QDoc: Remove `CppCodeParser::metaCommands`

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 `metaCommands`, to list the
available "meta commands" in a comment-block.

`metaCommands` returns a static member, `metaComamnds_`.
This static member is initialized during the construction of an
`CppCodeParser` instance, and the initialization is made so that it
doesn't run more than once, albeit this is done in a non-thread-safe
way.

The initialization is based on `CppCodeParser::common_meta_commands`, as
a base, plus some other commands that are not in `common_meta_commands`.

Generally, this process could be better expressed by the use of a static
with in-place initialization. There are two probable reasons why this
has not been the way it was written in the past.

Supposedly, when this code was written, there was no suitable way to
initialize a `QSet<QString>`, the type of `metaCommands_`,
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 `metaCommands_`, 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 `metaCommands()` method is removed, along with
`metaCommands_`, in favor of a public static,
`meta_commands`, that is initialized in-place, to simplify the
related code.

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

As the initialization of `metaCommands_` was the only thing that was
being done in the constructor for `CppCodeParser`, the constructor was
removed in favor of a default one.

Change-Id: I6e54b95a50d07a394d727c0af8c409599a088d4c
Reviewed-by: Topi Reiniö <topi.reinio@qt.io>

4 files changed, 9 insertions, 29 deletions

diff --git a/src/qdoc/clangcodeparser.cpp b/src/qdoc/clangcodeparser.cpp
index b9aa27fbe..4589df9ed 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 = CppCodeParser::topic_commands + metaCommands();
+    const QSet<QString> &commands = CppCodeParser::topic_commands + CppCodeParser::meta_commands;
     clang_tokenize(tu, clang_getCursorExtent(tuCur), &tokens, &numTokens);
 
     for (unsigned int i = 0; i < numTokens; ++i) {
diff --git a/src/qdoc/cppcodeparser.cpp b/src/qdoc/cppcodeparser.cpp
index 7c0cee764..341acb6b3 100644
--- a/src/qdoc/cppcodeparser.cpp
+++ b/src/qdoc/cppcodeparser.cpp
@@ -33,8 +33,6 @@ QT_BEGIN_NAMESPACE
 QSet<QString> CppCodeParser::m_excludeDirs;
 QSet<QString> CppCodeParser::m_excludeFiles;
 
-static QSet<QString> metaCommands_;
-
 /*
   All these can appear in a C++ namespace. Don't add
   anything that can't be in a C++ namespace.
@@ -57,20 +55,6 @@ static const QMap<QString, NodeTypeTestFunc> s_nodeTypeTestFuncMap{
 };
 
 /*!
-  The constructor initializes some regular expressions
-  and initializes the tokenizer variables.
- */
-CppCodeParser::CppCodeParser()
-{
-    if (metaCommands_.isEmpty()) {
-        metaCommands_ = CodeParser::common_meta_commands;
-        metaCommands_ << COMMAND_INHEADERFILE << COMMAND_NEXTPAGE
-                      << COMMAND_OVERLOAD << COMMAND_PREVIOUSPAGE << COMMAND_QMLINSTANTIATES
-                      << COMMAND_REIMP << COMMAND_RELATES;
-    }
-}
-
-/*!
   The constructor initializes a map of special node types
   for identifying important nodes. And it initializes
   some filters for identifying and excluding certain kinds of files.
@@ -377,15 +361,6 @@ void CppCodeParser::processQmlProperties(const Doc &doc, NodeList &nodes, DocLis
 }
 
 /*!
-  Returns the set of strings representing the common metacommands
-  plus some other metacommands.
- */
-const QSet<QString> &CppCodeParser::metaCommands()
-{
-    return metaCommands_;
-}
-
-/*!
   Process the metacommand \a command in the context of the
   \a node associated with the topic command and the \a doc.
   \a arg is the argument to the metacommand.
diff --git a/src/qdoc/cppcodeparser.h b/src/qdoc/cppcodeparser.h
index 7854850db..6cf63f740 100644
--- a/src/qdoc/cppcodeparser.h
+++ b/src/qdoc/cppcodeparser.h
@@ -27,8 +27,14 @@ public:
         COMMAND_QMLMODULE, COMMAND_STRUCT, COMMAND_UNION,
     };
 
+    static inline const QSet<QString> meta_commands = QSet<QString>(CodeParser::common_meta_commands)
+        << COMMAND_INHEADERFILE << COMMAND_NEXTPAGE
+        << COMMAND_OVERLOAD << COMMAND_PREVIOUSPAGE
+        << COMMAND_QMLINSTANTIATES << COMMAND_REIMP
+        << COMMAND_RELATES;
+
 public:
-    CppCodeParser();
+    CppCodeParser() = default;
 
     void initializeParser() override;
     void terminateParser() override;
@@ -41,7 +47,6 @@ public:
     static bool isQMLPropertyTopic(const QString &t);
 
 protected:
-    static const QSet<QString> &metaCommands();
     virtual Node *processTopicCommand(const Doc &doc, const QString &command,
                                       const ArgPair &arg);
     void processQmlProperties(const Doc &doc, NodeList &nodes, DocList &docs);
diff --git a/src/qdoc/puredocparser.cpp b/src/qdoc/puredocparser.cpp
index 86b9bdaa2..931ca253c 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 = CppCodeParser::topic_commands + metaCommands();
+    const QSet<QString> &commands = CppCodeParser::topic_commands + CppCodeParser::meta_commands;
 
     int token = tokenizer.getToken();
     while (token != Tok_Eoi) {