PluginInstance.forEach is typed incorrectly after v0.86

[seanwu1105]

Description

After v0.86, PluginInstance.forEach is typed incorrectly. This is what the generated type before:

forEach<T extends IrTopLevelKind = IrTopLevelKind>(...args: [...events: ReadonlyArray<T>, callback: (event: WalkEvent<T>) => void]): 

and this is what we have now (note the T$1):

forEach<T extends IrTopLevelKind = IrTopLevelKind>(...args: [...events: ReadonlyArray<T$1>, callback: (event: WalkEvent<T$1>) => void]): 

Reproducible example or configuration

You can find the live minimal example here.

import type { DefinePlugin } from '@hey-api/openapi-ts';

type MyPluginConfig = { readonly name: 'myplugin' };
type MyConfig = DefinePlugin<MyPluginConfig>;

export const handler: MyConfig['Handler'] = ({ plugin }) => {
  plugin.forEach('schema', 'operation', (event) => {
    console.log(event);
  });
};

will produce the type checking error:

No overload matches this call.
  Argument of type '[string, string, (event: never) => void]' is not assignable to parameter of type '[...events: Types<MyPluginConfig, MyPluginConfig, never>[], callback: (event: never) => void]'.
    Type at positions 0 through 1 in source is not compatible with type at position 0 in target.
      Type 'string' is not assignable to type 'Types<MyPluginConfig, MyPluginConfig, never>'.
        Type 'string' is not assignable to type '{ config: MyPluginConfig; resolvedConfig: MyPluginConfig; }'.
  Argument of type '[string, string, (event: never) => void]' is not assignable to parameter of type '[...events: Types<MyPluginConfig, MyPluginConfig, never>[], callback: (event: never) => void, options: WalkOptions<Types<MyPluginConfig, MyPluginConfig, never>>]'.
    Type at position 0 in source is not compatible with type at position 0 in target.
      Type 'string' is not assignable to type 'Types<MyPluginConfig, MyPluginConfig, never>'.(2769)

OpenAPI specification (optional)

No response

System information (optional)

No response

[bolt-new-by-stackblitz]

Start a new pull request in StackBlitz Codeflow.

• vitejs-vite-4eqybc1n (Open reproduction)

[dosubot]

Hi @seanwu1105! I'm Dosu and I’m helping the openapi-ts team.

The type error you're seeing with plugin.forEach after v0.86 is due to a change in its type signature: it now expects event arguments to match a stricter Types<...> type, not plain string event names like 'schema' or 'operation'. This breaks the previous usage pattern, where string event types were accepted and the callback received a properly typed event. Now, passing string literals results in the callback's event parameter being inferred as never, causing the type mismatch error you described.

The official documentation and migration guides still show usage with string event types and do not mention this typing change or provide guidance on adapting to it. They also warn that the Plugin API is in development and may change, which suggests this could be an unintended regression or an unstable API surface source.

Currently, there is no documented workaround or fix for this issue. If you need to use string event types with plugin.forEach, you may need to cast types manually or pin to a version before v0.86 until the API stabilizes. Keep an eye on the documentation or changelogs for updates, as this area appears to be actively evolving source.

To reply, just mention @dosu.

---

^{How did I do? Good | Irrelevant | Incorrect | Verbose | Hallucination | Report 🐛 | Other}   

[mrlubos]

Huh, definitely a "this is wild" moment for me. Will be fixed in the next release, thanks for reporting!