fix(highlight): prevent duplicate extmarks from two-pass rendering (#145)

## Problem

Two-pass rendering (Pass 1: backgrounds + intra-line; Pass 2:
treesitter) caused Pass 2 to re-apply all extmarks that Pass 1 already
set, doubling the extmark count on affected lines.

## Solution

Add `syntax_only` mode to `highlight_hunk`. When `syntax_only = true`,
only treesitter syntax and content `DiffsClear` extmarks are applied —
backgrounds, intra-line, prefix clears, and per-char prefix highlights
are skipped. Pass 2 now uses `syntax_only = true` and no longer calls
`nvim_buf_clear_namespace`, so Pass 1's extmarks persist while Pass 2
layers syntax on top.

Closes #143
This commit is contained in:
Barrett Ruth 2026-03-05 09:16:04 -05:00 committed by GitHub
parent 7106bcc291
commit 90b312e8df
No known key found for this signature in database
GPG key ID: B5690EEEBB952194
3 changed files with 190 additions and 69 deletions

View file

@ -65,6 +65,7 @@ end
---@field hide_prefix boolean
---@field highlights diffs.Highlights
---@field defer_vim_syntax? boolean
---@field syntax_only? boolean
---@param bufnr integer
---@param ns integer
@ -381,7 +382,13 @@ 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 pw == 1 and #hunk.lines <= intra_cfg.max_lines then
if
not opts.syntax_only
and 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
@ -494,28 +501,70 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
or content:match('^|||||||')
end
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 = { { string.rep(' ', pw), virt_hl } },
virt_text_pos = 'overlay',
})
end
if not opts.syntax_only then
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 = { { string.rep(' ', pw), virt_hl } },
virt_text_pos = 'overlay',
})
end
if pw > 1 then
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
end_col = pw,
hl_group = 'DiffsClear',
priority = p.clear,
})
for ci = 0, pw - 1 do
local ch = line:sub(ci + 1, ci + 1)
if ch == '+' or ch == '-' then
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, ci, {
end_col = ci + 1,
hl_group = ch == '+' and '@diff.plus' or '@diff.minus',
priority = p.syntax,
if pw > 1 then
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
end_col = pw,
hl_group = 'DiffsClear',
priority = p.clear,
})
for ci = 0, pw - 1 do
local ch = line:sub(ci + 1, ci + 1)
if ch == '+' or ch == '-' then
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, ci, {
end_col = ci + 1,
hl_group = ch == '+' and '@diff.plus' or '@diff.minus',
priority = p.syntax,
})
end
end
end
if opts.highlights.background and is_diff_line then
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
line_hl_group = line_hl,
number_hl_group = opts.highlights.gutter and number_hl or nil,
priority = p.line_bg,
})
end
if is_marker and line_len > pw then
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, pw, {
end_col = line_len,
hl_group = 'DiffsConflictMarker',
priority = p.char_bg,
})
end
if char_spans_by_line[i] then
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"',
i,
buf_line,
span.col_start,
span.col_end,
char_hl,
line:sub(span.col_start + 1, span.col_end)
)
local ok, err = pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, span.col_start, {
end_col = span.col_end,
hl_group = char_hl,
priority = p.char_bg,
})
if not ok then
dbg('char extmark FAILED: %s', err)
end
extmark_count = extmark_count + 1
end
end
end
@ -527,46 +576,6 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
priority = p.clear,
})
end
if opts.highlights.background and is_diff_line then
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
line_hl_group = line_hl,
number_hl_group = opts.highlights.gutter and number_hl or nil,
priority = p.line_bg,
})
end
if is_marker and line_len > pw then
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, pw, {
end_col = line_len,
hl_group = 'DiffsConflictMarker',
priority = p.char_bg,
})
end
if char_spans_by_line[i] then
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"',
i,
buf_line,
span.col_start,
span.col_end,
char_hl,
line:sub(span.col_start + 1, span.col_end)
)
local ok, err = pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, span.col_start, {
end_col = span.col_end,
hl_group = char_hl,
priority = p.char_bg,
})
if not ok then
dbg('char extmark FAILED: %s', err)
end
extmark_count = extmark_count + 1
end
end
end
dbg('hunk %s:%d applied %d extmarks', hunk.filename, hunk.start_line, extmark_count)

View file

@ -797,18 +797,13 @@ local function init()
return
end
local t1 = config.debug and vim.uv.hrtime() or nil
local full_opts = {
local syntax_opts = {
hide_prefix = config.hide_prefix,
highlights = config.highlights,
syntax_only = true,
}
for _, hunk in ipairs(deferred_syntax) do
local start_row = hunk.start_line - 1
local end_row = hunk.start_line + #hunk.lines
if hunk.header_start_line then
start_row = hunk.header_start_line - 1
end
vim.api.nvim_buf_clear_namespace(bufnr, ns, start_row, end_row)
highlight.highlight_hunk(bufnr, ns, hunk, full_opts)
highlight.highlight_hunk(bufnr, ns, hunk, syntax_opts)
end
if t1 then
dbg('deferred pass: %d hunks in %.2fms', #deferred_syntax, (vim.uv.hrtime() - t1) / 1e6)

View file

@ -1249,6 +1249,123 @@ describe('highlight', function()
end
delete_buffer(bufnr)
end)
it('two-pass rendering produces no duplicate extmarks', function()
vim.api.nvim_set_hl(0, 'DiffsAddText', { bg = 0x00FF00 })
vim.api.nvim_set_hl(0, 'DiffsDeleteText', { bg = 0xFF0000 })
vim.api.nvim_set_hl(0, 'DiffsAddNr', { fg = 0x80c080, bg = 0x2e4a3a })
vim.api.nvim_set_hl(0, 'DiffsDeleteNr', { fg = 0xc08080, bg = 0x4a2e3a })
local bufnr = create_buffer({
'@@ -1,2 +1,2 @@',
'-local x = 1',
'+local x = 2',
})
local hunk = {
filename = 'test.lua',
lang = 'lua',
start_line = 1,
lines = { '-local x = 1', '+local x = 2' },
}
local fast = default_opts({
highlights = {
treesitter = { enabled = false },
background = true,
gutter = true,
intra = { enabled = true, algorithm = 'default', max_lines = 500 },
},
})
local syntax = default_opts({
highlights = {
treesitter = { enabled = true },
background = true,
gutter = true,
intra = { enabled = true, algorithm = 'default', max_lines = 500 },
},
})
syntax.syntax_only = true
highlight.highlight_hunk(bufnr, ns, hunk, fast)
highlight.highlight_hunk(bufnr, ns, hunk, syntax)
local extmarks = get_extmarks(bufnr)
for row = 1, 2 do
local line_hl_count = 0
local number_hl_count = 0
local intra_count = 0
for _, mark in ipairs(extmarks) do
if mark[2] == row then
local d = mark[4]
if d.line_hl_group then
line_hl_count = line_hl_count + 1
end
if d.number_hl_group then
number_hl_count = number_hl_count + 1
end
if d.hl_group == 'DiffsAddText' or d.hl_group == 'DiffsDeleteText' then
intra_count = intra_count + 1
end
end
end
assert.are.equal(1, line_hl_count, 'row ' .. row .. ' has duplicate line_hl_group')
assert.are.equal(1, number_hl_count, 'row ' .. row .. ' has duplicate number_hl_group')
assert.is_true(intra_count <= 1, 'row ' .. row .. ' has duplicate intra extmarks')
end
delete_buffer(bufnr)
end)
it('syntax_only pass adds treesitter without duplicating backgrounds', function()
local bufnr = create_buffer({
'@@ -1,2 +1,3 @@',
' local x = 1',
'+local y = 2',
' return x',
})
local hunk = {
filename = 'test.lua',
lang = 'lua',
start_line = 1,
lines = { ' local x = 1', '+local y = 2', ' return x' },
}
local fast = default_opts({
highlights = {
treesitter = { enabled = false },
background = true,
},
})
local syntax = default_opts({
highlights = {
treesitter = { enabled = true },
background = true,
},
})
syntax.syntax_only = true
highlight.highlight_hunk(bufnr, ns, hunk, fast)
highlight.highlight_hunk(bufnr, ns, hunk, syntax)
local extmarks = get_extmarks(bufnr)
local has_ts = false
local line_hl_count = 0
for _, mark in ipairs(extmarks) do
local d = mark[4]
if d and d.hl_group and d.hl_group:match('^@.*%.lua$') then
has_ts = true
end
if d and d.line_hl_group then
line_hl_count = line_hl_count + 1
end
end
assert.is_true(has_ts)
assert.are.equal(1, line_hl_count)
delete_buffer(bufnr)
end)
end)
describe('diff header highlighting', function()