Improve reporting of index problems (closes #128)

climix/metadata.py

@@ -175,6 +175,7 @@ class IndexDefinition:
     output: OutputVariable
     input: InputVariable
     index_function: IndexFunction
+    source: str
 
     def instantiate(self, parameters):
         idx = IndexDefinition(
@@ -182,7 +183,8 @@ class IndexDefinition:
             self.period,
             self.output.instantiate(parameters),
             self.input.instantiate(parameters),
-            self.index_function.instantiate(parameters))
+            self.index_function.instantiate(parameters),
+            self.source)
         return idx
 
 
@@ -190,28 +192,30 @@ def build_parameter(metadata):
     return PARAMETER_KINDS[metadata['kind']](**metadata)
 
 
-def build_index(metadata):
-    idx = IndexDefinition(
-        metadata['reference'],
-        metadata['period'],
-        OutputVariable(
-            metadata['output']['var_name'],
-            metadata['output']['standard_name'],
-            metadata['output'].get('proposed_standard_name', None),
-            metadata['output']['long_name'],
-            metadata['output']['units'],
-            [CellMethod(*cm.popitem())
-             for cm in metadata['output']['cell_methods']]),
-        InputVariable(
-            metadata['input']['var_name'],
-            metadata['input']['standard_name'],
-            [CellMethod(*cm.popitem())
-             for cm in metadata['input']['cell_methods']]),
-        IndexFunction(
-            metadata['index_function']['name'],
-            {name: build_parameter(param)
-             for name, param in
-             metadata['index_function']['parameters'].items()}))
+def build_index(metadata, source=None):
+    output = OutputVariable(
+        metadata['output']['var_name'],
+        metadata['output']['standard_name'],
+        metadata['output'].get('proposed_standard_name', None),
+        metadata['output']['long_name'],
+        metadata['output']['units'],
+        [CellMethod(*cm.popitem())
+         for cm in metadata['output']['cell_methods']])
+    input = InputVariable(
+        metadata['input']['var_name'],
+        metadata['input']['standard_name'],
+        [CellMethod(*cm.popitem())
+         for cm in metadata['input']['cell_methods']])
+    params = metadata['index_function']['parameters']
+    if params is None:
+        parameters = {}
+    else:
+        parameters = {name: build_parameter(params[name])
+                      for name in params}
+    index_function = IndexFunction(metadata['index_function']['name'],
+                                   parameters)
+    idx = IndexDefinition(metadata['reference'], metadata['period'],
+                          output, input, index_function, source)
     return idx
 
 
@@ -289,7 +293,13 @@ class IndexCatalog:
         for index in requested_indices:
             definition = self.get_index_definition(index)
             period_spec = select_period(definition.period)
-            index_function = build_index_function(definition.index_function)
+            try:
+                index_function = build_index_function(
+                    definition.index_function)
+            except TypeError:
+                logging.error(f'Could not build index function for index '
+                              f'{index} from definition {definition}')
+                raise
             index = Index(index_function, definition.output, period_spec)
             indices.append(index)
         return indices