Python client code improperly escaping regex strings

[Raznic]

Description

I've got a web server running Django + REST Framework that I am trying to generate Python client code for. One of my Serializers defines a RegexField that includes \d as a part of the regular expression. The generator appears to be escaping these characters in the generated client code.

Serializer regex: r'^\d$'
Actual Python client code: re.search(r'^\\d$', value)
Expected Python client code: re.search(r'^\d$', value)

openapi-generator version

I've pulled the latest from master and the version shows as 3.3.4-SNAPSHOT.

OpenAPI declaration file content or url

Command line used for generation

$ java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate -g python -i <development Swagger URL> -o python

Steps to reproduce

1. Define a Serializer class with a RegexField in your Django + REST Framework app.

from rest_framework.serializers import ModelSerializer, RegexField
from .model import MyModel
class MyModelSeralizer(ModelSerializer):
    value = RegexField(regex=r'^\d$')

    class Meta:
        model = MyModel
        fields = '__all__'

2. Generate Python client code.

3. Try to create a model.

import openapi_client

config = openapi_client.Configuration()
client = openapi_client.ApiClient(client)
api_instance = openapi_client.MyModelApi(client)

data = openapi_client.MyModel(value='9')
api_instance.my_model_create(data)

Related issues/PRs

#1392

Suggest a fix/enhancement

My Java is pretty rusty, but I would assume the fix for the Python client would be similar to the one for the Ruby client from the related issue/PR.

[Raznic]

After a little more testing, it appears the problem is not just limited to \d. Any backslash character in the regex string is getting escaped.