Allow for catch and finally in try expression to be on a new line

[ckipp01]

I noticed that try_expressions weren't quite looking right when they were on a new line. However, I'm having a hard time understanding exactly how to actually take the new line into account.

To give an example.

def main() = {
  try {
   doThing()
  } catch {
    case _: Throwable => 3
  }
}

This parses correctly and the finally_clause is recognized as part of the try_expression.

(compilation_unit [0, 0] - [7, 0]
  (function_definition [0, 0] - [6, 1]
    name: (identifier [0, 4] - [0, 8])
    parameters: (parameters [0, 8] - [0, 10])
    body: (block [0, 13] - [6, 1]
      (try_expression [1, 2] - [5, 3]
        body: (block [1, 6] - [3, 3]
          (call_expression [2, 3] - [2, 12]
            function: (identifier [2, 3] - [2, 10])
            arguments: (arguments [2, 10] - [2, 12])))
        (catch_clause [3, 4] - [5, 3]
          (case_block [3, 10] - [5, 3]
            (case_clause [4, 4] - [5, 2]
              pattern: (typed_pattern [4, 9] - [4, 21]
                pattern: (wildcard [4, 9] - [4, 10])
                type: (type_identifier [4, 12] - [4, 21]))
              body: (number [4, 25] - [4, 26]))))))))

However, if you simply bump the catch down a line to create:

def main() = {
  try {
   doThing()
  }
  catch {
    case _: Throwable => 3
  }
}

I then totally misses the catch_clause.

(compilation_unit [0, 0] - [8, 0]
  (function_definition [0, 0] - [7, 1]
    name: (identifier [0, 4] - [0, 8])
    parameters: (parameters [0, 8] - [0, 10])
    body: (block [0, 13] - [7, 1]
      (try_expression [1, 2] - [3, 3]
        body: (block [1, 6] - [3, 3]
          (call_expression [2, 3] - [2, 12]
            function: (identifier [2, 3] - [2, 10])
            arguments: (arguments [2, 10] - [2, 12]))))
      (ERROR [4, 2] - [4, 7]
        (identifier [4, 2] - [4, 7]))
      (case_block [4, 8] - [6, 3]
        (case_clause [5, 4] - [6, 2]
          pattern: (typed_pattern [5, 9] - [5, 21]
            pattern: (wildcard [5, 9] - [5, 10])
            type: (type_identifier [5, 12] - [5, 21]))
          body: (number [5, 25] - [5, 26]))))))

This happen when using finally as well on a newline.

So this seems to make sense to me:

tree-sitter-scala/grammar.js

Lines 540 to 545 in 262797b

	try_expression: $ => prec.right(seq(
	'try',
	field('body', $._expression),
	optional($.catch_clause),
	optional($.finally_clause)
	)),

Although I'm not really sure how that works with newlines. Do you maybe have any pointers or insights into what I'm missing here? I'd love to get a better understanding of what's going on here and start tackling some of these missing features for the Scala grammar. I'm increasingly wanting a complete grammar as all the great stuff around Neovim and tree-sitter is happening, and I feel like Scala is missing out!

[maxbrunsfeld]

I think that what's needed is a change to the external scanner's logic for inserting automatic_semicolon tokens, implemented here.

We need to do the same thing for catch and finally that is already done for else: prevent automatic semicolons for lines that begin with else/finally/catch.

[maxbrunsfeld]

This describes Scala's rules for automatic semicolon insertion.

In short, a line ending is treated as a semicolon unless one of the following conditions is true:

1. The line in question ends in a word that would not be legal as the end of a statement, such as a period or an infix operator.
2. The next line begins with a word that cannot start a statement.
3. The line ends while inside parentheses(...) or brackets[...], because these cannot contain multiple statements anyway.

[ckipp01]

Cool, thanks a lot for the pointers @maxbrunsfeld. I think this should be ready to go!

[ckipp01]

I'm not sure if this isn't trigger the build. It may be since this was already opened when the actions pr was merged that it doesn't register. Do you by chance want me to close this and reopen to try and trigger it?

EDIT: Tried and that didn't work. I think I have a fix included for it an a commit here.

[ckipp01]

I took this from how we do it in Metals. https://github.com/scalameta/metals/blob/6001b60afb2774c342a73fea4856d42ff5fa5d1e/.github/workflows/ci.yml#L4-L6

[maxbrunsfeld]

Thanks!