[WIP] Support of ultisnips snippet

[chemzqm]

The goal is better support for ultinips python features, including:

• Dependencies of placeholder with python block, like:

  ${1:`!p snip.rv = t[2]`} ${2:`!p snip.rv = t[3]`} ${3:`!p snip.rv = t[4][0]`} ${4:bar}

• Variables like snip.c:

  #ifndef ${1:`!p
  if not snip.c:
  	import random, string
  	name = re.sub(r'[^A-Za-z0-9]+','_', snip.fn).upper()
  	rand = ''.join(random.sample(string.ascii_letters+string.digits, 8))
  	snip.rv = ('%s_%s' % (name,rand)).upper()
  else:
  	snip.rv = snip.c`}
  #define $1

• Calculate code blocks on placeholder change, like:

  `!p
  box = make_box(len(t[1]))
  snip.rv = box[0]
  snip += box[1]
  `${1:${VISUAL:content}}`!p
  box = make_box(len(t[1]))
  snip.rv = box[2]
  snip += box[3]`
  $0

Other changes:

• Fixed the changed placeholder could be wrong.
• Add highlight support for current active placeholders.
• Improved text edit on change by reduce the range as much as possible.
• Nested placeholder support when insert nested snippet.
• New synchronize logic which support cancellation.
• Not jump to last placeholder when invoke g:coc_snippet_prev on first placeholder
• Use <Cmd> for key mapping to avoid mode change.
• Improve python code error by include python code.
• Improve snippet preview by resolve python code.

New VSCode snippet variables:

• RELATIVE_FILEPATH
• RANDOM
• RANDOM_HEX
• UUID
• BLOCK_COMMENT_START
• BLOCK_COMMENT_END
• LINE_COMMENT
• WORKSPACE_NAME
• WORKSPACE_FOLDER

[codecov]

Codecov Report

Merging #3682 (3012045) into master (1f60c3d) will increase coverage by 0.56%.
The diff coverage is 90.03%.

@@            Coverage Diff             @@
##           master    #3682      +/-   ##
==========================================
+ Coverage   78.44%   79.00%   +0.56%     
==========================================
  Files         210      211       +1     
  Lines       20912    21402     +490     
  Branches     4724     4848     +124     
==========================================
+ Hits        16404    16909     +505     
+ Misses       2776     2755      -21     
- Partials     1732     1738       +6     

Impacted Files	Coverage Δ
src/model/document.ts	73.94% <ø> (+0.28%)	⬆️
src/types.ts	100.00% <ø> (ø)
src/util/position.ts	100.00% <ø> (+9.63%)	⬆️
src/sources/source-language.ts	60.15% <55.26%> (+0.69%)	⬆️
src/commands.ts	46.84% <66.66%> (+1.33%)	⬆️
src/model/status.ts	90.90% <85.71%> (-1.60%)	⬇️
src/snippets/variableResolve.ts	90.58% <87.87%> (-3.03%)	⬇️
src/snippets/parser.ts	86.76% <89.50%> (+4.07%)	⬆️
src/snippets/session.ts	88.27% <91.37%> (+6.62%)	⬆️
src/snippets/eval.ts	93.50% <93.50%> (ø)
... and 22 more

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[oblitum]

@chemzqm hi. I'm a little confused, do I need coc-snippets to have ultisnip snippet support or this builtin support is sufficient? Maybe wikipage on snippets now needs an update? https://github.com/neoclide/coc.nvim/wiki/Using-snippets

[chemzqm]

It only add support for parse ultisnips snippets, not provide them, https://github.com/neoclide/coc.nvim/pull/3682/files#diff-4f45caa500ef03d94d3c2bfa556caa1642df95d4e2b980d76b876a8fd2e8c522 coc-snippets needs upgrade to make use of it.