Tern does not infer types through promises.

[mseddon]

Using either Promise or Q, tern fails to infer the type of the success handler arguments. I wouldn't say this is a limitation of the tern type inferencer, but it seems like a good candidate for a plugin. Before I look too far into implementing one I was wondering:

a) does such a plugin exist?
b) is this possible with a plugin?
c) how much pain would be involved implementing such a plugin?

And perhaps, more abstractly:
d) is there a central location where developers contribute their tern plugins?

[angelozerr]

a) does such a plugin exist?

Promise is for ECMAScript6. Today tern provides only ecma5.json

I have created a PR for ecma6.json #475

But it's very basic. I think Promise should be improved https://github.com/marijnh/tern/pull/475/files#diff-86d0e1883fb47a3188ad9f50734bc5deR465

b) is this possible with a plugin?

here it's a JSON Type Definition. I think Promise should be improved with custom inference function (infer.registerFunction).

d) is there a central location where developers contribute their tern plugins?

No but I have created this issues #424 We would like to provide a plugins.json which list the whole tern plugins.

I try to integrate tern plugins see https://github.com/angelozerr/tern.java/wiki/Getting-Started#tern-modules

To search tern plugins today, you can use those 2 urls :

• https://www.npmjs.com/search?q=tern
• https://github.com/search?o=desc&q=tern&s=updated&type=Repositories

[marijnh]

Patch 57cf35f adds some magic to the definition of Promises in ecma6.json to make Tern mostly able to see through them, as far as result values are concerned. Let me know whether that works for you (you'll have to include the ecma6 defs to get it).

[mseddon]

Yes, this is exactly the sort of thing I'm looking for 👍

If I get some time, I will attempt a Q plugin based around this.

[othree]

I like to add fetch def file.
But I don't know how to assign the fulfill value of returned Promise in def file.
Here is what I expect:

"fetch": {
  "!type": "fn(url: string) -> +Promise[value=string]"
 }

(fulfill string is just for test)
I copy the return type format from Promise.resolve.
But the function parameter in then is still ?
Is it possible to given a specified fulfill value for promise in def file now?

[marijnh]

@othree That was a type parser issue. Patch 0958506 solves it.

[othree]

Thanks @marijnh

It looks work great but still have some problem.
I complete the fetch.json file.
And use it with following codes:

fetch().then(function(res) {
  res;
  res.blob().then(function (bbb) {
    bbb
  });
});

The first strange behavior I found is that bbb is not a blob object.
So I use TernType to inspect.
And it shows res is ArrayBuffer|string, not Response.
But res did have method and properties of Response.
bbb is similar as res.

[othree]

Finally I got this solved.
I forgot to include ecma6 in my project.