typescript-strict-plugin/README.md

Typescript tools that help with migration to the strict mode

# Typescript strict mode plugin

Typescript plugin that allows turning on strict mode in specific files or directories.

## Do I need this plugin?

`typescript-strict-plugin` was created mainly for existing projects that want to incorporate
typescript strict mode, but project is so big that refactoring everything would take ages.

Our plugin allows adding strict mode to a TypeScript project without fixing all the errors at once.
By adding `//@ts-strict-ignore` comment at the top of a file, its whole content will be removed from
strict type checking. To ease migrating a project to use this plugin, you can use
`update-strict-comments` script, which adds the ignore comment to all files that contain at least
one strict error.

TypeScript plugins don't work at compile-time. They will show errors in your IDE, but they won't
appear during compilation. To check strict errors in marked files you can use `tsc-strict` script.
This command line tool is created to check for files that should be checked with strict rules in
compilation time. It finds all relevant files and checks for strict typescript errors only for that
files. Therefore, we have strict errors inside our files and during build time.

## How to install

Use `npm`:

```bash
npm i --save-dev typescript-strict-plugin
```

or yarn

```bash
yarn add -D typescript-strict-plugin
```

add plugin to your `tsconfig.json`:

```json
{
 "compilerOptions": {
   ...
   "strict": false,
   "plugins": [
    {
     "name": "typescript-strict-plugin"
    }
   ]
 }
}
```

and run the migration script

```
./node_modules/.bin/update-strict-comments
```

That's it! You should be able to see strict typechecking in files without the `@ts-strict-ignore`
comment. To make these files strict too, just remove its' ignore comments.

## Configuration

Plugin takes extra, non-mandatory arguments `paths`, `exlude` and `excludePattern`. Args `paths` and
`exclude` accept an array of relative or absolute paths that should be included (property `paths`)
or excluded (property `exclude`). Arg `excludePattern` accepts an array of strings that will be
matched with [minimatch](https://github.com/isaacs/minimatch). To add strict mode to files from
ignored paths you can insert `//@ts-strict` comment.

```json
{
  "compilerOptions": {
    ...
    "strict": false,
    "plugins": [
      {
        "name": "typescript-strict-plugin",
        "paths": [
          "./src",
          "/absolute/path/to/source/"
        ],
        "exclude": [
          "./src/tests",
          "./src/fileToExclude.ts"
        ],
        "excludePattern": [
          "**/*.spec.ts"
        ]
      }
    ]
  }
}
```

All files contained in those paths will be strictly checked. Yay!

To add cli tool to your build time you can add a script to scripts list in package.json

```json
{
  "scripts": {
    ...,
    "typecheck": "tsc && tsc-strict",
  },
}
```

Then you can simply run

```shell
yarn tsc-strict
```

All your strict files should be checked from command line.

You can also pass some `tsc` arguments to the `tsc-strict` to override default compiler options e.g.

```shell
yarn tsc-strict --strictNullChecks false
```

would not check for the strict null check in your files. The `tsc-strict` accepts all the arguments
that regular `tsc` command accepts.

## Migrating to v2

Because of difficulties with migrating large projects to strict mode with original `//@ts-strict`
comment, we've taken an another approach. Now in version 2.0+ typescript files are strict by
default, and to ignore a file, you can use special `//@ts-strict-ignore` comment. It allows to have
strict mode in newly created files without remembering about adding strict comment at the top of it.
Version 2.0 comes with a new script `update-strict-comments`, which detects all files with at least
one strict error and adds the ignore comment to ease the migration. To update from v1 to v2, you
just need to run:

```
update-strict-comments
```

## VSCode support

VSCode supports this plugin out of the box. However, sometimes it can use its own typescript version
instead of the project one, resulting in not reading the local tsconfig. If you are using VSCode be
sure to have `Use workspace version` option selected in `Typescript: Select Typescript Version...`
command available in the
[command pallete](https://code.visualstudio.com/docs/getstarted/userinterface#_command-palette).

<img width="729" alt="image" src="https://user-images.githubusercontent.com/35625949/153884371-e0f488d4-05b8-4b88-93d2-1caa7e6081f7.png">

## Testing the plugin

### Manually

run

```bash
npm i
```

inside root folder and `sample-project` folder and then run

```bash
npm run build
```

or

```bash
npm run dev
```

and restart typescript service inside `sample-project`. Files in `sample-project` folder should use
a local plugin. After you made changes to a plugin you should probably restart typescript service in
order to reload the plugin.

### Tests

In order to run tests run

```bash
npm run test
```

## Contributing

Feel free to create PR's and issues.