ClangFormat: Do not refuse to build against unpatched clang

The plugin builds just fine and should be mostly (fully?) functional with
upstream clang, so it seems excessive to force-disable it entirely for
everybody not using our custom patch.

Change-Id: Id6a179c20325290a8205218c9514a16c1adc9076
Reviewed-by: hjk <hjk@qt.io>

README.md

@@ -209,7 +209,7 @@ The ClangFormat plugin depends on the additional patch
 
     https://code.qt.io/cgit/clang/llvm-project.git/commit/?h=release_100-based&id=9b992a0f7f160dd6c75f20a4dcfcf7c60a4894df
 
-While the plugin builds without it, it will be disabled on start with an error message.
+While the plugin builds without it, it might not be fully functional.
 
 Note that the plugin is disabled by default.
 

src/plugins/clangformat/clangformatplugin.cpp

@@ -59,6 +59,7 @@
 #include <clang/Format/Format.h>
 
 #include <utils/algorithm.h>
+#include <utils/infobar.h>
 
 #include <QAction>
 #include <QDebug>
@@ -70,7 +71,6 @@ using namespace ProjectExplorer;
 
 namespace ClangFormat {
 
-#ifdef KEEP_LINE_BREAKS_FOR_NON_EMPTY_LINES_BACKPORTED
 class ClangFormatStyleFactory : public CppTools::CppCodeStylePreferencesFactory
 {
 public:
@@ -101,13 +101,11 @@ static void replaceCppCodeStyle()
     ICodeStylePreferencesFactory *factory = new ClangFormatStyleFactory();
     TextEditorSettings::registerCodeStyleFactory(factory);
 }
-#endif
 
 bool ClangFormatPlugin::initialize(const QStringList &arguments, QString *errorString)
 {
     Q_UNUSED(arguments)
     Q_UNUSED(errorString)
-#ifdef KEEP_LINE_BREAKS_FOR_NON_EMPTY_LINES_BACKPORTED
     replaceCppCodeStyle();
 
     Core::ActionContainer *contextMenu = Core::ActionManager::actionContainer(
@@ -151,18 +149,25 @@ bool ClangFormatPlugin::initialize(const QStringList &arguments, QString *errorS
                         openClangFormatConfigAction->setData(doc->filePath().toString());
                 });
     }
-    return true;
-#else
+#ifndef KEEP_LINE_BREAKS_FOR_NON_EMPTY_LINES_BACKPORTED
 #ifdef _MSC_VER
 #pragma message( \
-    "ClangFormat: building dummy plugin due to unmodified Clang, see README.md for more info")
+    "ClangFormat: building against unmodified Clang, see README.md for more info")
 #else
-#warning ClangFormat: building dummy plugin due to unmodified Clang, see README.md for more info
+#warning ClangFormat: building against unmodified Clang, see README.md for more info
 #endif
-    *errorString = "Disabling ClangFormat plugin as it has not been built against a modified Clang's libFormat."
-                   "For more information see the Qt Creator README at "
-                   "https://code.qt.io/cgit/qt-creator/qt-creator.git/tree/README.md";
-    return false;
+    static const char clangFormatFormatWarningKey[] = "ClangFormatFormatWarning";
+    if (!Core::ICore::infoBar()->canInfoBeAdded(clangFormatFormatWarningKey))
+        return true;
+    Utils::InfoBarEntry
+        info(clangFormatFormatWarningKey,
+             tr("The ClangFormat plugin has been built against an unmodified Clang. "
+                "You might experience formatting glitches in certain circumstances. "
+                "See https://code.qt.io/cgit/qt-creator/qt-creator.git/tree/README.md for more "
+                 "information."),
+             Utils::InfoBarEntry::GlobalSuppression::Enabled);
+    Core::ICore::infoBar()->addInfo(info);
+    return true;
 #endif
 }