Node: 12.3.0 introduces a breaking change in the way require.resolve's options.paths is validated

[lddubeau]

• Version: 12.3.0
• Platform: Linux localhost 4.19.0-5-amd64 #1 SMP Debian 4.19.37-3 (2019-05-15) x86_64 GNU/Linux
• Subsystem: Modules

Steps to reproduce

Save the following file as test.js:

console.log(require.resolve("./test", { paths: "." }));

Run it:

node test.js

Expected Behavior

This output on stdout:

/tmp/t1/test.js

Actual Behavior

In node 12.3.0 this is what I get:

internal/modules/cjs/loader.js:603
      throw new ERR_INVALID_OPT_VALUE('options.paths', options.paths);
      ^

TypeError [ERR_INVALID_OPT_VALUE]: The value "." is invalid for option "options.paths"
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:603:13)
    at Function.resolve (internal/modules/cjs/helpers.js:21:19)
    at Object.<anonymous> (/tmp/t1/test.js:1:21)
    at Module._compile (internal/modules/cjs/loader.js:774:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:785:10)
    at Module.load (internal/modules/cjs/loader.js:641:32)
    at Function.Module._load (internal/modules/cjs/loader.js:556:12)
    at Function.Module.runMain (internal/modules/cjs/loader.js:837:10)
    at internal/main/run_main_module.js:17:11

Observations

I get the expected behavior in Node 12.2.0, Node 10.14.2 and Node 8.15.0.

The documentation for require.resolve has been at least as far back as Node 8 that an array must be passed for the paths option. However, in reality, Node has been accepting a string for paths, without complaint, for quite a while.

The upshot is that code that worked just fine with Node prior to 12.3.0 breaks with 12.3.0.

[cjihrig]

The previous behavior wasn't working at all. It was problematic to silently ignore the problem too because it made it possible to get incorrect results.

[lddubeau]

I get that there was a problem with the way paths was handled. The problem now though is that a minor version update breaks code that used to work. I thought Node follows semver, which mandates that breaking changes happen with major releases.

I ran into the issue with a third-party tool I use. Whatever problems there existed before, they did not prevent this tool from running just fine with Node 12.x prior to 12.3.0.

[cjihrig]

All bug fixes change behavior in some way. Sometimes it's a grey area, and this one probably could have gone either way. I do apologize for any inconvenience that it causes you, but I think that resolving modules to the wrong location seems like a pretty significant bug.

[jasnell]

Closing given that there's really not much actionable here.