feat(completion): update signature help without delay if currently shown

Details:
- This improves experience when cursor jumps in Insert mode (like during
  snippet session) compared to only accounting for user typing.

Resolve #1680

Author: echasnovski

CHANGELOG.md

@@ -38,6 +38,7 @@
 - FEATURE: both info and signature help windows now use tree-sitter highlighting:
     - Info window uses "markdown" parser (works best on Neovim>=0.10 as its parser is built-in). Special markdown characters are concealed (i.e. hidden) which might result into seemingly unnecessary whitespace as dimensions are computed not accounting for that.
     - Signature help uses same parser as in current filetype.
+- FEATURE: update signature help without delay if it is already shown. This helps to keep signature help up to date after cursor jumps in Insert mode (like during snippet session).
 - FEATURE: add support for item defaults in `CompletionList` response.
 - BREAKING FEATURE: rework how LSP completion items are converted to Neovim's completion items:
     - Show `detail` highlighted as buffer's language at the start of info window, but only if `detail` provides information not already present in `documentation`. It was previously used as extra text in the popup menu (via `menu` field), but this doesn't quite follow LSP specification: `detail` and `documentation` fields can be delayed up until `completionItem/resolve` request which implies they should be treated similarly.

doc/mini-completion.txt

@@ -31,10 +31,13 @@ Features:
 
 - Automatic display in floating window of completion item info (via
   'completionItem/resolve' request) and signature help (with highlighting
-  of active parameter if LSP server provides such information). After opening,
-  window for signature help is fixed and is closed when there is nothing to
-  show, text is different or when leaving Insert mode.
-  Scroll in either info/signature window (`<C-f>` / `<C-b>` by default).
+  of active parameter if LSP server provides such information).
+  Signature help is shown if character to cursor's left is a dedicated trigger
+  character (configured in `signatureHelpProvider.triggerCharacters` of LSP
+  server capabilities) and updated without delay if is currently opened.
+  Already shown window for signature help is fixed and is closed when there
+  is nothing to show, its text is different, or when leaving Insert mode.
+  Scroll in either info/signature window with `<C-f>` / `<C-b>` (by default).
 
 - Automatic actions are done after some configurable amount of delay. This
   reduces computational load and allows fast typing (completion and

lua/mini/completion.lua

@@ -31,10 +31,13 @@
 ---
 --- - Automatic display in floating window of completion item info (via
 ---   'completionItem/resolve' request) and signature help (with highlighting
----   of active parameter if LSP server provides such information). After opening,
----   window for signature help is fixed and is closed when there is nothing to
----   show, text is different or when leaving Insert mode.
----   Scroll in either info/signature window (`<C-f>` / `<C-b>` by default).
+---   of active parameter if LSP server provides such information).
+---   Signature help is shown if character to cursor's left is a dedicated trigger
+---   character (configured in `signatureHelpProvider.triggerCharacters` of LSP
+---   server capabilities) and updated without delay if is currently opened.
+---   Already shown window for signature help is fixed and is closed when there
+---   is nothing to show, its text is different, or when leaving Insert mode.
+---   Scroll in either info/signature window with `<C-f>` / `<C-b>` (by default).
 ---
 --- - Automatic actions are done after some configurable amount of delay. This
 ---   reduces computational load and allows fast typing (completion and
@@ -225,8 +228,8 @@
 --     - On `CursorMovedI` start auto signature (if there is any active LSP
 --       client) with similar to completion timer pattern. Better event might
 --       be `InsertCharPre` but there are issues with 'autopair-type' plugins.
---     - Check if character left to cursor is appropriate (')' or LSP's
---       signature help trigger characters). If not, do nothing.
+--       Update immediately if already shown or after delay if character to the
+--       left is signature help trigger (after delay has passed).
 --     - If timer is activated, send 'textDocument/signatureHelp' request to
 --       all LSP clients. On callback, process their results. Window is opened
 --       if not already with the same text (its characteristics are computed
@@ -787,11 +790,12 @@ H.auto_signature = function()
   H.signature.timer:stop()
   if not H.has_lsp_clients('signatureHelpProvider') then return end
 
-  local left_char = H.get_left_char()
-  local char_is_trigger = left_char == ')' or H.is_lsp_trigger(left_char, 'signature')
-  if not char_is_trigger then return end
+  local is_shown = H.is_valid_win(H.signature.win_id)
+  local left_char_is_trigger = H.is_lsp_trigger(H.get_left_char(), 'signature')
+  if not (is_shown or left_char_is_trigger) then return end
 
-  H.signature.timer:start(H.get_config().delay.signature, 0, vim.schedule_wrap(H.show_signature_window))
+  local delay = is_shown and 0 or H.get_config().delay.signature
+  H.signature.timer:start(delay, 0, vim.schedule_wrap(H.show_signature_window))
 end
 
 H.on_completedonepre = function()

tests/dir-completion/mock-months-lsp.lua

@@ -169,8 +169,8 @@ Months.requests = {
     local _, active_param_id = after_open_paren:gsub('%,', '%,')
 
     -- Compute what is displayed in signature help: text and parameter info
-    -- (for highlighting) based on latest word
-    local word = line:match('%S+$')
+    -- (for highlighting) based on latest function call
+    local word = line:match('(%S+%()[^%(]*$')
     local label, parameters
     if word == 'long(' then
       label = string.rep('a ', 1000)

tests/screenshots/tests-test_completion.lua---Signature-help---updates-highlighting-of-active-parameter-003

@@ -1,10 +1,10 @@
 -|---------|---------|---------|
-1|abc(1,2,                      
+1|abc(1,222,                    
 2|~   ┌ Signature ────────┐     
 3|~   │abc(param1, param2)│     
 4|~   └───────────────────┘     
 5|~                             
-6|[No Name] [+]  1,9         All
+6|[No Name] [+]  1,11        All
 7|-- INSERT --                  
 
 -|---------|---------|---------|

tests/screenshots/tests-test_completion.lua---Signature-help---updates-highlighting-of-active-parameter-004

@@ -0,0 +1,17 @@
+-|---------|---------|---------|
+1|abc(1,222,                    
+2|~   ┌ Signature ────────┐     
+3|~   │abc(param1, param2)│     
+4|~   └───────────────────┘     
+5|~                             
+6|[No Name] [+]  1,8         All
+7|-- INSERT --                  
+
+-|---------|---------|---------|
+1|000000000000000000000000000000
+2|111123333333333322222222211111
+3|111124444444444445555554211111
+4|111122222222222222222222211111
+5|111111111111111111111111111111
+6|666666666666666666666666666666
+7|777777777777888888888888888888

tests/screenshots/tests-test_completion.lua---Signature-help---updates-without-delay-with-different-window

@@ -0,0 +1,19 @@
+-|---------|---------|---------|-----
+1|multiline(                         
+2|abc(111, 2┌ Signature ───────────┐ 
+3|~         │multiline( arg1, arg2)│ 
+4|~         └──────────────────────┘ 
+5|~                                  
+6|~                                  
+7|[No Name] [+]     1,11          All
+8|-- INSERT --                       
+
+-|---------|---------|---------|-----
+1|00000000000000000000000000000000000
+2|00000000001222222222221111111111110
+3|33333333331444444444444444444444413
+4|33333333331111111111111111111111113
+5|33333333333333333333333333333333333
+6|33333333333333333333333333333333333
+7|55555555555555555555555555555555555
+8|66666666666677777777777777777777777

tests/screenshots/tests-test_completion.lua---Signature-help---updates-without-delay-with-different-window-002

@@ -0,0 +1,19 @@
+-|---------|---------|---------|-----
+1|multiline(                         
+2|abc(111, 222)                      
+3|~          ┌ Signature ────────┐   
+4|~          │abc(param1, param2)│   
+5|~          └───────────────────┘   
+6|~                                  
+7|[No Name] [+]     2,12          All
+8|-- INSERT --                       
+
+-|---------|---------|---------|-----
+1|00000000000000000000000000000000000
+2|00000000000000000000000000000000000
+3|11111111111233333333333222222222111
+4|11111111111244444444444455555542111
+5|11111111111222222222222222222222111
+6|11111111111111111111111111111111111
+7|66666666666666666666666666666666666
+8|77777777777788888888888888888888888

tests/test_completion.lua

@@ -1271,14 +1271,34 @@ T['Signature help']['updates highlighting of active parameter'] = function()
   sleep(default_signature_delay + small_time)
   child.expect_screenshot()
 
+  -- Should update without configurable delay as window is already shown
   type_keys('1,')
-  sleep(default_signature_delay + small_time)
+  sleep(small_time)
   child.expect_screenshot()
 
   -- As there are only two parameters, nothing should be highlighted
-  type_keys('2,')
+  type_keys('222,')
+  sleep(small_time)
+  child.expect_screenshot()
+
+  -- Should update if cursor is moved without typing (like during snippet jump)
+  set_cursor(1, 7)
+  sleep(small_time)
+  child.expect_screenshot()
+end
+
+T['Signature help']['updates without delay with different window'] = function()
+  child.set_size(8, 35)
+  set_lines({ 'multiline(', 'abc(111, 222)' })
+  child.cmd('startinsert')
+  set_cursor(1, 10)
+
   sleep(default_signature_delay + small_time)
   child.expect_screenshot()
+
+  set_cursor(2, 11)
+  sleep(small_time)
+  child.expect_screenshot()
 end
 
 local validate_signature_window_config = function(keys, win_config)