Fixes #80: Update problem matcher

[jonaprieto]

This PR closes

• The pop-up window for errors doesn't contain proper error message #80

[lukaszcz]

Seems to work now!

[jonaprieto]

I'm not sure, I just tested it on another machine, and it didn't work. Did you test it with typecheckOn set to "none"

[lukaszcz]

I'm not sure, I just tested it on another machine, and it didn't work. Did you test it with typecheckOn set to "none"

Oh, yes, it doesn't work with typecheckOn set to "none". It's a bit strange and random. For the first typecheck, I got only the first line of the error message. When I repeat the type checking, I don't get the error message at all.

[lukaszcz]

I looked into this, and it seems to be completely impossible to use a ProblemMatcher for an error message spanning several lines. Theoretically, there are multiline problem matchers, but they are intended to work for stuff like:

test.js
  1:0   error  Missing "use strict" statement                 strict
  1:9   error  foo is defined but never used                  no-unused-vars
  2:5   error  x is defined but never used                    no-unused-vars
  2:11  error  Missing semicolon                              semi
  3:1   error  "bar" is not defined                           no-undef
  4:1   error  Newline required at end of file but not found  eol-last
✖ 6 problems (6 errors, 0 warnings)

When you get several error messages for one file, and not a single message on multiple lines. VSCode extensions for Haskell, which need to parse multiline error messages, do this by manually parsing all errors without using any problem matchers.

See:

• Problem-matchers for error *messages* that span multiple lines microsoft/vscode#112686
• Problem matchers for error messages that span multiple lines microsoft/vscode#9635

[lukaszcz]

Even for the simple case of one line break between file/location info and the message, this line break is precisely what causes the error messages to get mangled up in the pop-up window, even though we seem to be correctly implementing a problem matcher for this case.