Fix --reuse-model --collapse-reuse-models to deduplicate identical inline definitions

src/datamodel_code_generator/parser/base.py

@@ -1125,6 +1125,38 @@ def __delete_duplicate_models(self, models: list[DataModel]) -> None:  # noqa: P
                         {f"{c.module_name}.{c.type_hint}": c for c in child.base_classes}.values()
                     )
                 models_to_remove.add(duplicate_model)
+
+        if self.reuse_model and self.collapse_reuse_models:
+            max_iterations, iteration = len(models), 0
+            while True:
+                iteration += 1
+                if iteration > max_iterations:  # pragma: no cover
+                    msg = f"Deduplication exceeded max iterations ({max_iterations})"
+                    raise RuntimeError(msg)
+
+                content_key_to_models: dict[tuple[Any, ...], list[DataModel]] = defaultdict(list)
+                for model in models:
+                    if model not in models_to_remove and not isinstance(model, self.data_model_root_type):
+                        model._dedup_key_cache.clear()  # noqa: SLF001
+                        content_key_to_models[model.get_dedup_key(None, use_default=True)].append(model)
+
+                if not (
+                    duplicates := [
+                        (canonical := group[0], dup)
+                        for group in content_key_to_models.values()
+                        if len(group) > 1
+                        for dup in group[1:]
+                        if dup not in models_to_remove
+                    ]
+                ):
+                    break
+
+                for canonical, duplicate in duplicates:
+                    duplicate.replace_children_in_models(models, canonical.reference)
+                    for child in duplicate.reference.iter_data_model_children():  # pragma: no cover
+                        child.base_classes = list({c.reference: c for c in child.base_classes}.values())
+                    models_to_remove.add(duplicate)
+
         # Batch removal: O(n) instead of O(n²)
         if models_to_remove:
             models[:] = [m for m in models if m not in models_to_remove]

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

@@ -0,0 +1,22 @@
+# generated by datamodel-codegen:
+#   filename:  reuse_model_inline_definitions.json
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from pydantic import BaseModel
+
+
+class Pos(BaseModel):
+    start: int | None = None
+    end: int | None = None
+
+
+class Node1(BaseModel):
+    pos: Pos | None = None
+
+
+class Model(BaseModel):
+    node1: Node1 | None = None
+    node2: Node1 | None = None
+    node3: Node1 | None = None

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

@@ -0,0 +1,26 @@
+# generated by datamodel-codegen:
+#   filename:  reuse_model_collapse_nested.json
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from pydantic import BaseModel
+
+
+class Start(BaseModel):
+    line: int | None = None
+    col: int | None = None
+
+
+class Pos(BaseModel):
+    start: Start | None = None
+    end: Start | None = None
+
+
+class Block1(BaseModel):
+    pos: Pos | None = None
+
+
+class Model(BaseModel):
+    block1: Block1 | None = None
+    block2: Block1 | None = None

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

@@ -0,0 +1,27 @@
+# generated by datamodel-codegen:
+#   filename:  reuse_model_collapse_with_root.json
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from pydantic import BaseModel, RootModel
+
+
+class Pos(BaseModel):
+    x: int | None = None
+    y: int | None = None
+
+
+class Nested1(BaseModel):
+    pos: Pos | None = None
+
+
+class StringType(RootModel[str]):
+    root: str
+
+
+class Model(BaseModel):
+    field1: StringType | None = None
+    field2: StringType | None = None
+    nested1: Nested1 | None = None
+    nested2: Nested1 | None = None

tests/data/jsonschema/reuse_model_collapse_nested.json

@@ -0,0 +1,54 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema",
+  "type": "object",
+  "properties": {
+    "block1": {
+      "type": "object",
+      "properties": {
+        "pos": {
+          "type": "object",
+          "properties": {
+            "start": {
+              "type": "object",
+              "properties": {
+                "line": {"type": "integer"},
+                "col": {"type": "integer"}
+              }
+            },
+            "end": {
+              "type": "object",
+              "properties": {
+                "line": {"type": "integer"},
+                "col": {"type": "integer"}
+              }
+            }
+          }
+        }
+      }
+    },
+    "block2": {
+      "type": "object",
+      "properties": {
+        "pos": {
+          "type": "object",
+          "properties": {
+            "start": {
+              "type": "object",
+              "properties": {
+                "line": {"type": "integer"},
+                "col": {"type": "integer"}
+              }
+            },
+            "end": {
+              "type": "object",
+              "properties": {
+                "line": {"type": "integer"},
+                "col": {"type": "integer"}
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+}

tests/data/jsonschema/reuse_model_collapse_with_root.json

@@ -0,0 +1,41 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema",
+  "type": "object",
+  "definitions": {
+    "StringType": {
+      "type": "string"
+    }
+  },
+  "properties": {
+    "field1": {
+      "$ref": "#/definitions/StringType"
+    },
+    "field2": {
+      "$ref": "#/definitions/StringType"
+    },
+    "nested1": {
+      "type": "object",
+      "properties": {
+        "pos": {
+          "type": "object",
+          "properties": {
+            "x": {"type": "integer"},
+            "y": {"type": "integer"}
+          }
+        }
+      }
+    },
+    "nested2": {
+      "type": "object",
+      "properties": {
+        "pos": {
+          "type": "object",
+          "properties": {
+            "x": {"type": "integer"},
+            "y": {"type": "integer"}
+          }
+        }
+      }
+    }
+  }
+}

tests/data/jsonschema/reuse_model_inline_definitions.json

@@ -0,0 +1,42 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema",
+  "type": "object",
+  "properties": {
+    "node1": {
+      "type": "object",
+      "properties": {
+        "pos": {
+          "type": "object",
+          "properties": {
+            "start": {"type": "integer"},
+            "end": {"type": "integer"}
+          }
+        }
+      }
+    },
+    "node2": {
+      "type": "object",
+      "properties": {
+        "pos": {
+          "type": "object",
+          "properties": {
+            "start": {"type": "integer"},
+            "end": {"type": "integer"}
+          }
+        }
+      }
+    },
+    "node3": {
+      "type": "object",
+      "properties": {
+        "pos": {
+          "type": "object",
+          "properties": {
+            "start": {"type": "integer"},
+            "end": {"type": "integer"}
+          }
+        }
+      }
+    }
+  }
+}

tests/main/jsonschema/test_main_jsonschema.py

@@ -1132,6 +1132,54 @@ def test_main_json_reuse_enum(output_file: Path) -> None:
     )
 
 
+def test_main_reuse_model_collapse_inline_definitions(output_file: Path) -> None:
+    """Test --reuse-model --collapse-reuse-models deduplicates identical inline definitions."""
+    run_main_and_assert(
+        input_path=JSON_SCHEMA_DATA_PATH / "reuse_model_inline_definitions.json",
+        output_path=output_file,
+        input_file_type="jsonschema",
+        assert_func=assert_file_content,
+        extra_args=[
+            "--reuse-model",
+            "--collapse-reuse-models",
+            "--output-model-type",
+            "pydantic_v2.BaseModel",
+        ],
+    )
+
+
+def test_main_reuse_model_collapse_with_root(output_file: Path) -> None:
+    """Test --reuse-model --collapse-reuse-models skips RootModel deduplication."""
+    run_main_and_assert(
+        input_path=JSON_SCHEMA_DATA_PATH / "reuse_model_collapse_with_root.json",
+        output_path=output_file,
+        input_file_type="jsonschema",
+        assert_func=assert_file_content,
+        extra_args=[
+            "--reuse-model",
+            "--collapse-reuse-models",
+            "--output-model-type",
+            "pydantic_v2.BaseModel",
+        ],
+    )
+
+
+def test_main_reuse_model_collapse_nested(output_file: Path) -> None:
+    """Test --reuse-model --collapse-reuse-models with deeply nested identical structures."""
+    run_main_and_assert(
+        input_path=JSON_SCHEMA_DATA_PATH / "reuse_model_collapse_nested.json",
+        output_path=output_file,
+        input_file_type="jsonschema",
+        assert_func=assert_file_content,
+        extra_args=[
+            "--reuse-model",
+            "--collapse-reuse-models",
+            "--output-model-type",
+            "pydantic_v2.BaseModel",
+        ],
+    )
+
+
 @pytest.mark.cli_doc(
     options=["--capitalize-enum-members"],
     option_description="""Capitalize enum member names to UPPER_CASE format.