allow var in TypeScript ambient declarations

[azat-io]

Motivation

The prefer-let rule was incorrectly flagging var declarations in TypeScript ambient contexts (declare global, declare module, declare namespace). In these contexts, var has special semantic meaning - it creates properties on the global object (e.g., window.fathom), while let would create lexical bindings that aren't accessible as properties.

This was forcing developers to add eslint-disable comments for legitimate TypeScript code:

declare global {
  // eslint-disable-next-line prefer-let/prefer-let
  var fathom: undefined | Fathom
}

Approach

Added a new helper function isInAmbientContext() that walks up the AST tree to check if a variable declaration is inside a TSModuleDeclaration with declare: true. When var is detected in an ambient context, the rule now skips it instead of reporting an error.

[changeset-bot]

🦋 Changeset detected

Latest commit: b2b469c

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[github-actions]

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[cowboyd]

This looks good to me.

[azat-io]

Thanks! Could you publish release?

[cowboyd]

@jbolda For some reason, this didn't open up a release PR. Any idea why? https://github.com/thefrontside/javascript/actions/runs/20697051068

GitHub

Merge pull request #68 from azat-io/feat/ts-declarations · thefrontside/javascript@f6167ad

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[azat-io]

@cowboyd Perhaps a changeset should have been added?

[jbolda]

@cowboyd the workflows have covector which looks for change files in the .change dir. Looks like the changeset bot threw you off, and you added one in .changeset instead? If you move that file, it should trigger the PR open.

[cowboyd]

@azat-io looks like I put the changes in the wrong dir! I don't currently have a checkout of this repo, would you mind moving it to the .change and we can get this out the door?

Also, @jbolda we will probably need to set this repo up with OIDC publishing, which I can do now. Were there some changes we needed to make to the publish action itself?

[jbolda]

@cowboyd just removing the token.

[azat-io]

Do I need to do something, or will you publish it?

[cowboyd]

Actually, I have some more time today, so I can take care of it.

[cowboyd]

This should be available now #69

[azat-io]

Thanks!