Fix TypeScript ESLint errors (Phase 1): Auto-fixes and simple manual fixes (#788)

## Summary

This PR addresses the first batch of ESLint errors in TypeScript files
that were previously suppressed via the ignore pattern `package/**/*.ts`
in `eslint.config.js`.

Part of #783 - TypeScript ESLint Technical Debt resolution.

## Changes Made

### Auto-fixes Applied
- Import ordering and organization (import/order, import/first,
import/newline-after-import)
- Removed unnecessary type assertions
(@typescript-eslint/no-unnecessary-type-assertion)

### Manual Fixes
- Replaced `@ts-ignore` with `@ts-expect-error` in .d.ts files for
webpack optional peer dependency
- Removed unnecessary `@ts-expect-error` from runtime .ts files (webpack
is installed in dev environment)
- Replaced `any` with `unknown` in loader option interfaces
- Fixed `no-use-before-define` error by moving `isValidDevServerConfig`
before `isValidConfig`

## Error Reduction

- **Before**: 293 ESLint errors
- **After**: 247 ESLint errors
- **Fixed**: 46 errors (15.7% reduction)

## Testing

- All existing linting passes with standard ignore patterns
- TypeScript compilation succeeds (`tsc --noEmit`)
- Pre-commit hooks pass (type checking, linting, prettier)

## Remaining Work

This is Phase 1 of the ESLint technical debt cleanup. The remaining 247
errors include:
- `@typescript-eslint/no-require-imports` (requires ES6 import
migration)
- Various `@typescript-eslint/no-unsafe-*` violations (require proper
typing)
- `@typescript-eslint/no-redundant-type-constituents` (type definition
improvements)

These will be addressed in subsequent PRs to keep changes focused and
reviewable.


## Summary by CodeRabbit

* **Refactor**
* Reorganized imports and simplified internal code structure for
improved maintainability.
* Strengthened type safety by replacing permissive type definitions with
stricter alternatives.
  * Enhanced validation mechanisms for configuration handling.

* **Chores**
  * Updated TypeScript compiler directives for better error detection.
  * Applied minor code formatting improvements.

Author: justin808

package/dev_server.ts

@@ -1,7 +1,8 @@
 // These are the raw shakapacker dev server config settings from the YML file with ENV overrides applied.
+import { DevServerConfig } from "./types"
+
 const { isBoolean } = require("./utils/helpers")
 const config = require("./config")
-import { DevServerConfig } from "./types"
 
 const envFetch = (key: string): string | boolean | undefined => {
   const value = process.env[key]

package/environments/base.ts

@@ -1,12 +1,12 @@
 /* eslint global-require: 0 */
 /* eslint import/no-dynamic-require: 0 */
 
+import { Dirent } from "fs"
+import type { Configuration, Entry } from "webpack"
+
 const { basename, dirname, join, relative, resolve } = require("path")
 const { existsSync, readdirSync } = require("fs")
-import { Dirent } from "fs"
 const extname = require("path-complete-extname")
-// @ts-ignore: webpack is an optional peer dependency (using type-only import)
-import type { Configuration, Entry } from "webpack"
 const config = require("../config")
 const { isProduction } = require("../env")
 
@@ -73,7 +73,7 @@ const getEntryObject = (): Entry => {
     const previousPaths = entries[name]
     if (previousPaths) {
       const pathArray = Array.isArray(previousPaths)
-        ? (previousPaths as string[])
+        ? previousPaths
         : [previousPaths as string]
       pathArray.push(assetPath)
       entries[name] = pathArray

package/environments/development.ts

@@ -3,19 +3,20 @@
  * @module environments/development
  */
 
-const { merge } = require("webpack-merge")
-const config = require("../config")
-const baseConfig = require("./base")
-const webpackDevServerConfig = require("../webpackDevServerConfig")
-const { runningWebpackDevServer } = require("../env")
-const { moduleExists } = require("../utils/helpers")
 import type {
   WebpackConfigWithDevServer,
   RspackConfigWithDevServer,
   ReactRefreshWebpackPlugin,
   ReactRefreshRspackPlugin
 } from "./types"
 
+const { merge } = require("webpack-merge")
+const config = require("../config")
+const baseConfig = require("./base")
+const webpackDevServerConfig = require("../webpackDevServerConfig")
+const { runningWebpackDevServer } = require("../env")
+const { moduleExists } = require("../utils/helpers")
+
 /**
  * Base development configuration shared between webpack and rspack
  */

package/environments/test.ts

@@ -3,10 +3,11 @@
  * @module environments/test
  */
 
+import type { Configuration as WebpackConfiguration } from "webpack"
+
 const { merge } = require("webpack-merge")
 const config = require("../config")
 const baseConfig = require("./base")
-import type { Configuration as WebpackConfiguration } from "webpack"
 
 interface TestConfig {
   mode: "development" | "production" | "none"

package/index.ts

@@ -4,7 +4,6 @@
 import * as webpackMerge from "webpack-merge"
 import { resolve } from "path"
 import { existsSync } from "fs"
-// @ts-ignore: webpack is an optional peer dependency (using type-only import)
 import type { Configuration, RuleSetRule } from "webpack"
 import config from "./config"
 import baseConfig from "./environments/base"

package/loaders.d.ts

@@ -1,8 +1,8 @@
-// @ts-ignore: webpack is an optional peer dependency (using type-only import)
+// @ts-expect-error: webpack is an optional peer dependency (using type-only import)
 import type { LoaderDefinitionFunction } from "webpack"
 
 export interface ShakapackerLoaderOptions {
-  [key: string]: any
+  [key: string]: unknown
 }
 
 export interface ShakapackerLoader {

package/optimization/webpack.ts

@@ -19,38 +19,36 @@ interface OptimizationConfig {
   minimizer: unknown[]
 }
 
-const getOptimization = (): OptimizationConfig => {
-  return {
-    minimizer: [
-      tryCssMinimizer(),
-      new TerserPlugin({
-        // SHAKAPACKER_PARALLEL env var: number of parallel workers, or true for auto (os.cpus().length - 1)
-        // If not set or invalid, defaults to true (automatic parallelization)
-        parallel: process.env.SHAKAPACKER_PARALLEL
-          ? Number.parseInt(process.env.SHAKAPACKER_PARALLEL, 10) || true
-          : true,
-        terserOptions: {
-          parse: {
-            // Let terser parse ecma 8 code but always output
-            // ES5 compliant code for older browsers
-            ecma: 8
-          },
-          compress: {
-            ecma: 5,
-            warnings: false,
-            comparisons: false
-          },
-          mangle: { safari10: true },
-          output: {
-            ecma: 5,
-            comments: false,
-            ascii_only: true
-          }
+const getOptimization = (): OptimizationConfig => ({
+  minimizer: [
+    tryCssMinimizer(),
+    new TerserPlugin({
+      // SHAKAPACKER_PARALLEL env var: number of parallel workers, or true for auto (os.cpus().length - 1)
+      // If not set or invalid, defaults to true (automatic parallelization)
+      parallel: process.env.SHAKAPACKER_PARALLEL
+        ? Number.parseInt(process.env.SHAKAPACKER_PARALLEL, 10) || true
+        : true,
+      terserOptions: {
+        parse: {
+          // Let terser parse ecma 8 code but always output
+          // ES5 compliant code for older browsers
+          ecma: 8
+        },
+        compress: {
+          ecma: 5,
+          warnings: false,
+          comparisons: false
+        },
+        mangle: { safari10: true },
+        output: {
+          ecma: 5,
+          comments: false,
+          ascii_only: true
         }
-      })
-    ].filter(Boolean)
-  }
-}
+      }
+    })
+  ].filter(Boolean)
+})
 
 export = {
   getOptimization

package/rspack/index.ts

@@ -4,10 +4,11 @@
 // Mixed require/import syntax:
 // - Using require() for compiled JS modules that may not have proper ES module exports
 // - Using import for type-only imports and Node.js built-in modules
-const webpackMerge = require("webpack-merge")
 import { resolve } from "path"
 import { existsSync } from "fs"
 import type { RspackConfigWithDevServer } from "../environments/types"
+
+const webpackMerge = require("webpack-merge")
 const config = require("../config")
 const baseConfig = require("../environments/base")
 const devServer = require("../dev_server")

package/rules/file.ts

@@ -1,4 +1,5 @@
 import { dirname, sep, normalize } from "path"
+
 const {
   additional_paths: additionalPaths,
   source_path: sourcePath

package/rules/jscommon.ts

@@ -1,5 +1,6 @@
 import { resolve } from "path"
 import { realpathSync } from "fs"
+
 const {
   source_path: sourcePath,
   additional_paths: additionalPaths