From 2535aea207faf590512bdb7d332b0440948b7043 Mon Sep 17 00:00:00 2001
From: Barrett Ruth <br.barrettruth@gmail.com>
Date: Thu, 19 Mar 2026 20:00:44 -0400
Subject: [PATCH 1/2] fix(highlight): use file context for header text
 treesitter parsing

Problem: the `@@ ... @@ end` header context text was parsed by
treesitter in isolation. Without surrounding code, tokens like `end`
produce ERROR nodes and get no highlight captures.

Solution: prepend `hunk.context_before` lines (already computed by
`compute_hunk_context`) to give the treesitter string parser enough
scope to recognize keywords, closing delimiters, etc. Only captures
on the target row produce extmarks.
---
 lua/diffs/highlight.lua | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/lua/diffs/highlight.lua b/lua/diffs/highlight.lua
index 806f782..325a588 100644
--- a/lua/diffs/highlight.lua
+++ b/lua/diffs/highlight.lua
@@ -11,12 +11,20 @@ local diff = require('diffs.diff')
 ---@param lang string
 ---@param context_lines? string[]
 ---@param priorities diffs.PrioritiesConfig
+---@param context_before? string[]
 ---@return integer
-local function highlight_text(bufnr, ns, hunk, col_offset, text, lang, context_lines, priorities)
-  local parse_text = text
+local function highlight_text(bufnr, ns, hunk, col_offset, text, lang, context_lines, priorities, context_before)
+  local prefix_count = 0
+  local parts = {}
+  if context_before and #context_before > 0 then
+    prefix_count = #context_before
+    parts[#parts + 1] = table.concat(context_before, '\n')
+  end
+  parts[#parts + 1] = text
   if context_lines and #context_lines > 0 then
-    parse_text = text .. '\n' .. table.concat(context_lines, '\n')
+    parts[#parts + 1] = table.concat(context_lines, '\n')
   end
+  local parse_text = table.concat(parts, '\n')
 
   local ok, parser_obj = pcall(vim.treesitter.get_string_parser, parse_text, lang)
   if not ok or not parser_obj then
@@ -35,10 +43,11 @@ local function highlight_text(bufnr, ns, hunk, col_offset, text, lang, context_l
 
   local extmark_count = 0
   local header_line = hunk.start_line - 1
+  local target_row = prefix_count
 
   for id, node, metadata in query:iter_captures(trees[1]:root(), parse_text) do
     local sr, sc, _, ec = node:range()
-    if sr == 0 then
+    if sr == target_row then
       local capture_name = '@' .. query.captures[id] .. '.' .. lang
 
       local buf_sr = header_line
@@ -412,7 +421,8 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
         hunk.header_context,
         hunk.lang,
         new_code,
-        p
+        p,
+        hunk.context_before
       )
       if header_extmarks > 0 then
         dbg('header %s:%d applied %d extmarks', hunk.filename, hunk.start_line, header_extmarks)

From 961037d0e50e57f1a6510e59e446c24c106e636b Mon Sep 17 00:00:00 2001
From: Barrett Ruth <br.barrettruth@gmail.com>
Date: Thu, 19 Mar 2026 20:23:04 -0400
Subject: [PATCH 2/2] ci: format

---
 lua/diffs/highlight.lua | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/lua/diffs/highlight.lua b/lua/diffs/highlight.lua
index 325a588..cbb544e 100644
--- a/lua/diffs/highlight.lua
+++ b/lua/diffs/highlight.lua
@@ -13,7 +13,17 @@ local diff = require('diffs.diff')
 ---@param priorities diffs.PrioritiesConfig
 ---@param context_before? string[]
 ---@return integer
-local function highlight_text(bufnr, ns, hunk, col_offset, text, lang, context_lines, priorities, context_before)
+local function highlight_text(
+  bufnr,
+  ns,
+  hunk,
+  col_offset,
+  text,
+  lang,
+  context_lines,
+  priorities,
+  context_before
+)
   local prefix_count = 0
   local parts = {}
   if context_before and #context_before > 0 then