Expose report-related APIs in another package

[ikatyang]

Currently, all the APIs are not exposed, so that it can't be reused by other linter-plugin, e.g. tslint-plugin-prettier (currently just copy-paste implementations from this repo).

It'd be better to expose report-related APIs in another package (since this repo has peerDeps for eslint), so that it can be reused in different linter plugin to have consistent behavior.

Suggested API

export declare function showInvisibles(str: string): string;
export declare function reportDifferences(source: string, formatted: string, reporters: Reporters);

export interface Reporters {
  reportInsert: (offset: number, text: string, message: string) => void;
  reportDelete: (offset: number, text: string, message: string) => void;
  reportReplace: (offset: number, deleteText: string, insertText: string, message: string) => void;
}

[not-an-aardvark]

I wouldn't mind doing this in theory, but it feels like the helper functions are sufficiently small and eslint-specific that it wouldn't be worthwhile. For example, all of the helpers use getLocFromIndex, context, and fixer, which are ESLint APIs and (as far as I know) have no direct equivalent in tslint.

I don't think your proposed interface would work, because something like reportInsert would need to have some way of actually reporting an error, and that can't happen unless they either return a value or accept a report function.

[ikatyang]

The context is not a necessary argument for reporters, for example if there is the suggested API:

return {
  Program() {
    if (!prettier) {
      // Prettier is expensive to load, so only load it if needed.
      prettier = require('prettier');
    }
    const prettierSource = prettier.format(source, prettierOptions);
    if (source !== prettierSource) {
      suggestedAPI.reportDifferences(source, prettierSource, {
        reportInsert: (...args) => reportInsert(context, ...args),
        reportDelete: (...args) => reportDelete(context, ...args),
        reportReplace: (...args) => reportReplace(context, ...args),
      });
    }
  }
};

We can call context as a contextual value so that it wouldn't have to pass in reporters directly.

For TSLint vs ESLint API, see this.

If you still think my proposed interface wouldn't work, I can send a PR here to show what it'd be in my proposal.

[ikatyang]

See #40 for my proposal

[not-an-aardvark]

cc @zertosh, any thoughts on this?

[zertosh]

Sounds good to me!