fix(pnp): esm - support unflagged JSON modules

.yarn/versions/736d10bb.yml

@@ -0,0 +1,28 @@
+releases:
+  "@yarnpkg/cli": patch
+  "@yarnpkg/plugin-pnp": patch
+  "@yarnpkg/pnp": patch
+
+declined:
+  - "@yarnpkg/esbuild-plugin-pnp"
+  - "@yarnpkg/plugin-compat"
+  - "@yarnpkg/plugin-constraints"
+  - "@yarnpkg/plugin-dlx"
+  - "@yarnpkg/plugin-essentials"
+  - "@yarnpkg/plugin-init"
+  - "@yarnpkg/plugin-interactive-tools"
+  - "@yarnpkg/plugin-nm"
+  - "@yarnpkg/plugin-npm-cli"
+  - "@yarnpkg/plugin-pack"
+  - "@yarnpkg/plugin-patch"
+  - "@yarnpkg/plugin-pnpm"
+  - "@yarnpkg/plugin-stage"
+  - "@yarnpkg/plugin-typescript"
+  - "@yarnpkg/plugin-version"
+  - "@yarnpkg/plugin-workspace-tools"
+  - "@yarnpkg/builder"
+  - "@yarnpkg/core"
+  - "@yarnpkg/doctor"
+  - "@yarnpkg/nm"
+  - "@yarnpkg/pnpify"
+  - "@yarnpkg/sdks"

CHANGELOG.md

@@ -65,6 +65,7 @@ The following changes only affect people writing Yarn plugins:
 ### Compatibility
 
 - Updates the PnP compatibility layer for TypeScript 4.8.1-rc
+- The ESM loader now supports unflagged JSON modules.
 
 ## 3.2.2
 

packages/acceptance-tests/pkg-tests-specs/package.json

@@ -16,10 +16,12 @@
     "@yarnpkg/fslib": "workspace:^",
     "@yarnpkg/monorepo": "workspace:^",
     "@yarnpkg/parsers": "workspace:^",
+    "@yarnpkg/pnp": "workspace:^",
     "lodash": "^4.17.15",
     "pkg-tests-core": "workspace:^",
     "semver": "^7.1.2",
-    "tar": "^6.0.5"
+    "tar": "^6.0.5",
+    "tslib": "^2.4.0"
   },
   "engines": {
     "node": ">=14.15.0"

packages/acceptance-tests/pkg-tests-specs/sources/pnp-esm.test.ts

@@ -1,4 +1,5 @@
 import {Filename, ppath, xfs} from '@yarnpkg/fslib';
+import * as loaderFlags       from '@yarnpkg/pnp/sources/esm-loader/loaderFlags';
 
 describe(`Plug'n'Play - ESM`, () => {
   test(
@@ -195,8 +196,8 @@ describe(`Plug'n'Play - ESM`, () => {
     ),
   );
 
-  test(
-    `it should not resolve JSON files`,
+  (loaderFlags.HAS_UNFLAGGED_JSON_MODULES === false ? test : test.skip)(
+    `it should not resolve JSON modules without --experimental-json-modules`,
     makeTemporaryEnv(
       {
         type: `module`,
@@ -218,6 +219,55 @@ describe(`Plug'n'Play - ESM`, () => {
     ),
   );
 
+  (loaderFlags.HAS_UNFLAGGED_JSON_MODULES ? test : test.skip)(
+    `it should not resolve JSON modules without an import assertion`,
+    makeTemporaryEnv(
+      {
+        type: `module`,
+      },
+      async ({path, run, source}) => {
+        await expect(run(`install`)).resolves.toMatchObject({code: 0});
+
+        await xfs.writeFilePromise(
+          ppath.join(path, `index.js` as Filename),
+          `import './foo.json';`,
+        );
+        await xfs.writeFilePromise(ppath.join(path, `foo.json` as Filename), `{"name": "foo"}`);
+
+        await expect(run(`node`, `./index.js`)).rejects.toMatchObject({
+          code: 1,
+          stderr: expect.stringContaining(`ERR_IMPORT_ASSERTION_TYPE_MISSING`),
+        });
+      },
+    ),
+  );
+
+  (loaderFlags.HAS_UNFLAGGED_JSON_MODULES ? test : test.skip)(
+    `it should resolve JSON modules with an import assertion`,
+    makeTemporaryEnv(
+      {
+        type: `module`,
+      },
+      async ({path, run, source}) => {
+        await expect(run(`install`)).resolves.toMatchObject({code: 0});
+
+        await xfs.writeFilePromise(
+          ppath.join(path, `index.js` as Filename),
+          `
+          import foo from './foo.json' assert { type: 'json' };
+          console.log(foo.name);
+          `,
+        );
+        await xfs.writeFilePromise(ppath.join(path, `foo.json` as Filename), `{"name": "foo"}`);
+
+        await expect(run(`node`, `./index.js`)).resolves.toMatchObject({
+          code: 0,
+          stdout: `foo\n`,
+        });
+      },
+    ),
+  );
+
   test(
     `it should respect exports`,
     makeTemporaryEnv(

packages/yarnpkg-pnp/sources/esm-loader/hooks/load.ts

@@ -1,12 +1,18 @@
-import fs               from 'fs';
-import {fileURLToPath}  from 'url';
+import fs                                      from 'fs';
+import {fileURLToPath}                         from 'url';
 
-import * as loaderUtils from '../loaderUtils';
+import {HAS_JSON_IMPORT_ASSERTION_REQUIREMENT} from '../loaderFlags';
+import * as loaderUtils                        from '../loaderUtils';
 
 // The default `load` doesn't support reading from zip files
 export async function load(
   urlString: string,
-  context: { format: string | null | undefined },
+  context: {
+    format: string | null | undefined;
+    importAssertions?: {
+      type?: 'json';
+    };
+  },
   nextLoad: typeof load,
 ): Promise<{ format: string, source: string, shortCircuit: boolean }> {
   const url = loaderUtils.tryParseURL(urlString);
@@ -19,6 +25,12 @@ export async function load(
   if (!format)
     return nextLoad(urlString, context, nextLoad);
 
+  if (HAS_JSON_IMPORT_ASSERTION_REQUIREMENT && format === `json` && context.importAssertions?.type !== `json`) {
+    const err = new TypeError(`[ERR_IMPORT_ASSERTION_TYPE_MISSING]: Module "${urlString}" needs an import assertion of type "json"`) as TypeError & { code: string };
+    err.code = `ERR_IMPORT_ASSERTION_TYPE_MISSING`;
+    throw err;
+  }
+
   return {
     format,
     source: await fs.promises.readFile(filePath, `utf8`),

packages/yarnpkg-pnp/sources/esm-loader/loader.ts

@@ -2,14 +2,10 @@ import {getFormat as getFormatHook} from './hooks/getFormat';
 import {getSource as getSourceHook} from './hooks/getSource';
 import {load as loadHook}           from './hooks/load';
 import {resolve as resolveHook}     from './hooks/resolve';
+import {HAS_CONSOLIDATED_HOOKS}     from './loaderFlags';
 import './fspatch';
 
-const [major, minor] = process.versions.node.split(`.`).map(value => parseInt(value, 10));
-
-// The hooks were consolidated in https://github.com/nodejs/node/pull/37468
-const hasConsolidatedHooks = major > 16 || (major === 16 && minor >= 12);
-
 export const resolve = resolveHook;
-export const getFormat = hasConsolidatedHooks ? undefined : getFormatHook;
-export const getSource = hasConsolidatedHooks ? undefined : getSourceHook;
-export const load = hasConsolidatedHooks ? loadHook : undefined;
+export const getFormat = HAS_CONSOLIDATED_HOOKS ? undefined : getFormatHook;
+export const getSource = HAS_CONSOLIDATED_HOOKS ? undefined : getSourceHook;
+export const load = HAS_CONSOLIDATED_HOOKS ? loadHook : undefined;

packages/yarnpkg-pnp/sources/esm-loader/loaderFlags.ts

@@ -0,0 +1,10 @@
+const [major, minor] = process.versions.node.split(`.`).map(value => parseInt(value, 10));
+
+// The hooks were consolidated in https://github.com/nodejs/node/pull/37468
+export const HAS_CONSOLIDATED_HOOKS = major > 16 || (major === 16 && minor >= 12);
+
+// JSON modules were unflagged in https://github.com/nodejs/node/pull/41736
+export const HAS_UNFLAGGED_JSON_MODULES = major > 17 || (major === 17 && minor >= 5) || (major === 16 && minor >= 15);
+
+// JSON modules requires import assertions after https://github.com/nodejs/node/pull/40250
+export const HAS_JSON_IMPORT_ASSERTION_REQUIREMENT = major > 17 || (major === 17 && minor >= 1) || (major === 16 && minor > 14);

packages/yarnpkg-pnp/sources/esm-loader/loaderUtils.ts

@@ -1,9 +1,11 @@
-import {NativePath}   from '@yarnpkg/fslib';
-import fs             from 'fs';
-import path           from 'path';
-import {URL}          from 'url';
+import {NativePath}                 from '@yarnpkg/fslib';
+import fs                           from 'fs';
+import path                         from 'path';
+import {URL}                        from 'url';
 
-import * as nodeUtils from '../loader/nodeUtils';
+import * as nodeUtils               from '../loader/nodeUtils';
+
+import {HAS_UNFLAGGED_JSON_MODULES} from './loaderFlags';
 
 export async function tryReadFile(path: NativePath): Promise<string | null> {
   try {
@@ -48,6 +50,9 @@ export function getFileFormat(filepath: string): string | null {
       );
     }
     case `.json`: {
+      if (HAS_UNFLAGGED_JSON_MODULES)
+        return `json`;
+
       // TODO: Enable if --experimental-json-modules is present
       // Waiting on https://github.com/nodejs/node/issues/36935
       throw new Error(

yarn.lock

@@ -20249,10 +20249,12 @@ __metadata:
     "@yarnpkg/fslib": "workspace:^"
     "@yarnpkg/monorepo": "workspace:^"
     "@yarnpkg/parsers": "workspace:^"
+    "@yarnpkg/pnp": "workspace:^"
     lodash: "npm:^4.17.15"
     pkg-tests-core: "workspace:^"
     semver: "npm:^7.1.2"
     tar: "npm:^6.0.5"
+    tslib: "npm:^2.4.0"
   languageName: unknown
   linkType: soft