Add plugin for croissant functionality

Register a template folder and automatically override the dataset read
page to add the Croissant serialization.

ckanext/dcat/helpers.py

@@ -21,7 +21,30 @@ def get_endpoint(_type="dataset"):
     return "dcat.read_dataset" if _type == "dataset" else "dcat.read_catalog"
 
 
-def structured_data(dataset_dict, profiles=None, _format="jsonld"):
+def _get_serialization(dataset_dict, profiles=None, _format="jsonld"):
+
+    serializer = RDFSerializer(profiles=profiles)
+
+    output = serializer.serialize_dataset(dataset_dict, _format=_format)
+
+    # parse result again to prevent UnicodeDecodeError and add formatting
+    if _format == "jsonld":
+        try:
+            json_data = json.loads(output)
+            return json.dumps(
+                json_data,
+                sort_keys=True,
+                indent=4,
+                separators=(",", ": "),
+                cls=json.JSONEncoderForHTML,
+            )
+        except ValueError:
+            # result was not JSON, return anyway
+            pass
+    return output
+
+
+def structured_data(dataset_dict, profiles=None):
     """
     Returns a string containing the structured data of the given
     dataset id and using the given profiles (if no profiles are supplied
@@ -33,20 +56,17 @@ def structured_data(dataset_dict, profiles=None, _format="jsonld"):
     if not profiles:
         profiles = ["schemaorg"]
 
-    serializer = RDFSerializer(profiles=profiles)
+    return _get_serialization(dataset_dict, profiles, "jsonld")
 
-    output = serializer.serialize_dataset(dataset_dict, _format=_format)
 
-    # parse result again to prevent UnicodeDecodeError and add formatting
-    try:
-        json_data = json.loads(output)
-        return json.dumps(
-            json_data,
-            sort_keys=True,
-            indent=4,
-            separators=(",", ": "),
-            cls=json.JSONEncoderForHTML,
-        )
-    except ValueError:
-        # result was not JSON, return anyway
-        return output
+def croissant(dataset_dict, profiles=None):
+    """
+    Returns a string containing the Croissant ML representation of the given
+    dataset using the `croissant` profile.
+    This string can be used in the frontend.
+    """
+
+    if not profiles:
+        profiles = ["croissant"]
+
+    return _get_serialization(dataset_dict, profiles, "jsonld")

ckanext/dcat/plugins/__init__.py

@@ -258,3 +258,21 @@ def get_helpers(self):
         return {
             'structured_data': helpers.structured_data,
         }
+
+
+class CroissantPlugin(p.SingletonPlugin):
+
+    p.implements(p.IConfigurer, inherit=True)
+    p.implements(p.ITemplateHelpers, inherit=True)
+
+    # IConfigurer
+
+    def update_config(self, config):
+        p.toolkit.add_template_directory(config, '../templates/croissant')
+
+    # ITemplateHelpers
+
+    def get_helpers(self):
+        return {
+            'croissant': helpers.croissant,
+        }

ckanext/dcat/templates/croissant/package/read_base.html

@@ -0,0 +1,13 @@
+{% ckan_extends %}
+
+{% block scripts %}
+
+  {{ super() }}
+
+  {% block croissant %}
+    <!-- Croissant ML -->
+    <script type="application/ld+json">
+      {{ h.croissant(pkg) | safe }}
+    </script>
+  {% endblock %}
+{% endblock %}

pyproject.toml

@@ -51,6 +51,7 @@ dcat_json_interface = "ckanext.dcat.plugins:DCATJSONInterface"
 dcat = "ckanext.dcat.plugins:DCATPlugin"
 
 structured_data = "ckanext.dcat.plugins:StructuredDataPlugin"
+croissant = "ckanext.dcat.plugins:CroissantPlugin"
 # Test plugins
 test_rdf_harvester = "ckanext.dcat.tests.harvester.test_harvester:TestRDFHarvester"
 test_rdf_null_harvester = "ckanext.dcat.tests.harvester.test_harvester:TestRDFNullHarvester"