"Assignment to itself has no effect"

[arcanis]

My understanding is that third-party packages shouldn't emit warning due to weird syntax (#395 (comment)), but it doesn't seem to be the case every time. I have the following construct coming from got (caused by this line):

url = url;

Which generates the following warning:

> [...]/got/dist/source/core/utils/url-to-options.js: warning: Assignment of "url" to itself has no effect
    6 │     url = url;
      ╵     ~~~~~~~~~

[arcanis]

Similarly, I have the following warning:

 > [...]/keyv/src/index.js: warning: This call to "require" will not be bundled because the argument is not a string literal (surround with a try/catch to silence this warning)
    18 │     return new (require(adapters[adapter]))(opts);
       ╵                 ~~~~~~~

While it could be a valid warning, in my case it's not, this code will never be triggered (it's caused by got depending on cacheable-request, itself on keyv, with keyv having optional compatibility with databases 🤷‍♀️). It would be nice to have a way to hide this warning (perhaps in relation to #665).

Edit: The suggestion from #665 is likely good enough for this particular problem - the url = url is probably something you still want to cover though, since this pattern doesn't sound too farfetched to see in the wild and sounds something that linters would be more apt to detect than bundlers.

[evanw]

> [...]/got/dist/source/core/utils/url-to-options.js: warning: Assignment of "url" to itself has no effect

I'd like to know what this error message originally looked like before you replaced part of it with [...]. I assume the path didn't originally look like that. Is this file in a node_modules folder?

 > [...]/keyv/src/index.js: warning: This call to "require" will not be bundled because the argument is not a string literal (surround with a try/catch to silence this warning)

This warning exists to tell you about code that isn't being bundled. The alternative of ignoring this code would mean that the generated bundle is likely to fail at run-time since some of the code is missing. It felt like a good idea to have this warning because other bundlers may actually bundle code like this successfully due to dynamic file system emulation, so people may actually expect it to work. And an extra warning is mostly harmless but a silently failing build can be very annoying and hard to debug.

[arcanis]

I'd like to know what this error message originally looked like before you replaced part of it with [...]. I assume the path didn't originally look like that. Is this file in a node_modules folder?

Yep. The full path was something like:

pnp:/home/arcanis/app/.yarn/cache/got-somehash/node_modules/got/dist/source/[...]

And an extra warning is mostly harmless but a silently failing build can be very annoying and hard to debug.

Fair enough 👍

[evanw]

Ah that makes sense. Looks like these warnings are only ignored for files inside node_modules if the path does not originate from a plugin. This is because this feature was added before plugins were added. Will fix.