Add --use-decimal-for-multiple-of option to avoid floating-point precision issues (#2656)

koxudaxi · web-flow · commit 493d02ea747c · 2025-12-13T10:45:32.000+09:00
* Add --use-decimal-for-multiple-of option to improve precision for float/number fields

* Add test and output for --use-decimal-for-multiple-of option
diff --git a/README.md b/README.md
@@ -381,6 +381,10 @@ Typing customization:
                         times.
   --use-annotated       Use typing.Annotated for Field(). Also, `--field-constraints` option
                         will be enabled.
+  --use-decimal-for-multiple-of
+                        Use condecimal instead of confloat for float/number fields with
+                        multipleOf constraint (Pydantic only). Avoids floating-point
+                        precision issues in validation.
   --use-enum-values-in-discriminator
                         Use enum member literals in discriminator fields instead of string
                         literals
diff --git a/docs/index.md b/docs/index.md
@@ -373,6 +373,10 @@ Typing customization:
                         times.
   --use-annotated       Use typing.Annotated for Field(). Also, `--field-constraints` option
                         will be enabled.
+  --use-decimal-for-multiple-of
+                        Use condecimal instead of confloat for float/number fields with
+                        multipleOf constraint (Pydantic only). Avoids floating-point
+                        precision issues in validation.
   --use-enum-values-in-discriminator
                         Use enum member literals in discriminator fields instead of string
                         literals
diff --git a/src/datamodel_code_generator/__init__.py b/src/datamodel_code_generator/__init__.py
@@ -420,6 +420,7 @@ def generate(  # noqa: PLR0912, PLR0913, PLR0914, PLR0915
     use_annotated: bool = False,
     use_serialize_as_any: bool = False,
     use_non_positive_negative_number_constrained_types: bool = False,
+    use_decimal_for_multiple_of: bool = False,
     original_field_name_delimiter: str | None = None,
     use_double_quotes: bool = False,
     use_union_operator: bool = False,
@@ -661,6 +662,7 @@ def get_header_and_first_line(csv_file: IO[str]) -> dict[str, Any]:
         use_annotated=use_annotated,
         use_serialize_as_any=use_serialize_as_any,
         use_non_positive_negative_number_constrained_types=use_non_positive_negative_number_constrained_types,
+        use_decimal_for_multiple_of=use_decimal_for_multiple_of,
         original_field_name_delimiter=original_field_name_delimiter,
         use_double_quotes=use_double_quotes,
         use_union_operator=use_union_operator,
diff --git a/src/datamodel_code_generator/__main__.py b/src/datamodel_code_generator/__main__.py
@@ -426,6 +426,7 @@ def validate_all_exports_collision_strategy(cls, values: dict[str, Any]) -> dict
     use_annotated: bool = False
     use_serialize_as_any: bool = False
     use_non_positive_negative_number_constrained_types: bool = False
+    use_decimal_for_multiple_of: bool = False
     original_field_name_delimiter: Optional[str] = None  # noqa: UP045
     use_double_quotes: bool = False
     collapse_root_models: bool = False
@@ -871,6 +872,7 @@ def main(args: Sequence[str] | None = None) -> Exit:  # noqa: PLR0911, PLR0912,
             use_annotated=config.use_annotated,
             use_serialize_as_any=config.use_serialize_as_any,
             use_non_positive_negative_number_constrained_types=config.use_non_positive_negative_number_constrained_types,
+            use_decimal_for_multiple_of=config.use_decimal_for_multiple_of,
             original_field_name_delimiter=config.original_field_name_delimiter,
             use_double_quotes=config.use_double_quotes,
             collapse_root_models=config.collapse_root_models,
diff --git a/src/datamodel_code_generator/arguments.py b/src/datamodel_code_generator/arguments.py
@@ -373,6 +373,13 @@ def start_section(self, heading: str | None) -> None:
     action="store_true",
     default=None,
 )
+typing_options.add_argument(
+    "--use-decimal-for-multiple-of",
+    help="Use condecimal instead of confloat for float/number fields with multipleOf constraint "
+    "(Pydantic only). Avoids floating-point precision issues in validation.",
+    action="store_true",
+    default=None,
+)
 typing_options.add_argument(
     "--use-one-literal-as-default",
     help="Use one literal as default value for one literal field",
diff --git a/src/datamodel_code_generator/model/dataclass.py b/src/datamodel_code_generator/model/dataclass.py
@@ -166,6 +166,7 @@ def __init__(  # noqa: PLR0913, PLR0917
         use_generic_container_types: bool = False,  # noqa: FBT001, FBT002
         strict_types: Sequence[StrictTypes] | None = None,
         use_non_positive_negative_number_constrained_types: bool = False,  # noqa: FBT001, FBT002
+        use_decimal_for_multiple_of: bool = False,  # noqa: FBT001, FBT002
         use_union_operator: bool = False,  # noqa: FBT001, FBT002
         use_pendulum: bool = False,  # noqa: FBT001, FBT002
         target_datetime_class: DatetimeClassType = DatetimeClassType.Datetime,
@@ -179,6 +180,7 @@ def __init__(  # noqa: PLR0913, PLR0917
             use_generic_container_types,
             strict_types,
             use_non_positive_negative_number_constrained_types,
+            use_decimal_for_multiple_of,
             use_union_operator,
             use_pendulum,
             target_datetime_class,
diff --git a/src/datamodel_code_generator/model/msgspec.py b/src/datamodel_code_generator/model/msgspec.py
@@ -414,6 +414,7 @@ def __init__(  # noqa: PLR0913, PLR0917
         use_generic_container_types: bool = False,  # noqa: FBT001, FBT002
         strict_types: Sequence[StrictTypes] | None = None,
         use_non_positive_negative_number_constrained_types: bool = False,  # noqa: FBT001, FBT002
+        use_decimal_for_multiple_of: bool = False,  # noqa: FBT001, FBT002
         use_union_operator: bool = False,  # noqa: FBT001, FBT002
         use_pendulum: bool = False,  # noqa: FBT001, FBT002
         target_datetime_class: DatetimeClassType | None = None,
@@ -427,6 +428,7 @@ def __init__(  # noqa: PLR0913, PLR0917
             use_generic_container_types,
             strict_types,
             use_non_positive_negative_number_constrained_types,
+            use_decimal_for_multiple_of,
             use_union_operator,
             use_pendulum,
             target_datetime_class,
diff --git a/src/datamodel_code_generator/model/pydantic/types.py b/src/datamodel_code_generator/model/pydantic/types.py
@@ -171,6 +171,7 @@ def __init__(  # noqa: PLR0913, PLR0917
         use_generic_container_types: bool = False,  # noqa: FBT001, FBT002
         strict_types: Sequence[StrictTypes] | None = None,
         use_non_positive_negative_number_constrained_types: bool = False,  # noqa: FBT001, FBT002
+        use_decimal_for_multiple_of: bool = False,  # noqa: FBT001, FBT002
         use_union_operator: bool = False,  # noqa: FBT001, FBT002
         use_pendulum: bool = False,  # noqa: FBT001, FBT002
         target_datetime_class: DatetimeClassType | None = None,
@@ -184,6 +185,7 @@ def __init__(  # noqa: PLR0913, PLR0917
             use_generic_container_types,
             strict_types,
             use_non_positive_negative_number_constrained_types,
+            use_decimal_for_multiple_of,
             use_union_operator,
             use_pendulum,
             target_datetime_class,
@@ -268,6 +270,12 @@ def get_data_float_type(  # noqa: PLR0911
         data_type_kwargs = self.transform_kwargs(kwargs, number_kwargs)
         strict = StrictTypes.float in self.strict_types
         if data_type_kwargs:
+            # Use Decimal instead of float when multipleOf is present to avoid floating-point precision issues
+            if self.use_decimal_for_multiple_of and "multiple_of" in data_type_kwargs:
+                return self.data_type.from_import(
+                    IMPORT_CONDECIMAL,
+                    kwargs={k: Decimal(str(v)) for k, v in data_type_kwargs.items()},
+                )
             if not strict:
                 if data_type_kwargs == {"gt": 0}:
                     return self.data_type.from_import(IMPORT_POSITIVE_FLOAT)
diff --git a/src/datamodel_code_generator/model/pydantic_v2/types.py b/src/datamodel_code_generator/model/pydantic_v2/types.py
@@ -70,6 +70,7 @@ def __init__(  # noqa: PLR0913, PLR0917
         use_generic_container_types: bool = False,  # noqa: FBT001, FBT002
         strict_types: Sequence[StrictTypes] | None = None,
         use_non_positive_negative_number_constrained_types: bool = False,  # noqa: FBT001, FBT002
+        use_decimal_for_multiple_of: bool = False,  # noqa: FBT001, FBT002
         use_union_operator: bool = False,  # noqa: FBT001, FBT002
         use_pendulum: bool = False,  # noqa: FBT001, FBT002
         target_datetime_class: DatetimeClassType | None = None,
@@ -83,6 +84,7 @@ def __init__(  # noqa: PLR0913, PLR0917
             use_generic_container_types=use_generic_container_types,
             strict_types=strict_types,
             use_non_positive_negative_number_constrained_types=use_non_positive_negative_number_constrained_types,
+            use_decimal_for_multiple_of=use_decimal_for_multiple_of,
             use_union_operator=use_union_operator,
             use_pendulum=use_pendulum,
             target_datetime_class=target_datetime_class,
diff --git a/src/datamodel_code_generator/model/types.py b/src/datamodel_code_generator/model/types.py
@@ -73,6 +73,7 @@ def __init__(  # noqa: PLR0913, PLR0917
         use_generic_container_types: bool = False,  # noqa: FBT001, FBT002
         strict_types: Sequence[StrictTypes] | None = None,
         use_non_positive_negative_number_constrained_types: bool = False,  # noqa: FBT001, FBT002
+        use_decimal_for_multiple_of: bool = False,  # noqa: FBT001, FBT002
         use_union_operator: bool = False,  # noqa: FBT001, FBT002
         use_pendulum: bool = False,  # noqa: FBT001, FBT002
         target_datetime_class: DatetimeClassType | None = None,
@@ -86,6 +87,7 @@ def __init__(  # noqa: PLR0913, PLR0917
             use_generic_container_types,
             strict_types,
             use_non_positive_negative_number_constrained_types,
+            use_decimal_for_multiple_of,
             use_union_operator,
             use_pendulum,
             target_datetime_class,
diff --git a/src/datamodel_code_generator/parser/base.py b/src/datamodel_code_generator/parser/base.py
@@ -542,6 +542,7 @@ def __init__(  # noqa: PLR0913, PLR0915
         use_annotated: bool = False,
         use_serialize_as_any: bool = False,
         use_non_positive_negative_number_constrained_types: bool = False,
+        use_decimal_for_multiple_of: bool = False,
         original_field_name_delimiter: str | None = None,
         use_double_quotes: bool = False,
         use_union_operator: bool = False,
@@ -582,6 +583,7 @@ def __init__(  # noqa: PLR0913, PLR0915
             use_standard_collections=use_standard_collections,
             use_generic_container_types=use_generic_container_types,
             use_non_positive_negative_number_constrained_types=use_non_positive_negative_number_constrained_types,
+            use_decimal_for_multiple_of=use_decimal_for_multiple_of,
             strict_types=strict_types,
             use_union_operator=use_union_operator,
             use_pendulum=use_pendulum,
diff --git a/src/datamodel_code_generator/parser/graphql.py b/src/datamodel_code_generator/parser/graphql.py
@@ -155,6 +155,7 @@ def __init__(  # noqa: PLR0913
         http_ignore_tls: bool = False,
         use_annotated: bool = False,
         use_non_positive_negative_number_constrained_types: bool = False,
+        use_decimal_for_multiple_of: bool = False,
         original_field_name_delimiter: str | None = None,
         use_double_quotes: bool = False,
         use_union_operator: bool = False,
@@ -248,6 +249,7 @@ def __init__(  # noqa: PLR0913
             http_ignore_tls=http_ignore_tls,
             use_annotated=use_annotated,
             use_non_positive_negative_number_constrained_types=use_non_positive_negative_number_constrained_types,
+            use_decimal_for_multiple_of=use_decimal_for_multiple_of,
             original_field_name_delimiter=original_field_name_delimiter,
             use_double_quotes=use_double_quotes,
             use_union_operator=use_union_operator,
diff --git a/src/datamodel_code_generator/parser/jsonschema.py b/src/datamodel_code_generator/parser/jsonschema.py
@@ -567,6 +567,7 @@ def __init__(  # noqa: PLR0913
         use_annotated: bool = False,
         use_serialize_as_any: bool = False,
         use_non_positive_negative_number_constrained_types: bool = False,
+        use_decimal_for_multiple_of: bool = False,
         original_field_name_delimiter: str | None = None,
         use_double_quotes: bool = False,
         use_union_operator: bool = False,
@@ -659,6 +660,7 @@ def __init__(  # noqa: PLR0913
             use_annotated=use_annotated,
             use_serialize_as_any=use_serialize_as_any,
             use_non_positive_negative_number_constrained_types=use_non_positive_negative_number_constrained_types,
+            use_decimal_for_multiple_of=use_decimal_for_multiple_of,
             original_field_name_delimiter=original_field_name_delimiter,
             use_double_quotes=use_double_quotes,
             use_union_operator=use_union_operator,
diff --git a/src/datamodel_code_generator/parser/openapi.py b/src/datamodel_code_generator/parser/openapi.py
@@ -240,6 +240,7 @@ def __init__(  # noqa: PLR0913
         use_annotated: bool = False,
         use_serialize_as_any: bool = False,
         use_non_positive_negative_number_constrained_types: bool = False,
+        use_decimal_for_multiple_of: bool = False,
         original_field_name_delimiter: str | None = None,
         use_double_quotes: bool = False,
         use_union_operator: bool = False,
@@ -332,6 +333,7 @@ def __init__(  # noqa: PLR0913
             use_annotated=use_annotated,
             use_serialize_as_any=use_serialize_as_any,
             use_non_positive_negative_number_constrained_types=use_non_positive_negative_number_constrained_types,
+            use_decimal_for_multiple_of=use_decimal_for_multiple_of,
             original_field_name_delimiter=original_field_name_delimiter,
             use_double_quotes=use_double_quotes,
             use_union_operator=use_union_operator,
diff --git a/src/datamodel_code_generator/types.py b/src/datamodel_code_generator/types.py
@@ -671,6 +671,7 @@ def __init__(  # noqa: PLR0913, PLR0917
         use_generic_container_types: bool = False,  # noqa: FBT001, FBT002
         strict_types: Sequence[StrictTypes] | None = None,
         use_non_positive_negative_number_constrained_types: bool = False,  # noqa: FBT001, FBT002
+        use_decimal_for_multiple_of: bool = False,  # noqa: FBT001, FBT002
         use_union_operator: bool = False,  # noqa: FBT001, FBT002
         use_pendulum: bool = False,  # noqa: FBT001, FBT002
         target_datetime_class: DatetimeClassType | None = None,
@@ -685,6 +686,7 @@ def __init__(  # noqa: PLR0913, PLR0917
         self.use_non_positive_negative_number_constrained_types: bool = (
             use_non_positive_negative_number_constrained_types
         )
+        self.use_decimal_for_multiple_of: bool = use_decimal_for_multiple_of
         self.use_union_operator: bool = use_union_operator
         self.use_pendulum: bool = use_pendulum
         self.target_datetime_class: DatetimeClassType | None = target_datetime_class
diff --git a/tests/data/expected/main_kr/use_decimal_for_multiple_of/output.py b/tests/data/expected/main_kr/use_decimal_for_multiple_of/output.py
@@ -0,0 +1,16 @@
+# generated by datamodel-codegen:
+#   filename:  use_decimal_for_multiple_of.json
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import Optional
+
+from pydantic import BaseModel, condecimal, confloat
+
+
+class Model(BaseModel):
+    price: Optional[condecimal(ge=0, le=99999.99, multiple_of=0.01)] = None
+    quantity: Optional[condecimal(multiple_of=0.1)] = None
+    rate: Optional[condecimal(multiple_of=0.001, lt=1.0, gt=0.0)] = None
+    simple_float: Optional[confloat(ge=0.0, le=100.0)] = None
diff --git a/tests/data/jsonschema/use_decimal_for_multiple_of.json b/tests/data/jsonschema/use_decimal_for_multiple_of.json
@@ -0,0 +1,26 @@
+{
+  "type": "object",
+  "properties": {
+    "price": {
+      "type": "number",
+      "multipleOf": 0.01,
+      "minimum": 0,
+      "maximum": 99999.99
+    },
+    "quantity": {
+      "type": "number",
+      "multipleOf": 0.1
+    },
+    "rate": {
+      "type": "number",
+      "multipleOf": 0.001,
+      "exclusiveMinimum": 0,
+      "exclusiveMaximum": 1
+    },
+    "simple_float": {
+      "type": "number",
+      "minimum": 0,
+      "maximum": 100
+    }
+  }
+}
diff --git a/tests/model/pydantic/test_types.py b/tests/model/pydantic/test_types.py
@@ -344,6 +344,49 @@ def test_get_data_decimal_type(types: Types, params: dict[str, Any], data_type:
     assert data_type_manager.get_data_decimal_type(types, **params) == data_type_manager.data_type(**data_type)
 
 
+@pytest.mark.parametrize(
+    ("types", "params", "data_type"),
+    [
+        (
+            Types.float,
+            {"multipleOf": 0.1},
+            {
+                "type": "condecimal",
+                "is_func": True,
+                "kwargs": {"multiple_of": Decimal("0.1")},
+                "import_": IMPORT_CONDECIMAL,
+            },
+        ),
+        (
+            Types.float,
+            {"multipleOf": 0.1, "minimum": 0, "maximum": 100},
+            {
+                "type": "condecimal",
+                "is_func": True,
+                "kwargs": {"multiple_of": Decimal("0.1"), "ge": Decimal(0), "le": Decimal(100)},
+                "import_": IMPORT_CONDECIMAL,
+            },
+        ),
+        (
+            Types.number,
+            {"multipleOf": 0.01, "exclusiveMinimum": 0},
+            {
+                "type": "condecimal",
+                "is_func": True,
+                "kwargs": {"multiple_of": Decimal("0.01"), "gt": Decimal(0)},
+                "import_": IMPORT_CONDECIMAL,
+            },
+        ),
+    ],
+)
+def test_get_data_float_type_with_use_decimal_for_multiple_of(
+    types: Types, params: dict[str, Any], data_type: dict[str, Any]
+) -> None:
+    """Test float type uses condecimal when use_decimal_for_multiple_of is True."""
+    data_type_manager = DataTypeManager(use_decimal_for_multiple_of=True)
+    assert data_type_manager.get_data_float_type(types, **params) == data_type_manager.data_type(**data_type)
+
+
 @pytest.mark.parametrize(
     ("types", "params", "data_type"),
     [
diff --git a/tests/test_main_kr.py b/tests/test_main_kr.py
@@ -16,6 +16,7 @@
 
 DATA_PATH: Path = Path(__file__).parent / "data"
 OPEN_API_DATA_PATH: Path = DATA_PATH / "openapi"
+JSON_SCHEMA_DATA_PATH: Path = DATA_PATH / "jsonschema"
 EXPECTED_MAIN_KR_PATH = DATA_PATH / "expected" / "main_kr"
 
 assert_file_content = create_assert_file_content(EXPECTED_MAIN_KR_PATH)
@@ -972,3 +973,16 @@ def test_allof_with_description_generates_class_not_alias(output_file: Path) ->
             "--use-schema-description",
         ],
     )
+
+
+@freeze_time("2019-07-26")
+def test_use_decimal_for_multiple_of(output_file: Path) -> None:
+    """Test --use-decimal-for-multiple-of generates condecimal for multipleOf fields."""
+    run_main_and_assert(
+        input_path=JSON_SCHEMA_DATA_PATH / "use_decimal_for_multiple_of.json",
+        output_path=output_file,
+        input_file_type="jsonschema",
+        assert_func=assert_file_content,
+        expected_file=EXPECTED_MAIN_KR_PATH / "use_decimal_for_multiple_of" / "output.py",
+        extra_args=["--use-decimal-for-multiple-of"],
+    )
