VLS uses snippet completion even when the client doesn't support them

[bstaletic]

• I have searched through existing issues
• I have read through docs
• I have read FAQ

Info

• Platform: Linux
• Vetur version: 0.0.61
• VS Code version: N/A

Problem

Sending snippet completions for clients that don't declare that capability can break said clients.

Ycmd client capabilities:

{"textDocument":{"completion":{"completionItem":{"documentationFormat":["plaintext","markdown"]},"completionItemKind":{"valueSet":[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25]}},"hover":{"contentFormat":["plaintext","markdown"]},"signatureHelp":{"signatureInformation":{"documentationFormat":["plaintext","markdown"],"parameterInformation":{"labelOffsetSupport":false}}}}}

As you can see, completionItem doesn't mention snippetSupport. However, this is how vls responds to textDocument/completion request:

2019-10-23 23:53:58,733 - DEBUG - TX: Sending message: b'Content-Length: 176\r\n\r\n{"id":2,"jsonrpc":"2.0","method":"textDocument/completion","params":{"position":{"character":0,"line":0},"textDocument":{"uri":"file:///home/bstaletic/work/test/vue/foo.vue"}}}'
2019-10-23 23:53:58,737 - DEBUG - RX: Received message: b'{"jsonrpc":"2.0","id":2,"result":{"isIncomplete":false,"items":[{"label":"<vue> with default.vue \xe2\x9c\x8c","insertText":"<template>\\n  ${0}\\n</template>\\n\\n<script>\\nexport default {\\n\\n}\\n</script>\\n\\n<style>\\n\\n</style>","insertTextFormat":2,"kind":17,"documentation":{"kind":"markdown","value":"```vue\\n<template>\\n  ${0}\\n</template>\\n\\n<script>\\nexport default {\\n\\n}\\n</script>\\n\\n<style>\\n\\n</style>\\n```"},"detail":"default.vue | .vue","sortText":"2a<vue> with default.vue \xe2\x9c\x8c"},{"label":"<template> html.vue \xe2\x9c\x8c","insertText":"<template>\\n\\t${0}\\n</template>","insertTextFormat":2,"kind":17,"documentation":{"kind":"markdown","value":"```vue\\n<template>\\n\\t${0}\\n</template>\\n```"},"detail":"html.vue | .html","sortText":"2b<template> html.vue \xe2\x9c\x8c"},{"label":"<template> pug.vue \xe2\x9c\x8c","insertText":"<template lang=\\"pug\\">\\n\\t${0}\\n</template>","insertTextFormat":2,"kind":17,"documentation":{"kind":"markdown","value":"```vue\\n<template lang=\\"pug\\">\\n\\t${0}\\n</template>\\n```"},"detail":"pug.vue | .html","sortText":"2b<template> pug.vue \xe2\x9c\x8c"},{"label":"<style> css-scoped.vue \xe2\x9c\x8c","insertText":"<style scoped>\\n${0}\\n</style>","insertTextFormat":2,"kind":17,"documentation":{"kind":"markdown","value":"```vue\\n<style scoped>\\n${0}\\n</style>\\n```"},"detail":"css-scoped.vue | .css","sortText":"2c<style> css-scoped.vue \xe2\x9c\x8c"},{"label":"<style> css.vue \xe2\x9c\x8c","insertText":"<style>\\n${0}\\n</style>","insertTextFormat":2,"kind":17,"documentation":{"kind":"markdown","value":"```vue\\n<style>\\n${0}\\n</style>\\n```"},"detail":"css.vue | .css","sortText":"2c<style> css.vue \xe2\x9c\x8c"},{"label":"<style> less-scoped.vue \xe2\x9c\x8c","insertText":"<style lang=\\"less\\" scoped>\\n${0}\\n</style>","insertTextFormat":2,"kind":17,"documentation":{"kind":"markdown","value":"```vue\\n<style lang=\\"less\\" scoped>\\n${0}\\n</style>\\n```"},"detail":"less-scoped.vue | .css","sortText":"2c<style> less-scoped.vue \xe2\x9c\x8c"},{"label":"<style> less.vue \xe2\x9c\x8c","insertText":"<style lang=\\"less\\">\\n${0}\\n</style>","insertTextFormat":2,"kind":17,"documentation":{"kind":"markdown","value":"```vue\\n<style lang=\\"less\\">\\n${0}\\n</style>\\n```"},"detail":"less.vue | .css","sortText":"2c<style> less.vue \xe2\x9c\x8c"},{"label":"<style> postcss-scoped.vue \xe2\x9c\x8c","insertText":"<style lang=\\"postcss\\" scoped>\\n${0}\\n</style>","insertTextFormat":2,"kind":17,"documentation":{"kind":"markdown","value":"```vue\\n<style lang=\\"postcss\\" scoped>\\n${0}\\n</style>\\n```"},"detail":"postcss-scoped.vue | .css","sortText":"2c<style> postcss-scoped.vue \xe2\x9c\x8c"},{"label":"<style> postcss.vue \xe2\x9c\x8c","insertText":"<style lang=\\"postcss\\">\\n${0}\\n</style>","insertTextFormat":2,"kind":17,"documentation":{"kind":"markdown","value":"```vue\\n<style lang=\\"postcss\\">\\n${0}\\n</style>\\n```"},"detail":"postcss.vue | .css","sortText":"2c<style> postcss.vue \xe2\x9c\x8c"},{"label":"<style> sass-scoped.vue \xe2\x9c\x8c","insertText":"<style lang=\\"sass\\" scoped>\\n${0}\\n</style>","insertTextFormat":2,"kind":17,"documentation":{"kind":"markdown","value":"```vue\\n<style lang=\\"sass\\" scoped>\\n${0}\\n</style>\\n```"},"detail":"sass-scoped.vue | .css","sortText":"2c<style> sass-scoped.vue \xe2\x9c\x8c"},{"label":"<style> sass.vue \xe2\x9c\x8c","insertText":"<style lang=\\"sass\\">\\n${0}\\n</style>","insertTextFormat":2,"kind":17,"documentation":{"kind":"markdown","value":"```vue\\n<style lang=\\"sass\\">\\n${0}\\n</style>\\n```"},"detail":"sass.vue | .css","sortText":"2c<style> sass.vue \xe2\x9c\x8c"},{"label":"<style> scss-scoped.vue \xe2\x9c\x8c","insertText":"<style lang=\\"scss\\" scoped>\\n${0}\\n</style>","insertTextFormat":2,"kind":17,"documentation":{"kind":"markdown","value":"```vue\\n<style lang=\\"scss\\" scoped>\\n${0}\\n</style>\\n```"},"detail":"scss-scoped.vue | .css","sortText":"2c<style> scss-scoped.vue \xe2\x9c\x8c"},{"label":"<style> scss.vue \xe2\x9c\x8c","insertText":"<style lang=\\"scss\\">\\n${0}\\n</style>","insertTextFormat":2,"kind":17,"documentation":{"kind":"markdown","value":"```vue\\n<style lang=\\"scss\\">\\n${0}\\n</style>\\n```"},"detail":"scss.vue | .css","sortText":"2c<style> scss.vue \xe2\x9c\x8c"},{"label":"<style> stylus-scoped.vue \xe2\x9c\x8c","insertText":"<style lang=\\"stylus\\" scoped>\\n${0}\\n</style>","insertTextFormat":2,"kind":17,"documentation":{"kind":"markdown","value":"```vue\\n<style lang=\\"stylus\\" scoped>\\n${0}\\n</style>\\n```"},"detail":"stylus-scoped.vue | .css","sortText":"2c<style> stylus-scoped.vue \xe2\x9c\x8c"},{"label":"<style> stylus.vue \xe2\x9c\x8c","insertText":"<style lang=\\"stylus\\">\\n${0}\\n</style>","insertTextFormat":2,"kind":17,"documentation":{"kind":"markdown","value":"```vue\\n<style lang=\\"stylus\\">\\n${0}\\n</style>\\n```"},"detail":"stylus.vue | .css","sortText":"2c<style> stylus.vue \xe2\x9c\x8c"},{"label":"<script> javascript.vue \xe2\x9c\x8c","insertText":"<script>\\nexport default {\\n\\t${0}\\n}\\n</script>","insertTextFormat":2,"kind":17,"documentation":{"kind":"markdown","value":"```vue\\n<script>\\nexport default {\\n\\t${0}\\n}\\n</script>\\n```"},"sortText":"2d<script> javascript.vue \xe2\x9c\x8c"},{"label":"<script> typescript.vue \xe2\x9c\x8c","insertText":"<script lang=\\"ts\\">\\nimport Vue from \'vue\'\\nexport default Vue.extend({\\n\\t${0}\\n})\\n</script>","insertTextFormat":2,"kind":17,"documentation":{"kind":"markdown","value":"```vue\\n<script lang=\\"ts\\">\\nimport Vue from \'vue\'\\nexport default Vue.extend({\\n\\t${0}\\n})\\n</script>\\n```"},"sortText":"2d<script> typescript.vue \xe2\x9c\x8c"}]}}'
Traceback (most recent call last):
  File "/home/bstaletic/.vim/pack/bundle/start/YouCompleteMe/third_party/ycmd/third_party/bottle/bottle.py", line 862, in _handle
    return route.call(**args)
  File "/home/bstaletic/.vim/pack/bundle/start/YouCompleteMe/third_party/ycmd/third_party/bottle/bottle.py", line 1740, in wrapper
    rv = callback(*a, **ka)
  File "/home/bstaletic/.vim/pack/bundle/start/YouCompleteMe/third_party/ycmd/ycmd/watchdog_plugin.py", line 104, in wrapper
    return callback( *args, **kwargs )
  File "/home/bstaletic/.vim/pack/bundle/start/YouCompleteMe/third_party/ycmd/ycmd/hmac_plugin.py", line 68, in wrapper
    body = callback( *args, **kwargs )
  File "/home/bstaletic/.vim/pack/bundle/start/YouCompleteMe/third_party/ycmd/ycmd/handlers.py", line 120, in GetCompletions
    completions = filetype_completer.ComputeCandidates( request_data )
  File "/home/bstaletic/.vim/pack/bundle/start/YouCompleteMe/third_party/ycmd/ycmd/completers/completer.py", line 271, in ComputeCandidates
    candidates = self._GetCandidatesFromSubclass( request_data )
  File "/home/bstaletic/.vim/pack/bundle/start/YouCompleteMe/third_party/ycmd/ycmd/completers/language_server/language_server_completer.py", line 933, in _GetCandidatesFromSubclass
    codepoint )
  File "/home/bstaletic/.vim/pack/bundle/start/YouCompleteMe/third_party/ycmd/ycmd/completers/language_server/language_server_completer.py", line 920, in ComputeCandidatesInner
    request_data ),
  File "/home/bstaletic/.vim/pack/bundle/start/YouCompleteMe/third_party/ycmd/ycmd/completers/language_server/language_server_completer.py", line 1033, in _CandidatesFromCompletionItems
    _InsertionTextForItem( request_data, item ) )
  File "/home/bstaletic/.vim/pack/bundle/start/YouCompleteMe/third_party/ycmd/ycmd/completers/language_server/language_server_completer.py", line 2089, in _InsertionTextForItem
    item.get( 'insertTextFormat' ) or 1 ] == 'PlainText'
AssertionError

The completion items contain "insertTextFormat":2 which indicates snippets instead of plain text completion.