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feat: treesitter highlighting for diff headers

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Apply treesitter highlighting to diff metadata lines (diff --git, index,
---, +++) using the diff language parser. Header info is attached only
to the first hunk of each file to avoid duplicate highlighting.

Based on PR #52 by @phanen with fixes:
- header_lines now only contains diff metadata, not hunk content
- header info attached only to first hunk per file
- removed arbitrary hunk count restriction
This commit is contained in:
Barrett Ruth 2026-02-04 14:49:27 -05:00
parent 4008df3558
commit a25f1e9d84
7 changed files with 292 additions and 5 deletions
Download patch file Download diff file Expand all files Collapse all files

8
.github/workflows/test.yaml vendored
View file

@ -20,3 +20,11 @@ jobs:
- uses: nvim-neorocks/nvim-busted-action@v1
with:
nvim_version: ${{ matrix.nvim }}
before: |
git clone --depth 1 https://github.com/the-mikedavis/tree-sitter-diff /tmp/tree-sitter-diff
cd /tmp/tree-sitter-diff && cc -shared -fPIC -o diff.so -I./src src/parser.c
PARSER_DIR=$(nvim --headless -c 'lua print(vim.fn.stdpath("data") .. "/site/parser")' -c 'q' 2>&1 | tail -1)
echo "Installing parser to: $PARSER_DIR"
mkdir -p "$PARSER_DIR"
cp diff.so "$PARSER_DIR/"
nvim --headless -c 'lua print("diff parser available:", pcall(vim.treesitter.language.inspect, "diff"))' -c 'q'

2
README.md
View file

@ -10,6 +10,7 @@ syntax highlighting.
## Features
- Treesitter syntax highlighting in `:Git` diffs and commit views
- Diff header highlighting (`diff --git`, `index`, `---`, `+++`)
- `:Gdiffsplit` / `:Gvdiffsplit` syntax through diff backgrounds
- Background-only diff colors for any `&diff` buffer (`:diffthis`, `vimdiff`)
- Vim syntax fallback for languages without a treesitter parser
@ -66,3 +67,4 @@ luarocks install diffs.nvim
- [`vim-fugitive`](https://github.com/tpope/vim-fugitive)
- [`codediff.nvim`](https://github.com/esmuellert/codediff.nvim)
- [`diffview.nvim`](https://github.com/sindrets/diffview.nvim)
- [@phanen](https://github.com/phanen) - diff header highlighting

9
doc/diffs.nvim.txt
View file

@ -12,6 +12,7 @@ built-in diff mode.
Features: ~
- Syntax highlighting in |:Git| summary diffs and commit detail views
- Diff header highlighting (`diff --git`, `index`, `---`, `+++`)
- Syntax highlighting in |:Gdiffsplit| / |:Gvdiffsplit| side-by-side diffs
- Background-only diff colors for any `&diff` buffer (vimdiff, diffthis, etc.)
- Vim syntax fallback for languages without a treesitter parser
@ -296,5 +297,13 @@ Checks performed:
- Neovim version >= 0.9.0
- vim-fugitive is installed (optional)
==============================================================================
ACKNOWLEDGEMENTS *diffs-acknowledgements*
- vim-fugitive (https://github.com/tpope/vim-fugitive)
- codediff.nvim (https://github.com/esmuellert/codediff.nvim)
- diffview.nvim (https://github.com/sindrets/diffview.nvim)
- @phanen (https://github.com/phanen) - diff header highlighting
==============================================================================
vim:tw=78:ts=8:ft=help:norl:

25
lua/diffs/highlight.lua
View file

@ -57,8 +57,9 @@ end
---@param ns integer
---@param hunk diffs.Hunk
---@param code_lines string[]
---@param col_offset integer?
---@return integer
local function highlight_treesitter(bufnr, ns, hunk, code_lines)
local function highlight_treesitter(bufnr, ns, hunk, code_lines, col_offset)
local lang = hunk.lang
if not lang then
return 0
@ -101,6 +102,8 @@ local function highlight_treesitter(bufnr, ns, hunk, code_lines)
end
end
col_offset = col_offset or 1
local extmark_count = 0
for id, node, _ in query:iter_captures(trees[1]:root(), code) do
local capture_name = '@' .. query.captures[id]
@ -108,8 +111,8 @@ local function highlight_treesitter(bufnr, ns, hunk, code_lines)
local buf_sr = hunk.start_line + sr
local buf_er = hunk.start_line + er
local buf_sc = sc + 1
local buf_ec = ec + 1
local buf_sc = sc + col_offset
local buf_ec = ec + col_offset
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_sr, buf_sc, {
end_row = buf_er,
@ -257,6 +260,22 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
extmark_count = highlight_vim_syntax(bufnr, ns, hunk, code_lines)
end
if
hunk.header_start_line
and hunk.header_lines
and #hunk.header_lines > 0
and opts.highlights.treesitter.enabled
then
extmark_count = extmark_count
+ highlight_treesitter(bufnr, ns, {
filename = hunk.filename,
start_line = hunk.header_start_line - 1,
lang = 'diff',
lines = hunk.header_lines,
header_lines = {},
}, hunk.header_lines, 0)
end
local syntax_applied = extmark_count > 0
for i, line in ipairs(hunk.lines) do

27
lua/diffs/parser.lua
View file

@ -6,6 +6,8 @@
---@field header_context string?
---@field header_context_col integer?
---@field lines string[]
---@field header_start_line integer?
---@field header_lines string[]?
local M = {}
@ -58,10 +60,16 @@ function M.parse_buffer(bufnr)
local hunk_header_context_col = nil
---@type string[]
local hunk_lines = {}
---@type integer?
local hunk_count = nil
---@type integer?
local header_start = nil
---@type string[]
local header_lines = {}
local function flush_hunk()
if hunk_start and #hunk_lines > 0 and (current_lang or current_ft) then
table.insert(hunks, {
local hunk = {
filename = current_filename,
ft = current_ft,
lang = current_lang,
@ -69,7 +77,12 @@ function M.parse_buffer(bufnr)
header_context = hunk_header_context,
header_context_col = hunk_header_context_col,
lines = hunk_lines,
})
}
if hunk_count == 1 and header_start and #header_lines > 0 then
hunk.header_start_line = header_start
hunk.header_lines = header_lines
end
table.insert(hunks, hunk)
end
hunk_start = nil
hunk_header_context = nil
@ -89,6 +102,9 @@ function M.parse_buffer(bufnr)
elseif current_ft then
dbg('file: %s -> ft: %s (no ts parser)', filename, current_ft)
end
hunk_count = 0
header_start = i
header_lines = {}
elseif line:match('^@@.-@@') then
flush_hunk()
hunk_start = i
@ -97,6 +113,9 @@ function M.parse_buffer(bufnr)
hunk_header_context = context
hunk_header_context_col = #prefix
end
if hunk_count then
hunk_count = hunk_count + 1
end
elseif hunk_start then
local prefix = line:sub(1, 1)
if prefix == ' ' or prefix == '+' or prefix == '-' then
@ -112,8 +131,12 @@ function M.parse_buffer(bufnr)
current_filename = nil
current_ft = nil
current_lang = nil
header_start = nil
end
end
if header_start and not hunk_start then
table.insert(header_lines, line)
end
end
flush_hunk()

156
spec/highlight_spec.lua
View file

@ -729,6 +729,162 @@ describe('highlight', function()
end)
end)
describe('diff header highlighting', function()
local ns
before_each(function()
ns = vim.api.nvim_create_namespace('diffs_test_header')
end)
local function create_buffer(lines)
local bufnr = vim.api.nvim_create_buf(false, true)
vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines)
return bufnr
end
local function delete_buffer(bufnr)
if vim.api.nvim_buf_is_valid(bufnr) then
vim.api.nvim_buf_delete(bufnr, { force = true })
end
end
local function get_extmarks(bufnr)
return vim.api.nvim_buf_get_extmarks(bufnr, ns, 0, -1, { details = true })
end
local function default_opts()
return {
hide_prefix = false,
highlights = {
background = false,
gutter = false,
treesitter = { enabled = true, max_lines = 500 },
vim = { enabled = false, max_lines = 200 },
},
}
end
it('applies treesitter extmarks to diff header lines', function()
local bufnr = create_buffer({
'diff --git a/parser.lua b/parser.lua',
'index 3e8afa0..018159c 100644',
'--- a/parser.lua',
'+++ b/parser.lua',
'@@ -1,2 +1,3 @@',
' local M = {}',
'+local x = 1',
})
local hunk = {
filename = 'parser.lua',
lang = 'lua',
start_line = 5,
lines = { ' local M = {}', '+local x = 1' },
header_start_line = 1,
header_lines = {
'diff --git a/parser.lua b/parser.lua',
'index 3e8afa0..018159c 100644',
'--- a/parser.lua',
'+++ b/parser.lua',
},
}
highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
local extmarks = get_extmarks(bufnr)
local header_extmarks = {}
for _, mark in ipairs(extmarks) do
if mark[2] < 4 and mark[4] and mark[4].hl_group then
table.insert(header_extmarks, mark)
end
end
assert.is_true(#header_extmarks > 0)
local has_function_hl = false
local has_keyword_hl = false
for _, mark in ipairs(header_extmarks) do
local hl = mark[4].hl_group
if hl == '@function' or hl == '@function.diff' then
has_function_hl = true
end
if hl == '@keyword' or hl == '@keyword.diff' then
has_keyword_hl = true
end
end
assert.is_true(has_function_hl or has_keyword_hl)
delete_buffer(bufnr)
end)
it('does not apply header highlights when header_lines missing', function()
local bufnr = create_buffer({
'@@ -1,2 +1,3 @@',
' local M = {}',
'+local x = 1',
})
local hunk = {
filename = 'parser.lua',
lang = 'lua',
start_line = 1,
lines = { ' local M = {}', '+local x = 1' },
}
highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
local extmarks = get_extmarks(bufnr)
local header_extmarks = 0
for _, mark in ipairs(extmarks) do
if mark[2] < 0 and mark[4] and mark[4].hl_group then
header_extmarks = header_extmarks + 1
end
end
assert.are.equal(0, header_extmarks)
delete_buffer(bufnr)
end)
it('does not apply header highlights when treesitter disabled', function()
local bufnr = create_buffer({
'diff --git a/parser.lua b/parser.lua',
'index 3e8afa0..018159c 100644',
'--- a/parser.lua',
'+++ b/parser.lua',
'@@ -1,2 +1,3 @@',
' local M = {}',
'+local x = 1',
})
local hunk = {
filename = 'parser.lua',
lang = 'lua',
start_line = 5,
lines = { ' local M = {}', '+local x = 1' },
header_start_line = 1,
header_lines = {
'diff --git a/parser.lua b/parser.lua',
'index 3e8afa0..018159c 100644',
'--- a/parser.lua',
'+++ b/parser.lua',
},
}
local opts = default_opts()
opts.highlights.treesitter.enabled = false
highlight.highlight_hunk(bufnr, ns, hunk, opts)
local extmarks = get_extmarks(bufnr)
local header_extmarks = 0
for _, mark in ipairs(extmarks) do
if mark[2] < 4 and mark[4] and mark[4].hl_group and mark[4].hl_group:match('^@') then
header_extmarks = header_extmarks + 1
end
end
assert.are.equal(0, header_extmarks)
delete_buffer(bufnr)
end)
end)
describe('coalesce_syntax_spans', function()
it('coalesces adjacent chars with same hl group', function()
local function query_fn(_line, _col)

70
spec/parser_spec.lua
View file

@ -215,5 +215,75 @@ describe('parser', function()
assert.are.equal(1, #hunks[2].lines)
delete_buffer(bufnr)
end)
it('attaches header_lines to first hunk only', function()
local bufnr = create_buffer({
'diff --git a/parser.lua b/parser.lua',
'index 3e8afa0..018159c 100644',
'--- a/parser.lua',
'+++ b/parser.lua',
'@@ -1,2 +1,3 @@',
' local M = {}',
'+local x = 1',
'@@ -10,2 +11,3 @@',
' function M.foo()',
'+ return true',
' end',
})
local hunks = parser.parse_buffer(bufnr)
assert.are.equal(2, #hunks)
assert.is_not_nil(hunks[1].header_start_line)
assert.is_not_nil(hunks[1].header_lines)
assert.are.equal(1, hunks[1].header_start_line)
assert.is_nil(hunks[2].header_start_line)
assert.is_nil(hunks[2].header_lines)
delete_buffer(bufnr)
end)
it('header_lines contains only diff metadata, not hunk content', function()
local bufnr = create_buffer({
'diff --git a/parser.lua b/parser.lua',
'index 3e8afa0..018159c 100644',
'--- a/parser.lua',
'+++ b/parser.lua',
'@@ -1,2 +1,3 @@',
' local M = {}',
'+local x = 1',
})
local hunks = parser.parse_buffer(bufnr)
assert.are.equal(1, #hunks)
assert.are.equal(4, #hunks[1].header_lines)
assert.are.equal('diff --git a/parser.lua b/parser.lua', hunks[1].header_lines[1])
assert.are.equal('index 3e8afa0..018159c 100644', hunks[1].header_lines[2])
assert.are.equal('--- a/parser.lua', hunks[1].header_lines[3])
assert.are.equal('+++ b/parser.lua', hunks[1].header_lines[4])
delete_buffer(bufnr)
end)
it('handles fugitive status format with diff headers', function()
local bufnr = create_buffer({
'Head: main',
'Push: origin/main',
'',
'Unstaged (1)',
'M parser.lua',
'diff --git a/parser.lua b/parser.lua',
'index 3e8afa0..018159c 100644',
'--- a/parser.lua',
'+++ b/parser.lua',
'@@ -1,2 +1,3 @@',
' local M = {}',
'+local x = 1',
})
local hunks = parser.parse_buffer(bufnr)
assert.are.equal(1, #hunks)
assert.are.equal(6, hunks[1].header_start_line)
assert.are.equal(4, #hunks[1].header_lines)
assert.are.equal('diff --git a/parser.lua b/parser.lua', hunks[1].header_lines[1])
delete_buffer(bufnr)
end)
end)
end)