feat: add rspack version detection helpers

packages/repack/src/commands/types.ts

@@ -63,7 +63,9 @@ export type RemoveRecord<T> = T extends infer U & Record<string, any>
 
 type ConfigKeys =
   | 'name'
+  | 'cache'
   | 'context'
+  | 'experiments'
   | 'mode'
   | 'devServer'
   | 'entry'

packages/repack/src/helpers/index.ts

@@ -1,2 +1,3 @@
 export * from './errors.js';
 export * from './helpers.js';
+export * from './rspackVersion.js';

packages/repack/src/helpers/rspackVersion.ts

@@ -0,0 +1,61 @@
+import type { Compiler as RspackCompiler } from '@rspack/core';
+import type { Compiler as WebpackCompiler } from 'webpack';
+
+/**
+ * Reads the version of the installed `@rspack/core` package without loading it.
+ *
+ * Resolving `@rspack/core/package.json` instead of importing the package keeps
+ * this helper safe to call in any context:
+ * - `@rspack/core` v2 is ESM-only, so a CJS `require('@rspack/core')` throws
+ *   `ERR_REQUIRE_ESM` on Node < 20.19,
+ * - `@rspack/core` is an optional peer dependency and may not be installed
+ *   at all (webpack-only projects).
+ *
+ * @param context Optional directory to resolve `@rspack/core` from. Defaults
+ * to Re.Pack's own resolution paths.
+ * @returns Version string or `null` when `@rspack/core` is not resolvable.
+ */
+export function getRspackVersion(context?: string): string | null {
+  try {
+    const options = context ? { paths: [context] } : undefined;
+    const packageJsonPath = require.resolve(
+      '@rspack/core/package.json',
+      options
+    );
+    const { version }: { version: string } = require(packageJsonPath);
+    return version;
+  } catch {
+    return null;
+  }
+}
+
+/**
+ * Major version of the installed `@rspack/core` package,
+ * or `null` when it's not resolvable.
+ */
+export function getRspackMajorVersion(context?: string): number | null {
+  const version = getRspackVersion(context);
+  if (!version) return null;
+  return Number(version.split('.')[0]);
+}
+
+/**
+ * Whether the installed `@rspack/core` package is version 2 or newer.
+ * Returns `false` when `@rspack/core` is not resolvable.
+ */
+export function isRspack2(context?: string): boolean {
+  return (getRspackMajorVersion(context) ?? 0) >= 2;
+}
+
+/**
+ * Major version of Rspack derived from an already-created compiler instance.
+ * Returns `null` for webpack compilers.
+ */
+export function getRspackMajorVersionFromCompiler(
+  compiler: RspackCompiler | WebpackCompiler
+): number | null {
+  if ('rspackVersion' in compiler.webpack && compiler.webpack.rspackVersion) {
+    return Number(compiler.webpack.rspackVersion.split('.')[0]);
+  }
+  return null;
+}