Replace TSLint with ESLint

[LoicPoullain]

Issue

TSLint is (unfortunately) no longer maintained and framework linting should be migrated to ESLint.

This was done four years ago in this PR for projects generated with Foal. This means that, when executing the createapp command, new projects generated with this command use ESLint.

But the framework monorepo itself has not yet been migrated to ESLint. This is a technical debt that should be resolved.

Guidelines

• If this PR, which updates the way dependencies are managed in monorepo, has not yet been merged, the new branch should be created from v4-5-0. Otherwise, it should be created from master. Not only will this facilitate the migration to ESLint, it will also avoid the need for additional work later on to manage ESLint dependencies with the new dependency system.
• Migration to ESLint should not change the style of the framework code (we don't want thousands of line changes to commit). A lot of work had been done at the time in this PR to make ESLint rules consistent with TSLint rules. There's probably a lot to be learned from this PR.
• When opening the framework repository with VSCode with the ESLint plugin enabled, VSCode should correctly highlight ESLint errors and correct them when saving (if the plugin is configurer to do so).

Notes

• There might be useful information here.
• The files packages/cli/src/generate/specs/app/.eslintrc.js and packages/cli/src/generate/templates/app/.eslintrc.js used by foal createapp to generate new projects may cause problems.

[deepanshu44]

Hello @LoicPoullain,
I am interested in contributing to this issue. Does this issue still has a priority?

Quickly glancing over the description, I believe that I should be creating a fork from the master branch?

And the tool that I should be using would be the one mentioned in the second last paragraph of this comment. palantir/tslint#4534 (comment)

tslint-to-eslint-config

[LoicPoullain]

Hello @deepanshu44

I am interested in contributing to this issue. Does this issue still has a priority?

Yes, you can take this one if you wish!

Quickly glancing over the description, I believe that I should be creating a fork from the master branch?

Yes

And the tool that I should be using would be the one mentioned in the second last paragraph of this comment. palantir/tslint#4534 (comment)

tslint-to-eslint-config

Perhaps. I have never migrated a project from TSLint to ESLint myself. But this has already be done in this PR to migrate the applications generated by createapp form TSLint to ESLint. The TSLint rules that were used by createapp are the same that the ones currently used for the framework linting.

[LoicPoullain]

Hello @deepanshu44
I received a notification about this issue in my Github inbox, but I couldn't find any new comments. Might it have been deleted in the meantime?

[deepanshu44]

Hello @LoicPoullain
Actually I did made a comment. But since then deleted it thinking I was getting ahead of myself.

One question though,
There are two ways to define eslint config file, the new flat config format or the legacy config format,
I just need to confirm that I think the legacy method will be the best way forward to migrate and integrate typed linting.

And some update on this issue,
I made some changes here, but I am running into a lot of linting errors and will probably figure out the solution myself.

$ npx eslint --ext ts --no-eslintrc -c .eslintrc.js packages/

=============

/home/dev/foal/packages/acceptance-tests/src/additional/session.config.spec.ts
  77:29  error  Strings must use singlequote  @typescript-eslint/quotes

/home/dev/foal/packages/acceptance-tests/src/additional/shell-scripts/create-group.spec.ts
  56:7  error  Unnecessary catch clause  no-useless-catch

/home/dev/foal/packages/acceptance-tests/src/additional/shell-scripts/create-perm.spec.ts
  41:7  error  Unnecessary catch clause  no-useless-catch

/home/dev/foal/packages/acceptance-tests/src/additional/typeorm.mongodb-store.spec.ts
  38:46  error  Promise returned in function argument where a void return was expected  @typescript-eslint/no-misused-promises

/home/dev/foal/packages/acceptance-tests/src/additional/typeorm.redis-store.spec.ts
  39:44  error  Promise returned in function argument where a void return was expected  @typescript-eslint/no-misused-promises

/home/dev/foal/packages/acceptance-tests/src/docs/architecture/architecture-overview/creating-a-service.feature.ts
  16:19  error  Invalid type "Date" of template literal expression  @typescript-eslint/restrict-template-expressions

...
✖ 462 problems (462 errors, 0 warnings)
  140 errors and 0 warnings potentially fixable with the `--fix` option.

[LoicPoullain]

One question though,
There are two ways to define eslint config file, the new flat config format or the legacy config format,
I just need to confirm that I think the legacy method will be the best way forward to migrate and integrate typed linting.

I'm not familiar with the different methods. I'll let you choose what you think is the best solution.

The ideal solution where we want to go is this:

• the method used in the monorepo framework should be the same as that used in new projects generated by foal createapp,
• and the linting rules used in the monorepo framework should be the same as those used in new projects generated by foal createapp.

In this way, when we write documentation and copy-paste code from the framework, the examples are always correctly “linted” when users then copy-paste the same code into their projects.

Note 1: if we have this ideal solution with the same rules and the createapp rules are still the same and there are linting errors that appear from the framework code, then we can fix them all. Go for it 👍

Note 2: in tests of the directory acceptance-tests/, there are pieces of code that are between comments such as ======== DOCUMENTATION BEGIN ======= and ====== DOCUMENTATION END =======. In this case, this means that these codes are present in the documentation and should be updated as well in the markdowns in case of modification. You can ignore files in docs/versioned_docs/ and docs/i18n/.

Thank you so much, for taking care of this. This is really a work that needs to be done. 🙂

[deepanshu44]

sign function in jwt.spec is returning never, hmm

[LoicPoullain]

Could this be related to the definition / existence of this file: https://github.com/FoalTS/foal/blob/master/packages/jwt/typings/jsonwebtoken/index.d.ts?

[ronakmaheshwari]

Is the issue closed or can I work on it

[LoicPoullain]

@deepanshu44 are you still working on it or should @ronakmaheshwari take this issue?