fix: address tech debt and bugs from fork

Data bugs in util.lua:
- Guard division by zero when LF:0 (produces NaN)
- Add num_branches/num_partial_branches to file summary and totals
- Deduplicate partial_lines when multiple BRDA records share a line
- Remove unused meta field from return value

Runtime bugs:
- watch.lua: cancel pending debounce timer in stop()
- watch.lua: fix uv fallback to vim.loop (not undefined global)
- report.lua: escape filename in vim.cmd("edit ...") for special chars
- report.lua: remove dead 7th argument from string.format with 6 specifiers
- init.lua: fire on_load callback after cache.set, not before
- neotest consumers: use named listener keys to avoid clobbering each other
- neotest.lua: wrap load() in vim.schedule for async safety

API modernization:
- Replace nvim_buf_set_option/nvim_win_set_option with vim.bo/vim.wo
- Replace vim.cmd("highlight") with nvim_set_hl in highlight.lua
- Replace nvim_buf_set_keymap with vim.keymap.set in report/heatmap
- Replace legacy au BufLeave with nvim_create_autocmd (once=true)

Refactoring:
- Rename report -> cache in overlay, quickfix, loclist, report modules
- Extract duplicated file lookup into cache.find_file()
- Convert O(n²) vim.tbl_contains to set lookups in signs.build()

Fixes neotest/go.lua docstring (wrong output path) and
neotest/python.lua misleading variable name.

Tests updated with new assertions and fixtures.

Author: iamralch

lua/coverage/cache.lua

@@ -32,4 +32,24 @@ M.clear = function()
 	loaded_file = nil
 end
 
+--- Finds file coverage by filename, falling back to buffer number matching.
+--- @param fname string absolute path to look up
+--- @return FileCoverage|nil coverage data for the file
+--- @return string|nil matched filename key
+M.find_file = function(fname)
+	if cached == nil then
+		return nil, nil
+	end
+	local file = cached.files[fname]
+	if file ~= nil then
+		return file, fname
+	end
+	for sf, cov in pairs(cached.files) do
+		if vim.fn.bufnr(sf, false) == vim.fn.bufnr(fname, false) then
+			return cov, sf
+		end
+	end
+	return nil, nil
+end
+
 return M

lua/coverage/heatmap.lua

@@ -240,9 +240,9 @@ local function render(bufnr, rects, W, H)
 	end
 
 	-- Flush lines into buffer
-	vim.api.nvim_buf_set_option(bufnr, "modifiable", true)
+	vim.bo[bufnr].modifiable = true
 	vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines)
-	vim.api.nvim_buf_set_option(bufnr, "modifiable", false)
+	vim.bo[bufnr].modifiable = false
 
 	-- Apply highlights
 	vim.api.nvim_buf_clear_namespace(bufnr, ns, 0, -1)
@@ -261,8 +261,8 @@ local function open_float()
 	local height = vim.o.lines - vim.o.cmdheight - 1
 
 	local bufnr = vim.api.nvim_create_buf(false, true)
-	vim.api.nvim_buf_set_option(bufnr, "bufhidden", "wipe")
-	vim.api.nvim_buf_set_option(bufnr, "filetype", "coverage-heatmap")
+	vim.bo[bufnr].bufhidden = "wipe"
+	vim.bo[bufnr].filetype = "coverage-heatmap"
 
 	local win = vim.api.nvim_open_win(bufnr, true, {
 		relative = "editor",
@@ -273,24 +273,24 @@ local function open_float()
 		style = "minimal",
 	})
 
-	vim.api.nvim_win_set_option(win, "cursorline", true)
-	vim.api.nvim_win_set_option(win, "wrap", false)
+	vim.wo[win].cursorline = true
+	vim.wo[win].wrap = false
 
 	return bufnr, win, width, height
 end
 
 --- Set keymaps on the heatmap buffer.
 local function set_keymaps(bufnr)
-	local close_cmd = ":lua require('coverage.heatmap').close()<CR>"
-	vim.api.nvim_buf_set_keymap(bufnr, "n", "q", close_cmd, { silent = true, noremap = true })
-	vim.api.nvim_buf_set_keymap(bufnr, "n", "<Esc>", close_cmd, { silent = true, noremap = true })
-	vim.api.nvim_buf_set_keymap(
-		bufnr,
-		"n",
-		"<CR>",
-		":lua require('coverage.heatmap').open_file()<CR>",
-		{ silent = true, noremap = true }
-	)
+	local opts = { buffer = bufnr, silent = true, noremap = true }
+	vim.keymap.set("n", "q", function()
+		require("coverage.heatmap").close()
+	end, opts)
+	vim.keymap.set("n", "<Esc>", function()
+		require("coverage.heatmap").close()
+	end, opts)
+	vim.keymap.set("n", "<CR>", function()
+		require("coverage.heatmap").open_file()
+	end, opts)
 end
 
 --- Find the rect at the current cursor position.

lua/coverage/highlight.lua

@@ -12,15 +12,26 @@ local config = require("coverage.config")
 --- @param group string name of the highlight group
 --- @param color Highlight
 local highlight = function(group, color)
-	local style = color.style and "gui=" .. color.style or "gui=NONE"
-	local fg = color.fg and "guifg=" .. color.fg or "guifg=NONE"
-	local bg = color.bg and "guibg=" .. color.bg or "guibg=NONE"
-	local sp = color.sp and "guisp=" .. color.sp or ""
-	local hl = "highlight default " .. group .. " " .. style .. " " .. fg .. " " .. bg .. " " .. sp
-	vim.cmd(hl)
 	if color.link then
-		vim.cmd("highlight default link " .. group .. " " .. color.link)
+		vim.api.nvim_set_hl(0, group, { link = color.link, default = true })
+		return
 	end
+	local opts = { default = true }
+	if color.fg then
+		opts.fg = color.fg
+	end
+	if color.bg then
+		opts.bg = color.bg
+	end
+	if color.sp then
+		opts.sp = color.sp
+	end
+	if color.style then
+		for attr in color.style:gmatch("[^,]+") do
+			opts[attr] = true
+		end
+	end
+	vim.api.nvim_set_hl(0, group, opts)
 end
 
 local create_highlight_groups = function()

lua/coverage/init.lua

@@ -155,11 +155,11 @@ M.load = function(file, opts)
 	end
 
 	local reload = function()
+		local data = util.lcov_to_table(p)
+		cache.set(data, file)
 		if config.opts.on_load ~= nil then
 			vim.schedule(config.opts.on_load)
 		end
-		local data = util.lcov_to_table(p)
-		cache.set(data, file)
 		local sign_list = signs.build(data)
 		if place or signs.is_enabled() then
 			signs.place(sign_list)

lua/coverage/loclist.lua

@@ -1,30 +1,20 @@
 local M = {}
 
-local report = require("coverage.cache")
+local cache = require("coverage.cache")
 
 --- Populates the location list for the current window with lines of the given type.
 --- @param sign_type? "uncovered"|"partial" Defaults to "uncovered".
 M.populate = function(sign_type)
 	sign_type = sign_type or "uncovered"
 
-	if not report.is_cached() then
+	if not cache.is_cached() then
 		vim.notify("Coverage report not loaded.", vim.log.levels.INFO)
 		return
 	end
 
-	local data = report.get()
 	local fname = vim.fn.expand("%:p")
-	local file = data.files[fname]
-
-	if file == nil then
-		for sf, cov in pairs(data.files) do
-			if vim.fn.bufnr(sf, false) == vim.fn.bufnr("%", false) then
-				file = cov
-				fname = sf
-				break
-			end
-		end
-	end
+	local file
+	file, fname = cache.find_file(fname)
 
 	if file == nil then
 		vim.notify("No coverage data for current file.", vim.log.levels.INFO)

lua/coverage/neotest.lua

@@ -11,9 +11,11 @@
 ---
 --- @type fun(client: table): table
 local consumer = function(client)
-	client.listeners.results = function(_, _, partial)
+	client.listeners.results["coverage.neotest"] = function(_, _, partial)
 		if not partial then
-			require("coverage").load(nil, { place = require("coverage.signs").is_enabled(), silent = true })
+			vim.schedule(function()
+				require("coverage").load(nil, { place = require("coverage.signs").is_enabled(), silent = true })
+			end)
 		end
 	end
 	return {}

lua/coverage/neotest/go.lua

@@ -4,9 +4,9 @@
 --- Expects tests to be run with `-coverprofile=coverage.out` (e.g. via ginkgo
 --- or neotest-go/neotest-golang with coverage flags enabled).
 ---
---- After tests finish the consumer globs for all `**/coverage.out` files under
---- cwd, converts each to lcov in pure Lua, concatenates the results
---- into `cwd/coverage/lcov.info`, and loads the merged file.
+--- After tests finish the consumer finds `coverage.out` in the neotest output
+--- directory, converts it to lcov in pure Lua, writes the result to
+--- `cwd/lcov.info`, and loads the merged file.
 ---
 --- Usage:
 ---   require("neotest").setup({
@@ -36,7 +36,7 @@ local function find_coverage_profile(results)
 end
 
 local consumer = function(client)
-	client.listeners.results = function(_, results, partial)
+	client.listeners.results["coverage.neotest.go"] = function(_, results, partial)
 		if partial then
 			return
 		end

lua/coverage/neotest/python.lua

@@ -14,17 +14,17 @@
 ---
 --- @type fun(client: table): table
 local consumer = function(client)
-	client.listeners.results = function(_, _, partial)
+	client.listeners.results["coverage.neotest.python"] = function(_, _, partial)
 		if partial then
 			return
 		end
 
 		vim.schedule(function()
 			local cwd = vim.fn.getcwd()
-			local dir = cwd .. "/.coverage"
+			local coverage_db = cwd .. "/.coverage"
 			local path = cwd .. "/coverage/lcov.info"
 
-			if vim.fn.filereadable(dir) ~= 1 then
+			if vim.fn.filereadable(coverage_db) ~= 1 then
 				return
 			end
 

lua/coverage/overlay.lua

@@ -1,6 +1,6 @@
 local M = {}
 
-local report = require("coverage.cache")
+local cache = require("coverage.cache")
 
 local float_win = nil
 local float_bufnr = nil
@@ -36,8 +36,8 @@ local show_for_line = function(lnum, branches)
 
 	float_bufnr = vim.api.nvim_create_buf(false, true)
 	vim.api.nvim_buf_set_lines(float_bufnr, 0, -1, false, lines)
-	vim.api.nvim_buf_set_option(float_bufnr, "modifiable", false)
-	vim.api.nvim_buf_set_option(float_bufnr, "filetype", "coverage-overlay")
+	vim.bo[float_bufnr].modifiable = false
+	vim.bo[float_bufnr].filetype = "coverage-overlay"
 
 	local width = 30
 	for _, l in ipairs(lines) do
@@ -59,7 +59,7 @@ local show_for_line = function(lnum, branches)
 		border = "rounded",
 	})
 
-	vim.api.nvim_win_set_option(float_win, "winhl", "Normal:CoverageReportNormal,FloatBorder:CoverageReportBorder")
+	vim.wo[float_win].winhl = "Normal:CoverageReportNormal,FloatBorder:CoverageReportBorder"
 
 	-- highlight header
 	vim.api.nvim_buf_add_highlight(float_bufnr, -1, "CoverageReportHeader", 0, 0, -1)
@@ -73,23 +73,13 @@ end
 
 --- Checks current cursor line and updates the overlay accordingly.
 local on_cursor_moved = function()
-	if not report.is_cached() then
+	if not cache.is_cached() then
 		close_float()
 		return
 	end
 
 	local fname = vim.fn.expand("%:p")
-	local data = report.get()
-	local file = data.files[fname]
-	if file == nil then
-		-- fallback: match by buffer number the same way signs.build does
-		for sf, cov in pairs(data.files) do
-			if vim.fn.bufnr(sf, false) == vim.fn.bufnr("%", false) then
-				file = cov
-				break
-			end
-		end
-	end
+	local file = cache.find_file(fname)
 	if file == nil then
 		close_float()
 		return

lua/coverage/quickfix.lua

@@ -1,16 +1,16 @@
 local M = {}
 
-local report = require("coverage.cache")
+local cache = require("coverage.cache")
 
 --- Populates the quickfix list with one entry per file showing coverage summary.
 --- @param filter? "uncovered" When given, only includes files with uncovered lines.
 M.populate = function(filter)
-	if not report.is_cached() then
+	if not cache.is_cached() then
 		vim.notify("Coverage report not loaded.", vim.log.levels.INFO)
 		return
 	end
 
-	local data = report.get()
+	local data = cache.get()
 	local rows = {}
 
 	for filename, file in pairs(data.files) do