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Uncaught exception when node_modules includes a .mjs file

See original GitHub issue

Version: 1.2.34
Rollup Version: 2.23.0
Typescript Version: 3.9.7
Operating System and version (if applicable): N/A
Node Version (if applicable): N/A
Does it work with tsc (if applicable): Yes

Reproduction

Install a node module that includes files with the .mjs extension such as svelte or acorn.

npm i svelte

Attempt to reference such a node module by its bare module specificer.

import 'svelte';

Attempt to generate a bundle.

Expected Behavior

A bundle is generated without error.

Actual Behavior

> rollup -c -w

rollup v2.23.0
bundles src/main.ts → public/build...
[!] (plugin Typescript) TypeError: Cannot read property 'flags' of undefined
node_modules/svelte/index.mjs
TypeError: Cannot read property 'flags' of undefined
    at resolveAlias (<REDACTED>/node_modules/typescript/lib/typescript.js:37340:37)
    at checkAliasSymbol (<REDACTED>/node_modules/typescript/lib/typescript.js:66174:26)
    at checkExportSpecifier (<REDACTED>/node_modules/typescript/lib/typescript.js:66348:13)
    at Object.forEach (<REDACTED>/node_modules/typescript/lib/typescript.js:317:30)
    at checkExportDeclaration (<REDACTED>/node_modules/typescript/lib/typescript.js:66286:24)
    at checkSourceElementWorker (<REDACTED>/node_modules/typescript/lib/typescript.js:66642:28)
    at checkSourceElement (<REDACTED>/node_modules/typescript/lib/typescript.js:66473:17)
    at Object.forEach (<REDACTED>/node_modules/typescript/lib/typescript.js:317:30)
    at checkSourceFileWorker (<REDACTED>/node_modules/typescript/lib/typescript.js:66810:20)
    at checkSourceFile (<REDACTED>/node_modules/typescript/lib/typescript.js:66778:13)

Issue Analytics

State:
Created 3 years ago
Comments:8 (2 by maintainers)

Top GitHub Comments

1reaction

wessbergcommented, Jul 31, 2020

Thanks for the update! Much appreciated. So, I found the cause of the issue. I simply thought TypeScript supported .mjs files, but it doesn’t. I thought the allowJs flag included and enabled type checking for .mjs files, but it doesn’t.

I’ve fixed it in v1.3.1 and aligned with the behavior of tsc. I’ve also written you a message on Twitter about the other issue you mentioned 😃 It has been fixed, but there are two small fixes that needs to be made in your monorepro to avoid type duplication 😃

0reactions

ggoodmancommented, Jul 31, 2020

Looks like we should be tracking microsoft/typescript#39840.