Expressions - Add a referencedExpressions method

python/PyQt6/core/auto_additions/qgsexpression.py

@@ -24,6 +24,7 @@
     QgsExpression.quoteFieldExpression = staticmethod(QgsExpression.quoteFieldExpression)
     QgsExpression.checkExpression = staticmethod(QgsExpression.checkExpression)
     QgsExpression.replaceExpressionText = staticmethod(QgsExpression.replaceExpressionText)
+    QgsExpression.referencedExpressions = staticmethod(QgsExpression.referencedExpressions)
     QgsExpression.evaluateToDouble = staticmethod(QgsExpression.evaluateToDouble)
     QgsExpression.registerFunction = staticmethod(QgsExpression.registerFunction)
     QgsExpression.unregisterFunction = staticmethod(QgsExpression.unregisterFunction)

python/PyQt6/core/auto_generated/expression/qgsexpression.sip.in

@@ -426,8 +426,6 @@ variables from the expression context ("project_distance_units") to determine di
 This function replaces each expression between [% and %]
 in the string with the result of its evaluation with the specified context
 
-Additional substitutions can be passed through the substitutionMap parameter
-
 :param action: The source string in which placeholders should be replaced.
 :param context: Expression context
 :param distanceArea: Optional :py:class:`QgsDistanceArea`. If specified, the :py:class:`QgsDistanceArea` is used for distance
@@ -441,6 +439,16 @@ This function returns variables in each expression between [% and %].
 :param text: The source string in which variables should be searched.
 
 .. versionadded:: 3.2
+%End
+
+    static QStringList referencedExpressions( const QString &text );
+%Docstring
+This function returns expressions found between [% and %].
+Expressions returned are guaranteed to be valid QGIS expressions.
+
+:param text: The source string in which expressions should be searched.
+
+.. versionadded:: 3.42
 %End
 
     static double evaluateToDouble( const QString &text, double fallbackValue );

python/core/auto_additions/qgsexpression.py

@@ -10,6 +10,7 @@
     QgsExpression.quoteFieldExpression = staticmethod(QgsExpression.quoteFieldExpression)
     QgsExpression.checkExpression = staticmethod(QgsExpression.checkExpression)
     QgsExpression.replaceExpressionText = staticmethod(QgsExpression.replaceExpressionText)
+    QgsExpression.referencedExpressions = staticmethod(QgsExpression.referencedExpressions)
     QgsExpression.evaluateToDouble = staticmethod(QgsExpression.evaluateToDouble)
     QgsExpression.registerFunction = staticmethod(QgsExpression.registerFunction)
     QgsExpression.unregisterFunction = staticmethod(QgsExpression.unregisterFunction)

python/core/auto_generated/expression/qgsexpression.sip.in

@@ -426,8 +426,6 @@ variables from the expression context ("project_distance_units") to determine di
 This function replaces each expression between [% and %]
 in the string with the result of its evaluation with the specified context
 
-Additional substitutions can be passed through the substitutionMap parameter
-
 :param action: The source string in which placeholders should be replaced.
 :param context: Expression context
 :param distanceArea: Optional :py:class:`QgsDistanceArea`. If specified, the :py:class:`QgsDistanceArea` is used for distance
@@ -441,6 +439,16 @@ This function returns variables in each expression between [% and %].
 :param text: The source string in which variables should be searched.
 
 .. versionadded:: 3.2
+%End
+
+    static QStringList referencedExpressions( const QString &text );
+%Docstring
+This function returns expressions found between [% and %].
+Expressions returned are guaranteed to be valid QGIS expressions.
+
+:param text: The source string in which expressions should be searched.
+
+.. versionadded:: 3.42
 %End
 
     static double evaluateToDouble( const QString &text, double fallbackValue );

src/core/expression/qgsexpression.cpp

@@ -516,6 +516,19 @@ QString QgsExpression::replaceExpressionText( const QString &action, const QgsEx
 QSet<QString> QgsExpression::referencedVariables( const QString &text )
 {
   QSet<QString> variables;
+  const QStringList expressions = QgsExpression::referencedExpressions( text );
+  for ( const QString &expression : expressions )
+  {
+    QgsExpression exp( expression );
+    variables.unite( exp.referencedVariables() );
+  }
+
+  return variables;
+}
+
+QStringList QgsExpression::referencedExpressions( const QString &text )
+{
+  QStringList expressions;
   int index = 0;
   while ( index < text.size() )
   {
@@ -527,11 +540,10 @@ QSet<QString> QgsExpression::referencedVariables( const QString &text )
     index = match.capturedStart() + match.capturedLength();
     QString to_replace = match.captured( 1 ).trimmed();
 
-    QgsExpression exp( to_replace );
-    variables.unite( exp.referencedVariables() );
+    expressions.append( to_replace );
   }
 
-  return variables;
+  return expressions;
 }
 
 double QgsExpression::evaluateToDouble( const QString &text, const double fallbackValue )

src/core/expression/qgsexpression.h

@@ -551,7 +551,6 @@ class CORE_EXPORT QgsExpression
      * This function replaces each expression between [% and %]
      * in the string with the result of its evaluation with the specified context
      *
-     * Additional substitutions can be passed through the substitutionMap parameter
      * \param action The source string in which placeholders should be replaced.
      * \param context Expression context
      * \param distanceArea Optional QgsDistanceArea. If specified, the QgsDistanceArea is used for distance
@@ -569,6 +568,16 @@ class CORE_EXPORT QgsExpression
      */
     static QSet<QString> referencedVariables( const QString &text );
 
+    /**
+     * This function returns expressions found between [% and %].
+     * Expressions returned are guaranteed to be valid QGIS expressions.
+     *
+     * \param text The source string in which expressions should be searched.
+     *
+     * \since QGIS 3.42
+     */
+    static QStringList referencedExpressions( const QString &text );
+
     /**
      * Attempts to evaluate a text string as an expression to a resultant double
      * value.

tests/src/core/testqgsexpression.cpp

@@ -5453,6 +5453,27 @@ class TestQgsExpression: public QObject
       QCOMPARE( zustaendigkeitskataster->dataProvider()->featureCount(), 4l );
     }
 
+    void testReferencedExpressions_data()
+    {
+      QTest::addColumn<QString>( "input" );
+      QTest::addColumn<QStringList>( "expected" );
+      QTest::newRow( "no exp" ) << "some text" << QStringList();
+      QTest::newRow( "simple exp" ) << "some text [% 1 + 2 %]" << ( QStringList() << QStringLiteral( "1 + 2" ) );
+      QTest::newRow( "multiple exp" ) << "some [% 3+ 7 %] text [% 1 + 2 %]" << ( QStringList() << QStringLiteral( "3+ 7" ) << QStringLiteral( "1 + 2" ) );
+      QTest::newRow( "complex" ) << "some [%map('a', 1, 'b', 2)['a']%] text [%map('a', 1, 'b', 2)['b']%]" << ( QStringList() << QStringLiteral( "map('a', 1, 'b', 2)['a']" ) << QStringLiteral( "map('a', 1, 'b', 2)['b']" ) );
+      QTest::newRow( "complex2" ) << "some [% 'my text]' %] text" << ( QStringList() << QStringLiteral( "'my text]'" ) );
+      QTest::newRow( "newline 1" ) << "some \n [% 1 + 2 %] \n text" << ( QStringList() << QStringLiteral( "1 + 2" ) );
+      QTest::newRow( "newline 2" ) << "some [% \n 1 \n + \n 2 %] \n text" << ( QStringList() << QStringLiteral( "\n 1 \n + \n 2" ) );
+      QTest::newRow( "field values" ) << "[% \"string_field\" %] - [% \"non_null_int\" %] - [% \"null_int\" %]" << ( QStringList() << QStringLiteral( "\"string_field\"" ) << QStringLiteral( "\"non_null_int\"" ) << QStringLiteral( "\"null_int\"" ) );
+    }
+
+    void testReferencedExpressions()
+    {
+      QFETCH( QString, input );
+      QFETCH( QStringList, expected );
+      QCOMPARE( QgsExpression::referencedExpressions( input ), expected );
+    }
+
     void testReplaceExpressionText_data()
     {
       QTest::addColumn<QString>( "input" );