feat(codegen): add operationIdTransformer option

[aryaemami59]

Summary

• Add an operationIdTransformer config option to @rtk-query/codegen-openapi that controls how OpenAPI operationId values are transformed into endpoint names.

Motivation

• @rtk-query/codegen-openapi currently passes every operationId through oazapfts, which applies lodash's camelCase.
  This mangles consecutive uppercase acronyms.
  For example, fetchMyJWTPlease becomes fetchMyJwtPlease, making it impossible to match the original operationId exactly.

This causes two categories of pain:

1. filterEndpoints breaks on acronym-heavy names. If your schema has operationId: fetchMyJWTPlease, you must filter by 'fetchMyJwtPlease' (the mangled form) even though the schema says fetchMyJWTPlease. This is surprising and easy to get wrong. See remove implicit conversion to camel case of openapi operation id. #4322.
2. Generated names silently diverge from the schema. Teams that use the operationId as a stable identifier (e.g. for analytics, logging, or cross-service contracts) find the camelCase conversion breaks their assumptions. See RTK-Query Codegen: Camel case applied incorrectly in some situations #2181.

Solution

• Add operationIdTransformer?: 'camelCase' | 'none' | ((operationId: string) => string) to CommonOptions.

Value	Behavior
'camelCase' (default)	Existing behavior. Applies lodash's camelCase via oazapfts. Fully backwards-compatible.
'none'	Uses the raw operationId verbatim, preserving exact casing from the schema.
(operationId: string) => string	Applies a custom transform for full control.

When 'none' or a function is used, every operation must have an operationId defined. The codegen throws an informative error if any operation is missing one.

filterEndpoints is always matched against the transformed name, consistent regardless of which transformer is active.

Usage

Preserve exact casing. fetchMyJWTPlease stays fetchMyJWTPlease:

import type { ConfigFile } from "@rtk-query/codegen-openapi";

const config = {
  schemaFile: "./openapi.json",
  apiFile: "./src/emptyApi.ts",
  outputFile: "./src/api.ts",
  operationIdTransformer: "none",
} satisfies ConfigFile;

export default config;

Custom transform:

import type { ConfigFile } from "@rtk-query/codegen-openapi";

const config = {
  schemaFile: "./openapi.json",
  apiFile: "./src/emptyApi.ts",
  outputFile: "./src/api.ts",
  operationIdTransformer: (operationId) => operationId.replace(/^get/, "fetch"),
} satisfies ConfigFile;

export default config;

Related

• Resolves remove implicit conversion to camel case of openapi operation id. #4322.
• Related to RTK-Query Codegen: Camel case applied incorrectly in some situations #2181.
• Related to [RTKQ Code Gen OpenAPI] feature request: convert case styles of request and response parameters #2675.
• Supersedes codegen: Add exactOperationIds option to generateEndpoints config #5174.

---

PR #5174 by @issy proposed a boolean exactOperationIds flag. A boolean is simpler to configure but can only toggle between two fixed behaviors. operationIdTransformer is a strict superset: passing 'none' is equivalent to exactOperationIds: true, while the function form covers everything else. The implementation PR takes direct inspiration from #5174's approach and @issy will be added as a co-author of the commit.

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[issy]

I'm glad this is gaining traction! Thanks for the acknowledgment. I like this idea

[aryaemami59]

@issy

I'm glad this is gaining traction! Thanks for the acknowledgment. I like this idea

Glad to hear it, and thanks for the original PR. It's what got the ball rolling on this!

The function form already lets you plug in any transform today (e.g. a snake_case or PascalCase library), but named shorthands like 'PascalCase' or 'snake_case' could be added as non-breaking additions to the union type down the line if there's enough demand. The architecture is there for it.