosen, Eq(cxxProjectPart));
 }
 
+TEST_F(ProjectPartChooser, IndicateMultiple)
+{
+    const ProjectPart::Ptr p1{new ProjectPart};
+    const ProjectPart::Ptr p2{new ProjectPart};
+    projectPartsForFile += { p1, p2 };
+
+    const ProjectPartInfo::Hint hint = choose().hint;
+
+    ASSERT_THAT(hint, Eq(ProjectPartInfo::Hint::IsAmbiguousMatch));
+}
+
 TEST_F(ProjectPartChooser, IfProjectIsGoneStickToPrevious) // Built-in Code Model
 {
     stickToPreviousProjectPart = true;
 
-    const ProjectPart::Ptr chosen = choose();
+    const ProjectPart::Ptr chosen = choose().projectPart;
 
     ASSERT_THAT(chosen, Eq(currentProjectPart));
 }
@@ -170,7 +182,7 @@ TEST_F(ProjectPartChooser, IfProjectIsGoneDoNotStickToPrevious) // Clang Code Mo
     currentProjectPart.clear();
     stickToPreviousProjectPart = true;
 
-    const ProjectPart::Ptr chosen = choose();
+    const ProjectPart::Ptr chosen = choose().projectPart;
 
     ASSERT_THAT(chosen, Eq(ProjectPart::Ptr()));
 }
@@ -180,7 +192,7 @@ TEST_F(ProjectPartChooser, ForMultipleChooseNewIfPreviousIsGone)
     const ProjectPart::Ptr newProjectPart{new ProjectPart};
     projectPartsForFile += newProjectPart;
 
-    const ProjectPart::Ptr chosen = choose();
+    const ProjectPart::Ptr chosen = choose().projectPart;
 
     ASSERT_THAT(chosen, Eq(newProjectPart));
 }
@@ -190,7 +202,7 @@ TEST_F(ProjectPartChooser, FallbackToProjectPartFromDependencies)
     const ProjectPart::Ptr fromDependencies{new ProjectPart};
     projectPartsFromDependenciesForFile += fromDependencies;
 
-    const ProjectPart::Ptr chosen = choose();
+    const ProjectPart::Ptr chosen = choose().projectPart;
 
     ASSERT_THAT(chosen, Eq(fromDependencies));
 }
@@ -199,11 +211,20 @@ TEST_F(ProjectPartChooser, FallbackToProjectPartFromModelManager)
 {
     fallbackProjectPart.reset(new ProjectPart);
 
-    const ProjectPart::Ptr chosen = choose();
+    const ProjectPart::Ptr chosen = choose().projectPart;
 
     ASSERT_THAT(chosen, Eq(fallbackProjectPart));
 }
 
+TEST_F(ProjectPartChooser, IndicateFallbacktoProjectPartFromModelManager)
+{
+    fallbackProjectPart.reset(new ProjectPart);
+
+    const ProjectPartInfo::Hint hint = choose().hint;
+
+    ASSERT_THAT(hint, Eq(ProjectPartInfo::Hint::IsFallbackMatch));
+}
+
 void ProjectPartChooser::SetUp()
 {
     chooser.setFallbackProjectPart([&](){
@@ -217,7 +238,7 @@ void ProjectPartChooser::SetUp()
     });
 }
 
-const ProjectPart::Ptr ProjectPartChooser::choose() const
+const ProjectPartInfo ProjectPartChooser::choose() const
 {
     return chooser.choose(filePath,
                           currentProjectPart,