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

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Problem: the deferred pass (pass 2) cleared the hunk range and called
`highlight_hunk` with full opts, reapplying line backgrounds, intra-line
diffs, prefix DiffsClear, and per-char prefix highlights that pass 1
already set. This doubled extmark counts on affected lines.

Solution: add `syntax_only` flag to `diffs.HunkOpts`. When set,
`highlight_hunk` skips non-syntax extmarks (line backgrounds, intra-line,
prefix DiffsClear, per-char prefix fg, hide_prefix overlay, conflict
markers). The deferred pass uses `syntax_only = true` and no longer
clears the namespace range, so pass 1's extmarks persist while pass 2
layers treesitter and content DiffsClear on top.
This commit is contained in:
Barrett Ruth 2026-03-05 01:27:00 -05:00
parent 91a856443f
commit a26e9a522c
3 changed files with 200 additions and 79 deletions
Download patch file Download diff file Expand all files Collapse all files

117
spec/highlight_spec.lua
View file

@ -1251,6 +1251,123 @@ 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()