feat: output preview with ghost text, including for snippets (#186)

* feat: show output preview with ghost-text

* feat: handle ghost text in the middle of line

* fix: buffer text being covered by ghost text

* feat: ghost text preview supports snippets

* feat: add highlight link for ghost text preview

* feat: add option to enable/disable ghost text preview

* refactor: rename ghost-text-preview to ghost-text

* feat: add default to ghost text config and update readme

* refactor: use text-edits libs textEdit item

* refactor: listen to autocomplete on_select to decide when to show ghost text

* feat: use smarter way to get ghost text result

* chore: remove previously added line break

README.md

@@ -346,6 +346,9 @@ MiniDeps.add({
       border = 'padded',
       winhighlight = 'Normal:BlinkCmpSignatureHelp,FloatBorder:BlinkCmpSignatureHelpBorder',
     },
+    ghost_text = {
+      enabled = false,
+    },
   },
 
   highlight = {

lua/blink/cmp/config.lua

@@ -90,6 +90,7 @@
 --- @field autocomplete? blink.cmp.AutocompleteConfig
 --- @field documentation? blink.cmp.DocumentationConfig
 --- @field signature_help? blink.cmp.SignatureHelpConfig
+--- @field ghost_text? GhostTextConfig
 
 --- @class blink.cmp.HighlightConfig
 --- @field ns? number
@@ -137,6 +138,9 @@
 --- @field border? blink.cmp.WindowBorder
 --- @field winhighlight? string
 
+--- @class GhostTextConfig
+--- @field enabled? boolean
+
 --- @class blink.cmp.Config
 --- @field keymap? blink.cmp.KeymapConfig
 --- @field accept? blink.cmp.AcceptConfig
@@ -340,6 +344,9 @@ local config = {
       border = 'padded',
       winhighlight = 'Normal:BlinkCmpSignatureHelp,FloatBorder:BlinkCmpSignatureHelpBorder',
     },
+    ghost_text = {
+      enabled = false,
+    },
   },
 
   highlight = {

lua/blink/cmp/init.lua

@@ -30,6 +30,7 @@ cmp.setup = function(opts)
     cmp.windows = {
       autocomplete = require('blink.cmp.windows.autocomplete').setup(),
       documentation = require('blink.cmp.windows.documentation').setup(),
+      ghost_text = require('blink.cmp.windows.ghost-text').setup(),
     }
 
     cmp.trigger.listen_on_show(function(context) cmp.sources.request_completions(context) end)
@@ -99,6 +100,8 @@ cmp.add_default_highlights = function()
     set_hl('BlinkCmpKind' .. kind, { link = use_nvim_cmp and 'CmpItemKind' .. kind or 'BlinkCmpKind' })
   end
 
+  set_hl('BlinkCmpGhostText', { link = use_nvim_cmp and 'CmpGhostText' or 'Comment' })
+
   set_hl('BlinkCmpMenu', { link = 'Pmenu' })
   set_hl('BlinkCmpMenuBorder', { link = 'Pmenu' })
   set_hl('BlinkCmpMenuSelection', { link = 'PmenuSel' })

lua/blink/cmp/windows/ghost-text.lua

@@ -0,0 +1,66 @@
+local config = require('blink.cmp.config')
+local autocomplete = require('blink.cmp.windows.autocomplete')
+
+local ghost_text_config = config.windows.ghost_text
+
+local ghost_text = {
+  enabled = ghost_text_config and ghost_text_config.enabled,
+  extmark_id = 1,
+  ns_id = config.highlight.ns,
+}
+
+function ghost_text.setup()
+  autocomplete.listen_on_select(function(item, context)
+    if ghost_text.enabled ~= true then return end
+    ghost_text.show_preview(item)
+  end)
+  autocomplete.listen_on_close(function() ghost_text.clear_preview() end)
+
+  return ghost_text
+end
+
+--- @param textEdit lsp.TextEdit
+local function get_still_untyped_text(textEdit)
+  local type_text_length = textEdit.range['end'].character - textEdit.range.start.character
+  local result = textEdit.newText:sub(type_text_length + 1)
+  return result
+end
+
+--- @param selected_item? blink.cmp.CompletionItem
+function ghost_text.show_preview(selected_item)
+  if selected_item == nil then return end
+  local text_edits_lib = require('blink.cmp.accept.text-edits')
+  local text_edit = text_edits_lib.get_from_item(selected_item)
+
+  if selected_item.insertTextFormat == vim.lsp.protocol.InsertTextFormat.Snippet then
+    local expanded_snippet = require('blink.cmp.sources.snippets.utils').safe_parse(text_edit.newText)
+    text_edit.newText = expanded_snippet and tostring(expanded_snippet) or text_edit.newText
+  end
+
+  local display_lines = vim.split(get_still_untyped_text(text_edit), '\n', { plain = true }) or {}
+
+  --- @type vim.api.keyset.set_extmark
+  local extmark = {
+    id = ghost_text.extmark_id,
+    virt_text_pos = 'inline',
+    virt_text = { { display_lines[1], 'BlinkCmpGhostText' } },
+    hl_mode = 'combine',
+  }
+
+  if #display_lines > 1 then
+    extmark.virt_lines = {}
+    for i = 2, #display_lines do
+      extmark.virt_lines[i - 1] = { { display_lines[i], 'BlinkCmpGhostText' } }
+    end
+  end
+
+  local cursor_pos = {
+    text_edit.range.start.line,
+    text_edit.range['end'].character,
+  }
+  vim.api.nvim_buf_set_extmark(0, ghost_text.ns_id, cursor_pos[1], cursor_pos[2], extmark)
+end
+
+function ghost_text.clear_preview() vim.api.nvim_buf_del_extmark(0, ghost_text.ns_id, ghost_text.extmark_id) end
+
+return ghost_text