A couple quick fixes

src/pygeometadata/mcf.py

@@ -239,7 +239,7 @@ def set_abstract(self, abstract):
         self.mcf['identification']['abstract'] = abstract
 
     def set_keywords(self, keywords, section='default', keywords_type='theme',
-                 vocabulary=None):
+                     vocabulary=None):
         """Describe a dataset with a list of keywords.
 
         Keywords are grouped into sections for the purpose of complying with
@@ -299,6 +299,7 @@ def describe_band(self, band_number, name=None, title=None, abstract=None,
     def describe_field(self, name, title=None, abstract=None,
                        units=None):
         """Define metadata for a tabular field.
+
         Args:
             name (str): name and unique identifier of the field
             title (str): title for the field
@@ -324,7 +325,16 @@ def get_attr(attribute_list):
         self.mcf['content_info']['attributes'][idx] = attribute
 
     def write(self):
-        """Write MCF to disk."""
+        """Write MCF and ISO-19139 XML to disk.
+
+        This creates sidecar files with '.yml' and '.xml' extensions
+        appended to the full filename of the data source. For example,
+
+        - 'myraster.tif'
+        - 'myraster.tif.yml'
+        - 'myraster.tif.xml'
+
+        """
         with open(self.mcf_path, 'w') as file:
             file.write(yaml.dump(self.mcf, Dumper=_NoAliasDumper))
         # TODO: allow user to override the iso schema choice
@@ -347,8 +357,9 @@ def to_string(self):
 
     def _set_spatial_info(self):
         """Populate the MCF using properties of the dataset."""
-        gis_type = pygeoprocessing.get_gis_type(self.datasource)
-        if gis_type == pygeoprocessing.UNKNOWN_TYPE:
+        try:
+            gis_type = pygeoprocessing.get_gis_type(self.datasource)
+        except ValueError:
             self.mcf['metadata']['hierarchylevel'] = 'nonGeographicDataset'
             return
 
@@ -388,7 +399,8 @@ def _set_spatial_info(self):
                 attribute['title'] = ''
                 attribute['abstract'] = ''
                 attributes.append(attribute)
-            self.mcf['content_info']['attributes'] = attributes
+            if len(attributes):
+                self.mcf['content_info']['attributes'] = attributes
             vector = None
             layer = None
 
@@ -412,7 +424,8 @@ def _set_spatial_info(self):
                 attribute['title'] = ''
                 attribute['abstract'] = band.GetDescription()
                 attributes.append(attribute)
-            self.mcf['content_info']['attributes'] = attributes
+            if len(attributes):
+                self.mcf['content_info']['attributes'] = attributes
             raster = None
 
             gis_info = pygeoprocessing.get_raster_info(self.datasource)

tests/test_mcf.py

@@ -29,11 +29,13 @@
 }
 
 
-def create_vector(target_filepath, field_map):
-    attribute_list = [{
-        k: _OGR_TYPES_VALUES_MAP[v]
-        for k, v in field_map.items()
-    }]
+def create_vector(target_filepath, field_map=None):
+    attribute_list = None
+    if field_map:
+        attribute_list = [{
+            k: _OGR_TYPES_VALUES_MAP[v]
+            for k, v in field_map.items()
+        }]
     projection = osr.SpatialReference()
     projection.ImportFromEPSG(3116)
     pygeoprocessing.shapely_geometry_to_vector(
@@ -112,6 +114,22 @@ def test_vector_MCF(self):
                 f'{e}')
         mcf.write()
 
+    def test_vector_no_fields(self):
+        """MCF: validate MCF for basic vector with no fields."""
+        from pygeometadata.mcf import MCF
+
+        datasource_path = os.path.join(self.workspace_dir, 'vector.geojson')
+        create_vector(datasource_path, None)
+
+        mcf = MCF(datasource_path)
+        try:
+            mcf.validate()
+        except (MCFValidationError, SchemaError) as e:
+            self.fail(
+                'unexpected validation error occurred\n'
+                f'{e}')
+        mcf.write()
+
     def test_raster_MCF(self):
         """MCF: validate basic raster MCF."""
         from pygeometadata.mcf import MCF