Increase the default maximum completion suggestions to a more useful but safe level, and filter before requesting details, which is faster

autoload/ale/completion.vim

@@ -43,7 +43,7 @@ let s:omni_start_map = {
 \   'typescript': '\v[a-zA-Z$_][a-zA-Z$_0-9]*$',
 \}
 
-function! ale#completion#FilterSuggestionsByPrefix(suggestions, prefix) abort
+function! ale#completion#Filter(suggestions, prefix) abort
     " For completing...
     "   foo.
     "       ^
@@ -57,14 +57,17 @@ function! ale#completion#FilterSuggestionsByPrefix(suggestions, prefix) abort
     " Filter suggestions down to those starting with the prefix we used for
     " finding suggestions in the first place.
     "
-    " Some completion tools will
-    " include suggestions which don't even start with the characters we have
-    " already typed.
-    for l:suggestion in a:suggestions
+    " Some completion tools will include suggestions which don't even start
+    " with the characters we have already typed.
+    for l:item in a:suggestions
+        " A List of String values or a List of completion item Dictionaries
+        " is accepted here.
+        let l:word = type(l:item) == type('') ? l:item : l:item.word
+
         " Add suggestions if the suggestion starts with a case-insensitive
         " match for the prefix.
-        if l:suggestion.word[: len(a:prefix) - 1] is? a:prefix
-            call add(l:filtered_suggestions, l:suggestion)
+        if l:word[: len(a:prefix) - 1] is? a:prefix
+            call add(l:filtered_suggestions, l:item)
         endif
     endfor
 
@@ -98,12 +101,7 @@ function! ale#completion#OmniFunc(findstart, base) abort
             unlet b:ale_completion_response
             unlet b:ale_completion_parser
 
-            let l:prefix = b:ale_completion_info.prefix
-
-            let b:ale_completion_result = ale#completion#FilterSuggestionsByPrefix(
-            \   function(l:parser)(l:response),
-            \   l:prefix
-            \)[: g:ale_completion_max_suggestions]
+            let b:ale_completion_result = function(l:parser)(l:response)
         endif
 
         call s:ReplaceCompleteopt()
@@ -191,7 +189,7 @@ function! ale#completion#ParseTSServerCompletionEntryDetails(response) abort
     return l:results
 endfunction
 
-function! s:HandleTSServerLSPResponse(conn_id, response) abort
+function! ale#completion#HandleTSServerLSPResponse(conn_id, response) abort
     if !s:CompletionStillValid(get(a:response, 'request_seq'))
         return
     endif
@@ -203,7 +201,10 @@ function! s:HandleTSServerLSPResponse(conn_id, response) abort
     let l:command = get(a:response, 'command', '')
 
     if l:command is# 'completions'
-        let l:names = ale#completion#ParseTSServerCompletions(a:response)
+        let l:names = ale#completion#Filter(
+        \   ale#completion#ParseTSServerCompletions(a:response),
+        \   b:ale_completion_info.prefix,
+        \)[: g:ale_completion_max_suggestions - 1]
 
         if !empty(l:names)
             let b:ale_completion_info.request_id = ale#lsp#Send(
@@ -229,7 +230,7 @@ function! s:GetLSPCompletions(linter) abort
     let l:lsp_details = ale#linter#StartLSP(
     \   l:buffer,
     \   a:linter,
-    \   function('s:HandleTSServerLSPResponse'),
+    \   function('ale#completion#HandleTSServerLSPResponse'),
     \)
 
     if empty(l:lsp_details)

doc/ale.txt

@@ -296,7 +296,7 @@ g:ale_completion_enabled                             *g:ale_completion_enabled*
 g:ale_completion_max_suggestions             *g:ale_completion_max_suggestions*
 
   Type: |Number|
-  Default: `20`
+  Default: `50`
 
   The maximum number of items ALE will suggest in completion menus for
   automatic completion.

plugin/ale.vim

@@ -190,7 +190,7 @@ call ale#Set('type_map', {})
 " Enable automatic completion with LSP servers and tsserver
 call ale#Set('completion_enabled', 0)
 call ale#Set('completion_delay', 100)
-call ale#Set('completion_max_suggestions', 20)
+call ale#Set('completion_max_suggestions', 50)
 
 function! ALEInitAuGroups() abort
     " This value used to be a Boolean as a Number, and is now a String.

test/test_completion.vader

@@ -1,6 +1,7 @@
 Before:
   Save g:ale_completion_enabled
   Save g:ale_completion_delay
+  Save g:ale_completion_max_suggestions
   Save &l:omnifunc
   Save &l:completeopt
 
@@ -25,6 +26,7 @@ After:
   unlet! b:ale_completion_parser
 
   runtime autoload/ale/completion.vim
+  runtime autoload/ale/lsp.vim
 
   if g:ale_completion_enabled
     call ale#completion#Enable()
@@ -108,6 +110,89 @@ Execute(TypeScript completion details responses should be parsed correctly):
   \ ],
   \})
 
+Execute(Prefix filtering should work for Lists of strings):
+  AssertEqual
+  \ ['FooBar', 'foo'],
+  \ ale#completion#Filter(['FooBar', 'FongBar', 'baz', 'foo'], 'foo')
+  AssertEqual
+  \ ['FooBar', 'FongBar', 'baz', 'foo'],
+  \ ale#completion#Filter(['FooBar', 'FongBar', 'baz', 'foo'], '.')
+
+Execute(Prefix filtering should work for completion items):
+  AssertEqual
+  \ [{'word': 'FooBar'}, {'word': 'foo'}],
+  \ ale#completion#Filter(
+  \   [
+  \     {'word': 'FooBar'},
+  \     {'word': 'FongBar'},
+  \     {'word': 'baz'},
+  \     {'word': 'foo'},
+  \   ],
+  \   'foo'
+  \ )
+  AssertEqual
+  \ [
+  \   {'word': 'FooBar'},
+  \   {'word': 'FongBar'},
+  \   {'word': 'baz'},
+  \   {'word': 'foo'},
+  \ ],
+  \ ale#completion#Filter(
+  \   [
+  \     {'word': 'FooBar'},
+  \     {'word': 'FongBar'},
+  \     {'word': 'baz'},
+  \     {'word': 'foo'},
+  \   ],
+  \   '.'
+  \ )
+
+Execute(The right message sent to the tsserver LSP when the first completion message is received):
+  " The cursor position needs to match what was saved before.
+  call setpos('.', [bufnr(''), 1, 1, 0])
+  let b:ale_completion_info = {
+  \ 'conn_id': 123,
+  \ 'prefix': 'f',
+  \ 'request_id': 4,
+  \ 'line': 1,
+  \ 'column': 1,
+  \}
+  " We should only show up to this many suggestions.
+  let g:ale_completion_max_suggestions = 3
+
+  " Replace the Send function for LSP, so we can monitor calls to it.
+  function! ale#lsp#Send(conn_id, message) abort
+    let g:test_vars.message = a:message
+  endfunction
+
+  " Handle the response for completions.
+  call ale#completion#HandleTSServerLSPResponse(123, {
+  \ 'request_seq': 4,
+  \ 'command': 'completions',
+  \ 'body': [
+  \   {'name': 'Baz'},
+  \   {'name': 'dingDong'},
+  \   {'name': 'Foo'},
+  \   {'name': 'FooBar'},
+  \   {'name': 'frazzle'},
+  \   {'name': 'FFS'},
+  \ ],
+  \})
+
+  " The entry details messages should have been sent.
+  AssertEqual
+  \ [
+  \   0,
+  \   'ts@completionEntryDetails',
+  \   {
+  \     'file': expand('%:p'),
+  \     'entryNames': ['Foo', 'FooBar', 'frazzle'],
+  \     'offset': 1,
+  \     'line': 1,
+  \   },
+  \ ],
+  \ g:test_vars.message
+
 Given typescript():
   let abc = y.
   let foo = ab