Typescript tools that help with migration to the strict mode

TypeScript Strict, TypeScript plugin, TypeScript Language Service, strict-mode, ts-strict, typescript, typescript-compiler, typescript-library, typescript-plugin
npm install typescript-strict-plugin@2.1.0


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:

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

or yarn

yarn add -D typescript-strict-plugin

add plugin to your tsconfig.json:

 "compilerOptions": {
   "strict": false,
   "plugins": [
     "name": "typescript-strict-plugin"

and run the migration script


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.


Plugin takes one extra non-mandatory argument paths that is an array of relative or absolute paths of directories that should be included. To add strict mode to files from ignored paths you can insert //@ts-strict comment.

  "compilerOptions": {
    "strict": false,
    "plugins": [
        "name": "typescript-strict-plugin",
        "paths": [

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

  "scripts": {
    "typecheck": "tsc && tsc-strict",

Then you can simply run

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.

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:


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.


Testing the plugin



npm i

inside root folder and sample-project folder and then run

npm run build


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.


In order to run tests run

npm run test


Feel free to create PR's and issues.