ClangCodeModel: fix crash on followSymbol

Big files are loaded in chunks inside a QEventLoop. If follow symbol is
triggered via mouse and opens such a big file and the mouse is moved
while loading that file ClangdFollowSymbol got deleted while opening the
file in ClangdClient::followSymbol. Instead of the hard deletion just
cancel that follow symbol operation and make sure done is emitted
afterwards. The handling of that done signal takes care of the deletion
of that follow symbol operation.

Change-Id: Iba4ad6abb541186c2f26506f82fe1bc582818fca
Reviewed-by: <[email protected]>
Reviewed-by: Christian Kandeler <[email protected]>

2 files changed, 33 insertions, 0 deletions

diff --git a/src/plugins/clangcodemodel/test/clangdtests.cpp b/src/plugins/clangcodemodel/test/clangdtests.cpp
index 5a52a207853..ceaf25787e8 100644
--- a/src/plugins/clangcodemodel/test/clangdtests.cpp
+++ b/src/plugins/clangcodemodel/test/clangdtests.cpp
@@ -4,6 +4,7 @@
 #include "clangdtests.h"
 
 #include "../clangdclient.h"
+#include "../clangdfollowsymbol.h"
 #include "../clangmodelmanagersupport.h"
 
 #include <coreplugin/editormanager/editormanager.h>
@@ -428,6 +429,37 @@ void ClangdTestFollowSymbol::test()
     QCOMPARE(actualLink.targetColumn + 1, targetColumn);
 }
 
+// Make sure it is safe to call follow symbol in a follow symbol handler. Since follow symbol
+// potentially opens a file that gets loaded in chunks which handles user events inbetween
+// the chunks we can potentially call a follow symbol while currently handling another one.
+void ClangdTestFollowSymbol::testFollowSymbolInHandler()
+{
+    TextEditor::TextDocument *const doc = document("header.h");
+    QVERIFY(doc);
+    QTimer timer;
+    timer.setSingleShot(true);
+    QEventLoop loop;
+    QTextCursor cursor(doc->document());
+    const int pos = Text::positionInText(doc->document(), 48, 9);
+    cursor.setPosition(pos);
+    QObject::connect(&timer, &QTimer::timeout, &loop, &QEventLoop::quit);
+
+    bool deleted = false;
+
+    const auto handler = [&](const Link &) {
+        client()->followSymbol(doc, cursor, nullptr, [&](const Link &) { loop.quit(); }, true,
+                               FollowTo::SymbolDef, false);
+        QVERIFY(!deleted);
+    };
+
+    client()->followSymbol(doc, cursor, nullptr, handler, true, FollowTo::SymbolDef, false);
+    QVERIFY(client()->currentFollowSymbolOperation());
+    connect(client()->currentFollowSymbolOperation(), &QObject::destroyed, [&] { deleted = true; });
+    timer.start(10000);
+    loop.exec();
+    QVERIFY(timer.isActive());
+    timer.stop();
+}
 
 ClangdTestLocalReferences::ClangdTestLocalReferences()
 {
diff --git a/src/plugins/clangcodemodel/test/clangdtests.h b/src/plugins/clangcodemodel/test/clangdtests.h
index 90f4eca45af..92bf4efe90c 100644
--- a/src/plugins/clangcodemodel/test/clangdtests.h
+++ b/src/plugins/clangcodemodel/test/clangdtests.h
@@ -86,6 +86,7 @@ public:
 private slots:
     void test_data();
     void test();
+    void testFollowSymbolInHandler();
 };
 
 class ClangdTestLocalReferences : public ClangdTest