ts-remove-unused

Remove unused code from your TypeScript Project

Features

• 🛠️ Auto-fix unused exports — removes the export keyword from the declaration or the whole declaration based on its usage
• 🧹 Deletes TypeScript modules that have no referenced exports
• 🕵️ --check mode — reports unused exports and deletable files without writing changes

Introduction

When TypeScript's compilerOptions.noUnusedLocals is enabled, it's possible to detect declarations that are not referenced in your file.

// TypeScript will throw error: 'a' is declared but its value is never read.
const a = 'a';

However when this declaration is exported and is not referenced by any file in the project, it's difficult to recognize this.

// no errors will be reported even if the declaration is not used across the entire project.
export const a = 'a';

This is when ts-remove-unused comes in handy. ts-remove-unused is a CLI tool built on top of TypeScript that finds unused exports and auto-fixes unused code.

Here are some examples of how ts-remove-unused auto-fixes unused code.

When a2 is not used within the project:

--- src/a.ts
+++ src/a.ts
@@ -1,3 +1 @@
 export const a = 'a';
-
-export const a2 = 'a2';

When b is not used within the project but f() is used within the project:

--- src/b.ts
+++ src/b.ts
@@ -1,5 +1,5 @@
-export const b = 'b';
+const b = 'b';
 
 export function f() {
     return b;
 }

When f() is not used within the project and when deleting it will result in import being unnecessary:

--- src/c.ts
+++ src/c.ts
@@ -1,7 +1 @@
-import { cwd } from "node:process";
-
 export const c = 'c';
-
-export function f() {
-    return cwd();
-}

When f() and exported are not used within the project and when deleting f() will result in exported and local being unnecessary:

--- src/d.ts
+++ src/d.ts
@@ -1,8 +1 @@
-export const exported = "exported";
-const local = "local";
-
 export const d = "d";
-
-export function f() {
-  return { exported, local };
-}

In addition to the behavior shown in the examples above, ts-remove-unused will delete files that have no used exports.

ts-remove-unused supports various types of exports including variable declarations (export const, export let), function declarations, class declarations, interface declarations, type alias declarations, default exports and more...

Now you don't have to worry about removing unused code by yourself!

Install

npm install @line/ts-remove-unused

TypeScript is a peer dependency so make sure that it's also installed.

Usage

Usage:
  $ ts-remove-unused

Commands:
    There are no subcommands. Simply execute ts-remove-unused

For more info, run any command with the `--help` flag:
  $ ts-remove-unused --help

Options:
  --project <file>         Path to your tsconfig.json
  --skip <regexp_pattern>  Specify the regexp pattern to match files that should be skipped from transforming
  --include-d-ts           Include .d.ts files in target for transformation
  --check                  Check if there are any unused exports without removing them
  -h, --help               Display this message
  -v, --version            Display version number

ts-remove-unused's behavior heavily depends on your tsconfig.json. TypeScript's compiler internally holds the list of project files by parsing relevant rules such as include and exclude. ts-remove-unused scans through this list and searches for references to determine if an export/file is "unused". You may need to maintain/update your tsconfig (or you can create another file for --project) so that the set of covered files are right.

Here's an example of using the CLI. Your entry point file must be skipped or else every file will be removed.

npx @line/ts-remove-unused --skip 'src/main\.ts'

Warning

THIS COMMAND WILL DELETE CODE FROM YOUR PROJECT. Using it in a git controlled environment is highly recommended. If you're just playing around use --check.

Options

--check

Use --check to check for unused files and exports without making changes to project files. The command will exit with exit code 1 if there are any unused files or exports discovered.

npx @line/ts-remove-unused --skip 'src/main\.ts' --check

--include-d-ts

By default, .d.ts files are skipped. If you want to include .d.ts files, use the --include-d-ts option.

--experimental-recursive

The default behavior of the CLI is to process all files once. Some issues may not be detected if the unused code is a result of the modification of another file in the project. When this option is enabled, ts-remove-unused will recursively re-edit/re-check files that may be affected by a file edit.

This option is still experimental since it's not optimized (yet) for large scale projects. Using this flag for large scale projects is not recommended.

Use the JavaScript API

Alternatively, you can use the JavaScript API to execute ts-remove-unused.

import { remove } from '@line/ts-remove-unused';

await remove({
  configPath: '/path/to/project/tsconfig.json',
  projectRoot: '/path/to/project',
  skip: [/main\.ts/],
  mode: 'write',
});

Skip

When you add a comment // ts-remove-unused-skip to your export declaration, it will be skipped from being removed

// ts-remove-unused-skip
export const hello = 'world';

The --skip option is also available to skip files that match a given regex pattern. Note that you can pass multiple patterns.

npx @line/ts-remove-unused --skip 'src/main\.ts' --skip '/pages/'

How does ts-remove-unused handle test files?

If you have a separate tsconfig for tests using Project References, that would be great! ts-remove-unused will remove exports/files that exist for the sake of testing.

If you pass a tsconfig.json to the CLI that includes both the implementation and the test files, ts-remove-unused will remove your test files since they are not referenced by your entry point file (which is specified in --skip). You can avoid tests being deleted by passing a pattern that matches your test files to --skip in the meantime, but the recommended way is to use project references to ensure your TypeScript config is more robust and strict (not just for using this tool).

Author

Kazushi Konosu (https://github.com/kazushisan)

License

Copyright (C) 2023 LINE Corp.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.