Experiment with adding webpack 4 support back

.github/workflows/push.yml

@@ -49,7 +49,8 @@ jobs:
     strategy:
       matrix:
         node: [26, 24, 22]
-        ts: [5.0.4, 5.1.3, 5.2.2, 5.3.3, 5.4.2, 5.5.3, 5.6.2, 5.7.2, 5.8.2, 5.9.2, 6.0.2] # next excluded for now
+        ts: [5.6.2, 5.7.2, 5.8.2, 5.9.2, 6.0.2] # next excluded for now
+        webpack: [4, 5]
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v6
@@ -68,6 +69,10 @@ jobs:
       - name: install typescript
         run: yarn add typescript@${{ matrix.ts }}
 
+      - name: install webpack 4
+        if: matrix.webpack == 4
+        run: yarn add webpack@^4.47.0 karma-webpack@^4.0.2
+
       - name: test
         run: yarn execution-tests
 
@@ -76,7 +81,8 @@ jobs:
     strategy:
       matrix:
         node: [26, 24, 22]
-        ts: [5.0.4, 5.1.3, 5.2.2, 5.3.3, 5.4.2, 5.5.3, 5.6.2, 5.7.2, 5.8.2, 5.9.2, 6.0.2] # next excluded for now
+        ts: [5.6.2, 5.7.2, 5.8.2, 5.9.2, 6.0.2] # next excluded for now
+        webpack: [4, 5]
     runs-on: windows-latest
     steps:
       - uses: actions/checkout@v6
@@ -104,6 +110,11 @@ jobs:
         run: yarn add typescript@${{ matrix.ts }}
         working-directory: C:\source\ts-loader
 
+      - name: install webpack 4
+        if: matrix.webpack == 4
+        run: yarn add webpack@^4.47.0 karma-webpack@^4.0.2
+        working-directory: C:\source\ts-loader
+
       - name: test
         run: yarn execution-tests
         working-directory: C:\source\ts-loader

.vscode/settings.json

@@ -7,5 +7,6 @@
     "git blame": true,
     "sed": true,
     "yarn": true,
+    "git check-ignore": true
   }
 }

AGENTS.md

@@ -8,6 +8,8 @@ Use `yarn` (not npm).
 
 ## Key commands
 
+Note: test scripts clean test directories first using `git clean -xfd`.
+
 ```bash
 yarn build              # compile src/ → dist/ (tsc --project "./src")
 yarn lint               # type-check + ESLint (no separate typecheck script)
@@ -43,7 +45,7 @@ yarn comparison-tests -- --save-output --single-test <name>       # regenerate o
 
 ## Execution tests (`test/execution-tests/`)
 
-Each sub-directory is a mini webpack project with a Karma/Jasmine test suite. The harness compiles the project and **runs the compiled code** — useful for asserting correct runtime behaviour. These are matrix-tested in CI across Node 20/22 and TypeScript 5.x versions.
+Each sub-directory is a mini webpack project with a Karma/Jasmine test suite. The harness compiles the project and **runs the compiled code** — useful for asserting correct runtime behaviour. These are matrix-tested in CI across multiple Node and TypeScript versions (see `.github/workflows/push.yml` for the current matrix).
 
 Full docs: [`test/execution-tests/README.md`](test/execution-tests/README.md)
 

CHANGELOG.md

@@ -1,5 +1,8 @@
 # Changelog
 
+## 9.6.0
+* [feat: add webpack 4 support back](https://github.com/TypeStrong/ts-loader/pull/1697) - thanks @johnnyreilly
+
 ## 9.5.7
 * [fix: TS5011 errors with TypeScript 6.0: transpileModule called with rootDir: undefined](https://github.com/TypeStrong/ts-loader/pull/1679) [#1678] - thanks @julioz and @errorx666
 * [feat: migrate to trusted publishing](https://github.com/TypeStrong/ts-loader/pull/1680) - thanks @johnnyreilly

README.md

@@ -133,10 +133,10 @@ If you'd like to see a simple setup take a look at [our example](examples/fork-t
 ### Compatibility
 
 * TypeScript: 3.6.3+
-* webpack: 5.x+ (please use `ts-loader` 8.x if you need webpack 4 support)
+* webpack: 4.x+ and 5.x+
 * node: 12.x+
 
-A full test suite runs each night (and on each pull request). It runs both on Linux and Windows, testing `ts-loader` against major releases of TypeScript. The test suite also runs against TypeScript@next (because we want to use it as much as you do).
+A full test suite runs each night (and on each pull request). It runs both on Linux and Windows, testing `ts-loader` against major releases of TypeScript and against both webpack 4 and webpack 5. Comparison tests run against webpack 5 only; execution tests run against both webpack 4 and webpack 5. The test suite also runs against TypeScript@next (because we want to use it as much as you do).
 
 If you become aware of issues not caught by the test suite then please let us know. Better yet, write a test and submit it in a PR!
 

eslint.config.mjs

@@ -0,0 +1,45 @@
+import js from '@eslint/js';
+import { defineConfig } from 'eslint/config';
+import tseslint from 'typescript-eslint';
+
+export default defineConfig(
+  js.configs.recommended,
+  tseslint.configs.recommendedTypeChecked,
+  {
+    files: ['eslint.config.mjs'],
+    extends: [tseslint.configs.disableTypeChecked],
+  },
+  {
+    files: ['**/*.ts', '**/*.tsx'],
+    languageOptions: {
+      parserOptions: {
+        projectService: true
+      },
+    },
+    rules: {
+      'no-prototype-builtins': 'off',
+      '@typescript-eslint/no-unsafe-enum-comparison': 'off',
+      '@typescript-eslint/unbound-method': 'off',
+      '@typescript-eslint/no-unsafe-call': 'off',
+      '@typescript-eslint/no-unsafe-assignment': 'off',
+      '@typescript-eslint/no-unsafe-member-access': 'off',
+      '@typescript-eslint/no-unsafe-return': 'off',
+      '@typescript-eslint/no-explicit-any': 'off',
+      '@typescript-eslint/no-require-imports': 'off',
+      '@typescript-eslint/consistent-type-imports': 'error',
+      '@typescript-eslint/no-unsafe-argument': 'off',
+      '@typescript-eslint/no-unused-vars': [
+        'error',
+        {
+          'args': 'all',
+          'argsIgnorePattern': '^_',
+          'caughtErrors': 'all',
+          'caughtErrorsIgnorePattern': '^_',
+          'destructuredArrayIgnorePattern': '^_',
+          'varsIgnorePattern': '^_',
+          'ignoreRestSiblings': true
+        }
+      ]
+    },
+  },
+);

package.json

@@ -6,7 +6,7 @@
   "types": "dist",
   "scripts": {
     "build": "tsc --version && tsc --project \"./src\"",
-    "lint": "tsc --project \"./src\" --noEmit && eslint -c .eslintrc.js --ext .ts ./src",
+    "lint": "tsc --project \"./src\" --noEmit && eslint --ext .ts ./src",
     "comparison-tests": "git clean -xfd test/comparison-tests && npm link --legacy-peer-deps ./test/comparison-tests/testLib && node test/comparison-tests/run-tests.js",
     "execution-tests": "git clean -xfd test/execution-tests && node test/execution-tests/run-tests.js",
     "test": "git clean -xfd test/comparison-tests && git clean -xfd test/execution-tests && node test/run-tests.js",
@@ -60,11 +60,10 @@
     "source-map": "^0.7.4"
   },
   "devDependencies": {
+    "@eslint/js": "^10.0.1",
     "@types/micromatch": "^4.0.0",
     "@types/node": "*",
     "@types/semver": "^7.3.4",
-    "@typescript-eslint/eslint-plugin": "^6.0.0",
-    "@typescript-eslint/parser": "^6.0.0",
     "babel": "^6.0.0",
     "babel-core": "^6.0.0",
     "babel-loader": "^7.0.0",
@@ -73,10 +72,9 @@
     "babel-preset-es2016": "^6.16.0",
     "babel-preset-react": "^6.0.0",
     "escape-string-regexp": "^2.0.0",
-    "eslint": "^8.0.0",
-    "eslint-config-prettier": "^8.0.0",
-    "eslint-plugin-node": "^11.1.0",
-    "eslint-plugin-prettier": "^4.0.0",
+    "eslint": "^10.0.0",
+    "eslint-config-prettier": "^10.0.0",
+    "eslint-plugin-n": "^17.0.0",
     "fs-extra": "^11.0.0",
     "glob": "^7.1.1",
     "husky": "^8.0.0",
@@ -88,18 +86,26 @@
     "karma-sourcemap-loader": "^0.4.0",
     "karma-webpack": "^5.0.0",
     "lint-staged": "^8.0.0",
+    "loader-utils": "^1.4.2",
     "markdown-toc": "^1.2.0",
     "mkdirp": "^0.5.1",
     "mocha": "^6.0.0",
     "prettier": "^2.0.5",
     "rimraf": "^2.6.2",
     "typescript": "^6.0.2",
+    "typescript-eslint": "^8.59.4",
     "webpack": "^5.74.0",
     "webpack-cli": "^4.10.0"
   },
   "peerDependencies": {
+    "loader-utils": "*",
     "typescript": "*",
-    "webpack": "^5.0.0"
+    "webpack": "^4.0.0 || ^5.0.0"
+  },
+  "peerDependenciesMeta": {
+    "loader-utils": {
+      "optional": true
+    }
   },
   "publishConfig": {
     "provenance": true