[RFC] Typescript type checking options

[miroslavstastny]

Stardust uses Typescript, but all it's type checking options are disabled, which kills a lot of Typescript's power.
Enabling (some of) the checks would make the code better and it'd easier to enable them in the early stage of the project.

I went through the list of compiler options which could be worth considering and also checked tsconfig in other projects which use Typescript.

option	project A	project B	ionic/react	vscode/src	rxjs	description
noImplicitReturns		true	true	true	true	Report error when not all code paths in function return a value.
noImplicitAny (1)		true	true		true	Raise error on expressions and declarations with an implied any type.
noImplicitThis (1)				true	true	Raise error on this expressions with an implied any type.
noUnusedParameters		true	true			Report errors on unused parameters.
noUnusedLocals		true	true	true		Report errors on unused locals.
alwaysStrict (1)	true			true		Parse in strict mode and emit "use strict" for each source file
strictNullChecks (1)						In strict null checking mode, the null and undefined values are not in the domain of every type and are only assignable to themselves and any (the one exception being that undefined is also assignable to void).
strictFunctionTypes (1)					true	Disable bivariant parameter checking for function types.
strictPropertyInitialization (1)						Ensure non-undefined class properties are initialized in the constructor. This option requires --strictNullChecks be enabled in order to take effect.

(1) part of --strict
Default value for all options is false.

Can we think of what would make sense to be enabled?

[kuzhelov]

There was a TS compilation problem caused by --strict flag which has enabled all these checks for our project (#158) - as a result, we've had to (temporarily) disable it.

Agree that proposed strategy to incrementally introduce this functionality back (by means of these discrete flags) is a good option for us, so that we will be able to carefully weight benefits and potential TS compilation problems (increased compilation time, overall stability of compilation process) with each option being introduced 👍

[levithomason]

Note, we resolved to disable strictNullChecks for now and align closely to projects A and B.

[miroslavstastny]

@kuzhelov - AFAIK the problem in #158 was caused by strictNullChecks, so, hopefully the others should be safe for build performance.
stringNullChecks is disabled in other projects as well, we are not going to enable it in stardust for now.

Plan: noImplicitReturns is now enabled by #185, I am going to enable others (noImplicitAny, noUnusedParameters, may be noUnusedLocals and noImplicitThis) - we agreed to enable one more each week and monitor it's impact on the build.

[jurokapsiar]

not valid anymore