Loose TS check

The loose-ts-check utility helps ignore particular types of TS error in specified files.

This is useful when migrating to a stricter tsconfig.json configuration incrementally, where only some existing files are allowed to have TS errors.

Features

• ignores specific TS errors from specific files
• detects files that no longer have to be loosely type-checked
• auto-updates the loosely type-checked list of files when a file no longer has errors
• auto-updates the ignored error codes when there are no errors of that type
• loosely type-checked files can be specified using globs

Why not exclude in tsconfig.json

The exclude option in tsconfig.json only tells tsc to not start type-checking from those files. If some already type-checked file imports a file listed in the exclude, it will still be type-checked.

Thus, it does not suit this use case.

Why not follow the idea from the VSCode project

The vscode team have already encountered a similar problem and solved it in another way. They created a new tsconfig.json that only included some files.

While this works great with existing files, it does not automatically enforce a stricter config for new files in the project.

Installation

Install the utility with:

npm install loose-ts-check --save-dev

Usage

Pipe the result of tsc to loose-ts-check to run the utility:

tsc --noEmit -p tsconfig.strict.json | npx loose-ts-check

To initialize the list of ignored errors and loosely type-checked files based on the current errors, run:

tsc --noEmit -p tsconfig.strict.json | npx loose-ts-check --init

To automatically update the list of loosely type-checked files, run:

tsc --noEmit -p tsconfig.strict.json | npx loose-ts-check --auto-update

Options

Display the list of options by running:

npx loose-ts-check --help

Recipes

Reusing the same tsc output

To avoid running tsc again and again when testing, save the output to a file:

tsc > errors.log;

And then, use the tool by redirecting the input:

npx loose-ts-check < errors.log

Migrating to a stricter tsconfig.json

To migrate the codebase to use a stricter tsconfig.json, you will need 2 tsconfigs:

1. tsconfig.json - the strict tsconfig. This config will be used by the IDE and by the loose-ts-check tool.

   The aim is to see the errors in the IDE, to feel motivated to fix the errors while modifying existing files.

2. tsconfig.loose.json - a tsconfig that extends tsconfig.json, but has the stricter options turned off.

   This config will be used by any linter, test runner, bundler you will have.

   If you are using ts-node, you need to pass tsconfig.loose.json as a TS_NODE_PROJECT variable, so it uses the correct tsconfig, e.g.

   cross-env TS_NODE_PROJECT="tsconfig.loose.json" webpack --mode=development

   To run tsc to do type-checking, pass -p tsconfig.loose.json option:

   tsc -p tsconfig.loose.json

Then, use the following command to initialize the config files:

tsc | npx loose-ts-check --init

After that, run

tsc | npx loose-ts-check

instead of tsc to do type-checking.

IDE plugin

In case you want to have the errors ignored in your IDE as well, use loose-ts-check-plugin.

Development

To verify the correctness, run:

npm run type-check
npm run lint:formatting
npm run test

Contributing

Contributions are welcome!

Make sure the CI passes on your PRs, and that your code is covered by unit tests.