QDoc: Remove `QmlCodeParser::m_engine`

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 element as
an instance member, `m_engine`.
Supposedly, this is intended as a way to avoid building the element more
than once.

Building a `QQmlJs::Engine` more than once does not provide any
meaningful overhead, moreover not in the code path where it is used.
Furthermore, `m_engine` 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_engine` and avoid requiring an
out-of-scope initialization for it, `m_engine` is now removed in favor
of a local instance in `QmlCodeParser::parseSourceFile`.

Change-Id: I73f23ec06c1fa3ba3fe50ff4dffc9ff9229c114d
Reviewed-by: Topi Reiniö <topi.reinio@qt.io>
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

2 files changed, 5 insertions, 6 deletions

diff --git a/src/qdoc/qmlcodeparser.cpp b/src/qdoc/qmlcodeparser.cpp
index f2fcea5d3..fadd7c307 100644
--- a/src/qdoc/qmlcodeparser.cpp
+++ b/src/qdoc/qmlcodeparser.cpp
@@ -57,14 +57,16 @@ void QmlCodeParser::parseSourceFile(const Location &location, const QString &fil
 
     QString newCode = document;
     extractPragmas(newCode);
-    QQmlJS::Lexer lexer{&m_engine};
+
+    QQmlJS::Engine engine{};
+    QQmlJS::Lexer lexer{&engine};
     lexer.setCode(newCode, 1);
 
-    QQmlJS::Parser parser{&m_engine};
+    QQmlJS::Parser parser{&engine};
 
     if (parser.parse()) {
         QQmlJS::AST::UiProgram *ast = parser.ast();
-        QmlDocVisitor visitor(filePath, newCode, &m_engine, topic_commands + CodeParser::common_meta_commands,
+        QmlDocVisitor visitor(filePath, newCode, &engine, topic_commands + CodeParser::common_meta_commands,
                               topic_commands);
         QQmlJS::AST::Node::accept(ast, &visitor);
         if (visitor.hasError())
diff --git a/src/qdoc/qmlcodeparser.h b/src/qdoc/qmlcodeparser.h
index 239e89473..dff493be4 100644
--- a/src/qdoc/qmlcodeparser.h
+++ b/src/qdoc/qmlcodeparser.h
@@ -31,9 +31,6 @@ public:
 
     /* Copied from src/declarative/qml/qdeclarativescriptparser.cpp */
     void extractPragmas(QString &script);
-
-private:
-    QQmlJS::Engine m_engine {};
 };
 
 QT_END_NAMESPACE