Try harder to get context help in presence of diagnostics

- even if there are diagnostics still try to retrieve symbol info
  and help
- fall back to text based keyword extraction in case code model
  info fails
- if both a code model tool tip (e.g. function signature or type)
  and help are available, show both

Task-number: QTCREATORBUG-15959
Change-Id: Id85a223c24849ead1b25d63776d64a7da1cc73ef
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

1 files changed, 90 insertions, 25 deletions

diff --git a/src/plugins/clangcodemodel/clanghoverhandler.cpp b/src/plugins/clangcodemodel/clanghoverhandler.cpp
index be59805170..1dc294cab5 100644
--- a/src/plugins/clangcodemodel/clanghoverhandler.cpp
+++ b/src/plugins/clangcodemodel/clanghoverhandler.cpp
@@ -28,6 +28,7 @@
 #include <coreplugin/helpmanager.h>
 #include <cpptools/baseeditordocumentprocessor.h>
 #include <cpptools/cppmodelmanager.h>
+#include <cpptools/cpptoolsreuse.h>
 #include <cpptools/editordocumenthandle.h>
 #include <texteditor/texteditor.h>
 
@@ -37,6 +38,7 @@
 
 #include <QFutureWatcher>
 #include <QLoggingCategory>
+#include <QRegularExpression>
 #include <QTextCodec>
 #include <QVBoxLayout>
 
@@ -105,6 +107,79 @@ ClangHoverHandler::~ClangHoverHandler()
     abort();
 }
 
+static int skipChars(QTextCursor *tc,
+                      QTextCursor::MoveOperation op,
+                      int offset,
+                      std::function<bool(const QChar &)> skip)
+{
+    const QTextDocument *doc = tc->document();
+    QChar ch = doc->characterAt(tc->position() + offset);
+    if (ch.isNull())
+        return 0;
+    int count = 0;
+    while (skip(ch)) {
+        if (tc->movePosition(op))
+            ++count;
+        else
+            break;
+        ch = doc->characterAt(tc->position() + offset);
+    }
+    return count;
+}
+
+static int skipCharsForward(QTextCursor *tc, std::function<bool(const QChar &)> skip)
+{
+    return skipChars(tc, QTextCursor::NextCharacter, 0, skip);
+}
+
+static int skipCharsBackward(QTextCursor *tc, std::function<bool(const QChar &)> skip)
+{
+    return skipChars(tc, QTextCursor::PreviousCharacter, -1, skip);
+}
+
+static QStringList fallbackWords(QTextDocument *document, int pos)
+{
+    const auto isSpace = [](const QChar &c) { return c.isSpace(); };
+    const auto isColon = [](const QChar &c) { return c == ':'; };
+    const auto isValidIdentifierChar = [document](const QTextCursor &tc) {
+        return CppTools::isValidIdentifierChar(document->characterAt(tc.position()));
+    };
+    // move to the end
+    QTextCursor endCursor(document);
+    endCursor.setPosition(pos);
+    do {
+        CppTools::moveCursorToEndOfIdentifier(&endCursor);
+        // possibly skip ::
+        QTextCursor temp(endCursor);
+        skipCharsForward(&temp, isSpace);
+        const int colons = skipCharsForward(&temp, isColon);
+        skipCharsForward(&temp, isSpace);
+        if (colons == 2 && isValidIdentifierChar(temp))
+            endCursor = temp;
+    } while (isValidIdentifierChar(endCursor));
+
+    QStringList results;
+    QTextCursor startCursor(endCursor);
+    do {
+        CppTools::moveCursorToStartOfIdentifier(&startCursor);
+        if (startCursor.position() == endCursor.position())
+            break;
+        QTextCursor temp(endCursor);
+        temp.setPosition(startCursor.position(), QTextCursor::KeepAnchor);
+        results.append(temp.selectedText().remove(QRegularExpression("\\s")));
+        // possibly skip ::
+        temp = startCursor;
+        skipCharsBackward(&temp, isSpace);
+        const int colons = skipCharsBackward(&temp, isColon);
+        skipCharsBackward(&temp, isSpace);
+        if (colons == 2
+                && CppTools::isValidIdentifierChar(document->characterAt(temp.position() - 1))) {
+            startCursor = temp;
+        }
+    } while (!isValidIdentifierChar(startCursor));
+    return results;
+}
+
 void ClangHoverHandler::identifyMatch(TextEditorWidget *editorWidget,
                                       int pos,
                                       BaseHoverHandler::ReportPriority report)
@@ -118,8 +193,6 @@ void ClangHoverHandler::identifyMatch(TextEditorWidget *editorWidget,
         qCDebug(hoverLog) << "Checking for diagnostic at" << pos;
         setPriority(Priority_Diagnostic);
         m_cursorPosition = pos;
-        report(priority());
-        return;
     }
 
     // Check for tooltips (async)
@@ -128,17 +201,25 @@ void ClangHoverHandler::identifyMatch(TextEditorWidget *editorWidget,
         qCDebug(hoverLog) << "Requesting tooltip info at" << pos;
         m_reportPriority = report;
         m_futureWatcher.reset(new QFutureWatcher<CppTools::ToolTipInfo>());
-        QObject::connect(m_futureWatcher.data(), &QFutureWatcherBase::finished, [this]() {
-            if (m_futureWatcher->isCanceled())
-                m_reportPriority(Priority_None);
-            else
-                processToolTipInfo(m_futureWatcher->result());
-        });
+        const QStringList fallback = fallbackWords(editorWidget->document(), pos);
+        QObject::connect(m_futureWatcher.data(),
+                         &QFutureWatcherBase::finished,
+                         [this, fallback]() {
+                             if (m_futureWatcher->isCanceled()) {
+                                 m_reportPriority(Priority_None);
+                             } else {
+                                 CppTools::ToolTipInfo info = m_futureWatcher->result();
+                                 qCDebug(hoverLog)
+                                     << "Appending word-based fallback lookup" << fallback;
+                                 info.qDocIdCandidates += fallback;
+                                 processToolTipInfo(info);
+                             }
+                         });
         m_futureWatcher->setFuture(future);
         return;
     }
 
-    report(Priority_None); // Ops, something went wrong.
+    report(priority()); // Ops, something went wrong.
 }
 
 void ClangHoverHandler::abort()
@@ -198,22 +279,6 @@ void ClangHoverHandler::processToolTipInfo(const CppTools::ToolTipInfo &info)
     m_reportPriority(priority());
 }
 
-void ClangHoverHandler::decorateToolTip()
-{
-    if (priority() == Priority_Diagnostic)
-        return;
-
-    if (Qt::mightBeRichText(toolTip()))
-        setToolTip(toolTip().toHtmlEscaped());
-
-    const HelpItem &help = lastHelpItemIdentified();
-    if (help.isValid()) {
-        const QString text = CppTools::CppHoverHandler::tooltipTextForHelpItem(help);
-        if (!text.isEmpty())
-            setToolTip(text);
-    }
-}
-
 void ClangHoverHandler::operateTooltip(TextEditor::TextEditorWidget *editorWidget,
                                        const QPoint &point)
 {