Add metadata validator

Adds a new abstract base class QgsMetadataValidator for validating
metadata against standard schemas.

Initially only QgsNativeMetadataValidator for validating against
the native QGIS metadata schema is implemented.

In future this could be extended with Dublin Core, ISO 19115
validators, etc...

python/core/core.sip

@@ -277,6 +277,7 @@
 %Include layertree/qgslayertreeutils.sip
 
 %Include metadata/qgslayermetadata.sip
+%Include metadata/qgslayermetadatavalidator.sip
 
 %Include processing/qgsprocessingalgorithm.sip
 %Include processing/qgsprocessingcontext.sip

python/core/metadata/qgslayermetadata.sip

@@ -253,7 +253,7 @@ class QgsLayerMetadata
 
     void setLanguage( const QString &language );
 %Docstring
- Sets the human language associated with the resource. While a formal vocabulary is not imposed,
+ Sets the human ``language`` associated with the resource. While a formal vocabulary is not imposed,
  ideally values should be taken from the ISO 639.2 or ISO 3166 specifications,
  e.g. 'ENG' or 'SPA' (ISO 639.2) or 'EN-AU' (ISO 3166).
  \see language()
@@ -269,7 +269,7 @@ class QgsLayerMetadata
 
     void setType( const QString &type );
 %Docstring
- Sets the type (nature) of the resource.  While a formal vocabulary is not imposed, it is advised
+ Sets the ``type`` (nature) of the resource.  While a formal vocabulary is not imposed, it is advised
  to use the ISO 19115 MD_ScopeCode values. E.g. 'dataset' or 'series'.
  \see type()
 %End
@@ -283,7 +283,7 @@ class QgsLayerMetadata
 
     void setTitle( const QString &title );
 %Docstring
- Sets the human readable title (name) of the resource, typically displayed in search results.
+ Sets the human readable ``title`` (name) of the resource, typically displayed in search results.
  \see title()
 %End
 
@@ -296,7 +296,7 @@ class QgsLayerMetadata
 
     void setAbstract( const QString &abstract );
 %Docstring
- Sets a free-form abstract (description) of the resource.
+ Sets a free-form ``abstract`` (description) of the resource.
  \see abstract()
 %End
 
@@ -310,7 +310,7 @@ class QgsLayerMetadata
 
     void setFees( const QString &fees );
 %Docstring
- Sets the fees associated with using the resource.
+ Sets the ``fees`` associated with using the resource.
  Use an empty string if no fees are set.
  \see fees()
 %End
@@ -324,7 +324,7 @@ class QgsLayerMetadata
 
     void setConstraints( const QgsLayerMetadata::ConstraintList &constraints );
 %Docstring
- Sets the list of constraints associated with using the resource.
+ Sets the list of ``constraints`` associated with using the resource.
  \see constraints()
 %End
 
@@ -337,7 +337,7 @@ class QgsLayerMetadata
 
     void setRights( const QStringList &rights );
 %Docstring
- Sets a list of rights (attribution or copyright strings) associated with the resource.
+ Sets a list of ``rights`` (attribution or copyright strings) associated with the resource.
  \see rights()
 %End
 
@@ -350,7 +350,7 @@ class QgsLayerMetadata
 
     void setEncoding( const QString &encoding );
 %Docstring
- Sets the character encoding of the data in the resource. Use an empty string if no encoding is set.
+ Sets the character ``encoding`` of the data in the resource. Use an empty string if no encoding is set.
  \see encoding()
 %End
 
@@ -401,7 +401,7 @@ class QgsLayerMetadata
 
     void setKeywords( const KeywordMap &keywords );
 %Docstring
- Sets the keywords map, which is a set of descriptive keywords associated with the resource.
+ Sets the ``keywords`` map, which is a set of descriptive keywords associated with the resource.
 
  The map key is the vocabulary string and map value is a list of keywords for that vocabulary.
  Calling this replaces any existing keyword vocabularies.
@@ -415,7 +415,7 @@ class QgsLayerMetadata
 
     void addKeywords( const QString &vocabulary, const QStringList &keywords );
 %Docstring
- Adds a list of descriptive keywords for a specified vocabulary. Any existing
+ Adds a list of descriptive ``keywords`` for a specified ``vocabulary``. Any existing
  keywords for the same vocabulary will be replaced. Other vocabularies
  will not be affected.
 
@@ -438,7 +438,7 @@ class QgsLayerMetadata
 
     QStringList keywords( const QString &vocabulary ) const;
 %Docstring
- Returns a list of keywords for the specified vocabulary.
+ Returns a list of keywords for the specified ``vocabulary``.
  If the vocabulary is not contained in the metadata, an empty
  list will be returned.
 
@@ -458,7 +458,7 @@ class QgsLayerMetadata
 
     void setContacts( const QgsLayerMetadata::ContactList &contacts );
 %Docstring
- Sets the list of contacts or entities associated with the resource. Any existing contacts
+ Sets the list of ``contacts`` or entities associated with the resource. Any existing contacts
  will be replaced.
  \see contacts()
  \see addContact()
@@ -466,7 +466,7 @@ class QgsLayerMetadata
 
     void addContact( const QgsLayerMetadata::Contact &contact );
 %Docstring
- Adds an individual contact to the existing contacts.
+ Adds an individual ``contact`` to the existing contacts.
  \see contacts()
  \see setContacts()
 %End
@@ -488,20 +488,20 @@ class QgsLayerMetadata
 
     void addLink( const QgsLayerMetadata::Link &link );
 %Docstring
- Adds an individual link to the existing links.
+ Adds an individual ``link`` to the existing links.
  \see links()
  \see setLinks()
 %End
 
     void saveToLayer( QgsMapLayer *layer ) const;
 %Docstring
- Saves the metadata to a layer's custom properties (see QgsMapLayer.setCustomProperty() ).
+ Saves the metadata to a ``layer``'s custom properties (see QgsMapLayer.setCustomProperty() ).
  \see readFromLayer()
 %End
 
     void readFromLayer( const QgsMapLayer *layer );
 %Docstring
- Reads the metadata state from a layer's custom properties (see QgsMapLayer.customProperty() ).
+ Reads the metadata state from a ``layer``'s custom properties (see QgsMapLayer.customProperty() ).
  \see saveToLayer()
 %End
 

python/core/metadata/qgslayermetadatavalidator.sip

@@ -0,0 +1,96 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/metadata/qgslayermetadatavalidator.h                        *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
+
+
+
+
+
+
+class QgsMetadataValidator
+{
+%Docstring
+ Abstract base class for metadata validators.
+.. versionadded:: 3.0
+%End
+
+%TypeHeaderCode
+#include "qgslayermetadatavalidator.h"
+%End
+  public:
+
+    struct ValidationResult
+    {
+
+      ValidationResult( const QString &section, const QString &note, const QVariant &identifier = QVariant() );
+%Docstring
+ Constructor for ValidationResult.
+%End
+
+      QString section;
+%Docstring
+Metadata section which failed the validation
+%End
+
+      QVariant identifier;
+%Docstring
+ Optional identifier for the failed metadata item.
+ For instance, in list type metadata elements this
+ will be set to the list index of the failed metadata
+ item.
+%End
+
+      QString note;
+%Docstring
+The reason behind the validation failure.
+%End
+    };
+
+    virtual ~QgsMetadataValidator();
+
+    virtual bool validate( const QgsLayerMetadata &metadata, QList< QgsMetadataValidator::ValidationResult > &results /Out/ ) const = 0;
+%Docstring
+ Validates a ``metadata`` object, and returns true if the
+ metadata is considered valid.
+ If validation fails, the ``results`` list will be filled with a list of
+ items describing why the validation failed and what needs to be rectified
+ to fix the metadata.
+ :rtype: bool
+%End
+
+};
+
+
+
+class QgsNativeMetadataValidator : QgsMetadataValidator
+{
+%Docstring
+ A validator for the native QGIS metadata schema definition.
+.. versionadded:: 3.0
+%End
+
+%TypeHeaderCode
+#include "qgslayermetadatavalidator.h"
+%End
+  public:
+
+    QgsNativeMetadataValidator();
+%Docstring
+ Constructor for QgsNativeMetadataValidator.
+%End
+
+    virtual bool validate( const QgsLayerMetadata &metadata, QList< QgsMetadataValidator::ValidationResult > &results /Out/ ) const;
+
+};
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/metadata/qgslayermetadatavalidator.h                        *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/

python/core/qgsmaplayer.sip

@@ -829,7 +829,7 @@ Return pointer to layer's undo stack
 
     virtual void setMetadata( const QgsLayerMetadata &metadata );
 %Docstring
- Sets the layer's metadata store.
+ Sets the layer's ``metadata`` store.
 .. versionadded:: 3.0
  \see metadata()
  \see metadataChanged()

src/core/CMakeLists.txt

@@ -72,6 +72,7 @@ SET(QGIS_CORE_SRCS
   layertree/qgslayertree.cpp
 
   metadata/qgslayermetadata.cpp
+  metadata/qgslayermetadatavalidator.cpp
 
   auth/qgsauthcertutils.cpp
   auth/qgsauthconfig.cpp
@@ -858,6 +859,7 @@ SET(QGIS_CORE_HDRS
   composer/qgspaperitem.h
 
   metadata/qgslayermetadata.h
+  metadata/qgslayermetadatavalidator.h
 
   processing/qgsprocessingalgorithm.h
   processing/qgsprocessingcontext.h

src/core/metadata/qgslayermetadatavalidator.cpp

@@ -0,0 +1,130 @@
+/***************************************************************************
+                             qgslayermetadatavalidator.cpp
+                             -----------------------------
+    begin                : April 2017
+    copyright            : (C) 2017 by Nyall Dawson
+    email                : nyall dot dawson at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgslayermetadatavalidator.h"
+#include "qgslayermetadata.h"
+
+bool QgsNativeMetadataValidator::validate( const QgsLayerMetadata &metadata, QList<ValidationResult> &results ) const
+{
+  results.clear();
+
+  bool result = true;
+  if ( metadata.identifier().isEmpty() )
+  {
+    result = false;
+    results << ValidationResult( QObject::tr( "identifier" ), QObject::tr( "Identifier element is required." ) );
+  }
+
+  if ( metadata.language().isEmpty() )
+  {
+    result = false;
+    results << ValidationResult( QObject::tr( "language" ), QObject::tr( "Language element is required." ) );
+  }
+
+  if ( metadata.type().isEmpty() )
+  {
+    result = false;
+    results << ValidationResult( QObject::tr( "type" ), QObject::tr( "Type element is required." ) );
+  }
+
+  if ( metadata.title().isEmpty() )
+  {
+    result = false;
+    results << ValidationResult( QObject::tr( "title" ), QObject::tr( "Title element is required." ) );
+  }
+
+  if ( metadata.abstract().isEmpty() )
+  {
+    result = false;
+    results << ValidationResult( QObject::tr( "abstract" ), QObject::tr( "Abstract element is required." ) );
+  }
+
+  //result = result && !metadata.license().isEmpty();
+
+  if ( !metadata.crs().isValid() )
+  {
+    result = false;
+    results << ValidationResult( QObject::tr( "crs" ), QObject::tr( "A valid CRS element is required." ) );
+  }
+
+  if ( metadata.contacts().isEmpty() )
+  {
+    result = false;
+    results << ValidationResult( QObject::tr( "contacts" ), QObject::tr( "At least one contact is required." ) );
+  }
+
+  if ( metadata.links().isEmpty() )
+  {
+    result = false;
+    results << ValidationResult( QObject::tr( "links" ), QObject::tr( "At least one link is required." ) );
+  }
+
+  // validate keywords
+  QgsLayerMetadata::KeywordMap keywords = metadata.keywords();
+  QgsLayerMetadata::KeywordMap::const_iterator keywordIt = keywords.constBegin();
+  int index = 0;
+  for ( ; keywordIt != keywords.constEnd(); ++keywordIt )
+  {
+    if ( keywordIt.key().isEmpty() )
+    {
+      result = false;
+      results << ValidationResult( QObject::tr( "keywords" ), QObject::tr( "Keyword vocabulary cannot be empty." ), index );
+    }
+    if ( keywordIt.value().isEmpty() )
+    {
+      result = false;
+      results << ValidationResult( QObject::tr( "keywords" ), QObject::tr( "Keyword list cannot be empty." ), index );
+    }
+    index++;
+  }
+
+  // validate contacts
+  index = 0;
+  Q_FOREACH ( const QgsLayerMetadata::Contact &contact, metadata.contacts() )
+  {
+    if ( contact.name.isEmpty() )
+    {
+      result = false;
+      results << ValidationResult( QObject::tr( "contacts" ), QObject::tr( "Contact name cannot be empty." ), index );
+    }
+    index++;
+  }
+
+  // validate links
+  index = 0;
+  Q_FOREACH ( const QgsLayerMetadata::Link &link, metadata.links() )
+  {
+    if ( link.name.isEmpty() )
+    {
+      result = false;
+      results << ValidationResult( QObject::tr( "links" ), QObject::tr( "Link name cannot be empty." ), index );
+    }
+    if ( link.type.isEmpty() )
+    {
+      result = false;
+      results << ValidationResult( QObject::tr( "links" ), QObject::tr( "Link type cannot be empty." ), index );
+    }
+    if ( link.url.isEmpty() )
+    {
+      result = false;
+      results << ValidationResult( QObject::tr( "links" ), QObject::tr( "Link url cannot be empty." ), index );
+    }
+    index++;
+  }
+
+  return result;
+}

src/core/metadata/qgslayermetadatavalidator.h

@@ -0,0 +1,104 @@
+/***************************************************************************
+                             qgslayermetadatavalidator.h
+                             ---------------------------
+    begin                : April 2017
+    copyright            : (C) 2017 by Nyall Dawson
+    email                : nyall dot dawson at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSLAYERMETADATAVALIDATOR_H
+#define QGSLAYERMETADATAVALIDATOR_H
+
+#include "qgis.h"
+#include "qgis_core.h"
+
+class QgsLayerMetadata;
+
+/**
+ * \ingroup core
+ * \class QgsMetadataValidator
+ * \brief Abstract base class for metadata validators.
+ * \since QGIS 3.0
+ */
+
+class CORE_EXPORT QgsMetadataValidator
+{
+
+  public:
+
+    /**
+     * Contains the parameters describing a metadata validation
+     * failure.
+     */
+    struct ValidationResult
+    {
+
+      /**
+       * Constructor for ValidationResult.
+       */
+      ValidationResult( const QString &section, const QString &note, const QVariant &identifier = QVariant() )
+        : section( section )
+        , identifier( identifier )
+        , note( note )
+      {}
+
+      //! Metadata section which failed the validation
+      QString section;
+
+      /**
+       * Optional identifier for the failed metadata item.
+       * For instance, in list type metadata elements this
+       * will be set to the list index of the failed metadata
+       * item.
+       */
+      QVariant identifier;
+
+      //! The reason behind the validation failure.
+      QString note;
+    };
+
+    virtual ~QgsMetadataValidator() = default;
+
+    /**
+     * Validates a \a metadata object, and returns true if the
+     * metadata is considered valid.
+     * If validation fails, the \a results list will be filled with a list of
+     * items describing why the validation failed and what needs to be rectified
+     * to fix the metadata.
+     */
+    virtual bool validate( const QgsLayerMetadata &metadata, QList< QgsMetadataValidator::ValidationResult > &results SIP_OUT ) const = 0;
+
+};
+
+
+/**
+ * \ingroup core
+ * \class QgsNativeMetadataValidator
+ * \brief A validator for the native QGIS metadata schema definition.
+ * \since QGIS 3.0
+ */
+
+class CORE_EXPORT QgsNativeMetadataValidator : public QgsMetadataValidator
+{
+
+  public:
+
+    /**
+     * Constructor for QgsNativeMetadataValidator.
+     */
+    QgsNativeMetadataValidator() = default;
+
+    bool validate( const QgsLayerMetadata &metadata, QList< QgsMetadataValidator::ValidationResult > &results SIP_OUT ) const override;
+
+};
+
+#endif // QGSLAYERMETADATAVALIDATOR_H

tests/src/python/test_qgslayermetadata.py

@@ -16,7 +16,8 @@ import qgis  # NOQA
 
 from qgis.core import (QgsLayerMetadata,
                        QgsCoordinateReferenceSystem,
-                       QgsVectorLayer)
+                       QgsVectorLayer,
+                       QgsNativeMetadataValidator)
 from qgis.testing import start_app, unittest
 
 start_app()
@@ -300,6 +301,117 @@ class TestQgsLayerMetadata(unittest.TestCase):
         m2.readFromLayer(vl)
         self.checkExpectedMetadata(m2)
 
+    def testValidateNative(self):  # spellok
+        """
+        Test validating metadata against QGIS native schema
+        """
+
+        m = self.createTestMetadata()
+        v = QgsNativeMetadataValidator()
+
+        res, list = v.validate(m)
+        self.assertTrue(res)
+        self.assertFalse(list)
+
+        # corrupt metadata piece by piece...
+        m = self.createTestMetadata()
+        m.setIdentifier('')
+        res, list = v.validate(m)
+        self.assertFalse(res)
+        self.assertEqual(list[0].section, 'identifier')
+
+        m = self.createTestMetadata()
+        m.setLanguage('')
+        res, list = v.validate(m)
+        self.assertFalse(res)
+        self.assertEqual(list[0].section, 'language')
+
+        m = self.createTestMetadata()
+        m.setType('')
+        res, list = v.validate(m)
+        self.assertFalse(res)
+        self.assertEqual(list[0].section, 'type')
+
+        m = self.createTestMetadata()
+        m.setTitle('')
+        res, list = v.validate(m)
+        self.assertFalse(res)
+        self.assertEqual(list[0].section, 'title')
+
+        m = self.createTestMetadata()
+        m.setAbstract('')
+        res, list = v.validate(m)
+        self.assertFalse(res)
+        self.assertEqual(list[0].section, 'abstract')
+
+        m = self.createTestMetadata()
+        m.setCrs(QgsCoordinateReferenceSystem())
+        res, list = v.validate(m)
+        self.assertFalse(res)
+        self.assertEqual(list[0].section, 'crs')
+
+        m = self.createTestMetadata()
+        m.setContacts([])
+        res, list = v.validate(m)
+        self.assertFalse(res)
+        self.assertEqual(list[0].section, 'contacts')
+
+        m = self.createTestMetadata()
+        m.setLinks([])
+        res, list = v.validate(m)
+        self.assertFalse(res)
+        self.assertEqual(list[0].section, 'links')
+
+        m = self.createTestMetadata()
+        m.setKeywords({'': ['kw1', 'kw2']})
+        res, list = v.validate(m)
+        self.assertFalse(res)
+        self.assertEqual(list[0].section, 'keywords')
+        self.assertEqual(list[0].identifier, 0)
+
+        m = self.createTestMetadata()
+        m.setKeywords({'AA': []})
+        res, list = v.validate(m)
+        self.assertFalse(res)
+        self.assertEqual(list[0].section, 'keywords')
+        self.assertEqual(list[0].identifier, 0)
+
+        m = self.createTestMetadata()
+        c = m.contacts()[0]
+        c.name = ''
+        m.setContacts([c])
+        res, list = v.validate(m)
+        self.assertFalse(res)
+        self.assertEqual(list[0].section, 'contacts')
+        self.assertEqual(list[0].identifier, 0)
+
+        m = self.createTestMetadata()
+        l = m.links()[0]
+        l.name = ''
+        m.setLinks([l])
+        res, list = v.validate(m)
+        self.assertFalse(res)
+        self.assertEqual(list[0].section, 'links')
+        self.assertEqual(list[0].identifier, 0)
+
+        m = self.createTestMetadata()
+        l = m.links()[0]
+        l.type = ''
+        m.setLinks([l])
+        res, list = v.validate(m)
+        self.assertFalse(res)
+        self.assertEqual(list[0].section, 'links')
+        self.assertEqual(list[0].identifier, 0)
+
+        m = self.createTestMetadata()
+        l = m.links()[0]
+        l.url = ''
+        m.setLinks([l])
+        res, list = v.validate(m)
+        self.assertFalse(res)
+        self.assertEqual(list[0].section, 'links')
+        self.assertEqual(list[0].identifier, 0)
+
 
 if __name__ == '__main__':
     unittest.main()