barrett/diffs.nvim
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feat(highlight): add treesitter context padding from disk

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Problem: treesitter parses each diff hunk in isolation, so incomplete
syntax constructs at hunk boundaries (e.g., a function definition with
no body) produce ERROR nodes and drop captures.

Solution: read N lines from the on-disk file before/after each hunk and
prepend/append them as unmapped padding lines. The line_map guard in
highlight_treesitter skips extmarks for unmapped lines, so padding
provides syntax context without visual output. Controlled by
highlights.context (default 25, 0 to disable). Also applies to the vim
syntax fallback path via a leading_offset filter.
This commit is contained in:
Barrett Ruth 2026-02-07 13:05:53 -05:00
parent ba1f830629
commit 2e1ebdee03
7 changed files with 308 additions and 24 deletions
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29
lua/diffs/parser.lua
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@ -8,6 +8,11 @@
---@field lines string[]
---@field header_start_line integer?
---@field header_lines string[]?
---@field file_old_start integer?
---@field file_old_count integer?
---@field file_new_start integer?
---@field file_new_count integer?
---@field repo_root string?
local M = {}
@ -132,6 +137,14 @@ function M.parse_buffer(bufnr)
local header_start = nil
---@type string[]
local header_lines = {}
---@type integer?
local file_old_start = nil
---@type integer?
local file_old_count = nil
---@type integer?
local file_new_start = nil
---@type integer?
local file_new_count = nil
local function flush_hunk()
if hunk_start and #hunk_lines > 0 then
@ -143,6 +156,11 @@ function M.parse_buffer(bufnr)
header_context = hunk_header_context,
header_context_col = hunk_header_context_col,
lines = hunk_lines,
file_old_start = file_old_start,
file_old_count = file_old_count,
file_new_start = file_new_start,
file_new_count = file_new_count,
repo_root = repo_root,
}
if hunk_count == 1 and header_start and #header_lines > 0 then
hunk.header_start_line = header_start
@ -154,6 +172,10 @@ function M.parse_buffer(bufnr)
hunk_header_context = nil
hunk_header_context_col = nil
hunk_lines = {}
file_old_start = nil
file_old_count = nil
file_new_start = nil
file_new_count = nil
end
for i, line in ipairs(lines) do
@ -174,6 +196,13 @@ function M.parse_buffer(bufnr)
elseif line:match('^@@.-@@') then
flush_hunk()
hunk_start = i
local hs, hc, hs2, hc2 = line:match('^@@ %-(%d+),?(%d*) %+(%d+),?(%d*) @@')
if hs then
file_old_start = tonumber(hs)
file_old_count = tonumber(hc) or 1
file_new_start = tonumber(hs2)
file_new_count = tonumber(hc2) or 1
end
local prefix, context = line:match('^(@@.-@@%s*)(.*)')
if context and context ~= '' then
hunk_header_context = context