ncc incorrectly includes __dirname in .mjs output

[henderea]

Version 0.29.x (#720) has made it so that if you have a .mjs file as an input, you get a .mjs file as an output. I would like a flag to get back the 0.28.x behavior of outputting it as a .js file that I can run directly with node, even v10. I can currently accomplish this by using version 0.28.x to build my scripts, but I would rather not be stuck on an old version forever.

Please add a flag to force the output of the build into a traditional-style .js regardless of what the input is, just like the behavior of v0.28.x.

[styfle]

Node.js 10.x reached End-Of-Life on 2021-04-30 and is no longer receiving updates.

If you wish to support older Node.js versions, you can continue using an older ncc version.

[henderea]

NodeJS 10 support isn't really the issue. I can't run node dist/script/index.mjs in newer nodejs version either.

My goal is to get a CJS output (with .js extension) from a MJS input. In other words, I want to be able to convert it while bundling.

[styfle]

I can't run node dist/script/index.mjs in newer nodejs version either

Why not?

[henderea]

Well, apparently something in the bundled file is using __dirname, though I'm not sure what. It runs fine if I run the original non-bundled .mjs file.

If I use v0.28.6 of @vercel/ncc, I don't have any issues with the output file.

[styfle]

__dirname isn't possible to use inside any .mjs file so I would expect node sourcefile.mjs to fail too

[henderea]

If I run node ./src/script.mjs, it has no issues. If I bundle it with ncc and run node ./dist/script/index.mjs, it fails with a complaint about __dirname. My best guess is that one of my dependencies uses it somewhere, but I'm not really sure, because it's clearly working fine if I run the original non-bundled file.

[henderea]

The main thing is, I don't want to have to convert everything I have to ESM, so I would like to be able to have ncc output with CJS. I have a lot of stuff, and I'd rather avoid a huge conversion project.

[styfle]

My best guess is that one of my dependencies uses it somewhere, but I'm not really sure, because it's clearly working fine if I run the original non-bundled file.

Can you share more information so we can reproduce the bug?

Sounds like a duplicate of #749

[henderea]

My main goal is to keep compatibility with CJS even when I use ESM in a few files. The core issue isn't the error, it's that I don't want an ESM output regardless of whether it works or not.

[henderea]

As for the source of the __dirname, it seems like it's coming from some dependency somewhere. There is one reference in the output, which contains __nccwpck_require2_.ab=__dirname+"/";. Thing is, when I do an ack for ab=__dirname+"/" in the node_modules, all of the results are in @vercel/ncc:

> ack -l --literal 'ab=__dirname+"/"' node_modules 
node_modules/@vercel/ncc/dist/ncc/index.js.cache.js
node_modules/@vercel/ncc/dist/ncc/cli.js.cache.js
node_modules/@vercel/ncc/dist/ncc/sourcemap-register.js.cache.js
node_modules/@vercel/ncc/dist/ncc/loaders/relocate-loader.js.cache.js
node_modules/@vercel/ncc/dist/ncc/loaders/stringify-loader.js.cache.js
node_modules/@vercel/ncc/dist/ncc/loaders/shebang-loader.js.cache.js
node_modules/@vercel/ncc/dist/ncc/loaders/ts-loader.js.cache.js

[henderea]

Well, I found I can get the old behavior in 0.29.x by using the API instead of the CLI. I'll just go that route, I guess.