doc/diffs.nvim.txt

@@ -225,20 +225,16 @@ Configuration is done via `vim.g.diffs`. Set this before the plugin loads:
                                                       *diffs.ContextConfig*
     Context config fields: ~
         {enabled}            (boolean, default: true)
-                             Read surrounding code from the working tree
-                             file and feed it into the treesitter string
-                             parser. Uses the hunk's `@@ +start,count @@`
-                             line numbers to read lines before and after
-                             the hunk from disk. Improves syntax accuracy
-                             when the hunk is inside an incomplete construct
-                             (e.g., a table literal or function body whose
-                             opening is not visible in the hunk's own
-                             context lines).
+                             Read lines from disk before and after each hunk
+                             to provide surrounding syntax context. Improves
+                             accuracy at hunk boundaries where incomplete
+                             constructs (e.g., a function definition with no
+                             body) would otherwise confuse the parser.
 
         {lines}              (integer, default: 25)
-                             Max context lines to read in each direction.
-                             Files are read once per parse and cached across
-                             hunks in the same file.
+                             Number of context lines to read in each
+                             direction. Lines are read with early exit —
+                             cost scales with this value, not file size.
 
                                                    *diffs.PrioritiesConfig*
     Priorities config fields: ~
@@ -697,14 +693,10 @@ KNOWN LIMITATIONS                                       *diffs-limitations*
 
 Incomplete Syntax Context ~
                                                       *diffs-syntax-context*
-Treesitter parses each diff hunk in isolation. When `highlights.context` is
-enabled (the default), surrounding code is read from the working tree file
-and fed into the parser to improve accuracy at hunk boundaries. This helps
-when a hunk is inside a table, function body, or loop whose opening is
-beyond the hunk's own context lines. Requires `repo_root` and
-`file_new_start` to be available on the hunk (true for standard unified
-diffs). In rare cases, hunks that start or end mid-expression may still
-produce imperfect highlights due to treesitter error recovery.
+Treesitter parses each diff hunk in isolation. Context lines within the hunk
+(lines with a ` ` prefix) provide syntactic context for the parser. In rare
+cases, hunks that start or end mid-expression may produce imperfect highlights
+due to treesitter error recovery.
 
 Syntax Highlighting Flash ~
                                                              *diffs-flash*

lua/diffs/highlight.lua

@@ -67,10 +67,6 @@ end
 ---@field defer_vim_syntax? boolean
 ---@field syntax_only? boolean
 
----@class diffs.TSContext
----@field before string[]?
----@field after string[]?
-
 ---@param bufnr integer
 ---@param ns integer
 ---@param code_lines string[]
@@ -80,7 +76,6 @@ end
 ---@param covered_lines? table<integer, true>
 ---@param priorities diffs.PrioritiesConfig
 ---@param force_high_priority? boolean
----@param context? diffs.TSContext
 ---@return integer
 local function highlight_treesitter(
   bufnr,
@@ -91,34 +86,9 @@ local function highlight_treesitter(
   col_offset,
   covered_lines,
   priorities,
-  force_high_priority,
-  context
+  force_high_priority
 )
-  local prefix_count = 0
-  local parse_lines = code_lines
-  if context then
-    local before = context.before
-    local after = context.after
-    if (before and #before > 0) or (after and #after > 0) then
-      parse_lines = {}
-      if before then
-        prefix_count = #before
-        for _, l in ipairs(before) do
-          parse_lines[#parse_lines + 1] = l
-        end
-      end
-      for _, l in ipairs(code_lines) do
-        parse_lines[#parse_lines + 1] = l
-      end
-      if after then
-        for _, l in ipairs(after) do
-          parse_lines[#parse_lines + 1] = l
-        end
-      end
-    end
-  end
-
-  local code = table.concat(parse_lines, '\n')
+  local code = table.concat(code_lines, '\n')
   if code == '' then
     return 0
   end
@@ -148,8 +118,6 @@ local function highlight_treesitter(
       if capture ~= 'spell' and capture ~= 'nospell' then
         local capture_name = '@' .. capture .. '.' .. tree_lang
         local sr, sc, er, ec = node:range()
-        sr = sr - prefix_count
-        er = er - prefix_count
 
         local buf_sr = line_map[sr]
         if buf_sr then
@@ -361,36 +329,10 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
       end
     end
 
-    local ts_context = nil
-    if opts.highlights.context.enabled and (hunk.context_before or hunk.context_after) then
-      ts_context = { before = hunk.context_before, after = hunk.context_after }
-    end
-
-    extmark_count = highlight_treesitter(
-      bufnr,
-      ns,
-      new_code,
-      hunk.lang,
-      new_map,
-      pw + qw,
-      covered_lines,
-      p,
-      nil,
-      ts_context
-    )
+    extmark_count =
+      highlight_treesitter(bufnr, ns, new_code, hunk.lang, new_map, pw + qw, covered_lines, p)
     extmark_count = extmark_count
-      + highlight_treesitter(
-        bufnr,
-        ns,
-        old_code,
-        hunk.lang,
-        old_map,
-        pw + qw,
-        covered_lines,
-        p,
-        nil,
-        ts_context
-      )
+      + highlight_treesitter(bufnr, ns, old_code, hunk.lang, old_map, pw + qw, covered_lines, p)
 
     if hunk.header_context and hunk.header_context_col then
       local header_extmarks = highlight_text(

lua/diffs/init.lua

@@ -297,69 +297,6 @@ local function carry_forward_highlighted(old_entry, new_hunks)
   return highlighted
 end
 
----@param path string
----@return string[]?
-local function read_file_lines(path)
-  local f = io.open(path, 'r')
-  if not f then
-    return nil
-  end
-  local lines = {}
-  for line in f:lines() do
-    lines[#lines + 1] = line
-  end
-  f:close()
-  return lines
-end
-
----@param hunks diffs.Hunk[]
----@param max_lines integer
-local function compute_hunk_context(hunks, max_lines)
-  ---@type table<string, string[]|false>
-  local file_cache = {}
-
-  for _, hunk in ipairs(hunks) do
-    if not hunk.repo_root or not hunk.filename or not hunk.file_new_start then
-      goto continue
-    end
-
-    local path = vim.fs.joinpath(hunk.repo_root, hunk.filename)
-    local file_lines = file_cache[path]
-    if file_lines == nil then
-      file_lines = read_file_lines(path) or false
-      file_cache[path] = file_lines
-    end
-    if not file_lines then
-      goto continue
-    end
-
-    local new_start = hunk.file_new_start
-    local new_count = hunk.file_new_count or 0
-    local total = #file_lines
-
-    local before_start = math.max(1, new_start - max_lines)
-    if before_start < new_start then
-      local before = {}
-      for i = before_start, new_start - 1 do
-        before[#before + 1] = file_lines[i]
-      end
-      hunk.context_before = before
-    end
-
-    local after_start = new_start + new_count
-    local after_end = math.min(total, after_start + max_lines - 1)
-    if after_start <= total then
-      local after = {}
-      for i = after_start, after_end do
-        after[#after + 1] = file_lines[i]
-      end
-      hunk.context_after = after
-    end
-
-    ::continue::
-  end
-end
-
 ---@param bufnr integer
 local function ensure_cache(bufnr)
   if not vim.api.nvim_buf_is_valid(bufnr) then
@@ -384,9 +321,6 @@ local function ensure_cache(bufnr)
   local lc = vim.api.nvim_buf_line_count(bufnr)
   local bc = vim.api.nvim_buf_get_offset(bufnr, lc)
   dbg('parsed %d hunks in buffer %d (tick %d)', #hunks, bufnr, tick)
-  if config.highlights.context.enabled then
-    compute_hunk_context(hunks, config.highlights.context.lines)
-  end
   local carried = entry and not entry.pending_clear and carry_forward_highlighted(entry, hunks)
   hunk_cache[bufnr] = {
     hunks = hunks,
@@ -1007,7 +941,6 @@ M._test = {
   hunks_eq = hunks_eq,
   process_pending_clear = process_pending_clear,
   ft_retry_pending = ft_retry_pending,
-  compute_hunk_context = compute_hunk_context,
 }
 
 return M

lua/diffs/parser.lua

@@ -15,8 +15,6 @@
 ---@field prefix_width integer
 ---@field quote_width integer
 ---@field repo_root string?
----@field context_before string[]?
----@field context_after string[]?
 
 local M = {}
 

spec/context_spec.lua

@@ -1,382 +0,0 @@
-require('spec.helpers')
-local diffs = require('diffs')
-local highlight = require('diffs.highlight')
-local compute_hunk_context = diffs._test.compute_hunk_context
-
-describe('context', function()
-  describe('compute_hunk_context', function()
-    local tmpdir
-
-    before_each(function()
-      tmpdir = vim.fn.tempname()
-      vim.fn.mkdir(tmpdir, 'p')
-    end)
-
-    after_each(function()
-      vim.fn.delete(tmpdir, 'rf')
-    end)
-
-    local function write_file(filename, lines)
-      local path = vim.fs.joinpath(tmpdir, filename)
-      local dir = vim.fn.fnamemodify(path, ':h')
-      if vim.fn.isdirectory(dir) == 0 then
-        vim.fn.mkdir(dir, 'p')
-      end
-      local f = io.open(path, 'w')
-      f:write(table.concat(lines, '\n') .. '\n')
-      f:close()
-    end
-
-    local function make_hunk(filename, opts)
-      return {
-        filename = filename,
-        ft = 'lua',
-        lang = 'lua',
-        start_line = opts.start_line or 1,
-        lines = opts.lines,
-        prefix_width = opts.prefix_width or 1,
-        quote_width = 0,
-        repo_root = tmpdir,
-        file_new_start = opts.file_new_start,
-        file_new_count = opts.file_new_count,
-      }
-    end
-
-    it('reads context_before from file lines preceding the hunk', function()
-      write_file('a.lua', {
-        'local M = {}',
-        'function M.foo()',
-        '  local x = 1',
-        '  local y = 2',
-        'end',
-        'return M',
-      })
-
-      local hunks = {
-        make_hunk('a.lua', {
-          file_new_start = 3,
-          file_new_count = 3,
-          lines = { ' local x = 1', '+local new = true', ' local y = 2' },
-        }),
-      }
-      compute_hunk_context(hunks, 25)
-
-      assert.same({ 'local M = {}', 'function M.foo()' }, hunks[1].context_before)
-    end)
-
-    it('reads context_after from file lines following the hunk', function()
-      write_file('a.lua', {
-        'local M = {}',
-        'function M.foo()',
-        '  local x = 1',
-        'end',
-        'return M',
-      })
-
-      local hunks = {
-        make_hunk('a.lua', {
-          file_new_start = 2,
-          file_new_count = 2,
-          lines = { ' function M.foo()', '+  local x = 1' },
-        }),
-      }
-      compute_hunk_context(hunks, 25)
-
-      assert.same({ 'end', 'return M' }, hunks[1].context_after)
-    end)
-
-    it('caps context_before to max_lines', function()
-      write_file('a.lua', {
-        'line1',
-        'line2',
-        'line3',
-        'line4',
-        'line5',
-        'target',
-      })
-
-      local hunks = {
-        make_hunk('a.lua', {
-          file_new_start = 6,
-          file_new_count = 1,
-          lines = { '+target' },
-        }),
-      }
-      compute_hunk_context(hunks, 2)
-
-      assert.same({ 'line4', 'line5' }, hunks[1].context_before)
-    end)
-
-    it('caps context_after to max_lines', function()
-      write_file('a.lua', {
-        'target',
-        'after1',
-        'after2',
-        'after3',
-        'after4',
-      })
-
-      local hunks = {
-        make_hunk('a.lua', {
-          file_new_start = 1,
-          file_new_count = 1,
-          lines = { '+target' },
-        }),
-      }
-      compute_hunk_context(hunks, 2)
-
-      assert.same({ 'after1', 'after2' }, hunks[1].context_after)
-    end)
-
-    it('skips hunks without file_new_start', function()
-      write_file('a.lua', { 'line1', 'line2' })
-
-      local hunks = {
-        make_hunk('a.lua', {
-          file_new_start = nil,
-          file_new_count = nil,
-          lines = { '+something' },
-        }),
-      }
-      compute_hunk_context(hunks, 25)
-
-      assert.is_nil(hunks[1].context_before)
-      assert.is_nil(hunks[1].context_after)
-    end)
-
-    it('skips hunks without repo_root', function()
-      local hunks = {
-        {
-          filename = 'a.lua',
-          ft = 'lua',
-          lang = 'lua',
-          start_line = 1,
-          lines = { '+x' },
-          prefix_width = 1,
-          quote_width = 0,
-          repo_root = nil,
-          file_new_start = 1,
-          file_new_count = 1,
-        },
-      }
-      compute_hunk_context(hunks, 25)
-
-      assert.is_nil(hunks[1].context_before)
-      assert.is_nil(hunks[1].context_after)
-    end)
-
-    it('skips when file does not exist on disk', function()
-      local hunks = {
-        make_hunk('nonexistent.lua', {
-          file_new_start = 1,
-          file_new_count = 1,
-          lines = { '+x' },
-        }),
-      }
-      compute_hunk_context(hunks, 25)
-
-      assert.is_nil(hunks[1].context_before)
-      assert.is_nil(hunks[1].context_after)
-    end)
-
-    it('returns nil context_before for hunk at line 1', function()
-      write_file('a.lua', { 'first', 'second' })
-
-      local hunks = {
-        make_hunk('a.lua', {
-          file_new_start = 1,
-          file_new_count = 1,
-          lines = { '+first' },
-        }),
-      }
-      compute_hunk_context(hunks, 25)
-
-      assert.is_nil(hunks[1].context_before)
-    end)
-
-    it('returns nil context_after for hunk at end of file', function()
-      write_file('a.lua', { 'first', 'last' })
-
-      local hunks = {
-        make_hunk('a.lua', {
-          file_new_start = 1,
-          file_new_count = 2,
-          lines = { ' first', '+last' },
-        }),
-      }
-      compute_hunk_context(hunks, 25)
-
-      assert.is_nil(hunks[1].context_after)
-    end)
-
-    it('reads file once for multiple hunks in same file', function()
-      write_file('a.lua', {
-        'local M = {}',
-        'function M.foo()',
-        '  return 1',
-        'end',
-        'function M.bar()',
-        '  return 2',
-        'end',
-        'return M',
-      })
-
-      local hunks = {
-        make_hunk('a.lua', {
-          file_new_start = 2,
-          file_new_count = 3,
-          lines = { ' function M.foo()', '+  return 1', ' end' },
-        }),
-        make_hunk('a.lua', {
-          file_new_start = 5,
-          file_new_count = 3,
-          lines = { ' function M.bar()', '+  return 2', ' end' },
-        }),
-      }
-      compute_hunk_context(hunks, 25)
-
-      assert.same({ 'local M = {}' }, hunks[1].context_before)
-      assert.same({ 'function M.bar()', '  return 2', 'end', 'return M' }, hunks[1].context_after)
-      assert.same({
-        'local M = {}',
-        'function M.foo()',
-        '  return 1',
-        'end',
-      }, hunks[2].context_before)
-      assert.same({ 'return M' }, hunks[2].context_after)
-    end)
-  end)
-
-  describe('highlight_treesitter with context', function()
-    local ns
-
-    before_each(function()
-      ns = vim.api.nvim_create_namespace('diffs_context_test')
-      local normal = vim.api.nvim_get_hl(0, { name = 'Normal' })
-      vim.api.nvim_set_hl(0, 'DiffsClear', { fg = normal.fg or 0xc0c0c0 })
-    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(overrides)
-      local opts = {
-        hide_prefix = false,
-        highlights = {
-          background = false,
-          gutter = false,
-          context = { enabled = true, lines = 25 },
-          treesitter = { enabled = true, max_lines = 500 },
-          vim = { enabled = false, max_lines = 200 },
-          intra = { enabled = false, algorithm = 'default', max_lines = 500 },
-          priorities = { clear = 198, syntax = 199, line_bg = 200, char_bg = 201 },
-        },
-      }
-      if overrides then
-        if overrides.highlights then
-          opts.highlights = vim.tbl_deep_extend('force', opts.highlights, overrides.highlights)
-        end
-      end
-      return opts
-    end
-
-    it('applies extmarks only to hunk lines, not context lines', function()
-      local bufnr = create_buffer({
-        '@@ -1,2 +1,3 @@',
-        ' local x = 1',
-        ' local y = 2',
-        '+local z = 3',
-      })
-
-      local hunk = {
-        filename = 'test.lua',
-        lang = 'lua',
-        start_line = 2,
-        lines = { ' local x = 1', ' local y = 2', '+local z = 3' },
-        prefix_width = 1,
-        quote_width = 0,
-        context_before = { 'local function foo()' },
-        context_after = { 'end' },
-      }
-
-      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
-
-      local extmarks = get_extmarks(bufnr)
-      for _, mark in ipairs(extmarks) do
-        local row = mark[2]
-        assert.is_true(row >= 1 and row <= 3, 'extmark row ' .. row .. ' outside hunk range')
-      end
-      assert.is_true(#extmarks > 0)
-      delete_buffer(bufnr)
-    end)
-
-    it('does not pass context when context.enabled = false', function()
-      local bufnr = create_buffer({
-        '@@ -1,1 +1,2 @@',
-        ' local x = 1',
-        '+local y = 2',
-      })
-
-      local hunk = {
-        filename = 'test.lua',
-        lang = 'lua',
-        start_line = 2,
-        lines = { ' local x = 1', '+local y = 2' },
-        prefix_width = 1,
-        quote_width = 0,
-        context_before = { 'local function foo()' },
-        context_after = { 'end' },
-      }
-
-      local opts_enabled = default_opts({ highlights = { context = { enabled = true } } })
-      highlight.highlight_hunk(bufnr, ns, hunk, opts_enabled)
-      local extmarks_with = get_extmarks(bufnr)
-
-      vim.api.nvim_buf_clear_namespace(bufnr, ns, 0, -1)
-
-      local opts_disabled = default_opts({ highlights = { context = { enabled = false } } })
-      highlight.highlight_hunk(bufnr, ns, hunk, opts_disabled)
-      local extmarks_without = get_extmarks(bufnr)
-
-      assert.is_true(#extmarks_with > 0)
-      assert.is_true(#extmarks_without > 0)
-      delete_buffer(bufnr)
-    end)
-
-    it('skips context fields that are nil', function()
-      local bufnr = create_buffer({
-        '@@ -1,1 +1,2 @@',
-        ' local x = 1',
-        '+local y = 2',
-      })
-
-      local hunk = {
-        filename = 'test.lua',
-        lang = 'lua',
-        start_line = 2,
-        lines = { ' local x = 1', '+local y = 2' },
-        prefix_width = 1,
-        quote_width = 0,
-      }
-
-      highlight.highlight_hunk(bufnr, ns, hunk, default_opts())
-
-      local extmarks = get_extmarks(bufnr)
-      assert.is_true(#extmarks > 0)
-      delete_buffer(bufnr)
-    end)
-  end)
-end)