fix(terser): support pure functions for nth_identifier

packages/vite/package.json

@@ -148,6 +148,7 @@
     "source-map-support": "^0.5.21",
     "strip-ansi": "^7.1.0",
     "strip-literal": "^2.1.0",
+    "terser": "^5.31.6",
     "tsconfck": "^3.1.3",
     "tslib": "^2.7.0",
     "types": "link:./types",

packages/vite/src/node/__tests__/plugins/terser.spec.ts

@@ -0,0 +1,45 @@
+import { resolve } from 'node:path'
+import { fileURLToPath } from 'node:url'
+import { describe, expect, test } from 'vitest'
+import { build } from 'vite'
+import type { RollupOutput } from 'rollup'
+
+const __dirname = resolve(fileURLToPath(import.meta.url), '..')
+
+describe('terser', () => {
+  test('nth', async () => {
+    const result = (await build({
+      root: resolve(__dirname, '../packages/build-project'),
+      logLevel: 'silent',
+      build: {
+        write: false,
+        minify: 'terser',
+        terserOptions: {
+          mangle: {
+            nth_identifier: {
+              get: (n) => {
+                return 'prefix_' + n.toString()
+              },
+            },
+          },
+        },
+      },
+      plugins: [
+        {
+          name: 'test',
+          resolveId(id) {
+            if (id === 'entry.js') {
+              return '\0' + id
+            }
+          },
+          load(id) {
+            if (id === '\0entry.js') {
+              return `const foo = 1;console.log(foo)`
+            }
+          },
+        },
+      ],
+    })) as RollupOutput
+    expect(result.output[0].code).toContain('prefix_')
+  })
+})

packages/vite/src/node/plugins/terser.ts

@@ -33,6 +33,12 @@ const loadTerserPath = (root: string) => {
   return terserPath
 }
 
+const toString = (obj: Record<string, any>, name: string) => {
+  if (name in obj && typeof obj[name] === 'function') {
+    obj[name] = obj[name].toString()
+  }
+}
+
 export function terserPlugin(config: ResolvedConfig): Plugin {
   const { maxWorkers, ...terserOptions } = config.build.terserOptions
 
@@ -47,6 +53,27 @@ export function terserPlugin(config: ResolvedConfig): Plugin {
           // test fails when using `import`. maybe related: https://github.com/nodejs/node/issues/43205
           // eslint-disable-next-line no-restricted-globals -- this function runs inside cjs
           const terser = require(terserPath)
+          const nth:
+            | Terser.SimpleIdentifierMangler
+            | Terser.WeightedIdentifierMangler
+            | undefined = (options.mangle as any)?.nth_identifier
+          if (nth && typeof nth === 'object') {
+            const toFunction = (obj: Record<string, any>, name: string) => {
+              if (name in obj && typeof obj[name] === 'string') {
+                const fn = eval(obj[name])
+                if (typeof fn !== 'function') {
+                  throw new Error(
+                    `Failed to eval nth_identifier.${name}: not a function`,
+                  )
+                }
+                obj[name] = fn
+              }
+            }
+            toFunction(nth, 'get')
+            toFunction(nth, 'consider')
+            toFunction(nth, 'sort')
+          }
+
           return terser.minify(code, options) as Terser.MinifyOutput
         },
       {
@@ -87,12 +114,25 @@ export function terserPlugin(config: ResolvedConfig): Plugin {
       worker ||= makeWorker()
 
       const terserPath = loadTerserPath(config.root)
+      const nth =
+        typeof terserOptions.mangle === 'object'
+          ? { ...terserOptions.mangle.nth_identifier }
+          : undefined
+      if (nth) {
+        toString(nth, 'get')
+        toString(nth, 'consider')
+        toString(nth, 'sort')
+      }
       const res = await worker.run(terserPath, code, {
         safari10: true,
         ...terserOptions,
         sourceMap: !!outputOptions.sourcemap,
         module: outputOptions.format.startsWith('es'),
         toplevel: outputOptions.format === 'cjs',
+        mangle:
+          typeof terserOptions.mangle === 'object'
+            ? { ...terserOptions.mangle, nth_identifier: nth as any }
+            : terserOptions.mangle,
       })
       return {
         code: res.code!,