syntax: correctly highlight paths with interpolation

[Ma27]

OK I nerdsniped myself into doing that now, damn it :upside_down_face: Anyways, this is a draft on purpose, because there's one known case of a wrong highlight (see commit message below) and I haven't tested this under real conditions yet. cc @LnL7 @figsoda @aszlig

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Closes https://github.com/LnL7/vim-nix/issues/41

A few implementation notes:

• nixInterpolatedPath is on purpose below nixPath, otherwise the highlighting of top-level expressions, i.e. files containing e.g.

  ./foo/bar${baz}

  break where $ is entirely unmatched and {baz} is misinterpreted as argument destructuring expression.

• The region's matching behavior now works like this:

  First, we expect a path start (i.e. either ~/<further path components> or <path components>) and then the beginning of a substitution (${), however this isn't part of our match anymore (hence \ze) to make sure this is matched by the subsequent nixInterpolation.

  Also, nixInterpolation is the only thing allowed in here because nixPath would conflict with our end & skip expression and would thus make vim expand the nixInterpolatedPath over the rest of the file.

  To summarize, after the start, two things are allowed:

  • An interpolation
  • Valid path chars.

  The skip regex is to make sure that the end isn't satisified too early, e.g. in

  ./foo/${bar}/${baz}/suff

  the path shouldn't terminate after ${bar}/ since another substitution is followed by only valid path chars.

  The end regex makes sure that the last substitution was closed (nixinterpolatedPath always contains a substitution because of start) and only valid path chars are matched after that. This means that e.g. in

  ./foo/${bar}!x

  everything after ${bar} is not part of the path anymore.

• In the end a region turned out to be slightly more suitable, so this cannot be composed into a single group with the matcher nixPath.

  Instead, nixInterpolatedPath's highlighting group now links to nixPath to make sure they look the same in the end.

[Ma27]

OK, this also breaks string interpolations like "foo ${./bar}" :(

So not usable yet.

[aszlig]

OK, this also breaks string interpolations like "foo ${./bar}" :(

Can you please add a specific test case for this?

Will look into this later.

[Ma27]

After playing around with regions, I got something which appears to work more reliably. Also added two new testcases for the issues I encountered with the previous matcher I wrote (path-with-invalid-infix and path-with-recursive-interpolation).

[Ma27]

Considering that I haven't found any issues in the past week, I decided to mark it as ready to review :)

cc @figsoda @lnl7 :)

[Ma27]

@figsoda cannot reproduce. Is the issue also observable with the vim from the repo's nix-shell? When I hover with the cursor over the - or the .nix int he editor and issue :Syntax it always prints out ['nixInterpolatedPath'] which seems correct to me.

[Ma27]

ping @LnL7 I think this is good to go now :)

[Ma27]

ping @LnL7

[Ma27]

ping @LnL7 I'd still need an approval from you to merge this. Would be cool if we could get this done :)

[Ma27]

I'm merging this now, I'm using this patch in my editor for the last months (and I have Nix code open more often than I'd like to admit) without noticing any issues and others seem to have tested it as well.