CompilationDB: Reparse only on actual project file change

Fixes: QTCREATORBUG-22574
Change-Id: I39fe58f96c1ff9118405be225f39e5348304222e
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

4 files changed, 49 insertions, 24 deletions

diff --git a/src/plugins/compilationdatabaseprojectmanager/compilationdatabaseproject.cpp b/src/plugins/compilationdatabaseprojectmanager/compilationdatabaseproject.cpp
index ec16d72bd5..9bb7cec9fc 100644
--- a/src/plugins/compilationdatabaseprojectmanager/compilationdatabaseproject.cpp
+++ b/src/plugins/compilationdatabaseprojectmanager/compilationdatabaseproject.cpp
@@ -406,10 +406,11 @@ CompilationDatabaseProject::CompilationDatabaseProject(const Utils::FilePath &pr
     m_kit.reset(KitManager::defaultKit()->clone());
     addTargetForKit(m_kit.get());
 
-    connect(this,
-            &CompilationDatabaseProject::rootProjectDirectoryChanged,
-            m_parseDelay,
-            QOverload<>::of(&QTimer::start));
+    connect(this, &CompilationDatabaseProject::rootProjectDirectoryChanged,
+            this, [this] {
+        m_projectFileHash.clear();
+        m_parseDelay->start();
+    });
 
     setExtraProjectFiles(
         {projectFile.stringAppended(Constants::COMPILATIONDATABASEPROJECT_FILES_SUFFIX)});
@@ -458,11 +459,13 @@ void CompilationDatabaseProject::reparseProject()
                                        m_mimeBinaryCache,
                                        guardParsingRun(),
                                        this);
-    connect(m_parser, &CompilationDbParser::finished, this, [this](bool success) {
-        if (success)
+    connect(m_parser, &CompilationDbParser::finished, this, [this](ParseResult result) {
+        m_projectFileHash = m_parser->projectFileHash();
+        if (result == ParseResult::Success)
             buildTreeAndProjectParts();
         m_parser = nullptr;
     });
+    m_parser->setPreviousProjectFileHash(m_projectFileHash);
     m_parser->start();
 }
 
diff --git a/src/plugins/compilationdatabaseprojectmanager/compilationdatabaseproject.h b/src/plugins/compilationdatabaseprojectmanager/compilationdatabaseproject.h
index ca829f312a..d5716c061b 100644
--- a/src/plugins/compilationdatabaseprojectmanager/compilationdatabaseproject.h
+++ b/src/plugins/compilationdatabaseprojectmanager/compilationdatabaseproject.h
@@ -70,6 +70,7 @@ private:
     std::unique_ptr<CppTools::CppProjectUpdater> m_cppCodeModelUpdater;
     std::unique_ptr<ProjectExplorer::Kit> m_kit;
     MimeBinaryCache m_mimeBinaryCache;
+    QByteArray m_projectFileHash;
     QTimer * const m_parseDelay;
     CompilationDbParser *m_parser = nullptr;
 };
diff --git a/src/plugins/compilationdatabaseprojectmanager/compilationdbparser.cpp b/src/plugins/compilationdatabaseprojectmanager/compilationdbparser.cpp
index 6c91311898..374c245b23 100644
--- a/src/plugins/compilationdatabaseprojectmanager/compilationdbparser.cpp
+++ b/src/plugins/compilationdatabaseprojectmanager/compilationdbparser.cpp
@@ -31,6 +31,7 @@
 #include <utils/mimetypes/mimetype.h>
 #include <utils/runextensions.h>
 
+#include <QCryptographicHash>
 #include <QDir>
 #include <QFileInfo>
 #include <QJsonArray>
@@ -59,12 +60,27 @@ CompilationDbParser::CompilationDbParser(const QString &projectName,
     connect(&m_parserWatcher, &QFutureWatcher<void>::finished, this, [this] {
         m_dbContents = m_parserWatcher.result();
         if (!m_treeScanner || m_treeScanner->isFinished())
-            finish();
+            finish(ParseResult::Success);
     });
 }
 
 void CompilationDbParser::start()
 {
+    // Check hash first.
+    QFile file(m_projectFilePath.toString());
+    if (!file.open(QIODevice::ReadOnly)) {
+        finish(ParseResult::Failure);
+        return;
+    }
+    m_projectFileContents = file.readAll();
+    const QByteArray newHash = QCryptographicHash::hash(m_projectFileContents,
+                                                        QCryptographicHash::Sha1);
+    if (m_projectFileHash == newHash) {
+        finish(ParseResult::Cached);
+        return;
+    }
+    m_projectFileHash = newHash;
+
     // Thread 1: Scan disk.
     if (!m_rootPath.isEmpty()) {
         m_treeScanner = new TreeScanner(this);
@@ -95,7 +111,7 @@ void CompilationDbParser::start()
                                        "CompilationDatabase.Scan.Tree");
         connect(m_treeScanner, &TreeScanner::finished, this, [this] {
             if (m_parserWatcher.isFinished())
-                finish();
+                finish(ParseResult::Success);
         });
     }
 
@@ -126,9 +142,9 @@ QList<FileNode *> CompilationDbParser::scannedFiles() const
             ? m_treeScanner->release() : QList<FileNode *>();
 }
 
-void CompilationDbParser::finish()
+void CompilationDbParser::finish(ParseResult result)
 {
-    emit finished(true);
+    emit finished(result);
     deleteLater();
 }
 
@@ -158,24 +174,20 @@ static FilePath jsonObjectFilename(const QJsonObject &object)
     return fileName;
 }
 
-static std::vector<DbEntry> readJsonObjects(const QString &filePath)
+std::vector<DbEntry> CompilationDbParser::readJsonObjects() const
 {
     std::vector<DbEntry> result;
-    QFile file(filePath);
-    if (!file.open(QIODevice::ReadOnly))
-        return result;
 
-    const QByteArray contents = file.readAll();
-    int objectStart = contents.indexOf('{');
-    int objectEnd = contents.indexOf('}', objectStart + 1);
+    int objectStart = m_projectFileContents.indexOf('{');
+    int objectEnd = m_projectFileContents.indexOf('}', objectStart + 1);
 
     QSet<QString> flagsCache;
     while (objectStart >= 0 && objectEnd >= 0) {
         const QJsonDocument document = QJsonDocument::fromJson(
-                    contents.mid(objectStart, objectEnd - objectStart + 1));
+                    m_projectFileContents.mid(objectStart, objectEnd - objectStart + 1));
         if (document.isNull()) {
             // The end was found incorrectly, search for the next one.
-            objectEnd = contents.indexOf('}', objectEnd + 1);
+            objectEnd = m_projectFileContents.indexOf('}', objectEnd + 1);
             continue;
         }
 
@@ -185,8 +197,8 @@ static std::vector<DbEntry> readJsonObjects(const QString &filePath)
                                                      fileName.toFileInfo().baseName());
         result.push_back({flags, fileName, object["directory"].toString()});
 
-        objectStart = contents.indexOf('{', objectEnd + 1);
-        objectEnd = contents.indexOf('}', objectStart + 1);
+        objectStart = m_projectFileContents.indexOf('{', objectEnd + 1);
+        objectEnd = m_projectFileContents.indexOf('}', objectStart + 1);
     }
 
     return result;
@@ -217,7 +229,7 @@ QStringList readExtraFiles(const QString &filePath)
 DbContents CompilationDbParser::parseProject()
 {
     DbContents dbContents;
-    dbContents.entries = readJsonObjects(m_projectFilePath.toString());
+    dbContents.entries = readJsonObjects();
     dbContents.extraFileName = m_projectFilePath.toString() +
             Constants::COMPILATIONDATABASEPROJECT_FILES_SUFFIX;
     dbContents.extras = readExtraFiles(dbContents.extraFileName);
diff --git a/src/plugins/compilationdatabaseprojectmanager/compilationdbparser.h b/src/plugins/compilationdatabaseprojectmanager/compilationdbparser.h
index fe3e319076..ac5fbb0afb 100644
--- a/src/plugins/compilationdatabaseprojectmanager/compilationdbparser.h
+++ b/src/plugins/compilationdatabaseprojectmanager/compilationdbparser.h
@@ -46,6 +46,8 @@ class TreeScanner;
 namespace CompilationDatabaseProjectManager {
 namespace Internal {
 
+enum class ParseResult { Success, Failure, Cached };
+
 class CompilationDbParser : public QObject
 {
     Q_OBJECT
@@ -57,6 +59,10 @@ public:
                                  ProjectExplorer::Project::ParseGuard &&guard,
                                  QObject *parent = nullptr);
 
+
+    void setPreviousProjectFileHash(const QByteArray &fileHash) { m_projectFileHash = fileHash; }
+    QByteArray projectFileHash() const { return m_projectFileHash; }
+
     void start();
     void stop();
 
@@ -68,11 +74,12 @@ public:
     }
 
 signals:
-    void finished(bool success);
+    void finished(ParseResult result);
 
 private:
-    void finish();
+    void finish(ParseResult result);
     DbContents parseProject();
+    std::vector<DbEntry> readJsonObjects() const;
 
     const QString m_projectName;
     const Utils::FilePath m_projectFilePath;
@@ -81,6 +88,8 @@ private:
     ProjectExplorer::TreeScanner *m_treeScanner = nullptr;
     QFutureWatcher<DbContents> m_parserWatcher;
     DbContents m_dbContents;
+    QByteArray m_projectFileContents;
+    QByteArray m_projectFileHash;
 
     ProjectExplorer::Project::ParseGuard m_guard;
 };