QDoc: Remove `QmlCodeParser::m_parser`

As part of producing a documentation set, QDoc parses a series of
user-defined input source files in various languages to extract the
user-provided documentation and certain source-code level elements.

For QML source files, the `QmlCodeParser` class is used, taking care of
reading the QML code and build an internal representation for some of
its elements.

`QmlCodeParser` uses the `QQmlJs` parsing api to do so.
As part of using the `QQmlJs` parsing api, `QmlCodeParser` has to build
a `QQmlJs::Engine`, `QQmlJs::Lexer` and `QQmlJsEngine::Parser`.

Currently, `QmlCodeParser` stores the engine and parser elements as
instance members.
For example, for the `QQmlJs::Parser` instance, a member
variable `m_parser` is used as storage.
Supposedly, this is intended as a way to avoid building the three
elements more than once.

Building a `QQmlJs::Parser` more than once does not provide any
meaningful overhead, moreover not in the code path where it is used.
Furthermore, `m_parser` is used only a few times, in
`QmlCodeParser::parseSourceFile`, the entry point for parsing a QML
source file.

Hence, to reduce the scope of `m_parser` and avoid requiring an
out-of-scope initialization for it, `m_parser` is now removed in favor
of a local instance in `QmlCodeParser::parseSourceFile`.

The initialization and deletion of `m_parser` in
`QmlCodeParser::initializeParser` and `QmlCodeParser::terminateParser`
was removed as a consequence of the removal of the member.

As `QmlCodeParser::initializeParser` and
`QmlCodeParser::terminateParser` were only taking care of `m_parser`,
their implementation is now removed as dead code.
As `initializeParser` and `terminateParser`are required to be
implemented, by `CodeParser`, `QmlCodeParser` base class, due to their
pure virtual nature, an empty implementation was added to
"qmlcodeparser.h".

Similarly, the constructor for `QmlCodeParser` was only taking care of
initializing `m_parser` and is now removed in favor of a defaulted
implementation.

Change-Id: Id07e6d9cf8083c83482232606fb9a2611dcce420
Reviewed-by: Topi Reiniö <topi.reinio@qt.io>
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

2 files changed, 8 insertions, 30 deletions

diff --git a/src/qdoc/qmlcodeparser.cpp b/src/qdoc/qmlcodeparser.cpp
index 3d8cd5483..f2fcea5d3 100644
--- a/src/qdoc/qmlcodeparser.cpp
+++ b/src/qdoc/qmlcodeparser.cpp
@@ -14,29 +14,6 @@
 QT_BEGIN_NAMESPACE
 
 /*!
-  Constructs the QML code parser.
- */
-QmlCodeParser::QmlCodeParser() : m_parser(nullptr) { }
-
-/*!
-  Initializes the code parser base class.
-  Also creates a parser from QQmlJS.
- */
-void QmlCodeParser::initializeParser()
-{
-    m_parser = new QQmlJS::Parser(&m_engine);
-}
-
-/*!
-  Terminates the QML code parser. Deletes the parser
-  created by the constructor.
- */
-void QmlCodeParser::terminateParser()
-{
-    delete m_parser;
-}
-
-/*!
   Returns "QML".
  */
 QString QmlCodeParser::language()
@@ -83,15 +60,17 @@ void QmlCodeParser::parseSourceFile(const Location &location, const QString &fil
     QQmlJS::Lexer lexer{&m_engine};
     lexer.setCode(newCode, 1);
 
-    if (m_parser->parse()) {
-        QQmlJS::AST::UiProgram *ast = m_parser->ast();
+    QQmlJS::Parser parser{&m_engine};
+
+    if (parser.parse()) {
+        QQmlJS::AST::UiProgram *ast = parser.ast();
         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.");
     }
-    const auto &messages = m_parser->diagnosticMessages();
+    const auto &messages = parser.diagnosticMessages();
     for (const auto &msg : messages) {
         qCDebug(lcQdoc, "%s: %d: %d: QML syntax error: %s", qUtf8Printable(filePath),
                 msg.loc.startLine, msg.loc.startColumn, qUtf8Printable(msg.message));
diff --git a/src/qdoc/qmlcodeparser.h b/src/qdoc/qmlcodeparser.h
index bbf2a1545..239e89473 100644
--- a/src/qdoc/qmlcodeparser.h
+++ b/src/qdoc/qmlcodeparser.h
@@ -20,11 +20,11 @@ class QString;
 class QmlCodeParser : public CodeParser
 {
 public:
-    QmlCodeParser();
+    QmlCodeParser() = default;
     ~QmlCodeParser() override = default;
 
-    void initializeParser() override;
-    void terminateParser() override;
+    void initializeParser() override {}
+    void terminateParser() override {}
     QString language() override;
     QStringList sourceFileNameFilter() override;
     void parseSourceFile(const Location &location, const QString &filePath, CppCodeParser&) override;
@@ -34,7 +34,6 @@ public:
 
 private:
     QQmlJS::Engine m_engine {};
-    QQmlJS::Parser *m_parser { nullptr };
 };
 
 QT_END_NAMESPACE