Remove the limitation that output formatters have to be exclusive

Introduce an aggregating output formatter that forwards its input to a
sub-formatter that feels responsible for it, or otherwise lets the base
class handle it.
Our output panes now use such an aggregating formatter.
In particular, this means that in the future, we won't have to stuff all
run control output formatting into the Qt output formatter anymore.

Change-Id: I5498f200a61db10ccff3ec8974c6825da7f7072d
Reviewed-by: hjk <hjk@qt.io>

src/plugins/python/pythonrunconfiguration.cpp

@@ -71,12 +71,16 @@ public:
     }
 
 private:
-    void doAppendMessage(const QString &text, OutputFormat format) final
+    Status handleMessage(const QString &text, OutputFormat format) final
     {
         if (!m_inTraceBack) {
             m_inTraceBack = format == StdErrFormat
                     && text.startsWith("Traceback (most recent call last):");
-            OutputFormatter::doAppendMessage(text, format);
+            if (m_inTraceBack) {
+                OutputFormatter::appendMessageDefault(text, format);
+                return Status::InProgress;
+            }
+            return Status::NotHandled;
         }
 
         const Core::Id category(PythonErrorTaskCategory);
@@ -90,9 +94,10 @@ private:
             const auto fileName = FilePath::fromString(match.captured(3));
             const int lineNumber = match.capturedRef(4).toInt();
             m_tasks.append({Task::Warning, QString(), fileName, lineNumber, category});
-            return;
+            return Status::InProgress;
         }
 
+        Status status = Status::InProgress;
         if (text.startsWith(' ')) {
             // Neither traceback start, nor file, nor error message line.
             // Not sure if that can actually happen.
@@ -111,18 +116,21 @@ private:
                 TaskHub::addTask(*rit);
             m_tasks.clear();
             m_inTraceBack = false;
+            status = Status::Done;
         }
-        OutputFormatter::doAppendMessage(text, format);
+        OutputFormatter::appendMessageDefault(text, format);
+        return status;
     }
 
-    void handleLink(const QString &href) final
+    bool handleLink(const QString &href) final
     {
         const QRegularExpressionMatch match = filePattern.match(href);
         if (!match.hasMatch())
-            return;
+            return false;
         const QString fileName = match.captured(3);
         const int lineNumber = match.capturedRef(4).toInt();
         Core::EditorManager::openEditorAt(fileName, lineNumber);
+        return true;
     }
 
     void reset() override