Highlight unreachable element in Cram files

[mnxn]

Highlight ***** UNREACHABLE ***** in Cram .t files.

ocaml/dune#4981 (comment)

[SaySayo]

I'd like to work on this

[tmattio]

Sounds good @SaySayo 🙂 FYI, here's a test that you can use to test the highlighting:

Syntax error inside a cram command
  $ mkdir foo && cd foo
  $ cat >dune-project <<EOF
  > (lang dune 3.0)
  > EOF

  $ cat >t1.t <<EOF
  >   $ foo-bar() { true; }
  > EOF

  $ dune runtest --auto-promote 2>&1 | sed -E -e 's/.+\.sh:/$SUBTEST.sh:/' -e 's/cd.*\&\&.*.sh/cd $DIR \&\& $SUBTEST.sh/'
  File "t1.t", line 1, characters 0-0:
  Error: Files _build/default/t1.t and _build/default/t1.t.corrected differ.
  Promoting _build/default/t1.t.corrected to t1.t.

  $ cat >t1.t <<EOF
  >   $ exit 1
  >   $ echo foobar
  > EOF
  $ dune runtest --auto-promote
  File "t1.t", line 1, characters 0-0:
  Error: Files _build/default/t1.t and _build/default/t1.t.corrected differ.
  Promoting _build/default/t1.t.corrected to t1.t.
  [1]
  $ cat t1.t
    $ exit 1
    ***** UNREACHABLE *****
    $ echo foobar
    ***** UNREACHABLE *****

[mnxn]

Making the syntax name start with invalid (for example invalid.unreachable.cram) will make most vscode themes highlight it in red.

I think that would be the best option if I'm correctly interpreting ***** UNREACHABLE ***** as an error.

[SaySayo]

Here's the language grammar I wrote for it. I added it to the cram.json file but I see no changes when I run it in development.

[mnxn]

In your grammar rule, match includes \\( and \\), which will look for parentheses in the cram files.
The unreachable element has no parentheses, so it will not be currently highlighted.

In other words,
you need to highlight ***** UNREACHABLE *****,
but you're currently highlighting (***** UNREACHABLE *****)

Another suggestion I can make is to remove the captures sections, because the entire unreachable element (both the word and asterisks) should be highlighted the same. There's no reason to capture anything.
You can replace the entire captures section with just "name": "invalid.unreachable.cram".

[mnxn]

Closed by #754