feat(experimental-esm): adds option for esm output

hedefalk · Jun 4, 2020 · f488ab6 · f488ab6
1 parent f3ac5b0
commit f488ab6
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Showing 6 changed files with 27 additions and 8 deletions.
diff --git a/cli.js b/cli.js
diff --git a/src/__helpers__/fakers.ts b/src/__helpers__/fakers.ts
@@ -22,6 +22,7 @@ export function tsJestConfig(options?: Partial<TsJestConfig>): TsJestConfig {
     packageJson: undefined,
     stringifyContentPathRegex: undefined,
     diagnostics: { ignoreCodes: [], pretty: false, throws: true },
+    experimentalEsm: false,
     ...options,
   }
 }

diff --git a/src/compiler/instance.ts b/src/compiler/instance.ts
@@ -2,6 +2,7 @@ import { Logger } from 'bs-logger'
 import { readFileSync } from 'fs'
 import mkdirp = require('mkdirp')
 import { basename, extname } from 'path'
+import { ModuleKind } from 'typescript'
 
 import { ConfigSet } from '../config/config-set'
 import { CompileFn, CompilerInstance, MemoryCache, TSFile, TsCompiler } from '../types'
@@ -103,10 +104,16 @@ export const createCompilerInstance = (configs: ConfigSet): TsCompiler => {
   /**
    * Get the extension for a transpiled file.
    */
-  const getExtension =
-    compilerOptions.jsx === ts.JsxEmit.Preserve
-      ? (path: string) => (/\.[tj]sx$/.test(path) ? '.jsx' : '.js')
-      : (_: string) => '.js'
+  const getExtension = (path: string) => {
+    const jsExtension = configs.tsJest.experimentalEsm && compilerOptions.module === ModuleKind.ESNext ? '.mjs' : '.js'
+
+    if (compilerOptions.jsx === ts.JsxEmit.Preserve) {
+      return /\.[tj]sx$/.test(path) ? '.jsx' : jsExtension
+    } else {
+      return jsExtension
+    }
+  }
+
   let compilerInstance: CompilerInstance
   if (!tsJest.isolatedModules) {
     // Use language services by default

diff --git a/src/config/__snapshots__/config-set.spec.ts.snap b/src/config/__snapshots__/config-set.spec.ts.snap
@@ -1,6 +1,6 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`cacheKey should be a string 1`] = `"{\\"digest\\":\\"a0d51ca854194df8191d0e65c0ca4730f510f332\\",\\"jest\\":{\\"__backported\\":true,\\"globals\\":{}},\\"projectDepVersions\\":{\\"dev\\":\\"1.2.5\\",\\"opt\\":\\"1.2.3\\",\\"peer\\":\\"1.2.4\\",\\"std\\":\\"1.2.6\\"},\\"transformers\\":[\\"hoisting-jest-mock@1\\"],\\"tsJest\\":{\\"compiler\\":\\"typescript\\",\\"diagnostics\\":{\\"ignoreCodes\\":[6059,18002,18003],\\"pretty\\":true,\\"throws\\":true},\\"isolatedModules\\":false,\\"packageJson\\":{\\"kind\\":\\"file\\"},\\"transformers\\":[]},\\"tsconfig\\":{\\"declaration\\":false,\\"inlineSourceMap\\":false,\\"inlineSources\\":true,\\"module\\":1,\\"noEmit\\":false,\\"removeComments\\":false,\\"sourceMap\\":true,\\"target\\":1}}"`;
+exports[`cacheKey should be a string 1`] = `"{\\"digest\\":\\"a0d51ca854194df8191d0e65c0ca4730f510f332\\",\\"jest\\":{\\"__backported\\":true,\\"globals\\":{}},\\"projectDepVersions\\":{\\"dev\\":\\"1.2.5\\",\\"opt\\":\\"1.2.3\\",\\"peer\\":\\"1.2.4\\",\\"std\\":\\"1.2.6\\"},\\"transformers\\":[\\"hoisting-jest-mock@1\\"],\\"tsJest\\":{\\"compiler\\":\\"typescript\\",\\"diagnostics\\":{\\"ignoreCodes\\":[6059,18002,18003],\\"pretty\\":true,\\"throws\\":true},\\"experimentalEsm\\":false,\\"isolatedModules\\":false,\\"packageJson\\":{\\"kind\\":\\"file\\"},\\"transformers\\":[]},\\"tsconfig\\":{\\"declaration\\":false,\\"inlineSourceMap\\":false,\\"inlineSources\\":true,\\"module\\":1,\\"noEmit\\":false,\\"removeComments\\":false,\\"sourceMap\\":true,\\"target\\":1}}"`;
 
 exports[`jest should merge parent config if any with globals is an empty object 1`] = `
 Object {
@@ -53,6 +53,7 @@ Object {
       "pretty": true,
       "throws": true,
     },
+    "experimentalEsm": false,
     "isolatedModules": false,
     "packageJson": Object {
       "kind": "file",
@@ -167,6 +168,7 @@ Object {
     "pretty": true,
     "throws": true,
   },
+  "experimentalEsm": false,
   "isolatedModules": false,
   "packageJson": Object {
     "kind": "file",

diff --git a/src/config/config-set.ts b/src/config/config-set.ts
@@ -305,6 +305,7 @@ export class ConfigSet {
       compiler: options.compiler ?? 'typescript',
       transformers,
       stringifyContentPathRegex,
+      experimentalEsm: !!options.experimentalEsm,
     }
     this.logger.debug({ tsJestConfig: res }, 'normalized ts-jest config')
 
@@ -617,9 +618,8 @@ export class ConfigSet {
       sourceRoot: undefined,
       tsBuildInfoFile: undefined,
     }
-    // force the module kind if not piping babel-jest
-    if (!this.tsJest.babelConfig) {
-      // commonjs is required for jest
+    // force the module kind if not piping babel-jest or using experimental esm feature
+    if (!this.tsJest.experimentalEsm && !this.tsJest.babelConfig) {
       options.module = this.compilerModule.ModuleKind.CommonJS
     }
 

diff --git a/src/types.ts b/src/types.ts
@@ -137,6 +137,14 @@ export interface TsJestGlobalOptions {
    * exporting the content of the file as a string
    */
   stringifyContentPathRegex?: string | RegExp
+
+  /**
+   * Output ecmascript modules. This will for now output files with .mjs extension to
+   * ensure jest treats them as modules.
+   *
+   * @default undefined (disabled)
+   */
+  experimentalEsm?: boolean
 }
 
 interface TsJestConfig$tsConfig$file {
@@ -183,6 +191,7 @@ export interface TsJestConfig {
   diagnostics: TsJestConfig$diagnostics
   babelConfig: TsJestConfig$babelConfig
   transformers: string[]
+  experimentalEsm: boolean
   // to deprecate / deprecated === === ===
   stringifyContentPathRegex: TsJestConfig$stringifyContentPathRegex
 }