[Loaders] Only return the format if it's builtin or commonjs (fixes #287)

Author: bjornstar

lib/loaders/get-format.mjs

@@ -13,6 +13,9 @@ export async function getFormat(url, context, defaultGetFormat) {
     return await defaultGetFormat(url, context, defaultGetFormat);
   } catch (error) {
     if (error.code !== 'ERR_UNKNOWN_FILE_EXTENSION') throw error;
-    return require('get-package-type')(required).then(format => ({ format }));
+    return require('get-package-type')(required).then(format => {
+      if (!['builtin', 'commonjs'].includes(format)) throw error;
+      return { format };
+    });
   }
 }

lib/loaders/load.mjs

@@ -13,6 +13,9 @@ export async function load(url, context, defaultLoad) {
     return await defaultLoad(url, context, defaultLoad);
   } catch (error) {
     if (error.code !== 'ERR_UNKNOWN_FILE_EXTENSION') throw error;
-    return require('get-package-type')(required).then(format => ({ format, source: null }));
+    return require('get-package-type')(required).then(format => {
+      if (!['builtin', 'commonjs'].includes(format)) throw error;
+      return { format };
+    });
   }
 }

package.json

@@ -36,23 +36,23 @@
     "dynamic-dedupe": "^0.3.0",
     "filewatcher": "~3.0.0",
     "get-package-type": "^0.1.0",
-    "minimist": "^1.2.5",
+    "minimist": "^1.2.6",
     "node-notifier": "^8.0.1",
-    "resolve": "^1.0.0",
-    "semver": "^7.3.5"
+    "resolve": "^1.22.0",
+    "semver": "^7.3.7"
   },
   "devDependencies": {
-    "@types/node": "^16.11.3",
-    "eslint": "^8.10.0",
-    "eslint-plugin-import": "^2.22.1",
+    "@types/node": "^17.0.24",
+    "eslint": "^8.13.0",
+    "eslint-plugin-import": "^2.26.0",
     "husky": "^7.0.4",
-    "lint-staged": "^11.2.3",
-    "prettier": "^2.2.1",
-    "tap": "^15.1.6",
+    "lint-staged": "^12.3.8",
+    "prettier": "^2.6.2",
+    "tap": "^16.0.1",
     "tap-xunit": "^2.4.1",
     "touch": "^3.1.0",
-    "ts-node": "^10.3.1",
-    "typescript": "^4.1.5"
+    "ts-node": "^10.7.0",
+    "typescript": "^4.6.3"
   },
   "lint-staged": {
     "*.{js,mjs}": "eslint --cache --fix",

test/fixture/typescript-module/index.ts

@@ -0,0 +1,2 @@
+// We should not be able to load typescript files as ESModules
+export default ['test', 'data'] as const

test/fixture/typescript-module/package.json

@@ -0,0 +1 @@
+{ "type": "module" }

test/spawn/typescript-module.js

@@ -0,0 +1,14 @@
+const tap = require('tap');
+
+const { spawn } = require('../utils');
+
+tap.test(
+  'Gives ERR_UNKNOWN_FILE_EXTENSION when loading typescript files and package type is "module"',
+  t => {
+    spawn('typescript-module/index.ts', out => {
+      if (out.match(/ERR_UNKNOWN_FILE_EXTENSION/)) {
+        return { exit: t.end.bind(t) };
+      }
+    });
+  }
+);