DefaultContext added via declaration-merging is strictly forcing HttpHeaders

[vz-tl]

Describe the bug

In apollo-angular v12, the @apollo/client DefaultContext interface becomes redefined via declaration-merging and specifies the headers property to be strictly of type HttpHeaders , which wasn't the case with pre-v12 versions.

This contradicts how headers are processed and handled in general, either by the underlying @apollo/client package, which just supports Record<string, string> or even apollo-angular, which finally checks if the headers provided in a query context are instanceof HttpHeaders and if not it will just accept a regular object.

Expected behavior

I'm requesting to at least define the headers prop as a union to allow HttpHeaders | Record<string, string>, as I'm currently forced to again redeclare the DefaultContext for supporting that.

Environment:

- @angular/cli@20.3.9
- @angular/core@20.3.10
- @apollo/client@4.0.9
- apollo-angular@12.1.0
- graphql@16.10.0
- typescript@5.9.3

[PowerKiKi]

Can you please illustrate the issue, and the possible solution by code ?

[vz-tl]

I'm referring to https://github.com/the-guild-org/apollo-angular/blob/master/packages/apollo-angular/http/src/types.ts#L6

export interface DefaultContext extends Context {}

which extends Context, which in turn extends

export type HttpRequestOptions = {
  headers?: HttpHeaders; // <-- this seems too strict 
  withCredentials?: boolean;
  useMultipart?: boolean;
};

and I'm requesting to change it to

export type HttpRequestOptions = {
  headers?: HttpHeaders | Record<string, string>;
  withCredentials?: boolean;
  useMultipart?: boolean;
};

[Destreyf]

Just want to chime in on this, the Angular HttpClient types for headers is this:

HttpHeaders | Record<string, string | string[]>

[PowerKiKi]

That sounds like a reasonable change. Feel free to open a PR for it.