Fix TypeScript Definitions for making lit-element happy

[mistyharsh]

This PR fixes issue #37.

[bennypowers]

Thank you so much for the PR. Please see review comments.

[mistyharsh]

@bennypowers Thank you for the review. I did think about these issues before raising the PR. I just hoped to fix TypeScript issues quickly. I will work it out these comments and see how we can adhere to the design.

[mistyharsh]

So there are a couple of things:

• After reading Anders' comment, It seems it is almost impossible to solve this problem. The only option is to use class and interface merging.
• ApolloMutation cannot be currently fixed unless we change update property as it conflicts with LitElement.update() method. We should implement RFC RFC: Rename update property to updateCache #35.
• With declaration merging, we get empty interfaces which fail the linting rules.

[bennypowers]

I'm ok with implementing #35, although it will represent a major release.

What I'd love to see would be some tests for these typings.

Another option we should consider is using JSDoc inline typings instead of .d.ts files.

[mistyharsh]

Having Tests for typescript definition files is not very common. We can treat our files and run tsc to validate our type definitions the way we run linter for our JS code. That is something I can think of. We can also probably look at dtslint though I have not really used it.

As far as JSDoc is concerned, it looks interesting but usually ends up being cumbersome to write than plain TS definitions.

[RSWilli]

what is the status for this? I am having the same issue with TS and lit-apollo.

This PR doesn't just "make lit-element happy", currently TS just doesn't compile the code because it complains that none of the apollo properties (client, query, etc.) are present on my class

[bennypowers]

@RSWilli can you send me a repro to tinker with? My volunteer time is short this week as I just moved apartment, but I'm really hoping to solve this for you ASAP, so if you have a ready made example repo, or some changes for this PR I'll try my best to get something out.

[RSWilli]

Repro: https://stackblitz.com/edit/typescript-hfggxi

for me, editing https://github.com/apollo-elements/apollo-elements/blob/master/packages/lit-apollo/apollo-query.d.ts#L1 from @apollo-elements/mixins/apollo-mutation-mixin to @apollo-elements/mixins/apollo-query-mixin fixes it, but I don't know if it brakes anything else that my usecase does not include

[bennypowers]

very nice work, thanks