[TypeScript] Any typescript codegen removes underscores and forces enum value naming to camelCase (thus breaking snake_case API's, see Zalando API guidelines) [with fix, 1 LOC]

Description

The abstract TypeScript codegen implementation has a bug that breaks any Enumeration described in any swagger.json file basically turning enum values like "TYPE_A" into "TYPEA":

https://github.com/swagger-api/swagger-codegen/blob/4607a90d7b69463a0ae8fc94fac68fc95d80965e/modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/AbstractTypeScriptClientCodegen.java#L466

Also, camelCase is forced, ignoring modelPropertyNaming option:

https://github.com/swagger-api/swagger-codegen/blob/4607a90d7b69463a0ae8fc94fac68fc95d80965e/modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/AbstractTypeScriptClientCodegen.java#L471

Swagger-codegen version

master, rev. e11d7646091ab75780fc69be938218ef5da15715

Swagger declaration file content or url

Any swagger.json that specifies Enum values in format as: A_B_C
https://raw.githubusercontent.com/logzio/public-api/master/alerts/swagger.json

Command line used for generation

Steps to reproduce

java -jar ./swagger-codegen-cli.jar generate \
   -i https://raw.githubusercontent.com/logzio/public-api/master/alerts/swagger.json \
   -l typescript-fetch \
   -D modelPropertyNaming=original \
   -o ./src

Or:

1. https://editor.swagger.io/#
2. Import from URL: https://raw.githubusercontent.com/logzio/public-api/master/alerts/swagger.json
3. Generate client: typescript-fetch
4. Extract zip -> open api.ts -> Line 323, OperationEnum

Related issues/PRs

Unknown

Suggest a fix/enhancement

Instead of manually replacing special characters and forcing camelCase, call:

    String enumName = sanitizeName(name);

It fixes the issue for me but (expectedly) breaks the tests.
Unfortunately, I have no time for a PR process atm.

For anyone running into the same issue, I hope this helps.

btw: Namespaces are deprecated and to be replaced by ES6 modules syntax. If you try to compile swagger-codegen based TypeScript libraries with Babel 7 instead of tsc, this is already impossible and the code will break once TypeScript removes support for namespaces officially.

Start in modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/AbstractTypeScriptClientCodegen.java at the referenced lines, then reproduce with the typescript-fetch command and logzio swagger.json. Verify that generated api.ts preserves enum underscores and respects modelPropertyNaming=original, while updating the relevant tests that currently fail with the proposed sanitization change.