Fix: print line comment after arrow in lamda between paranthesis

[nojaf]

In #539 I tried to fix bug #534 and by I ended up with two broken tests that were somewhat strange and debatable.

This PR contains the same fix for #534 and also refactors the way SynExpr.IfThenElse is formatted.
As close to the F# style guide as possible.

In the case of

If either cond, e1 or e2 are longer, but not multi-line

the guide leaves some room for interpretation. What is "longer" exactly?
Because of this question I introduced a new setting MaxIfThenElseShortWidth to let the user control this.

The main motivation to rewrite the formatting of SynExpr.IfThenElse is the support for comments around keywords (if, elif, else if), this have been tested extensively in IfThenElseTests.fs.

[jindraivanek]

IMO there should be indent after else.

[jindraivanek]

no indent after else

[jindraivanek]

no indent after else

[nojaf]

The no indentation after the else part was intended after reading the style guide

Multiple conditionals with elif and else are indented at the same scope as the if:

I consider else if and elif to be the same thing.

The fsharp lang ref seems to confirm this.

When chaining if...then...else expressions together, you can use the keyword elif instead of else if; they are equivalent.

So that is why no indentation.

In an extreme example I wouldn't imagine you would write the following code like this right?

if aaaa then
    meh
else 
    if bbbb then
        fooo
    else
        if ccc then
            baaarrr
        else
            if dddd then
                meehhh
            else
                ()

[jindraivanek]

Multiple conditionals with elif and else are indented at the same scope as the if:

IMO this means only that elif and else is in same indentation as if not the block after else.

The fsharp lang ref seems to confirm this.

I know it is valid code, I just always considered this as bad style.

But "it is same as elif" is quite good argument.

In an extreme example I wouldn't imagine you would write the following code like this right?

Yeah, I would write it with elif ;)

---

To move forward, I think we can merge this, and raise an issue in style docs to clarify this.

[nojaf]

I've created dotnet/docs#15922, we can always later change the formatting to whatever the outcome ends up being.
@jindraivanek could you approve to move forward?

[jindraivanek]

@nojaf Thanks!

[knocte]

After this PR has been merged, is there a way to configure fantomas to make ifs always multi-line?

[nojaf]

@knocte try setting --maxIfThenElseShortWidth to 0.