Add method to combine two QGIS metadata objects

All non-empty elements from one metadata object are copied onto
the target metadata object

python/core/auto_generated/metadata/qgsabstractmetadatabase.sip.in

@@ -424,6 +424,15 @@ Stores state in a DOM node.
 
 Subclasses which override this method should take care to also call the base
 class method in order to write common metadata properties.
+%End
+
+    virtual void combine( const QgsAbstractMetadataBase *other );
+%Docstring
+Combines the metadata from this object with the metadata from an ``other`` object.
+
+Any existing values in this object will be overwritten by non-empty values from ``other``.
+
+.. versionadded:: 3.20
 %End
 
   protected:

python/core/auto_generated/metadata/qgslayermetadata.sip.in

@@ -275,6 +275,8 @@ Reads the metadata state from a ``layer``'s custom properties (see :py:func:`Qgs
 
     virtual bool writeMetadataXml( QDomElement &metadataElement, QDomDocument &document ) const;
 
+    virtual void combine( const QgsAbstractMetadataBase *other );
+
 
     bool operator==( const QgsLayerMetadata &metadataOther ) const;
 

python/core/auto_generated/metadata/qgsprojectmetadata.sip.in

@@ -82,6 +82,8 @@ Sets the project's creation date/timestamp.
 
     virtual bool writeMetadataXml( QDomElement &metadataElement, QDomDocument &document ) const;
 
+    virtual void combine( const QgsAbstractMetadataBase *other );
+
 
     bool operator==( const QgsProjectMetadata &metadataOther ) const;
 

src/core/metadata/qgsabstractmetadatabase.cpp

@@ -432,6 +432,42 @@ bool QgsAbstractMetadataBase::writeMetadataXml( QDomElement &metadataElement, QD
   return true;
 }
 
+void QgsAbstractMetadataBase::combine( const QgsAbstractMetadataBase *other )
+{
+  if ( !other )
+    return;
+
+  if ( !other->identifier().isEmpty() )
+    mIdentifier = other->identifier();
+
+  if ( !other->parentIdentifier().isEmpty() )
+    mParentIdentifier = other->parentIdentifier();
+
+  if ( !other->language().isEmpty() )
+    mLanguage = other->language();
+
+  if ( !other->type().isEmpty() )
+    mType = other->type();
+
+  if ( !other->title().isEmpty() )
+    mTitle = other->title();
+
+  if ( !other->abstract().isEmpty() )
+    mAbstract = other->abstract();
+
+  if ( !other->history().isEmpty() )
+    mHistory = other->history();
+
+  if ( !other->keywords().isEmpty() )
+    mKeywords = other->keywords();
+
+  if ( !other->contacts().isEmpty() )
+    mContacts = other->contacts();
+
+  if ( !other->links().isEmpty() )
+    mLinks = other->links();
+}
+
 bool QgsAbstractMetadataBase::equals( const QgsAbstractMetadataBase &metadataOther )  const
 {
   return ( ( mIdentifier == metadataOther.mIdentifier ) &&

src/core/metadata/qgsabstractmetadatabase.h

@@ -524,6 +524,15 @@ class CORE_EXPORT QgsAbstractMetadataBase
      */
     virtual bool writeMetadataXml( QDomElement &metadataElement, QDomDocument &document ) const;
 
+    /**
+     * Combines the metadata from this object with the metadata from an \a other object.
+     *
+     * Any existing values in this object will be overwritten by non-empty values from \a other.
+     *
+     * \since QGIS 3.20
+     */
+    virtual void combine( const QgsAbstractMetadataBase *other );
+
   protected:
 
     /**

src/core/metadata/qgslayermetadata.cpp

@@ -341,6 +341,38 @@ bool QgsLayerMetadata::writeMetadataXml( QDomElement &metadataElement, QDomDocum
   return true;
 }
 
+void QgsLayerMetadata::combine( const QgsAbstractMetadataBase *other )
+{
+  QgsAbstractMetadataBase::combine( other );
+
+  if ( const QgsLayerMetadata *otherLayerMetadata = dynamic_cast< const QgsLayerMetadata * >( other ) )
+  {
+    if ( !otherLayerMetadata->fees().isEmpty() )
+      mFees = otherLayerMetadata->fees();
+
+    if ( !otherLayerMetadata->constraints().isEmpty() )
+      mConstraints = otherLayerMetadata->constraints();
+
+    if ( !otherLayerMetadata->rights().isEmpty() )
+      mRights = otherLayerMetadata->rights();
+
+    if ( !otherLayerMetadata->licenses().isEmpty() )
+      mLicenses = otherLayerMetadata->licenses();
+
+    if ( !otherLayerMetadata->encoding().isEmpty() )
+      mEncoding = otherLayerMetadata->encoding();
+
+    if ( otherLayerMetadata->crs().isValid() )
+      mCrs = otherLayerMetadata->crs();
+
+    if ( !otherLayerMetadata->extent().spatialExtents().isEmpty() )
+      mExtent.setSpatialExtents( otherLayerMetadata->extent().spatialExtents() );
+
+    if ( !otherLayerMetadata->extent().temporalExtents().isEmpty() )
+      mExtent.setTemporalExtents( otherLayerMetadata->extent().temporalExtents() );
+  }
+}
+
 const QgsLayerMetadata::Extent &QgsLayerMetadata::extent() const
 {
   return mExtent;

src/core/metadata/qgslayermetadata.h

@@ -315,6 +315,7 @@ class CORE_EXPORT QgsLayerMetadata : public QgsAbstractMetadataBase
 
     bool readMetadataXml( const QDomElement &metadataElement ) override;
     bool writeMetadataXml( QDomElement &metadataElement, QDomDocument &document ) const override;
+    void combine( const QgsAbstractMetadataBase *other ) override;
 
     bool operator==( const QgsLayerMetadata &metadataOther ) const;
 

src/core/metadata/qgsprojectmetadata.cpp

@@ -55,6 +55,20 @@ bool QgsProjectMetadata::writeMetadataXml( QDomElement &metadataElement, QDomDoc
   return true;
 }
 
+void QgsProjectMetadata::combine( const QgsAbstractMetadataBase *other )
+{
+  QgsAbstractMetadataBase::combine( other );
+
+  if ( const QgsProjectMetadata *otherProjectMetadata = dynamic_cast< const QgsProjectMetadata * >( other ) )
+  {
+    if ( !otherProjectMetadata->author().isEmpty() )
+      mAuthor = otherProjectMetadata->author();
+
+    if ( otherProjectMetadata->creationDateTime().isValid() )
+      mCreationDateTime = otherProjectMetadata->creationDateTime();
+  }
+}
+
 bool QgsProjectMetadata::operator==( const QgsProjectMetadata &metadataOther )  const
 {
   return equals( metadataOther ) &&

src/core/metadata/qgsprojectmetadata.h

@@ -87,6 +87,7 @@ class CORE_EXPORT QgsProjectMetadata : public QgsAbstractMetadataBase
 
     bool readMetadataXml( const QDomElement &metadataElement ) override;
     bool writeMetadataXml( QDomElement &metadataElement, QDomDocument &document ) const override;
+    void combine( const QgsAbstractMetadataBase *other ) override;
 
     bool operator==( const QgsProjectMetadata &metadataOther ) const;
 

tests/src/python/test_qgslayermetadata.py

@@ -481,6 +481,202 @@ def testValidateNative(self):  # spellok
         self.assertEqual(list[0].section, 'links')
         self.assertEqual(list[0].identifier, 0)
 
+    def testCombine(self):
+        m1 = QgsLayerMetadata()
+        m2 = QgsLayerMetadata()
+
+        # should be retained
+        m1.setIdentifier('i1')
+        m1.combine(m2)
+        self.assertEqual(m1.identifier(), 'i1')
+
+        # should be overwritten
+        m1.setIdentifier(None)
+        m2.setIdentifier('i2')
+        m1.combine(m2)
+        self.assertEqual(m1.identifier(), 'i2')
+
+        # should be overwritten
+        m1.setIdentifier('i1')
+        m2.setIdentifier('i2')
+        m1.combine(m2)
+        self.assertEqual(m1.identifier(), 'i2')
+
+        m1.setParentIdentifier('pi1')
+        m2.setParentIdentifier(None)
+        m1.combine(m2)
+        self.assertEqual(m1.parentIdentifier(), 'pi1')
+
+        m1.setParentIdentifier(None)
+        m2.setParentIdentifier('pi2')
+        m1.combine(m2)
+        self.assertEqual(m1.parentIdentifier(), 'pi2')
+
+        m1.setLanguage('l1')
+        m2.setLanguage(None)
+        m1.combine(m2)
+        self.assertEqual(m1.language(), 'l1')
+
+        m1.setLanguage(None)
+        m2.setLanguage('l2')
+        m1.combine(m2)
+        self.assertEqual(m1.language(), 'l2')
+
+        m1.setType('ty1')
+        m2.setType(None)
+        m1.combine(m2)
+        self.assertEqual(m1.type(), 'ty1')
+
+        m1.setType(None)
+        m2.setType('ty2')
+        m1.combine(m2)
+        self.assertEqual(m1.type(), 'ty2')
+
+        m1.setTitle('t1')
+        m2.setTitle(None)
+        m1.combine(m2)
+        self.assertEqual(m1.title(), 't1')
+
+        m1.setTitle(None)
+        m2.setTitle('t2')
+        m1.combine(m2)
+        self.assertEqual(m1.title(), 't2')
+
+        m1.setAbstract('a1')
+        m2.setAbstract(None)
+        m1.combine(m2)
+        self.assertEqual(m1.abstract(), 'a1')
+
+        m1.setAbstract(None)
+        m2.setAbstract('a2')
+        m1.combine(m2)
+        self.assertEqual(m1.abstract(), 'a2')
+
+        m1.setHistory(['h1', 'hh1'])
+        m2.setHistory([])
+        m1.combine(m2)
+        self.assertEqual(m1.history(), ['h1', 'hh1'])
+
+        m1.setHistory([])
+        m2.setHistory(['h2', 'hh2'])
+        m1.combine(m2)
+        self.assertEqual(m1.history(), ['h2', 'hh2'])
+
+        m1.setKeywords({'words': ['k1', 'kk1']})
+        m2.setKeywords({})
+        m1.combine(m2)
+        self.assertEqual(m1.keywords(), {'words': ['k1', 'kk1']})
+
+        m1.setKeywords({})
+        m2.setKeywords({'words': ['k2', 'kk2']})
+        m1.combine(m2)
+        self.assertEqual(m1.keywords(), {'words': ['k2', 'kk2']})
+
+        m1.setContacts([QgsLayerMetadata.Contact('c1'), QgsLayerMetadata.Contact('cc1')])
+        m2.setContacts([])
+        m1.combine(m2)
+        self.assertEqual(m1.contacts(), [QgsLayerMetadata.Contact('c1'), QgsLayerMetadata.Contact('cc1')])
+
+        m1.setContacts([])
+        m2.setContacts([QgsLayerMetadata.Contact('c2'), QgsLayerMetadata.Contact('cc2')])
+        m1.combine(m2)
+        self.assertEqual(m1.contacts(), [QgsLayerMetadata.Contact('c2'), QgsLayerMetadata.Contact('cc2')])
+
+        m1.setLinks([QgsLayerMetadata.Link('l1'), QgsLayerMetadata.Link('ll1')])
+        m2.setLinks([])
+        m1.combine(m2)
+        self.assertEqual(m1.links(), [QgsLayerMetadata.Link('l1'), QgsLayerMetadata.Link('ll1')])
+
+        m1.setLinks([])
+        m2.setLinks([QgsLayerMetadata.Link('l2'), QgsLayerMetadata.Link('ll2')])
+        m1.combine(m2)
+        self.assertEqual(m1.links(), [QgsLayerMetadata.Link('l2'), QgsLayerMetadata.Link('ll2')])
+
+        m1.setFees('f1')
+        m2.setFees(None)
+        m1.combine(m2)
+        self.assertEqual(m1.fees(), 'f1')
+
+        m1.setFees(None)
+        m2.setFees('f2')
+        m1.combine(m2)
+        self.assertEqual(m1.fees(), 'f2')
+
+        m1.setConstraints([QgsLayerMetadata.Constraint('c1'), QgsLayerMetadata.Constraint('cc1')])
+        m2.setConstraints([])
+        m1.combine(m2)
+        self.assertEqual(m1.constraints(), [QgsLayerMetadata.Constraint('c1'), QgsLayerMetadata.Constraint('cc1')])
+
+        m1.setConstraints([])
+        m2.setConstraints([QgsLayerMetadata.Constraint('c2'), QgsLayerMetadata.Constraint('cc2')])
+        m1.combine(m2)
+        self.assertEqual(m1.constraints(), [QgsLayerMetadata.Constraint('c2'), QgsLayerMetadata.Constraint('cc2')])
+
+        m1.setRights(['r1', 'rr1'])
+        m2.setRights([])
+        m1.combine(m2)
+        self.assertEqual(m1.rights(), ['r1', 'rr1'])
+
+        m1.setRights([])
+        m2.setRights(['r2', 'rr2'])
+        m1.combine(m2)
+        self.assertEqual(m1.rights(), ['r2', 'rr2'])
+
+        m1.setLicenses(['li1', 'lli1'])
+        m2.setLicenses([])
+        m1.combine(m2)
+        self.assertEqual(m1.licenses(), ['li1', 'lli1'])
+
+        m1.setLicenses([])
+        m2.setLicenses(['li2', 'lli2'])
+        m1.combine(m2)
+        self.assertEqual(m1.licenses(), ['li2', 'lli2'])
+
+        m1.setEncoding('e1')
+        m2.setEncoding(None)
+        m1.combine(m2)
+        self.assertEqual(m1.encoding(), 'e1')
+
+        m1.setEncoding(None)
+        m2.setEncoding('e2')
+        m1.combine(m2)
+        self.assertEqual(m1.encoding(), 'e2')
+
+        m1.setCrs(QgsCoordinateReferenceSystem('EPSG:3111'))
+        m2.setCrs(QgsCoordinateReferenceSystem())
+        m1.combine(m2)
+        self.assertEqual(m1.crs().authid(), 'EPSG:3111')
+
+        m1.setCrs(QgsCoordinateReferenceSystem())
+        m2.setCrs(QgsCoordinateReferenceSystem('EPSG:3113'))
+        m1.combine(m2)
+        self.assertEqual(m1.crs().authid(), 'EPSG:3113')
+
+        s = QgsLayerMetadata.SpatialExtent()
+        s.bounds = QgsBox3d(1, 2, 3, 4, 5, 6)
+        m1.extent().setSpatialExtents([s])
+        m2.extent().setSpatialExtents([])
+        m1.combine(m2)
+        self.assertEqual(m1.extent().spatialExtents()[0].bounds, QgsBox3d(1, 2, 3, 4, 5, 6))
+
+        s.bounds = QgsBox3d(11, 12, 13, 14, 15, 16)
+        m1.extent().setSpatialExtents([])
+        m2.extent().setSpatialExtents([s])
+        m1.combine(m2)
+        self.assertEqual(m1.extent().spatialExtents()[0].bounds, QgsBox3d(11, 12, 13, 14, 15, 16))
+
+        s = QgsDateTimeRange(QDateTime(2020, 1, 1, 0, 0, 0), QDateTime(2020, 2, 1, 0, 0, 0))
+        m1.extent().setTemporalExtents([s])
+        m2.extent().setTemporalExtents([])
+        m1.combine(m2)
+        self.assertEqual(m1.extent().temporalExtents()[0], s)
+
+        s = QgsDateTimeRange(QDateTime(2021, 1, 1, 0, 0, 0), QDateTime(2021, 2, 1, 0, 0, 0))
+        m1.extent().setTemporalExtents([])
+        m2.extent().setTemporalExtents([s])
+        m1.combine(m2)
+        self.assertEqual(m1.extent().temporalExtents()[0], s)
+
 
 if __name__ == '__main__':
     unittest.main()