feat: Add migrate-config CLI tool

.github/ISSUE_TEMPLATE/bug-report.yml

@@ -13,6 +13,8 @@ body:
                 required: false
               - label: "`@eslint/config-array`"
                 required: false
+              - label: "`@eslint/migrate-config`"
+                required: false
               - label: "`@eslint/object-schema`"
                 required: false
     - type: textarea

.github/ISSUE_TEMPLATE/change.yml

@@ -12,6 +12,8 @@ body:
                 required: false
               - label: "`@eslint/config-array`"
                 required: false
+              - label: "`@eslint/migrate-config`"
+                required: false
               - label: "`@eslint/object-schema`"
                 required: false
     - type: textarea

.github/workflows/release-please.yml

@@ -49,6 +49,34 @@ jobs:
             # most internal dependencies are released last.
             #-----------------------------------------------------------------------------
 
+            #-----------------------------------------------------------------------------
+            # @eslint/migrate-config
+            #-----------------------------------------------------------------------------
+
+            - name: Publish @eslint/migrate-config package to npm
+              run: npm publish -w packages/migrate-config
+              if: ${{ steps.release.outputs['packages/migrate-config--release_created'] }}
+              env:
+                  NODE_AUTH_TOKEN: ${{secrets.NPM_TOKEN}}
+
+            # NOTE: No JSR package because JSR doesn't support CLIs
+
+            - name: Tweet Release Announcement
+              run: npx @humanwhocodes/tweet "@eslint/migrate-config v${{ steps.release.outputs['packages/migrate-config--major'] }}.${{ steps.release.outputs['packages/migrate-config--minor'] }}.${{ steps.release.outputs['packages/migrate-config--patch'] }} has been released!\n\n${{ github.event.repository.html_url }}/releases/tag/v${{ steps.release.outputs['packages/migrate-config--tag_name'] }}"
+              if: ${{ steps.release.outputs['packages/migrate-config--release_created'] }}
+              env:
+                  TWITTER_CONSUMER_KEY: ${{ secrets.TWITTER_CONSUMER_KEY }}
+                  TWITTER_CONSUMER_SECRET: ${{ secrets.TWITTER_CONSUMER_SECRET }}
+                  TWITTER_ACCESS_TOKEN_KEY: ${{ secrets.TWITTER_ACCESS_TOKEN_KEY }}
+                  TWITTER_ACCESS_TOKEN_SECRET: ${{ secrets.TWITTER_ACCESS_TOKEN_SECRET }}
+
+            - name: Toot Release Announcement
+              run: npx @humanwhocodes/toot "@eslint/migrate-config v${{ steps.release.outputs['packages/migrate-config--major'] }}.${{ steps.release.outputs['packages/migrate-config--minor'] }}.${{ steps.release.outputs['packages/migrate-config--patch'] }} has been released!\n\n${{ github.event.repository.html_url }}/releases/tag/v${{ steps.release.outputs['packages/migrate-config--tag_name'] }}"'
+              if: ${{ steps.release.outputs['packages/migrate-config--release_created'] }}
+              env:
+                  MASTODON_ACCESS_TOKEN: ${{ secrets.MASTODON_ACCESS_TOKEN }}
+                  MASTODON_HOST: ${{ secrets.MASTODON_HOST }}
+
             #-----------------------------------------------------------------------------
             # @eslint/compat
             #-----------------------------------------------------------------------------

.prettierignore

@@ -1,2 +1,3 @@
 dist
 CHANGELOG.md
+packages/*/tests/fixtures

.release-please-manifest.json

@@ -1,5 +1,6 @@
 {
   "packages/object-schema": "2.1.1",
   "packages/config-array": "0.14.1",
-  "packages/compat": "1.0.1"
+  "packages/compat": "1.0.1",
+  "packages/migrate-config": "0.0.0"
 }

eslint.config.js

@@ -2,6 +2,9 @@ import js from "@eslint/js";
 
 export default [
 	js.configs.recommended,
+	{
+		ignores: ["**/tests/fixtures/**/*.*"],
+	},
 	{
 		files: ["**/*.test.js"],
 		languageOptions: {

packages/migrate-config/LICENSE

@@ -0,0 +1,201 @@
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packages/migrate-config/README.md

@@ -0,0 +1,73 @@
+# ESLint Configuration Migrator
+
+## Overview
+
+This package aids in the migration of the legacy ESLint configuration file format (`.eslintrc.`) to the new ESLint configuration file format (`eslint.config.js`).
+
+**Note:** The generated configuration file isn't guaranteed to work in all cases, but it should get you a lot closer to a working configuration file than manually trying to migrate.
+
+## Limitations
+
+This tool currently works well for the following config file formats:
+
+-   `.eslintrc`
+-   `.eslintrc.json`
+-   `.eslintrc.yml`
+
+If you are using a JavaScript configuration file (`.eslintrc.js`, `.eslintrc.cjs`, `.eslintrc.mjs`), this tool currently is only capable of migrating the _evaluated_ configuration. That means any logic you may have inside of the file will be lost. If your configuration file is mostly static, then you'll get a good result; if your configuration file is more complex (using functions, calculating paths, etc.) then this tool will not provide an equivalent configuration file.
+
+## Usage
+
+You can run this package on the command line without installing it first by using `npx` or a similar tool:
+
+```shell
+npx @eslint/migrate-config .eslintrc.json
+# or
+bunx @eslint/migrate-config .eslintrc.json
+```
+
+The tool will automatically find your `.eslintignore` file in the same directory and migrate that into your new configuration file.
+
+### CommonJS Output
+
+By default, this tool generates an ESM file (`.mjs` extension). If you'd like to generate a CommonJS file instead, pass the `--commonjs` flag:
+
+```shell
+npx @eslint/migrate-config .eslintrc.json --commonjs
+# or
+bunx @eslint/migrate-config .eslintrc.json --commonjs
+```
+
+## Followup Steps
+
+Once you have completed the migration, you may need to manually modify the resulting config file.
+
+### Double-Check Compatibility
+
+There are some plugins that might be used with compatibility features in the output that may no longer need them. You should double-check your plugins to see if they have fully ESLint v9-compatible versions of the packages.
+
+### `--ext`
+
+If you are using `--ext` on the command line, such as:
+
+```shell
+npx eslint --ext .ts .
+```
+
+You'll need to remove the `--ext` from the command line and add an equivalent object into your configuration file. For example, `--ext .ts` requires an object like this in your configuration file:
+
+```js
+export default [
+	{
+		files: ["**/*.ts"],
+	},
+
+	// the rest of your config
+];
+```
+
+This tells ESLint to search for all files ending with `.ts` when a directory is passed on the command line. You can choose to add additional properties to this object if you'd like, but it's not required.
+
+## License
+
+Apache 2.0