if/else each on one line not supported

[lucaswerkmeister]

if (true) { print(1); }
else { print(2); }

The formatter turns this into

if (true) { print(1); } else { print(2); }

because an else normally goes on the same line as the preceding }, under the assumption that this } is already on its own line. Single-line ifs violate that assumption.

Which solution would be preferred here?

• Don’t allow single-line ifs with an else: turn this into

  if (true) {
    print(1);
  } else {
    print(2);
  }

  Tricky because we need to propagate this information into visitBlock.

• Detect the “single-line if” case at the else, and preserve the code unchanged. Also tricky because we need to propagate this information from visitIfClause to visitElseClause.

Thoughts?

[lucaswerkmeister]

If we decide to not allow single-line ifs with an else (first solution), then the implementation would probably be a Category of Blocks that are not allowed to be single-line (FormattingVisitor member), which visitIf adds blocks to and visitBlock consults. And in that case, I think I’d also like to add method blocks (and, if necessary, class/interface bodies) to that category as well.

[quintesse]

Personally I'm a proponent of the first solution. I never write single line ifs in Java for example, I always use blocks even for the tiniest of statements, I find the visual regularity more readable myself and prefer it over making the code shorter. But I admit it's completely personal, I can perfectly understand people seeing things differently.

[lucaswerkmeister]

Well, those people still have to live with the fact that we didn’t make braces optional in Ceylon ;)

I think I prefer the first solution as well. I wrote the original code in the issue, but still, it looks weird to me now.

[gavinking]

@lucaswerkmeister I think whatever you do, it should be consistent with how you handle switch statements and try statements with catch clauses.

[lucaswerkmeister]

Well, currently, this is allowed:

try { print("hi"); } catch (Exception e) { e.printStackTrace(); } finally { print("done"); }

So I’d say those are some more candidates for blocks that aren’t allowed to have a single-line form.

It might actually make more sense to turn this around and say that only these kinds of blocks are allowed to be single-line (if they contain at most one statement):

• if with no else
• case
• dynamic, probably
• setters? not sure

Anything else? I looked for Block in the spec, and these are the only productions where single-line blocks make sense IMO. (Some constructs, like functions and getters, should instead use => in these cases; others should never be single-line IMO.)