WIP: Suggestion to expand func types to func snippets (#1553)

[joncalhoun]

Given a type that defines a function, this change adds a code completion suggestion to expand the type into a closure. Eg:

type Demo func(int) string

Will expand into the the suggest with the name Demo and upon triggering it the following snippet will be used:

Demo(func(${1:arg1} int) {
  $2
})

Similarly, given the following type:

type Demo func(i int) string

The variable name that exists will be used (i in this example).

If accepted, this resolves #1553

[msftclas]

All CLA requirements met.

[joncalhoun]

@ramya-rao-a I suspect this needs a test, but at first glance I'm not sure I understand the tests very well. I suspect I need to add something here - https://github.com/Microsoft/vscode-go/blob/0.6.77/test/go.test.ts#L698 - but that's about all the further I got. I'll probably dive into them more tomorrow, but I don't use typescript often so any help would probably speed this up.

The actual PR might be worth refactoring a bit, since a good chunk of the code is reused from the function building section, but it was different enough that I opted to duplicate the similar code. I'm open to changing it if desired.

[joncalhoun]

@ramya-rao-a I'd love to figure out what needs done to get this submitted.

I think it needs a test of some sort; can you point me to an area in the tests where you think this would be most easily tested?

After a test is added, is there anything else you feel will need altered in the PR?

[ramya-rao-a]

There is just one test failing and that too only on tip, that's unrelated to your PR, I'll take a look at it soon.

Pointer to existing test for completion that you can use as reference: https://github.com/Microsoft/vscode-go/blob/0.6.78/test/go.test.ts#L747

You can add another test file to https://github.com/Microsoft/vscode-go/tree/0.6.78/test/fixtures/completions for your case and test it

[joncalhoun]

Thank you!

[OneOfOne]

ping

[joncalhoun]

So I'm currently swamped and won't have time to finish this for at least a week. If you want to close this in the meantime its fine - I'll just reference it with a new PR when it is ready.

[ramya-rao-a]

No worries, take your time.
If I get some time next week, then I'll add the test and merge the PR

[joncalhoun]

👍 Thanks for the help on this. Psyched to see it make it into master finally 😄

[ramya-rao-a]

Yup, I finally got around to adding some tests (See 8dd3f33)

I'll release an update early next week.

[ramya-rao-a]

@joncalhoun I just realized that if the function has a return type, then the snippet doesnt reflect that.

[ramya-rao-a]

Take the below code

package main

type Demo func(int) string

func main() {

	mycallback :=

	takeDemo(mycallback)
}

func takeDemo(callback Demo) {
	callback(1)
}

Next to mycallback := type D to get the completion. You will get

mycallback := Demo(func(arg1 int) {

	})

which wont compile as there is no return value in the func declaration

[joncalhoun]

I think you are right looking the code - I see nothing there for return types. I must have forgot about that use case when writing it, and I haven't touched this code in a while.

Want me to take a stab at fixing it or are you going to? Regardless it might make sense to roll back the change since it can break things 😦

[ramya-rao-a]

Fixed with 8bb08f6

There is no need to roll back.
A very small percentage of users have the setting to expand snippets and I doubt among them everyone will encounter this issue. Even if they do, the fix is easy, they just need to add the return type manually.