fix: address newline issues in output window

lua/watchexec/runner.lua

@@ -30,11 +30,49 @@ local state = {
 ---@return string
 local function strip_ansi(text)
   local result =
-    text:gsub("\x1b%[%??[0-9;]*[a-zA-Z]", ""):gsub("\x1b%][0-9;]*.-(\x1b\\|\x07)", ""):gsub("\x1b[()][0-9A-Za-z]", "")
+      text:gsub("\x1b%[%??[0-9;]*[a-zA-Z]", ""):gsub("\x1b%][0-9;]*.-(\x1b\\|\x07)", ""):gsub("\x1b[()][0-9A-Za-z]", "")
 
   return result
 end
 
+---Normalize output text: strip ANSI, handle \\r characters (CRLF -> LF,
+---inline progress overwrites), and detect leading \\r for line overwrite.
+---@param text string
+---@return string, boolean
+local function normalize_output(text)
+  if not text or text == "" then
+    return "", false
+  end
+
+  text = text:gsub("\r\n", "\n")
+  text =
+      text:gsub("\x1b%[%??[0-9;]*[a-zA-Z]", ""):gsub("\x1b%][0-9;]*.-(\x1b\\|\x07)", ""):gsub("\x1b[()][0-9A-Za-z]", "")
+
+  local start_cr = text:len() > 0 and text:byte(1) == 0x0D
+
+  local lines = vim.split(text, "\n", { plain = true })
+  local out_lines = {}
+
+  for i = 1, #lines do
+    local current = lines[i]
+    local found = false
+
+    for p = #current, 1, -1 do
+      if current:byte(p) == 0x0D then
+        current = current:sub(p + 1)
+        found = true
+        break
+      end
+    end
+
+    if not found or current ~= "" then
+      table.insert(out_lines, current)
+    end
+  end
+
+  return table.concat(out_lines, "\n"), start_cr
+end
+
 ---Apply diagnostic highlights to keywords found in a line.
 ---Matches error, warning, success patterns using case-insensitive patterns.
 ---@param buf integer
@@ -42,17 +80,17 @@ end
 ---@param line string
 local function apply_highlights(buf, line_idx, line)
   for _, p in ipairs({
-    { p = "[Ee][Rr][Rr][Oo][Rr]", h = "DiagnosticError" },
-    { p = "[Ff][Aa][Ii][Ll][Ee][Dd]?", h = "DiagnosticError" },
-    { p = "[Ee][Rr][Rr]!", h = "DiagnosticError" },
-    { p = "[Ff][Aa][Tt][Aa][Ll]", h = "DiagnosticError" },
+    { p = "[Ee][Rr][Rr][Oo][Rr]",         h = "DiagnosticError" },
+    { p = "[Ff][Aa][Ii][Ll][Ee][Dd]?",    h = "DiagnosticError" },
+    { p = "[Ee][Rr][Rr]!",                h = "DiagnosticError" },
+    { p = "[Ff][Aa][Tt][Aa][Ll]",         h = "DiagnosticError" },
     { p = "[Ww][Aa][Rr][Nn][Ii][Nn][Gg]", h = "DiagnosticWarn" },
-    { p = "[Ww][Aa][Rr][Nn]!", h = "DiagnosticWarn" },
+    { p = "[Ww][Aa][Rr][Nn]!",            h = "DiagnosticWarn" },
     { p = "[Ss][Uu][Cc][Cc][Ee][Ss][Ss]", h = "DiagnosticOk" },
-    { p = "[Pp][Aa][Ss][Ss][Ee][Dd]", h = "DiagnosticOk" },
-    { p = "%^%d+ .-[Ss]ucceed", h = "DiagnosticOk" },
-    { p = "%[ok%]", h = "DiagnosticOk" },
-    { p = "[Oo][Kk]!", h = "DiagnosticOk" },
+    { p = "[Pp][Aa][Ss][Ss][Ee][Dd]",     h = "DiagnosticOk" },
+    { p = "%^%d+ .-[Ss]ucceed",           h = "DiagnosticOk" },
+    { p = "%[ok%]",                       h = "DiagnosticOk" },
+    { p = "[Oo][Kk]!",                    h = "DiagnosticOk" },
   }) do
     local s, e = line:find(p.p)
 
@@ -69,9 +107,13 @@ local function process_data(text)
     return
   end
 
-  local clean = strip_ansi(text)
+  local clean, overwrite = normalize_output(text)
 
-  require("watchexec.window").append(clean)
+  if clean == "" then
+    return
+  end
+
+  require("watchexec.window").append(clean, overwrite)
   require("watchexec.indicator").process_output(clean)
   require("watchexec.indicator").refresh()
 
@@ -159,7 +201,7 @@ function M.start(command)
     on_stderr = function(_, data, _)
       vim.schedule(function()
         local text = table.concat(data, "\n")
-        local clean = strip_ansi(text)
+        local clean, _ = normalize_output(text)
 
         if clean ~= "" then
           process_data(clean)
@@ -228,4 +270,7 @@ function M.get_cmd()
   return state.cmd
 end
 
+M._normalize_output = normalize_output
+M._strip_ansi = strip_ansi
+
 return M

lua/watchexec/window.lua

@@ -25,6 +25,7 @@ local state = {
 ---@return integer buf
 function M.create_buf()
   local existing = state.buf
+
   if existing and vim.api.nvim_buf_is_valid(existing) then
     return existing
   end
@@ -155,10 +156,13 @@ end
 
 ---Append text to the output buffer.
 ---On first append, replaces the "waiting for output" placeholder.
+---When overwrite is true and the buffer has content, replaces the last line
+---instead of appending (handles \\r-based progress overwrites).
 ---Truncates the buffer when max_lines is exceeded.
 ---Auto-scrolls to the bottom when enabled.
 ---@param text string
-function M.append(text)
+---@param overwrite boolean|nil
+function M.append(text, overwrite)
   local buf = state.buf
 
   if not buf or not vim.api.nvim_buf_is_valid(buf) then
@@ -174,6 +178,8 @@ function M.append(text)
 
   if first_line:match("^ No job running") then
     vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines)
+  elseif overwrite and current > 0 then
+    vim.api.nvim_buf_set_lines(buf, current - 1, -1, false, lines)
   else
     vim.api.nvim_buf_set_lines(buf, current, -1, false, lines)
   end

tests/watchexec/runner_spec.lua

@@ -186,6 +186,58 @@ describe("watchexec runner", function()
     end)
   end)
 
+  describe("normalize_output", function()
+    it("removes ANSI sequences", function()
+      local result = runner._strip_ansi("\x1b[31mred\x1b[0m")
+
+      assert.equals("red", result)
+    end)
+
+    it("converts \\r\\n to \\n", function()
+      local result, _ = runner._normalize_output("line1\r\nline2\r\nline3")
+
+      assert.equals("line1\nline2\nline3", result)
+    end)
+
+    it("resolves inline overwrites (\\r splits)", function()
+      local result, _ = runner._normalize_output("a\rb\rc")
+
+      assert.equals("c", result)
+    end)
+
+    it("resolves mixed inline and line (\\r in last line)", function()
+      local result, _ = runner._normalize_output("a\rb\nc\rd")
+
+      assert.equals("b\nd", result)
+    end)
+
+    it("detects leading overwrite", function()
+      local _, overwrite = runner._normalize_output("\rxyz")
+
+      assert.is_true(overwrite)
+    end)
+
+    it("does not detect overwrite on normal text", function()
+      local _, overwrite = runner._normalize_output("xyz")
+
+      assert.is_false(overwrite)
+    end)
+
+
+    it("does not detect overwrite on CRLF that starts with \\r", function()
+      local _, overwrite = runner._normalize_output("\r\nxyz")
+
+      assert.is_false(overwrite)
+    end)
+
+    it("handles empty text", function()
+      local result, overwrite = runner._normalize_output("")
+
+      assert.equals("", result)
+      assert.is_false(overwrite)
+    end)
+  end)
+
   describe("on_exit guard", function()
     it("ignores stale on_exit from replaced job", function()
       local call_count = 0

tests/watchexec/window_spec.lua

@@ -254,6 +254,48 @@ describe("watchexec window", function()
 
       assert.equals(line_count, cursor[1])
     end)
+
+    it("overwrite replaces the last line", function()
+      window.open()
+      local buf = window.get_buf()
+
+      window.append("first")
+      window.append("second")
+      window.append("replacement", true)
+
+      local lines = vim.api.nvim_buf_get_lines(buf, 0, -1, false)
+
+      assert.equals(2, #lines)
+      assert.equals("first", lines[1])
+      assert.equals("replacement", lines[2])
+    end)
+
+    it("overwrite with multiple lines replaces last line and appends", function()
+      window.open()
+      local buf = window.get_buf()
+
+      window.append("first")
+      window.append("second")
+      window.append("replacement1\nreplacement2", true)
+
+      local lines = vim.api.nvim_buf_get_lines(buf, 0, -1, false)
+
+      assert.equals(3, #lines)
+      assert.equals("first", lines[1])
+      assert.equals("replacement1", lines[2])
+      assert.equals("replacement2", lines[3])
+    end)
+
+    it("overwrite on empty buffer appends normally", function()
+      window.open()
+      local buf = window.get_buf()
+
+      window.append("first", true)
+
+      local lines = vim.api.nvim_buf_get_lines(buf, 0, -1, false)
+
+      assert.equals("first", lines[1])
+    end)
   end)
 
   describe("keymaps", function()
@@ -262,12 +304,14 @@ describe("watchexec window", function()
       local buf = window.get_buf()
       local maps = vim.api.nvim_buf_get_keymap(buf, "n")
       local found = false
+      
       for _, m in ipairs(maps) do
         if m.lhs == "<Esc>" then
           found = true
           break
         end
       end
+
       assert.is_true(found)
     end)
 
@@ -276,12 +320,14 @@ describe("watchexec window", function()
       local buf = window.get_buf()
       local maps = vim.api.nvim_buf_get_keymap(buf, "n")
       local found = false
+
       for _, m in ipairs(maps) do
         if m.lhs == "q" then
           found = true
           break
         end
       end
+
       assert.is_true(found)
     end)