BDRSPS-1122 Make the cached ABISMapper.metadata() method return a fro…

…zen type

This is to avoid accidental mutation of the cached return value.
Plus returning a pydantic model, rather than a dict leads to better type-checked code

abis_mapping/base/mapper.py

@@ -335,7 +335,7 @@ def template(cls) -> pathlib.Path:
 
         # Template File is the name and filetype as extension from metadata
         md = cls.metadata()
-        template_file = directory / f"{md['name']}.{md['file_type'].lower()}"
+        template_file = directory / f"{md.name}.{md.file_type.lower()}"
 
         # Return
         return template_file
@@ -347,27 +347,27 @@ def template_id(self) -> str:
         Returns:
             str: template id from metadata
         """
-        return self.metadata()["id"]
+        return self.metadata().id
 
     @final
     @classmethod
     @functools.cache
-    def metadata(cls) -> dict[str, str]:
+    def metadata(cls) -> models.metadata.TemplateMetadata:
         """Retrieves and Caches the Template Metadata for this Template
 
         Returns:
-            dict[str, Any]: Template Metadata for this Template
+            Template Metadata for this Template
         """
         # Retrieve Metadata Filepath
         directory = pathlib.Path(inspect.getfile(cls)).parent
         metadata_file = directory / "metadata.json"
 
         # Read Metadata and validate
-        md_dict = json.loads(metadata_file.read_text())
-        md_class = models.metadata.TemplateMetadata.model_validate(md_dict, strict=False)
+        md_content = metadata_file.read_bytes()
+        md_class = models.metadata.TemplateMetadata.model_validate_json(md_content)
 
         # Return
-        return md_class.model_dump()
+        return md_class
 
     @final
     @classmethod
@@ -436,7 +436,7 @@ def register_mapper(mapper: type[ABISMapper]) -> None:
         mapper: Mapper class to be registered.
     """
     # Register the mapper with its template id
-    template_id = mapper.metadata()["id"]
+    template_id = mapper.metadata().id
     _registry[template_id] = mapper
 
 

abis_mapping/models/metadata.py

@@ -22,6 +22,11 @@ class TemplateMetadataLifecycleStatus(enum.StrEnum):
 class TemplateMetadata(pydantic.BaseModel):
     """Model for the template `metadata.json` file."""
 
+    model_config = pydantic.ConfigDict(
+        # Frozen because this class is returned by the cached ABISMapper.metadata() method
+        frozen=True,
+    )
+
     name: str
     label: str
     version: str

tests/templates/test_common.py

@@ -67,7 +67,7 @@ def test_get_metadata(self, test_params: conftest.TemplateTestParameters) -> Non
         real_mapper = abis_mapping.base.mapper.get_mapper(test_params.template_id)
         assert real_mapper is not None
         metadata = real_mapper.metadata()
-        assert isinstance(metadata, dict)
+        assert isinstance(metadata, abis_mapping.models.metadata.TemplateMetadata)
 
     def test_metadata_id_match(self, test_params: conftest.TemplateTestParameters) -> None:
         """Tests the metadata id matches the mapper id"""
@@ -77,7 +77,7 @@ def test_metadata_id_match(self, test_params: conftest.TemplateTestParameters) -
 
         # Retrieve metadata
         metadata = real_mapper.metadata()
-        assert metadata.get("id") == real_mapper().template_id
+        assert metadata.id == real_mapper().template_id
 
     def test_get_schema(self, test_params: conftest.TemplateTestParameters) -> None:
         """Tests able to retrieve template schema."""
@@ -117,7 +117,7 @@ def test_metadata_sampling_type(self, test_params: conftest.TemplateTestParamete
         metadata = mapper().metadata()
 
         # Confirm field set correctly
-        assert metadata.get("sampling_type") == test_params.metadata_sampling_type
+        assert metadata.sampling_type == test_params.metadata_sampling_type
 
     def test_schema_is_valid(self, test_params: conftest.TemplateTestParameters) -> None:
         """Tests that the schema.json is a valid frictionless schema."""