QDoc: Remove `CppCodeParser::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 some of the `CodeParser` child classes provides
series of methods to retrieve the required commands for each parser.

`CppCodeParser`, the parser that provides the semantic for QDoc's
comment-blocks, for example, provides `topicCommands`, to list the
available "topic commands" in a commnet-block.

`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 public static,
`topic_commands`, that is initialized in-place, to simplify the
related code.

All usages of `topicCommands` were modified to refer to
`CppCodeParser::topic_commands`, keeping an equivalent semantic, as a
consequence of the change.

Change-Id: I9de2332bf557254e7ffd33290e6af678c2b121aa
Reviewed-by: Topi Reiniö <topi.reinio@qt.io>

4 files changed, 16 insertions, 28 deletions

diff --git a/src/qdoc/clangcodeparser.cpp b/src/qdoc/clangcodeparser.cpp
index 5bf7a7521..b9aa27fbe 100644
--- a/src/qdoc/clangcodeparser.cpp
+++ b/src/qdoc/clangcodeparser.cpp
@@ -1563,7 +1563,7 @@ void ClangCodeParser::parseSourceFile(const Location & /*location*/, const QStri
 
     CXToken *tokens;
     unsigned int numTokens = 0;
-    const QSet<QString> &commands = topicCommands() + metaCommands();
+    const QSet<QString> &commands = CppCodeParser::topic_commands + metaCommands();
     clang_tokenize(tu, clang_getCursorExtent(tuCur), &tokens, &numTokens);
 
     for (unsigned int i = 0; i < numTokens; ++i) {
@@ -1579,7 +1579,7 @@ void ClangCodeParser::parseSourceFile(const Location & /*location*/, const QStri
         Doc::trimCStyleComment(loc, comment);
 
         // Doc constructor parses the comment.
-        Doc doc(loc, end_loc, comment, commands, topicCommands());
+        Doc doc(loc, end_loc, comment, commands, CppCodeParser::topic_commands);
         if (hasTooManyTopics(doc))
             continue;
 
diff --git a/src/qdoc/cppcodeparser.cpp b/src/qdoc/cppcodeparser.cpp
index 01434f352..7c0cee764 100644
--- a/src/qdoc/cppcodeparser.cpp
+++ b/src/qdoc/cppcodeparser.cpp
@@ -33,7 +33,6 @@ QT_BEGIN_NAMESPACE
 QSet<QString> CppCodeParser::m_excludeDirs;
 QSet<QString> CppCodeParser::m_excludeFiles;
 
-static QSet<QString> topicCommands_;
 static QSet<QString> metaCommands_;
 
 /*
@@ -63,19 +62,6 @@ static const QMap<QString, NodeTypeTestFunc> s_nodeTypeTestFuncMap{
  */
 CppCodeParser::CppCodeParser()
 {
-    if (topicCommands_.isEmpty()) {
-        topicCommands_ << COMMAND_CLASS << COMMAND_DONTDOCUMENT << COMMAND_ENUM << COMMAND_EXAMPLE
-                       << COMMAND_EXTERNALPAGE << COMMAND_FN << COMMAND_GROUP << COMMAND_HEADERFILE
-                       << COMMAND_MACRO << COMMAND_MODULE << COMMAND_NAMESPACE << COMMAND_PAGE
-                       << COMMAND_PROPERTY << COMMAND_TYPEALIAS << COMMAND_TYPEDEF
-                       << COMMAND_VARIABLE << COMMAND_QMLTYPE << COMMAND_QMLPROPERTY
-                       << COMMAND_QMLPROPERTYGROUP // mws 13/03/2019
-                       << COMMAND_QMLATTACHEDPROPERTY << COMMAND_QMLSIGNAL
-                       << COMMAND_QMLATTACHEDSIGNAL << COMMAND_QMLMETHOD
-                       << COMMAND_QMLATTACHEDMETHOD << COMMAND_QMLVALUETYPE << COMMAND_QMLBASICTYPE
-                       << COMMAND_QMLMODULE
-                       << COMMAND_STRUCT << COMMAND_UNION;
-    }
     if (metaCommands_.isEmpty()) {
         metaCommands_ = CodeParser::common_meta_commands;
         metaCommands_ << COMMAND_INHEADERFILE << COMMAND_NEXTPAGE
@@ -138,14 +124,6 @@ QStringList CppCodeParser::sourceFileNameFilter()
 }
 
 /*!
-  Returns the set of strings representing the topic commands.
- */
-const QSet<QString> &CppCodeParser::topicCommands()
-{
-    return topicCommands_;
-}
-
-/*!
   Process the topic \a command found in the \a doc with argument \a arg.
  */
 Node *CppCodeParser::processTopicCommand(const Doc &doc, const QString &command,
@@ -971,7 +949,7 @@ void CppCodeParser::processMetaCommands(NodeList &nodes, DocList &docs)
   */
 bool CppCodeParser::hasTooManyTopics(const Doc &doc) const
 {
-    const QSet<QString> topicCommandsUsed = topicCommands() & doc.metaCommandsUsed();
+    const QSet<QString> topicCommandsUsed = CppCodeParser::topic_commands & doc.metaCommandsUsed();
 
     if (topicCommandsUsed.empty() || topicCommandsUsed.size() == 1)
         return false;
diff --git a/src/qdoc/cppcodeparser.h b/src/qdoc/cppcodeparser.h
index 7869f97c5..7854850db 100644
--- a/src/qdoc/cppcodeparser.h
+++ b/src/qdoc/cppcodeparser.h
@@ -15,6 +15,17 @@ class Aggregate;
 
 class CppCodeParser : public CodeParser
 {
+public:
+    static inline const QSet<QString> topic_commands{
+        COMMAND_CLASS, COMMAND_DONTDOCUMENT, COMMAND_ENUM, COMMAND_EXAMPLE,
+        COMMAND_EXTERNALPAGE, COMMAND_FN, COMMAND_GROUP, COMMAND_HEADERFILE,
+        COMMAND_MACRO, COMMAND_MODULE, COMMAND_NAMESPACE, COMMAND_PAGE,
+        COMMAND_PROPERTY, COMMAND_TYPEALIAS, COMMAND_TYPEDEF, COMMAND_VARIABLE,
+        COMMAND_QMLTYPE, COMMAND_QMLPROPERTY, COMMAND_QMLPROPERTYGROUP,
+        COMMAND_QMLATTACHEDPROPERTY, COMMAND_QMLSIGNAL, COMMAND_QMLATTACHEDSIGNAL,
+        COMMAND_QMLMETHOD, COMMAND_QMLATTACHEDMETHOD, COMMAND_QMLVALUETYPE, COMMAND_QMLBASICTYPE,
+        COMMAND_QMLMODULE, COMMAND_STRUCT, COMMAND_UNION,
+    };
 
 public:
     CppCodeParser();
@@ -30,7 +41,6 @@ public:
     static bool isQMLPropertyTopic(const QString &t);
 
 protected:
-    static const QSet<QString> &topicCommands();
     static const QSet<QString> &metaCommands();
     virtual Node *processTopicCommand(const Doc &doc, const QString &command,
                                       const ArgPair &arg);
diff --git a/src/qdoc/puredocparser.cpp b/src/qdoc/puredocparser.cpp
index 7bbc17b73..86b9bdaa2 100644
--- a/src/qdoc/puredocparser.cpp
+++ b/src/qdoc/puredocparser.cpp
@@ -56,7 +56,7 @@ void PureDocParser::processQdocComments(QFile& input_file)
 {
     Tokenizer tokenizer(Location{input_file.fileName()}, input_file);
 
-    const QSet<QString> &commands = topicCommands() + metaCommands();
+    const QSet<QString> &commands = CppCodeParser::topic_commands + metaCommands();
 
     int token = tokenizer.getToken();
     while (token != Tok_Eoi) {
@@ -72,7 +72,7 @@ void PureDocParser::processQdocComments(QFile& input_file)
         Location end_loc(tokenizer.location());
 
         // Doc constructor parses the comment.
-        Doc doc(start_loc, end_loc, comment, commands, topicCommands());
+        Doc doc(start_loc, end_loc, comment, commands, CppCodeParser::topic_commands);
         const TopicList &topics = doc.topicsUsed();
         if (topics.isEmpty()) {
             doc.location().warning(QStringLiteral("This qdoc comment contains no topic command "