ClangCodeModel: Properly display clangd auxiliary diagnostic messages

... in text marks.
The main message can be followed by additional messages, separated by
pairs of newlines. Properly parse their contents and also display them
as clickable links, if applicable.

Change-Id: I341ce0a6bf0e628dfabdb3806fb8ef1b8ca019c6
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/clangcodemodel/clangtextmark.cpp

@@ -48,6 +48,8 @@
 #include <QApplication>
 #include <QClipboard>
 #include <QLayout>
+#include <QRegularExpression>
+#include <QRegularExpressionMatch>
 #include <QString>
 
 using namespace CppEditor;
@@ -317,7 +319,46 @@ ClangBackEnd::DiagnosticContainer convertDiagnostic(const ClangdDiagnostic &src,
     ClangBackEnd::DiagnosticContainer target;
     target.ranges.append(convertRange(filePath, src.range()));
     target.location = target.ranges.first().start;
-    target.text = src.message();
+    const QStringList messages = src.message().split("\n\n", Qt::SkipEmptyParts);
+    if (!messages.isEmpty())
+        target.text = messages.first();
+    for (int i = 1; i < messages.size(); ++i) {
+        QString auxMessage = messages.at(i);
+        auxMessage.replace('\n', ' ');
+
+        // TODO: Taken from ClangParser; consolidate
+        static const QRegularExpression msgRegex(
+                    "^(<command line>|([A-Za-z]:)?[^:]+\\.[^:]+)"
+                    "(:(\\d+):(\\d+)|\\((\\d+)\\) *): +(fatal +)?(error|warning|note): (.*)$");
+
+        ClangBackEnd::DiagnosticContainer aux;
+        if (const QRegularExpressionMatch match = msgRegex.match(auxMessage); match.hasMatch()) {
+            bool ok = false;
+            int line = match.captured(4).toInt(&ok);
+            int column = match.captured(5).toInt();
+            if (!ok) {
+                line = match.captured(6).toInt(&ok);
+                column = 0;
+            }
+            FilePath auxFilePath = FilePath::fromUserInput(match.captured(1));
+            if (auxFilePath.isRelativePath() && auxFilePath.fileName() == filePath.fileName())
+                auxFilePath = filePath;
+            aux.location = {auxFilePath.toString(), line, column};
+            aux.text = match.captured(9);
+            const QString type = match.captured(8);
+            if (type == "fatal")
+                aux.severity = ClangBackEnd::DiagnosticSeverity::Fatal;
+            else if (type == "error")
+                aux.severity = ClangBackEnd::DiagnosticSeverity::Error;
+            else if (type == "warning")
+                aux.severity = ClangBackEnd::DiagnosticSeverity::Warning;
+            else if (type == "note")
+                aux.severity = ClangBackEnd::DiagnosticSeverity::Note;
+        } else {
+            aux.text = auxMessage;
+        }
+        target.children << aux;
+    }
     target.category = src.category();
     if (src.severity())
         target.severity = convertSeverity(*src.severity());