fix(typescript): correct response type of Subscription.get

[merlinnot]

Resolves #507

• Tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

[callmehiphop]

Looks like we're getting a small lint error

src/topic.ts:181:49 - error TS2345: Argument of type 'ResourceCallback<Topic, ITopic> | undefined' is not assignable to parameter of type 'ResourceCallback<Topic, ITopic>'.
  Type 'undefined' is not assignable to type 'ResourceCallback<Topic, ITopic>'.

181     this.pubsub.createTopic(this.name, gaxOpts, callback);

I think we just need to make the following edit

this.pubsub.createTopic(this.name, gaxOpts, callback!);

[merlinnot]

The call relied on an internal implementation (checking if the argument is equal to undefined), so I made it more correct so it actually conforms to a function interface.

[callmehiphop]

@merlinnot we actually use a decorator to promisify everything, so callback will never be undefined, however we've been marking it as optional for the Promise signature overload.

[codecov]

Codecov Report

Merging #525 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #525   +/-   ##
=======================================
  Coverage   94.95%   94.95%           
=======================================
  Files          16       16           
  Lines         992      992           
  Branches       87       87           
=======================================
  Hits          942      942           
  Misses         42       42           
  Partials        8        8

Impacted Files	Coverage Δ
src/subscription.ts	100% <ø> (ø)	⬆️
src/pubsub.ts	100% <ø> (ø)	⬆️
src/topic.ts	91.25% <100%> (ø)	⬆️

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[merlinnot]

Ok, changed and rebased on master.

[callmehiphop]

@merlinnot awesome, thank you so much!

[merlinnot]

I can't see CI logs, both lint and compile work for me locally. It's hard to contribute when only Googlers see build logs ;)

[callmehiphop]

@merlinnot yeah T_T I don't think there's anything wrong with your code, Kokoro (CI) has been super flakey today. @JustinBeckwith do we have any idea what's going on with it?