Expose schema $id and path to template context (#2798)

* Expose schema $id and path to template context

* Replace unit tests with e2e test for schema_id feature

* Remove duplicate set_schema_id call

* Update test template with escape_docstring filter

* Use simple class attributes instead of ClassVar in test template

* Refactor _set_schema_metadata to call individual setter methods

Author: koxudaxi

src/datamodel_code_generator/model/base.py

@@ -887,6 +887,7 @@ def render(self, *, class_name: str | None = None) -> str:
             methods=self.methods,
             description=self.description,
             dataclass_arguments=self.dataclass_arguments,
+            path=self.path,
             **self.extra_template_data,
         )
 

src/datamodel_code_generator/parser/jsonschema.py

@@ -1168,14 +1168,17 @@ def set_title(self, path: str, obj: JsonSchemaObject) -> None:
         if obj.title:
             self.extra_template_data[path]["title"] = obj.title
 
+    def set_schema_id(self, path: str, obj: JsonSchemaObject) -> None:
+        """Set $id in extra template data."""
+        if obj.id:
+            self.extra_template_data[path]["schema_id"] = obj.id
+
     def _set_schema_metadata(self, path: str, obj: JsonSchemaObject) -> None:
-        """Set title, additionalProperties and unevaluatedProperties in extra template data."""
-        if obj.title:
-            self.extra_template_data[path]["title"] = obj.title
-        if isinstance(obj.additionalProperties, bool):
-            self.extra_template_data[path]["additionalProperties"] = obj.additionalProperties
-        if isinstance(obj.unevaluatedProperties, bool):
-            self.extra_template_data[path]["unevaluatedProperties"] = obj.unevaluatedProperties
+        """Set title, $id, additionalProperties and unevaluatedProperties in extra template data."""
+        self.set_title(path, obj)
+        self.set_schema_id(path, obj)
+        self.set_additional_properties(path, obj)
+        self.set_unevaluated_properties(path, obj)
 
     def set_schema_extensions(self, path: str, obj: JsonSchemaObject) -> None:
         """Set schema extensions (x-* fields) in extra template data."""
@@ -1926,6 +1929,7 @@ def _parse_object_common_part(  # noqa: PLR0912, PLR0913, PLR0915
         reference = self.model_resolver.add(path, name, class_name=True, loaded=True)
         self.set_additional_properties(reference.path, obj)
         self.set_unevaluated_properties(reference.path, obj)
+        self.set_schema_id(reference.path, obj)
         self.set_schema_extensions(reference.path, obj)
 
         generates_separate = self._should_generate_separate_models(fields, base_classes)
@@ -2268,6 +2272,7 @@ def parse_object(
         )
         class_name = reference.name
         self.set_title(reference.path, obj)
+        self.set_schema_id(reference.path, obj)
         if self.read_only_write_only_model_type is not None and obj.properties:
             for prop in obj.properties.values():
                 if isinstance(prop, JsonSchemaObject) and prop.ref:

tests/data/expected/main/jsonschema/schema_id.py

@@ -0,0 +1,21 @@
+# generated by datamodel-codegen:
+#   filename:  schema_id.json
+#   timestamp: 1985-10-26T08:21:00+00:00
+
+from __future__ import annotations
+
+from pydantic import BaseModel
+
+
+class Model(BaseModel):
+    __schema_id__ = "https://example.com/schemas/user"
+    __path__ = "#"
+    id: str
+    name: str
+
+
+class Address(BaseModel):
+    __schema_id__ = "#address"
+    __path__ = "#/definitions/Address"
+    street: str
+    city: str | None = None

tests/data/jsonschema/schema_id.json

@@ -0,0 +1,29 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "$id": "https://example.com/schemas/user",
+  "type": "object",
+  "properties": {
+    "id": {
+      "type": "string"
+    },
+    "name": {
+      "type": "string"
+    }
+  },
+  "required": ["id", "name"],
+  "definitions": {
+    "Address": {
+      "$id": "#address",
+      "type": "object",
+      "properties": {
+        "street": {
+          "type": "string"
+        },
+        "city": {
+          "type": "string"
+        }
+      },
+      "required": ["street"]
+    }
+  }
+}

tests/data/templates_schema_id/pydantic_v2/BaseModel.jinja2

@@ -0,0 +1,63 @@
+{% if base_class != "BaseModel" and "," not in base_class and not fields and not config and not description -%}
+
+{# if this is just going to be `class Foo(Bar): pass`, then might as well just make Foo
+an alias for Bar: every pydantic model class consumes considerable memory. #}
+{{ class_name }} = {{ base_class }}
+
+{% else -%}
+
+{% for decorator in decorators -%}
+{{ decorator }}
+{% endfor -%}
+class {{ class_name }}({{ base_class }}):{% if comment is defined %}  # {{ comment }}{% endif %}
+{%- if description %}
+    """
+    {{ description | escape_docstring | indent(4) }}
+    """
+{%- endif %}
+{%- if schema_id is defined and schema_id %}
+    __schema_id__ = "{{ schema_id }}"
+{%- endif %}
+{%- if path is defined and path %}
+    __path__ = "{{ path }}"
+{%- endif %}
+{%- if not fields and not description and not config and not (schema_id is defined and schema_id) %}
+    pass
+{%- endif %}
+{%- if config %}
+{%- filter indent(4) %}
+{% include 'ConfigDict.jinja2' %}
+{%- endfilter %}
+{%- endif %}
+{%- for field in fields %}
+    {%- if not field.annotated and field.field %}
+    {{ field.name }}: {{ field.type_hint }} = {{ field.field }}
+    {%- else %}
+    {%- if field.annotated %}
+    {{ field.name }}: {{ field.annotated }}
+    {%- else %}
+    {{ field.name }}: {{ field.type_hint }}
+    {%- endif %}
+    {%- if not field.has_default_factory_in_field and not field.required and (field.represented_default != 'None' or not field.strip_default_none or field.data_type.is_optional)
+            %} = {{ field.represented_default }}
+    {%- endif -%}
+    {%- endif %}
+    {%- if field.docstring %}
+    """
+    {{ field.docstring | escape_docstring | indent(4) }}
+    """
+{%- if field.use_inline_field_description and not loop.last %}
+
+{% endif %}
+    {%- elif field.inline_field_docstring %}
+    {{ field.inline_field_docstring }}
+{%- if not loop.last %}
+
+{% endif %}
+    {%- endif %}
+{%- for method in methods -%}
+    {{ method }}
+{%- endfor -%}
+{%- endfor -%}
+
+{%- endif %}

tests/main/jsonschema/test_main_jsonschema.py

@@ -23,6 +23,7 @@
 )
 from datamodel_code_generator.__main__ import Exit, main
 from datamodel_code_generator.format import is_supported_in_black
+from datamodel_code_generator.model import base as model_base
 from tests.conftest import assert_directory_content, freeze_time
 from tests.main.conftest import (
     ALIASES_DATA_PATH,
@@ -6342,3 +6343,26 @@ def test_main_use_root_model_type_alias(output_file: Path) -> None:
             "3.10",
         ],
     )
+
+
+def test_main_jsonschema_schema_id(
+    capsys: pytest.CaptureFixture, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    """Test that $id is exposed as schema_id in custom templates (issue #2098)."""
+    model_base._get_environment.cache_clear()
+    model_base._get_template_with_custom_dir.cache_clear()
+    monkeypatch.chdir(tmp_path)
+    with freeze_time(TIMESTAMP):
+        run_main_and_assert(
+            input_path=JSON_SCHEMA_DATA_PATH / "schema_id.json",
+            output_path=None,
+            expected_stdout_path=EXPECTED_JSON_SCHEMA_PATH / "schema_id.py",
+            capsys=capsys,
+            input_file_type=None,
+            extra_args=[
+                "--custom-template-dir",
+                str(DATA_PATH / "templates_schema_id"),
+                "--output-model-type",
+                "pydantic_v2.BaseModel",
+            ],
+        )