Enable tslint with basic rules

[simark]

Add tslint as a plugin to tsc, so that they will show up in vscode or
whatever editor people use. I only enabled two basic rules that I think
are very useful, prefer-const and no-var-keyword. Violations of these
rules were fixed with "tslint -p . --fix". There was one unused
variable (in the isExpandable) function that I removed by hand.

[simark]

Context: We are looking into adding C/C++ debug support using GDB in the Theia project. We are already planning on using the Debug Adapter Protocol for other debuggers. Instead of starting from scratch for C/C++, I am considering using code-debug (and therefore probably contributing to it). Since I really appreciate what tslint does when writing code for Theia, I thought I would test the water by contributing this simple patch.

[WebFreak001]

hm why no-var-keyword? Isn't var just the same as let...

[simark]

hm why no-var-keyword? Isn't var just the same as let...

No, var is there only for compatibility with Javascript (so that Javascript code is also valid Typescript code). But the behavior is different regarding to scopes, let doing the thing you would expect from any other language.

See this for example: https://basarat.gitbooks.io/typescript/content/docs/let.html

The tslint rule pages also have very good explanations of the rationales: https://palantir.github.io/tslint/rules/no-var-keyword/

[WebFreak001]

var foo = 123;
if (true) {
    var foo = 456;
}
console.log(foo); // 456

wtf js...

[WebFreak001]

uh this variable gets changed (in line 65)

[simark]

const prevents of the variable from being reassigned, not the object they "point" to from being modified. In C++, it would be equivalent to this:

const Object *stack;

and not:

const Object * const stack;

[simark]

var foo = 123;
if (true) {
var foo = 456;
}
console.log(foo); // 456

wtf js...

Indeed. And in my opinion, Typescript is really good at making you follow good practices if you use it properly. A next step would be to have stronger type checking (noImplicitAny and strictNullChecks in the compiler options).

[WebFreak001]

cool thanks