Better JSON-Schema output for Decimal (#692)

Co-authored-by: konstantin <konstantin.klein@hochfrequenz.de>

Author: lord-haffi

generate_or_validate_json_schemas.py

@@ -15,6 +15,9 @@
 
 import click
 from pydantic import BaseModel, TypeAdapter
+from pydantic.json_schema import GenerateJsonSchema as _GenerateJsonSchema
+from pydantic.json_schema import JsonSchemaValue
+from pydantic_core import core_schema
 
 from bo4e import ZusatzAttribut
 
@@ -34,6 +37,24 @@
 PARSABLE_CLASS_TYPE = type[BaseModel] | type[Enum]
 
 
+class GenerateJsonSchema(_GenerateJsonSchema):
+    """
+    This class is a copy of pydantic.json_schema.GenerateJsonSchema with the only difference that the
+    decimal_schema method is overwritten to generate a JSON schema that can be used by the
+    BO4E-Python-Generator (https://github.com/bo4e/BO4E-Python-Generator).
+    """
+
+    def decimal_schema(self, schema: core_schema.DecimalSchema) -> JsonSchemaValue:
+        """
+        Generates a JSON schema that matches a decimal value.
+        The output format is changed to work well with BO4E-Python-Generator.
+        """
+        json_schema = self.str_schema(core_schema.str_schema())
+        if self.mode == "validation":
+            json_schema["format"] = "decimal"
+        return json_schema
+
+
 def delete_json_schemas(packages: list[str]) -> None:
     """delete all json schemas"""
     for pkg in packages:
@@ -84,9 +105,9 @@ def get_schema_json_dict(cls: Any) -> dict[str, Any]:
     Get the json schema for a class
     """
     if issubclass(cls, BaseModel):
-        schema_json_dict = cls.model_json_schema()
+        schema_json_dict = cls.model_json_schema(schema_generator=GenerateJsonSchema)
     elif issubclass(cls, Enum):
-        schema_json_dict = TypeAdapter(cls).json_schema()
+        schema_json_dict = TypeAdapter(cls).json_schema(schema_generator=GenerateJsonSchema)
     else:
         raise ValueError(f"Class {cls} is neither a pydantic BaseModel nor an enum.")
     if "$defs" in schema_json_dict: