Add method to retrieve dependent parameters for a parameter

Author: nyalldawson

python/core/processing/qgsprocessingparameters.sip

@@ -338,6 +338,13 @@ class QgsProcessingParameterDefinition
 .. seealso:: metadata()
 %End
 
+    virtual QStringList dependsOnOtherParameters() const;
+%Docstring
+ Returns a list of other parameter names on which this parameter is dependent (e.g.
+ field parameters which depend on a parent layer parameter).
+ :rtype: list of str
+%End
+
   protected:
 
 
@@ -1261,6 +1268,8 @@ class QgsProcessingParameterExpression : QgsProcessingParameterDefinition
     virtual QString type() const;
     virtual QString valueAsPythonString( const QVariant &value, QgsProcessingContext &context ) const;
 
+    virtual QStringList dependsOnOtherParameters() const;
+
 
     QString parentLayerParameter() const;
 %Docstring
@@ -1357,6 +1366,8 @@ class QgsProcessingParameterField : QgsProcessingParameterDefinition
 
     virtual QString asScriptCode() const;
 
+    virtual QStringList dependsOnOtherParameters() const;
+
 
     QString parentLayerParameter() const;
 %Docstring

src/core/processing/qgsprocessingparameters.cpp

@@ -2047,6 +2047,14 @@ QString QgsProcessingParameterExpression::valueAsPythonString( const QVariant &v
   return s.prepend( '\'' ).append( '\'' );
 }
 
+QStringList QgsProcessingParameterExpression::dependsOnOtherParameters() const
+{
+  QStringList depends;
+  if ( !mParentLayerParameter.isEmpty() )
+    depends << mParentLayerParameter;
+  return depends;
+}
+
 QString QgsProcessingParameterExpression::parentLayerParameter() const
 {
   return mParentLayerParameter;
@@ -2229,6 +2237,14 @@ QString QgsProcessingParameterField::asScriptCode() const
   return code.trimmed();
 }
 
+QStringList QgsProcessingParameterField::dependsOnOtherParameters() const
+{
+  QStringList depends;
+  if ( !mParentLayerParameter.isEmpty() )
+    depends << mParentLayerParameter;
+  return depends;
+}
+
 QString QgsProcessingParameterField::parentLayerParameter() const
 {
   return mParentLayerParameter;

src/core/processing/qgsprocessingparameters.h

@@ -373,6 +373,12 @@ class CORE_EXPORT QgsProcessingParameterDefinition
      */
     void setMetadata( const QVariantMap &metadata ) { mMetadata = metadata; }
 
+    /**
+     * Returns a list of other parameter names on which this parameter is dependent (e.g.
+     * field parameters which depend on a parent layer parameter).
+     */
+    virtual QStringList dependsOnOtherParameters() const { return QStringList(); }
+
   protected:
 
     //! Parameter name
@@ -1219,6 +1225,7 @@ class CORE_EXPORT QgsProcessingParameterExpression : public QgsProcessingParamet
 
     QString type() const override { return QStringLiteral( "expression" ); }
     QString valueAsPythonString( const QVariant &value, QgsProcessingContext &context ) const override;
+    QStringList dependsOnOtherParameters() const override;
 
     /**
      * Returns the name of the parent layer parameter, or an empty string if this is not set.
@@ -1306,6 +1313,7 @@ class CORE_EXPORT QgsProcessingParameterField : public QgsProcessingParameterDef
     bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = nullptr ) const override;
     QString valueAsPythonString( const QVariant &value, QgsProcessingContext &context ) const override;
     QString asScriptCode() const override;
+    QStringList dependsOnOtherParameters() const override;
 
     /**
      * Returns the name of the parent layer parameter, or an empty string if this is not set.

tests/src/core/testqgsprocessing.cpp

@@ -1314,6 +1314,7 @@ void TestQgsProcessing::parameterGeneral()
   QCOMPARE( param.description(), QString( "desc" ) );
   QCOMPARE( param.defaultValue(), QVariant( true ) );
   QVERIFY( param.flags() & QgsProcessingParameterDefinition::FlagOptional );
+  QVERIFY( param.dependsOnOtherParameters().isEmpty() );
 
   // test getters and setters
   param.setDescription( "p2" );
@@ -2951,6 +2952,10 @@ void TestQgsProcessing::parameterExpression()
   def.reset( dynamic_cast< QgsProcessingParameterExpression *>( QgsProcessingParameters::parameterFromVariantMap( map ) ) );
   QVERIFY( dynamic_cast< QgsProcessingParameterExpression *>( def.get() ) );
 
+  QVERIFY( def->dependsOnOtherParameters().isEmpty() );
+  def->setParentLayerParameter( QStringLiteral( "test_layer" ) );
+  QCOMPARE( def->dependsOnOtherParameters(), QStringList() << QStringLiteral( "test_layer" ) );
+
   // optional
   def.reset( new QgsProcessingParameterExpression( "optional", QString(), QString( "default" ), QString(), true ) );
   QVERIFY( def->checkValueIsAcceptable( 1 ) );
@@ -3011,7 +3016,10 @@ void TestQgsProcessing::parameterField()
   QCOMPARE( fromCode->dataType(), def->dataType() );
   QCOMPARE( fromCode->allowMultiple(), def->allowMultiple() );
 
+  QVERIFY( def->dependsOnOtherParameters().isEmpty() );
   def->setParentLayerParameter( "my_parent" );
+  QCOMPARE( def->dependsOnOtherParameters(), QStringList() << QStringLiteral( "my_parent" ) );
+
   code = def->asScriptCode();
   fromCode.reset( dynamic_cast< QgsProcessingParameterField * >( QgsProcessingParameters::parameterFromScriptCode( code ) ) );
   QVERIFY( fromCode.get() );