[Regression from 0.45 -> 0.46] resolve_dirname no longer applies

[DanielHeath]

After upgrading from 0.45 to 0.46, we have hundreds of Required module not found errors.

The relevant flowconfig snippet is:

[options]
module.system.node.resolve_dirname=src/js
module.system.node.resolve_dirname=test/unit

An example of the new error:

src/js/client/<snip>/<snip>/<snip>/__tests__/index-spec.js:3
  3: import { within } from 'helpers/stubs';
                            ^^^^^^^^^^^^^^^ helpers/stubs. Required module not found

This file is present:

  $ ls test/unit/helpers/stubs.js
test/unit/helpers/stubs.js

[gabelevi]

Can confirm this repros with https://gist.github.com/gabelevi/edc83db958db739fdf81749f205877b5 and that the issue was introduced with v0.46.0

@avikchaudhuri - was this your moving of require resolution that you landed near the end of April?

[valscion]

We are facing the same regression and as a result almost every one of our files have errors.

Is there anything I could do to help? I could whip up a reproduction repository if that helps.

An alternative we are considering is to stop using resolve_dirname to completely hide the root folder and introduce a new variable, say appJS, that would point to our JS root that we could use.

# .flowconfig

[options]
module.name_mapper='appJS' -> '<PROJECT_ROOT>/app/assets/javascripts'

// webpack
return {
  resolve: {
    alias: {
      appJS: path.join(projectRoot, 'app/assets/javascripts')
    }
  }
};

[leethree]

Got the same problem. This no longer works after upgrade beyond 0.45.

module.system.node.resolve_dirname=.

[valscion]

The way we resolved it for now was to list out all the "root" directories separately with module.name_mapper option.

So instead of

module.system.node.resolve_dirname=app/assets/javascripts

we have this:

module.name_mapper='boot' -> '<PROJECT_ROOT>/app/assets/javascripts/boot'
module.name_mapper='common' -> '<PROJECT_ROOT>/app/assets/javascripts/common'
module.name_mapper='conversation' -> '<PROJECT_ROOT>/app/assets/javascripts/conversation'
# ... and so on ...

It isn't nearly as nice as having the resolve_dirname work as before, as now when we want to add a new root directory, we will need to amend this list of name mappers to cover it.

[valscion]

Looks like the functionality this regression issue points out has been added back, with a combination like this:

module.system.node.allow_root_relative=true
module.system.node.root_relative_dirname=./app

(Example copied from #8156 (comment))

We were able to get rid of our

module.name_mapper='boot' -> '<PROJECT_ROOT>/js/src/boot'
module.name_mapper='common' -> '<PROJECT_ROOT>/js/src/common'
module.name_mapper='conversation' -> '<PROJECT_ROOT>/js/src/conversation'
....

configuration by changing the .flowconfig options to this:

module.system.node.allow_root_relative=true
module.system.node.root_relative_dirname=./js/src

---

References:

• https://github.com/facebook/flow/releases/tag/v0.111.0
• [FEATURE] Add module_alias resolution capabilities - round 2 #8098 (comment)
• d17ed03
• Setting content root causes modules to be not found #8156

Pull requests that never got merged but tried to get this feature back:

• [FEATURE] Add module_alias resolution capabilities #7185
• [FEATURE] Add module_alias resolution capabilities - round 2 #8098

Sooooo... is this issue fixed now? Granted, it was a bit difficult to find out the correct configuration options to use as the docs haven't been updated yet.

[spoulson]

Can confirm resolve_dirname broken as of 0.111.0. My .flowconfig:

[options]
module.system.node.resolve_dirname=node_modules
module.system.node.resolve_dirname=src/libs

Getting "Cannot resolve module" errors on 0.111.0. No error on prior versions.

[valscion]

Did you try the other approach I defined above, @spoulson?

[spoulson]

@valscion Yes, the name_mapper setting does work. But, it's not ideal because I need to 1) update all my repos that use previously working resolve_dirname and 2) explicitly state the individual module mappings, which is a configuration burden. I enjoyed the ability to just point to a relative directory and add that to the module import paths.

Technically, I can migrate to name_mapper, but if resolve_dirname is supported functionality I'd rather use that.

[spoulson]

@TrySound Why close this bug?

[TrySound]

resolve_dirname is not supposed to be used this way. It allows to specify node_modules alias. For node_modules flow does not watch file changes. This is implemented to solve your problem

module.system.node.allow_root_relative=true
module.system.node.root_relative_dirname=./js/src

So it's not really a bug. The change was made intentionally to solve performance issues.