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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

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)