fix: make pre_highlight hook modifications work for hl_color and hlgroup (#294)

Author: y3owk1n

README.md

@@ -774,14 +774,12 @@ api.register_hook("pre_highlight", function(data)
 
   -- Modify the highlight color
   if data.operation == "undo" then
-    data.hl_color = { bg = "#FF0000" }
+    data.hl_color = { bg = "#FF0000" } -- Override the background color
+ -- data.hlgroup = "TermCursor" -- Use other group
+    -- Or set the highlight group directly:
+    -- vim.api.nvim_set_hl(0, "UgUndo", { bg = "#FF0000" })
   end
 end, 100) -- priority (higher = runs first)
-
--- Run after highlighting completes
-api.register_hook("post_highlight", function(data)
-  print("Highlighted:", data.operation)
-end)
 ```
 
 **Available Hooks:**
@@ -792,6 +790,12 @@ end)
 - `on_error` - Error handling
 - `pre_highlight_setup` / `post_highlight_setup` - Highlight group creation
 
+**Hook Data Modifications:**
+
+- `data.hl_color` - Override the highlight color (takes precedence over config)
+- `data.hlgroup` - Change the highlight group used
+- Other fields like `data.operation` are read-only
+
 ### Event System
 
 Subscribe to plugin events:

lua/undo-glow/commands.lua

@@ -31,6 +31,9 @@ function M.undo(opts)
 	local api = require("undo-glow.api")
 	api.emit("command_executed", { command = "undo", opts = opts })
 
+	-- Call pre_highlight hook to allow modifications
+	api.call_hook("pre_highlight", opts)
+
 	-- Always trigger hooks by calling highlight_region_enhanced
 	-- This ensures all hooks fire even if there are no text changes to highlight
 	require("undo-glow.api").highlight_region_enhanced(
@@ -69,6 +72,9 @@ function M.redo(opts)
 	local api = require("undo-glow.api")
 	api.emit("command_executed", { command = "redo", opts = opts })
 
+	-- Call pre_highlight hook to allow modifications
+	api.call_hook("pre_highlight", opts)
+
 	-- Always trigger hooks by calling highlight_region_enhanced
 	-- This ensures all hooks fire even if there are no text changes to highlight
 	require("undo-glow.api").highlight_region_enhanced(
@@ -106,6 +112,9 @@ function M.yank(opts)
 	opts = require("undo-glow.utils").merge_command_opts("UgYank", opts)
 	opts.operation = "yank"
 
+	-- Call pre_highlight hook to allow modifications
+	api.call_hook("pre_highlight", opts)
+
 	-- Always trigger hooks by calling highlight_region directly
 	require("undo-glow.api").highlight_region_enhanced(
 		vim.tbl_extend("force", opts, {
@@ -149,6 +158,9 @@ function M.paste_below(opts)
 	local api = require("undo-glow.api")
 	api.emit("command_executed", { command = "paste_below", opts = opts })
 
+	-- Call pre_highlight hook to allow modifications
+	api.call_hook("pre_highlight", opts)
+
 	-- Always trigger hooks by calling highlight_region directly
 	require("undo-glow.api").highlight_region_enhanced(
 		vim.tbl_extend("force", opts, {
@@ -186,6 +198,9 @@ function M.paste_above(opts)
 	local api = require("undo-glow.api")
 	api.emit("command_executed", { command = "paste_above", opts = opts })
 
+	-- Call pre_highlight hook to allow modifications
+	api.call_hook("pre_highlight", opts)
+
 	-- Always trigger hooks by calling highlight_region directly
 	require("undo-glow.api").highlight_region_enhanced(
 		vim.tbl_extend("force", opts, {
@@ -229,6 +244,10 @@ function M.search_cmd(opts)
 	opts = require("undo-glow.utils").merge_command_opts("UgSearch", opts)
 	opts.operation = "search_cmd"
 
+	local api = require("undo-glow.api")
+	-- Call pre_highlight hook to allow modifications
+	api.call_hook("pre_highlight", opts)
+
 	local region = require("undo-glow.utils").get_current_cursor_row()
 
 	require("undo-glow.api").highlight_region_enhanced(
@@ -270,6 +289,9 @@ function M.search_next(opts)
 	local api = require("undo-glow.api")
 	api.emit("command_executed", { command = "search_next", opts = opts })
 
+	-- Call pre_highlight hook to allow modifications
+	api.call_hook("pre_highlight", opts)
+
 	require("undo-glow.api").highlight_region_enhanced(
 		vim.tbl_extend("force", opts, {
 			s_row = region.s_row,
@@ -303,6 +325,9 @@ function M.search_prev(opts)
 	local api = require("undo-glow.api")
 	api.emit("command_executed", { command = "search_prev", opts = opts })
 
+	-- Call pre_highlight hook to allow modifications
+	api.call_hook("pre_highlight", opts)
+
 	require("undo-glow.api").highlight_region_enhanced(
 		vim.tbl_extend("force", opts, {
 			s_row = region.s_row,
@@ -336,6 +361,9 @@ function M.search_star(opts)
 	local api = require("undo-glow.api")
 	api.emit("command_executed", { command = "search_star", opts = opts })
 
+	-- Call pre_highlight hook to allow modifications
+	api.call_hook("pre_highlight", opts)
+
 	require("undo-glow.api").highlight_region_enhanced(
 		vim.tbl_extend("force", opts, {
 			s_row = region.s_row,
@@ -369,6 +397,9 @@ function M.search_hash(opts)
 	local api = require("undo-glow.api")
 	api.emit("command_executed", { command = "search_hash", opts = opts })
 
+	-- Call pre_highlight hook to allow modifications
+	api.call_hook("pre_highlight", opts)
+
 	require("undo-glow.api").highlight_region_enhanced(
 		vim.tbl_extend("force", opts, {
 			s_row = region.s_row,
@@ -449,6 +480,10 @@ function M.cursor_moved(opts, cursor_moved_opts)
 	opts = require("undo-glow.utils").merge_command_opts("UgCursor", opts)
 	opts.operation = "cursor_moved"
 
+	local api = require("undo-glow.api")
+	-- Call pre_highlight hook to allow modifications
+	api.call_hook("pre_highlight", opts)
+
 	cursor_moved_opts = vim.tbl_deep_extend("force", {
 		ignored_ft = {},
 		steps_to_trigger = 10,

lua/undo-glow/types.lua

@@ -126,6 +126,7 @@ local M = {}
 ---State for the undo-glow highlight.
 ---@class UndoGlow.State
 ---@field current_hlgroup string The current highlight group in use.
+---@field hl_color? UndoGlow.HlColor Override color for the highlight.
 ---@field should_detach boolean Whether the highlight should detach.
 ---@field animation? UndoGlow.Config.Animation Animation configuration.
 ---@field force_edge? boolean Whether to force edge highlighting.
@@ -146,6 +147,7 @@ local M = {}
 ---Command options for triggering highlights.
 ---@class UndoGlow.CommandOpts
 ---@field hlgroup? string Optional highlight group to use.
+---@field hl_color? UndoGlow.HlColor Override color for the highlight.
 ---@field animation? UndoGlow.Config.Animation Optional animation configuration.
 ---@field force_edge? boolean Optional flag to force edge highlighting.
 ---@field operation? string Operation type.

lua/undo-glow/utils.lua

@@ -121,8 +121,13 @@ function M.handle_highlight(opts)
 			opts.state.current_hlgroup
 		)
 
-	local init_color =
-		require("undo-glow.color").init_colors(current_hlgroup_detail)
+	local init_color
+	if opts.state.hl_color then
+		init_color = vim.deepcopy(opts.state.hl_color)
+	else
+		init_color =
+			require("undo-glow.color").init_colors(current_hlgroup_detail)
+	end
 
 	opts.s_row, opts.s_col, opts.e_row, opts.e_col = M.sanitize_coords(
 		opts.bufnr,
@@ -136,6 +141,11 @@ function M.handle_highlight(opts)
 
 	opts.ns = M.create_namespace(opts.bufnr, opts.state.animation.window_scoped)
 
+	-- If hl_color is set, update the highlight group with the custom color
+	if opts.state.hl_color then
+		vim.api.nvim_set_hl(0, unique_hlgroup, opts.state.hl_color)
+	end
+
 	--- If disabled animation, set extmark and clear it afterwards
 	if opts.state.animation.enabled ~= true then
 		local extmark_opts = M.create_extmark_opts({
@@ -475,6 +485,7 @@ function M.create_state(opts)
 	return {
 		should_detach = false,
 		current_hlgroup = opts.hlgroup or "UgUndo",
+		hl_color = opts.hl_color,
 		force_edge = type(opts.force_edge) == "nil" and false
 			or opts.force_edge,
 		operation = opts.operation,

tests/enhanced_api_spec.lua

@@ -476,9 +476,22 @@ describe("Enhanced API", function()
 
 				assert.is_true(color_changed)
 
+				-- Verify that hl_color modification is preserved in the hook data
+				local hook_called_with_color = false
+				local test_hook_id = api.register_hook("pre_highlight", function(data)
+					if data.operation == "undo" and data.hl_color and data.hl_color.bg == "#2D1B69" then
+						hook_called_with_color = true
+					end
+				end, 100)
+
+				require("undo-glow").undo()
+
+				assert.is_true(hook_called_with_color)
+
 				-- Cleanup
 				os.date = original_os_date
 				api.remove_hook("pre_highlight", hook_id)
+				api.remove_hook("pre_highlight", test_hook_id)
 			end)
 
 			it("should react to configuration changes", function()