Draft: implement indentation as virtual text

after/syntax/gitlab.vim

@@ -1,9 +1,11 @@
-if filereadable($VIMRUNTIME . '/syntax/markdown.vim')
+" Don't source the markdown syntax again when reloading this file after Treesitter
+" highlighting is started, see `actions/discussions/init.lua`.
+if !exists("b:markdown_syntax_loaded") && filereadable($VIMRUNTIME . '/syntax/markdown.vim')
   source $VIMRUNTIME/syntax/markdown.vim
+  let b:markdown_syntax_loaded = 1
 endif
 
-let expanders = '^\s*\%(' . g:gitlab_discussion_tree_expander_open . '\|' . g:gitlab_discussion_tree_expander_closed . '\)'
-let username = '@[a-zA-Z0-9.]\+'
+let username = '@[a-zA-Z0-9._]\+'
 
 " Covers times like '14 days ago', 'just now', as well as 'October  3, 2024', and '02/28/2025 at 00:50'
 let time_ago = '\d\+ \w\+ ago'
@@ -14,15 +16,19 @@ let date = '\%(' . time_ago . '\|' . formatted_date . '\|' . absolute_time . '\|
 let published = date . ' \%(' . g:gitlab_discussion_tree_resolved . '\|' . g:gitlab_discussion_tree_unresolved . '\|' . g:gitlab_discussion_tree_unlinked . '\)\?'
 let state = ' \%(' . published . '\|' . g:gitlab_discussion_tree_draft . '\)'
 
-execute 'syntax match GitlabNoteHeader "' . expanders . username . state . '" contains=GitlabDate,GitlabUnresolved,GitlabUnlinked,GitlabResolved,GitlabExpander,GitlabDraft,GitlabUsername'
+" Require that the `@` in a GitlabMention is not preceded by a word character, so that
+" @doe.com in john@doe.com is not highlighted as a mention.
+execute 'syntax match GitlabMention "\(\w\)\@<!' . username . '"'
+
+" The tree draws indentation and the expander icons as virtual text, so a note's header
+" starts at the very beginning of the line.
+execute 'syntax match GitlabNoteHeader "^' . username . state . '" contains=GitlabDate,GitlabUnresolved,GitlabUnlinked,GitlabResolved,GitlabDraft,GitlabUsername'
 
 execute 'syntax match GitlabDate "' . date . '" contained'
 execute 'syntax match GitlabUnresolved "' . g:gitlab_discussion_tree_unresolved . '" contained'
 execute 'syntax match GitlabUnlinked "' . g:gitlab_discussion_tree_unlinked . '" contained'
 execute 'syntax match GitlabResolved "' . g:gitlab_discussion_tree_resolved . '" contained'
-execute 'syntax match GitlabExpander "' . expanders . '" contained'
 execute 'syntax match GitlabDraft "' . g:gitlab_discussion_tree_draft . '" contained'
 execute 'syntax match GitlabUsername "' . username . '" contained'
-execute 'syntax match GitlabMention "' . username . '"'
 
 let b:current_syntax = 'gitlab'

doc/gitlab.nvim.txt

@@ -326,8 +326,15 @@ you call this function with no values the defaults will be used:
       expanders = { -- Discussion tree icons
         expanded = " ", -- Icon for expanded discussion thread
         collapsed = " ", -- Icon for collapsed discussion thread
-        indentation = "  ", -- Indentation Icon
       },
+      indent_width = 2, -- Display columns that one level of nesting indents by. Indentation is drawn as virtual text, so it never enters the buffer and is not copied along with note text
+      indent_guides = { -- Guides tying replies to the initial comment. The characters are padded out to `indent_width`. Set `indent_guides = false` to turn the guides off
+        vertical = "│", -- Drawn down a discussion that has more replies below
+        branch = "├", -- Drawn against a reply's header
+        last = "╰", -- Drawn against the header of the last reply
+        horizontal = "─", -- Pads `branch` and `last` out to the indent width
+      },
+      wrap_marker = "↪ ", -- Marker drawn inside the tree's indentation at the start of a wrapped line. Dropped if wider than the indentation. Set `wrap_marker = ""` to turn the marker off
       spinner_chars = { "/", "|", "\\", "-" }, -- Characters for the refresh animation
       auto_open = true, -- Automatically open when the reviewer is opened
       focus_on_open = true, -- Automatically focus the discussion tree when it is opened
@@ -348,8 +355,12 @@ you call this function with no values the defaults will be used:
       winopts = { -- Window-local options for the discussion tree split
         number = false,
         relativenumber = false,
-        breakindent = true, -- Every wrapped line will continue visually indented
-        showbreak = "+ ", -- String to put at the start of lines that have been wrapped
+        -- The tree indents lines with virtual text and enforces 'breakindent=false',
+        -- 'linebreak=true', and 'showbreak=' because other values ruin the indentation
+        -- on wrapped lines. Use discussion_tree.wrap_marker instead of 'showbreak'.
+        -- The global 'breakat' option which controls at which characters lines can wrap
+        -- cannot be set per-window. If you want to enable soft-wrapping for long Gitlab
+        -- URLS, add this to your global configuration: `set breakat+==#`.
       }
       winbar = nil, -- Custom function to return winbar title, should return a string. Provided with WinbarTable (defined in annotations.lua)
                    -- If using lualine, add "gitlab" to disabled file types, otherwise you will not see the winbar.
@@ -477,6 +488,8 @@ you call this function with no values the defaults will be used:
         mention = "WarningMsg",
         date = "Comment",
         expander = "DiffviewNonText",
+        wrap_marker = "DiffviewNonText",
+        indent_guide = "DiffviewNonText",
         directory = "Directory",
         directory_icon = "DiffviewFolderSign",
         file_name = "Normal",

lua/gitlab/actions/discussions/init.lua

@@ -15,13 +15,16 @@ local common = require("gitlab.actions.common")
 local List = require("gitlab.utils.list")
 local tree_utils = require("gitlab.actions.discussions.tree")
 local discussions_tree = require("gitlab.actions.discussions.tree")
+local virtual_indent = require("gitlab.actions.discussions.virtual_indent")
 local draft_notes = require("gitlab.actions.draft_notes")
 local signs = require("gitlab.indicators.signs")
 local diagnostics = require("gitlab.indicators.diagnostics")
 local winbar = require("gitlab.actions.discussions.winbar")
 local help = require("gitlab.actions.help")
 local emoji = require("gitlab.emoji")
 
+local indent_group = vim.api.nvim_create_augroup("gitlab.discussions.indentation", {})
+
 local M = {
   split_visible = false,
   split = nil,
@@ -33,8 +36,25 @@ local M = {
   discussion_tree = nil,
   ---@type NuiTree?
   unlinked_discussion_tree = nil,
+  ---@type ("discussions"|"notes")?
+  current_view_type = nil,
 }
 
+---Attach Treesitter's markdown parser to a discussion tree buffer.
+---This enables code blocks (e.g. ```python) to get real language-specific syntax
+---highlighting, instead of the legacy regex syntax defined for the `gitlab` filetype in
+---`after/syntax/gitlab.vim`. A no-op if the `markdown` parser isn't installed.
+---@param bufnr number
+local function attach_markdown_treesitter(bufnr)
+  vim.treesitter.language.register("markdown", "gitlab")
+  if pcall(vim.treesitter.start, bufnr, "markdown") then
+    -- `vim.treesitter.start()` clears 'syntax' on the buffer but that also wipes the
+    -- note header highlighting, which the markdown parser knows nothing about. Reload
+    -- it on top (markdown regex syntax is skipped in that case).
+    vim.bo[bufnr].syntax = "ON"
+  end
+end
+
 ---Delete discussion buffers to prevent leaked buffers on each M.open/M.close cycle.
 ---@param split_bufnr integer? Passed in because `unmount` has already nil'd `M.split.bufnr`.
 local function delete_bufs(split_bufnr)
@@ -46,6 +66,29 @@ local function delete_bufs(split_bufnr)
   end
 end
 
+---Return the currently selected tree.
+---Nil if the split is not a valid window or the window is not in the current tabpage.
+---@preturn tree? NuiTree
+local get_current_tree = function()
+  if M.split == nil or not (M.split.winid and vim.api.nvim_win_is_valid(M.split.winid)) then
+    return
+  end
+  local win_in_tabpage = false
+  for _, i in ipairs(vim.api.nvim_tabpage_list_wins(0)) do
+    if i == M.split.winid then
+      win_in_tabpage = true
+    end
+  end
+  if not win_in_tabpage then
+    return
+  end
+  if M.current_view_type == "discussions" then
+    return M.discussion_tree
+  elseif M.current_view_type == "notes" then
+    return M.unlinked_discussion_tree
+  end
+end
+
 ---Re-fetch all discussions and re-render the relevant view.
 ---TODO: simplify the function signature - "unlinked" and "all" should not be two booleans
 ---@param unlinked boolean
@@ -142,13 +185,11 @@ M.open = function(callback, view_type)
   M.split_visible = true
   split:mount()
 
-  -- Set window and buffer local options to discussion tree split after mounting the split
-  for opt, val in pairs(state.settings.discussion_tree.winopts) do
-    vim.api.nvim_set_option_value(opt, val, { win = M.split.winid })
-  end
-
+  -- Set buffer-local options to discussion tree buffers.
   vim.api.nvim_set_option_value("filetype", "gitlab", { buf = M.linked_bufnr })
   vim.api.nvim_set_option_value("filetype", "gitlab", { buf = M.unlinked_bufnr })
+  attach_markdown_treesitter(M.linked_bufnr)
+  attach_markdown_treesitter(M.unlinked_bufnr)
 
   -- Set autocmds to clean up state when discussions buffers are deleted manually
   vim.api.nvim_create_autocmd("BufWipeout", {
@@ -164,6 +205,27 @@ M.open = function(callback, view_type)
     end,
   })
 
+  -- Where a line wraps depends on the window width, so a resize has to redraw the
+  -- indentation of the wrapped lines. The buffer's contents do not change, so the tree
+  -- needs no re-render.
+  -- vim.api.nvim_create_autocmd({ "WinResized", "VimResized", "TabEnter" }, {
+  vim.api.nvim_create_autocmd({ "WinResized", "VimResized" }, {
+    -- TODO: Find out why "WinResized" fires three times after toggling a node.
+    callback = function()
+      virtual_indent.apply(get_current_tree())
+    end,
+    desc = "Re-apply virtual indentation in discussion tree",
+    group = indent_group,
+  })
+  vim.api.nvim_create_autocmd("OptionSet", {
+    pattern = { "wrap", "breakat", "number", "relativenumber" },
+    callback = function()
+      virtual_indent.apply(get_current_tree())
+    end,
+    desc = "Re-apply virtual indentation in discussion tree when options change",
+    group = indent_group,
+  })
+
   -- Set autocmd to clean up state when discussions split is closed manually
   vim.api.nvim_create_autocmd("WinClosed", {
     pattern = tostring(M.split.winid),
@@ -224,8 +286,10 @@ M.close = function()
   end)
   M.split_visible = false
   M.discussion_tree = nil
+  M.unlinked_discussion_tree = nil
   delete_bufs(split_bufnr)
   winbar.cleanup_timer()
+  vim.api.nvim_clear_autocmds({ group = indent_group })
 end
 
 ---Move to the discussion tree at the discussion from diagnostic on current line.
@@ -250,7 +314,7 @@ M.move_to_discussion_tree = function()
         end
         discussion_node:expand()
       end
-      M.discussion_tree:render()
+      discussions_tree.render(M.discussion_tree)
       vim.api.nvim_set_current_win(M.split.winid)
       M.switch_view_type("discussions")
       vim.api.nvim_win_set_cursor(M.split.winid, { line_number, 0 })
@@ -525,21 +589,20 @@ M.rebuild_discussion_tree = function()
   -- Combine inline draft notes with regular comments
   local all_nodes = u.join(draft_comment_nodes, existing_comment_nodes)
 
-  local discussion_tree = NuiTree({
+  M.discussion_tree = NuiTree({
     nodes = all_nodes,
     bufnr = M.linked_bufnr,
     prepare_node = tree_utils.nui_tree_prepare_node,
   })
 
   -- Re-expand already expanded nodes
   for _, id in ipairs(expanded_node_ids) do
-    tree_utils.open_node_by_id(discussion_tree, id)
+    tree_utils.open_node_by_id(M.discussion_tree, id)
   end
-  discussion_tree:render()
-  discussions_tree.restore_cursor_position(M.split.winid, discussion_tree, current_cursor_column, current_node, nil)
+  discussions_tree.render(M.discussion_tree)
+  discussions_tree.restore_cursor_position(M.split.winid, M.discussion_tree, current_cursor_column, current_node, nil)
 
-  M.set_tree_keymaps(discussion_tree, M.linked_bufnr, false)
-  M.discussion_tree = discussion_tree
+  M.set_tree_keymaps(M.discussion_tree, M.linked_bufnr, false)
   common.switch_can_edit_bufs(false, M.linked_bufnr, M.unlinked_bufnr)
   state.discussion_tree.resolved_expanded = false
   state.discussion_tree.unresolved_expanded = false
@@ -564,21 +627,25 @@ M.rebuild_unlinked_discussion_tree = function()
   -- Combine draft notes with regular notes
   local all_nodes = u.join(draft_comment_nodes, existing_note_nodes)
 
-  local unlinked_discussion_tree = NuiTree({
+  M.unlinked_discussion_tree = NuiTree({
     nodes = all_nodes,
     bufnr = M.unlinked_bufnr,
     prepare_node = tree_utils.nui_tree_prepare_node,
   })
 
   -- Re-expand already expanded nodes
   for _, id in ipairs(expanded_node_ids) do
-    tree_utils.open_node_by_id(unlinked_discussion_tree, id)
-  end
-  unlinked_discussion_tree:render()
-  discussions_tree.restore_cursor_position(M.split.winid, unlinked_discussion_tree, current_cursor_column, current_node)
+    tree_utils.open_node_by_id(M.unlinked_discussion_tree, id)
+  end
+  discussions_tree.render(M.unlinked_discussion_tree)
+  discussions_tree.restore_cursor_position(
+    M.split.winid,
+    M.unlinked_discussion_tree,
+    current_cursor_column,
+    current_node
+  )
 
-  M.set_tree_keymaps(unlinked_discussion_tree, M.unlinked_bufnr, true)
-  M.unlinked_discussion_tree = unlinked_discussion_tree
+  M.set_tree_keymaps(M.unlinked_discussion_tree, M.unlinked_bufnr, true)
   common.switch_can_edit_bufs(false, M.linked_bufnr, M.unlinked_bufnr)
   state.unlinked_discussion_tree.resolved_expanded = false
   state.unlinked_discussion_tree.unresolved_expanded = false
@@ -876,7 +943,22 @@ M.switch_view_type = function(override)
     vim.api.nvim_set_current_buf(M.unlinked_bufnr)
   end
   vim.api.nvim_set_option_value("winfixbuf", true, { win = M.split.winid })
+
+  -- Set window local options to the discussion tree split. This needs to be done after
+  -- switching the view type because window-local options are in fact tied to the
+  -- buffer as well: see https://github.com/neovim/neovim/issues/11525.
+  local winopts = u.merge(state.settings.discussion_tree.winopts, {
+    -- These are required to make the virtual indentation work
+    breakindent = false,
+    linebreak = true,
+    showbreak = "NONE",
+  })
+  for opt, val in pairs(winopts) do
+    vim.api.nvim_set_option_value(opt, val, { win = M.split.winid })
+  end
+
   winbar.update_winbar()
+  virtual_indent.apply(get_current_tree())
 end
 
 ---Toggle comments tree type between "simple" and "by_file_name".

lua/gitlab/actions/discussions/tree.lua

@@ -3,6 +3,7 @@
 
 local u = require("gitlab.utils")
 local common = require("gitlab.actions.common")
+local virtual_indent = require("gitlab.actions.discussions.virtual_indent")
 local List = require("gitlab.utils.list")
 local state = require("gitlab.state")
 local NuiTree = require("nui.tree")
@@ -345,17 +346,10 @@ M.nui_tree_prepare_node = function(node)
 
   for i, text in ipairs(texts) do
     local line = NuiLine()
-    local expanders = state.settings.discussion_tree.expanders
 
-    line:append(string.rep(expanders.indentation, node._depth - 1))
-
-    if i == 1 and node:has_children() then
-      line:append(node:is_expanded() and expanders.expanded or expanders.collapsed)
-      if node.icon then
-        line:append(node.icon .. " ", node.icon_hl)
-      end
-    else
-      line:append(expanders.indentation)
+    -- Draw the filetype icon in the `by_file_name` tree type
+    if i == 1 and node:has_children() and node.icon then
+      line:append(node.icon .. " ", node.icon_hl)
     end
 
     line:append(text, node.text_hl)
@@ -384,6 +378,15 @@ M.nui_tree_prepare_node = function(node)
   return lines
 end
 
+---Render the tree and redraw its virtual-text indentation and indent guides.
+---Use this instead of calling `tree:render()` directly, since the indentation lives on
+---a separate namespace that `tree:render()` does not clear or repopulate on its own.
+---@param tree NuiTree
+M.render = function(tree)
+  tree:render()
+  virtual_indent.apply(tree)
+end
+
 ---@class ToggleNodesOptions
 ---@field toggle_resolved boolean Whether to toggle resolved discussions.
 ---@field toggle_unresolved boolean Whether to toggle unresolved discussions.
@@ -439,7 +442,7 @@ M.toggle_nodes = function(winid, tree, unlinked, opts)
       state.discussion_tree.unresolved_expanded = not state.discussion_tree.unresolved_expanded
     end
   end
-  tree:render()
+  M.render(tree)
   M.restore_cursor_position(winid, tree, current_cursor_column, current_node, root_node)
 end
 
@@ -564,7 +567,7 @@ M.toggle_node = function(winid, tree)
     node:expand()
   end
 
-  tree:render()
+  M.render(tree)
   M.restore_cursor_position(winid, tree, current_cursor_column, node, common.get_root_node(tree, node))
 end