Remove models with same set of field.

[gk-patel]

It would be good if we can identify that a similar model exists and use that model instead of creating a new model, especially when the FIELDS and DATA-TYPE are same.

For example, when my data is as follows,

{
    "Arm Right": {
        "Joint 1": 5,
        "Joint 2": 3, 
        "Joint 3": 66
    }, 
    "Arm Left": {
        "Joint 1": 55,
        "Joint 2": 13, 
        "Joint 3": 6
    }
}

we get the following output,

class ArmRight(BaseModel):
    Joint_1: int = Field(..., alias='Joint 1')
    Joint_2: int = Field(..., alias='Joint 2')
    Joint_3: int = Field(..., alias='Joint 3')

class ArmLeft(BaseModel):
    Joint_1: int = Field(..., alias='Joint 1')
    Joint_2: int = Field(..., alias='Joint 2')
    Joint_3: int = Field(..., alias='Joint 3')

class Model(BaseModel):
    Arm_Right: ArmRight = Field(..., alias='Arm Right')
    Arm_Left: ArmLeft = Field(..., alias='Arm Left')

Describe the solution you'd like
I think it would be good if we can detect that models for ArmLeft and ArmRight are the same, and then to just use one of these models. For example,

class ArmRight (BaseModel):
    Joint_1: int = Field(..., alias='Joint 1')
    Joint_2: int = Field(..., alias='Joint 2')
    Joint_3: int = Field(..., alias='Joint 3')

class Model(BaseModel):
    Arm_Right: ArmRight = Field(..., alias='Arm Right')
    Arm_Left: ArmRight = Field(..., alias='Arm Left')

Describe alternatives you've considered
Currently, I just delete manually. But, we have a big system with many similar structures in JSON and many time we need to manually delete about 1000 models. :(

Thank you very much for this excellent tool.

[koxudaxi]

@gk-patel
Thank you for creating this issue.
I think it's a good idea.
The behavior may have to be an option of the command line 🤔

I will implement this feature after remove bugs.

[koxudaxi]

@gk-patel
I have released a new version as 0.6.15.
The version has the --reuse-model option that you want.

I put an example.

Input

datamodel-code-generator/tests/data/json/duplicate_models.json

Lines 1 to 15 in 681ca87

	{
	"Arm Right": {
	"Joint 1": 5,
	"Joint 2": 3,
	"Joint 3": 66
	},
	"Arm Left": {
	"Joint 1": 55,
	"Joint 2": 13,
	"Joint 3": 6
	},
	"Head": {
	"Joint 1": 10
	}
	}

Output

datamodel-code-generator/tests/data/expected/main/main_json_resuse_model/output.py

Lines 10 to 29 in 681ca87

	class ArmRight(BaseModel):
	Joint_1: int = Field(..., alias='Joint 1')
	Joint_2: int = Field(..., alias='Joint 2')
	Joint_3: int = Field(..., alias='Joint 3')
	class ArmLeft(BaseModel):
	Joint_1: int = Field(..., alias='Joint 1')
	Joint_2: int = Field(..., alias='Joint 2')
	Joint_3: int = Field(..., alias='Joint 3')
	class Head(BaseModel):
	Joint_1: int = Field(..., alias='Joint 1')
	class Model(BaseModel):
	Arm_Right: ArmRight = Field(..., alias='Arm Right')
	Arm_Left: ArmRight = Field(..., alias='Arm Left')
	Head: Head

I'm sorry, My work is too late.

[gk-patel]

@koxudaxi No worries man, looks nice.

Although, the following would have been much more cooler,

...
class ArmLeft(ArmRight): 
   pass 
...

If you can do that, it would look much nicer. But if you cannot, then you can close the issue. I leave it up to you.

[koxudaxi]

@gk-patel
No problem, It's a good idea.
I can implement the changes easily.

But, I found a problem with a case.
The code generator generates the Enum class from JSONSchema/OpenAPI.
Enum class can't be extended.

>> class B(A): pass
TypeError: Cannot extend enumerations

We should assign to another value. or we don't touch duplicated enum 🤔

[gk-patel]

Well, IMHO the easiest way would be to check if the content of enums is exactly the same,

• if it is exactly the same, just use the same name everywhere (so in that case, dont create class B)
• if it not exactly the same, the create a seperate enum without inheritance, (so in that case, create class A and B)

Do you have any arguments against this idea ?

[koxudaxi]

@gk-patel
OK. I released a new version as 0.6.17
This version has changed your idea.

datamodel-code-generator/tests/data/expected/main/main_json_reuse_model/output.py

Lines 16 to 26 in ada9b19

	class ArmLeft(ArmRight):
	pass
	class Head(BaseModel):
	Joint_1: int = Field(..., alias='Joint 1')
	class Model(BaseModel):
	Arm_Right: ArmRight = Field(..., alias='Arm Right')
	Arm_Left: ArmLeft = Field(..., alias='Arm Left')

The enum will reuse the same model. A duplicate model will be created too. Because some models may need the enum from other modules.

datamodel-code-generator/tests/data/expected/main/main_json_reuse_enum/output.py

Lines 13 to 28 in ada9b19

	class Animal(Enum):
	dog = 'dog'
	cat = 'cat'
	snake = 'snake'
	class Pet(Enum):
	dog = 'dog'
	cat = 'cat'
	snake = 'snake'
	class User(BaseModel):
	name: Optional[str] = None
	animal: Optional[Animal] = None
	pet: Optional[Animal] = None