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fix(highlight): support combined diff format for unmerged files

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Problem: fugitive shows combined diffs (@@@ headers, 2-char prefixes)
for unmerged (UU) files. The parser and highlight pipeline assumed
unified diff format (@@, 1-char prefix), causing broken prefix
concealment, missing background colors on ` +`/`+ ` lines, and no
treesitter highlights due to garbage prefix chars in code arrays.

Solution: detect prefix width from the number of leading @ signs in
hunk headers. Propagate prefix_width through the parser (new field on
diffs.Hunk) and highlight pipeline (prefix stripping, col_offset,
concealment, line classification). Add U to filename pattern for
unmerged file detection. Skip intra-line diffing for combined diffs
since the 2-char prefix semantics don't produce meaningful change
groups.
This commit is contained in:
Barrett Ruth 2026-02-09 17:03:17 -05:00
parent 59fcf14817
commit a6dd0503b3
4 changed files with 232 additions and 29 deletions
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43
lua/diffs/highlight.lua
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@ -239,13 +239,14 @@ local function highlight_vim_syntax(
pcall(vim.api.nvim_buf_delete, scratch, { force = true })
local hunk_line_count = #hunk.lines
local col_off = (hunk.prefix_width or 1) - 1
local extmark_count = 0
for _, span in ipairs(spans) do
local adj = span.line - leading_offset
if adj >= 1 and adj <= hunk_line_count then
local buf_line = hunk.start_line + adj - 1
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, span.col_start, {
end_col = span.col_end,
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, span.col_start + col_off, {
end_col = span.col_end + col_off,
hl_group = span.hl_name,
priority = priorities.syntax,
})
@ -265,6 +266,7 @@ end
---@param opts diffs.HunkOpts
function M.highlight_hunk(bufnr, ns, hunk, opts)
local p = opts.highlights.priorities
local pw = hunk.prefix_width or 1
local use_ts = hunk.lang and opts.highlights.treesitter.enabled
local use_vim = not use_ts and hunk.ft and opts.highlights.vim.enabled
@ -296,14 +298,16 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
local old_map = {}
for i, line in ipairs(hunk.lines) do
local prefix = line:sub(1, 1)
local stripped = line:sub(2)
local prefix = line:sub(1, pw)
local stripped = line:sub(pw + 1)
local buf_line = hunk.start_line + i - 1
local has_add = prefix:find('+', 1, true) ~= nil
local has_del = prefix:find('-', 1, true) ~= nil
if prefix == '+' then
if has_add and not has_del then
new_map[#new_code] = buf_line
table.insert(new_code, stripped)
elseif prefix == '-' then
elseif has_del and not has_add then
old_map[#old_code] = buf_line
table.insert(old_code, stripped)
else
@ -314,9 +318,9 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
end
extmark_count =
highlight_treesitter(bufnr, ns, new_code, hunk.lang, new_map, 1, covered_lines, p)
highlight_treesitter(bufnr, ns, new_code, hunk.lang, new_map, pw, covered_lines, p)
extmark_count = extmark_count
+ highlight_treesitter(bufnr, ns, old_code, hunk.lang, old_map, 1, covered_lines, p)
+ highlight_treesitter(bufnr, ns, old_code, hunk.lang, old_map, pw, covered_lines, p)
if hunk.header_context and hunk.header_context_col then
local header_line = hunk.start_line - 1
@ -344,7 +348,7 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
---@type string[]
local code_lines = {}
for _, line in ipairs(hunk.lines) do
table.insert(code_lines, line:sub(2))
table.insert(code_lines, line:sub(pw + 1))
end
extmark_count = highlight_vim_syntax(bufnr, ns, hunk, code_lines, covered_lines, 0, p)
end
@ -367,7 +371,7 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
---@type diffs.IntraChanges?
local intra = nil
local intra_cfg = opts.highlights.intra
if intra_cfg and intra_cfg.enabled and #hunk.lines <= intra_cfg.max_lines then
if intra_cfg and intra_cfg.enabled and pw == 1 and #hunk.lines <= intra_cfg.max_lines then
dbg('computing intra for hunk %s:%d (%d lines)', hunk.filename, hunk.start_line, #hunk.lines)
intra = diff.compute_intra_hunks(hunk.lines, intra_cfg.algorithm)
if intra then
@ -401,22 +405,23 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
for i, line in ipairs(hunk.lines) do
local buf_line = hunk.start_line + i - 1
local line_len = #line
local prefix = line:sub(1, 1)
local is_diff_line = prefix == '+' or prefix == '-'
local line_hl = is_diff_line and (prefix == '+' and 'DiffsAdd' or 'DiffsDelete') or nil
local number_hl = is_diff_line and (prefix == '+' and 'DiffsAddNr' or 'DiffsDeleteNr') or nil
local prefix = line:sub(1, pw)
local has_add = prefix:find('+', 1, true) ~= nil
local has_del = prefix:find('-', 1, true) ~= nil
local is_diff_line = has_add or has_del
local line_hl = is_diff_line and (has_add and 'DiffsAdd' or 'DiffsDelete') or nil
local number_hl = is_diff_line and (has_add and 'DiffsAddNr' or 'DiffsDeleteNr') or nil
if opts.hide_prefix then
local virt_hl = (opts.highlights.background and line_hl) or nil
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
virt_text = { { ' ', virt_hl } },
virt_text = { { string.rep(' ', pw), virt_hl } },
virt_text_pos = 'overlay',
})
end
if line_len > 1 and covered_lines[buf_line] then
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 1, {
if line_len > pw and covered_lines[buf_line] then
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, pw, {
end_col = line_len,
hl_group = 'DiffsClear',
priority = p.clear,
@ -439,7 +444,7 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
end
if char_spans_by_line[i] then
local char_hl = prefix == '+' and 'DiffsAddText' or 'DiffsDeleteText'
local char_hl = has_add and 'DiffsAddText' or 'DiffsDeleteText'
for _, span in ipairs(char_spans_by_line[i]) do
dbg(
'char extmark: line=%d buf_line=%d col=%d..%d hl=%s text="%s"',