Fix internal reference resolution for stdin JSON Schema input (#2578)

Author: koxudaxi

src/datamodel_code_generator/reference.py

@@ -175,6 +175,8 @@ def short_name(self) -> str:
 
 ID_PATTERN: Pattern[str] = re.compile(r"^#[^/].*")
 
+SPECIAL_PATH_MARKER: str = "#-datamodel-code-generator-#-"
+
 T = TypeVar("T")
 
 
@@ -509,7 +511,7 @@ def resolve_ref(self, path: Sequence[str] | str) -> str:  # noqa: PLR0911, PLR09
             joined_path = get_relative_path(self._base_path, resolved_file_path).as_posix()
             if fragment:
                 joined_path += f"#{fragment}"
-        if ID_PATTERN.match(joined_path):
+        if ID_PATTERN.match(joined_path) and SPECIAL_PATH_MARKER not in joined_path:
             id_scope = "/".join(self.current_root)
             scoped_ids = self.ids[id_scope]
             ref: str | None = scoped_ids.get(joined_path)

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

@@ -0,0 +1,17 @@
+# generated by datamodel-codegen:
+#   filename:  <stdin>
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import Optional
+
+from pydantic import BaseModel
+
+
+class Test(BaseModel):
+    name: Optional[str] = None
+
+
+class Model(BaseModel):
+    __root__: Test

tests/data/jsonschema/stdin_oneof_ref.json

@@ -0,0 +1,15 @@
+{
+  "$schema": "https://json-schema.org/draft/2019-09/schema",
+  "type": "object",
+  "oneOf": [
+    { "$ref": "#/definitions/test" }
+  ],
+  "definitions": {
+    "test": {
+      "type": "object",
+      "properties": {
+        "name": { "type": "string" }
+      }
+    }
+  }
+}

tests/main/jsonschema/test_main_jsonschema.py

@@ -561,6 +561,18 @@ def test_main_jsonschema_id_as_stdin(monkeypatch: pytest.MonkeyPatch, output_fil
     )
 
 
+def test_main_jsonschema_stdin_oneof_ref(monkeypatch: pytest.MonkeyPatch, output_file: Path) -> None:
+    """Test JSON Schema with oneOf $ref from stdin."""
+    run_main_and_assert(
+        stdin_path=JSON_SCHEMA_DATA_PATH / "stdin_oneof_ref.json",
+        output_path=output_file,
+        monkeypatch=monkeypatch,
+        input_file_type="jsonschema",
+        assert_func=assert_file_content,
+        expected_file="stdin_oneof_ref.py",
+    )
+
+
 def test_main_jsonschema_ids(output_dir: Path) -> None:
     """Test JSON Schema with multiple IDs."""
     with freeze_time(TIMESTAMP):