fix(core): file parsing handling esnext correctly

Author: anymaniax

packages/core/src/generators/mutator.ts

@@ -1,11 +1,12 @@
-import { Parser } from 'acorn';
+import acorn, { Parser } from 'acorn';
 import chalk from 'chalk';
 import fs from 'fs-extra';
 import {
   GeneratorMutator,
   GeneratorMutatorParsingInfo,
   NormalizedMutator,
   Tsconfig,
+  TsConfigTarget,
 } from '../types';
 import { createLogger, getFileInfo, loadFile, pascal, upath } from '../utils';
 
@@ -69,7 +70,12 @@ export const generateMutator = async ({
 
   if (file) {
     const mutatorInfoName = isDefault ? 'default' : mutator.name!;
-    const mutatorInfo = parseFile(file, mutatorInfoName);
+
+    const mutatorInfo = parseFile(
+      file,
+      mutatorInfoName,
+      getEcmaVersion(tsconfig?.compilerOptions?.target),
+    );
 
     if (!mutatorInfo) {
       createLogger().error(
@@ -122,12 +128,31 @@ export const generateMutator = async ({
   }
 };
 
+const getEcmaVersion = (
+  target?: TsConfigTarget,
+): acorn.ecmaVersion | undefined => {
+  if (!target) {
+    return;
+  }
+
+  if (target.toLowerCase() === 'esnext') {
+    return 'latest';
+  }
+
+  try {
+    return Number(target.toLowerCase().replace('es', '')) as acorn.ecmaVersion;
+  } catch {
+    return;
+  }
+};
+
 const parseFile = (
   file: string,
   name: string,
+  ecmaVersion: acorn.ecmaVersion = 6,
 ): GeneratorMutatorParsingInfo | undefined => {
   try {
-    const ast = Parser.parse(file, { ecmaVersion: 6 }) as any;
+    const ast = Parser.parse(file, { ecmaVersion }) as any;
 
     const node = ast?.body?.find((childNode: any) => {
       if (childNode.type === 'ExpressionStatement') {

packages/core/src/types.ts

@@ -410,9 +410,24 @@ export interface Tsconfig {
     allowSyntheticDefaultImports?: boolean;
     exactOptionalPropertyTypes?: boolean;
     paths?: Record<string, string[]>;
+    target?: TsConfigTarget;
   };
 }
 
+export type TsConfigTarget =
+  | 'es3'
+  | 'es5'
+  | 'es6'
+  | 'es2015'
+  | 'es2016'
+  | 'es2017'
+  | 'es2018'
+  | 'es2019'
+  | 'es2020'
+  | 'es2021'
+  | 'es2022'
+  | 'esnext'; // https://www.typescriptlang.org/tsconfig#target
+
 export interface PackageJson {
   dependencies?: Record<string, string>;
   devDependencies?: Record<string, string>;

packages/core/src/utils/file.ts

@@ -210,8 +210,13 @@ async function bundleFile(
     format: mjs ? 'esm' : 'cjs',
     sourcemap: 'inline',
     metafile: true,
-    target: 'es6',
-    minifyWhitespace: true,
+    target: compilerOptions?.target || 'es6',
+    minify: false,
+    minifyIdentifiers: false,
+    minifySyntax: false,
+    minifyWhitespace: false,
+    treeShaking: false,
+    keepNames: false,
     plugins: [
       ...(alias || compilerOptions?.paths
         ? [

tests/tsconfig.json

@@ -3,7 +3,7 @@
   "include": ["generated/**/*", "regressions/**/*"],
   "compilerOptions": {
     "skipLibCheck": true,
-    "target": "es5",
+    "target": "es6",
     "module": "commonjs",
     "lib": ["es2019", "dom", "es2016.array.include", "es2017.object"],
     "declaration": true,