Flow: "inconsistent use of library definitions"

[tmcw]

For the code

destroy(id : string) {
      return promiseReturningFunction(id)
        .then(() => {
           // logic
        }, function(error) {
          // logic
        });
    },

I'm getting the following from flow:

/Users/tmcw/src/mapbox-gl-online/src/actions/actions.js: inconsistent use of library definitions
  /private/var/folders/lh/rwmhbvnd5rdc2qc5t5n2pv4w0000gn/T/flow_tmcw/flowlib_62a1d48/lib/core.js:296:1,305:1: Promise
This type is incompatible with
  /private/var/folders/lh/rwmhbvnd5rdc2qc5t5n2pv4w0000gn/T/flow_tmcw/flowlib_62a1d48/lib/core.js:298:25,52: function type

It's unclear what this error is trying to say, whether it's a problem in my code or with flow's internal definitions.

[avikchaudhuri]

This is a known annoyance: basically this arises when, e.g., a result of lib function 1 in a user call is passed as an argument of lib function 2 in another user call, and the result and argument types are incompatible. The two end points are library functions, which get blamed instead of the two call sites in user code.

[tmcw]

Is there a workaround possible by annotating both calls?

[ghost]

Thank you for reporting this issue and appreciate your patience. We've notified the core team for an update on this issue. We're looking for a response within the next 30 days or the issue may be closed.

[samwgoldman]

Since this issue doesn't include runnable repro code, I can't confirm that this specific case is resolved, but I have tested a number of similar cases and found improvements. Please reply if you are still experiencing a bad error message and I'll reopen.

[lambdabaa]

@samwgoldman: Here's a test case!

// @flow

const url = require('url');
url.format(url.parse('https://example.com/foo'));

and some outputs

test.js:0
inconsistent use of library definitions
1280:     href?: string;
                 ^^^^^^ undefined. This type is incompatible with. See lib: /tmp/flow/flowlib_cdecff4/node.js:1280
1277:     href: string;
                ^^^^^^ string. See lib: /tmp/flow/flowlib_cdecff4/node.js:1277

test.js:0
inconsistent use of library definitions
1285:     port?: string | number;
                          ^^^^^^ number. This type is incompatible with. See lib: /tmp/flow/flowlib_cdecff4/node.js:1285
1270:     port?: string;
                 ^^^^^^ string. See lib: /tmp/flow/flowlib_cdecff4/node.js:1270

[lambdabaa]

/cc @avikchaudhuri

[samwgoldman]

That error is expected, but it's easy to fix. I just put up a diff internally which will sync out soon.