QDoc: Remove `QmlCodeParser::topicCommands`

As part of extracting user-provided documentation, QDoc has to parse a
variety of source files in a variety of languages.

`CodeParser` is the base class of objects that take care of performing
this parsing process in QDoc.

When extracting the documentation in one of the `CodeParser`s QDoc
generally tries to parse the extracted documentation in-place.

The documentation has a series of available commands that might depend
on the currently used parser.
To support this process various `CodeParser` child classes provides a
way to access the available commands.

In particular, `QmlCodeParser`, the class that processes QML files,
provides `topicCommands`, a method to retrieve the available topic
commands for documentation extracted by QML files.

`topicCommands` initializes a static member, `topicCommands_`
and then returns it, avoiding initialization if the method is called
more than once.

While this process can be better expressed by the simple use of a
`static` there are two probable reason for why it wasn't done in this
way.

Supposedly, when this code was written, there was no suitable way to
initialize a `QSet<QString>`, the type of `topicCommands_`,
in-place, as similar patterns can be found in other legacy parts of QDoc
that are confirmed to have had this issue due to their age.

Additionally, the expansion of the `COMMAND_*` macros, which form the
content for `topicCommands_`, were, until recently, dependent on
certain data being available in another part of the system, so that
expanding them in a static context that would be processed before this
data was available would incur into a series of errors.
This dependency was removed in a recent patch, so that the issue is no
more.

Hence, the `topicCommands()` method is removed, along with
`topicCommands_`, in favor of a static,
`topic_commands`, that is initialized in-place, to simplify the
related code.

`topicCommands()` only uses were in `QmlCodeParser::parseSourceFile`,
the entry point for the extraction of documentation from a specific QML
file.
Thus, `topic_commands` is now scoped as a static in `parseSourceFile`,
the smaller scope where it is required.

All usages of `topicCommands()` were modified to refer to
`topic_commands`, keeping an equivalent semantic.

Change-Id: Ic97166a9a563f4e8d5ac840999231d92045a6f0d
Reviewed-by: Topi Reiniö <topi.reinio@qt.io>

2 files changed, 9 insertions, 21 deletions

diff --git a/src/qdoc/qmlcodeparser.cpp b/src/qdoc/qmlcodeparser.cpp
index ce8ddce72..65f107154 100644
--- a/src/qdoc/qmlcodeparser.cpp
+++ b/src/qdoc/qmlcodeparser.cpp
@@ -64,6 +64,13 @@ QStringList QmlCodeParser::sourceFileNameFilter()
  */
 void QmlCodeParser::parseSourceFile(const Location &location, const QString &filePath)
 {
+    static const QSet<QString> topic_commands{
+        COMMAND_VARIABLE, COMMAND_QMLCLASS, COMMAND_QMLTYPE, COMMAND_QMLPROPERTY,
+        COMMAND_QMLPROPERTYGROUP, COMMAND_QMLATTACHEDPROPERTY, COMMAND_QMLSIGNAL,
+        COMMAND_QMLATTACHEDSIGNAL, COMMAND_QMLMETHOD, COMMAND_QMLATTACHEDMETHOD,
+        COMMAND_QMLVALUETYPE, COMMAND_QMLBASICTYPE,
+    };
+
     QFile in(filePath);
     if (!in.open(QIODevice::ReadOnly)) {
         location.error(QStringLiteral("Cannot open QML file '%1'").arg(filePath));
@@ -79,8 +86,8 @@ void QmlCodeParser::parseSourceFile(const Location &location, const QString &fil
 
     if (m_parser->parse()) {
         QQmlJS::AST::UiProgram *ast = m_parser->ast();
-        QmlDocVisitor visitor(filePath, newCode, &m_engine, topicCommands() + CodeParser::common_meta_commands,
-                              topicCommands());
+        QmlDocVisitor visitor(filePath, newCode, &m_engine, topic_commands + CodeParser::common_meta_commands,
+                              topic_commands);
         QQmlJS::AST::Node::accept(ast, &visitor);
         if (visitor.hasError())
             Location(filePath).warning("Could not analyze QML file, output is incomplete.");
@@ -92,22 +99,6 @@ void QmlCodeParser::parseSourceFile(const Location &location, const QString &fil
     }
 }
 
-static QSet<QString> topicCommands_;
-/*!
-  Returns the set of strings representing the topic commands.
- */
-const QSet<QString> &QmlCodeParser::topicCommands()
-{
-    if (topicCommands_.isEmpty()) {
-        topicCommands_ << COMMAND_VARIABLE << COMMAND_QMLCLASS << COMMAND_QMLTYPE
-                       << COMMAND_QMLPROPERTY << COMMAND_QMLPROPERTYGROUP // mws 13/03/2019
-                       << COMMAND_QMLATTACHEDPROPERTY << COMMAND_QMLSIGNAL
-                       << COMMAND_QMLATTACHEDSIGNAL << COMMAND_QMLMETHOD
-                       << COMMAND_QMLATTACHEDMETHOD << COMMAND_QMLVALUETYPE << COMMAND_QMLBASICTYPE;
-    }
-    return topicCommands_;
-}
-
 /*!
   Copy and paste from src/declarative/qml/qdeclarativescriptparser.cpp.
   This function blanks out the section of the \a str beginning at \a idx
diff --git a/src/qdoc/qmlcodeparser.h b/src/qdoc/qmlcodeparser.h
index 243c552fb..61e9d6c6d 100644
--- a/src/qdoc/qmlcodeparser.h
+++ b/src/qdoc/qmlcodeparser.h
@@ -32,9 +32,6 @@ public:
     /* Copied from src/declarative/qml/qdeclarativescriptparser.cpp */
     void extractPragmas(QString &script);
 
-protected:
-    const QSet<QString> &topicCommands();
-
 private:
     QQmlJS::Engine m_engine {};
     QQmlJS::Lexer *m_lexer { nullptr };