awful.spawn.with_line_callback: Use an arguments table

Having many arguments can easily get confusing and hard to understand. This
commit uses a table instead so that we have names that identify what each
callback does.

Signed-off-by: Uli Schlachter <psychon@znc.in>

lib/awful/spawn.lua

@@ -91,20 +91,24 @@ end
 
 --- Spawn a program and asynchronously and capture its output line by line.
 -- @tparam string|table cmd The command.
--- @tparam[opt] function stdout_callback Function that is called with each line of
+-- @tab callbacks Table containing callbacks that should be
---   output on stdout, e.g. `stdout_callback(line)`.
+--   invoked on various conditions.
--- @tparam[opt] function stderr_callback Function that is called with each line of
+-- @tparam[opt] function callbacks.stdout Function that is called with each line of
---   output on stderr, e.g. `stderr_callback(line)`.
+--   output on stdout, e.g. `stdout(line)`.
--- @tparam[opt] function done_callback Function to call when no more output is
+-- @tparam[opt] function callbacks.stderr Function that is called with each line of
---   produced.
+--   output on stderr, e.g. `stderr(line)`.
--- @tparam[opt] function exit_callback Function to call when the spawned process
+-- @tparam[opt] function callbacks.output_done Function to call when no more output
+--   is produced.
+-- @tparam[opt] function callbacks.exit Function to call when the spawned process
 -- exits. This function gets the exit reason and code as its argument. The
 -- reason can be "exit" or "signal". For "exit", the second argument is the exit
 -- code. For "signal", the second argument is the signal causing process
 -- termination.
 -- @treturn[1] Integer the PID of the forked process.
 -- @treturn[2] string Error message.
-function spawn.with_line_callback(cmd, stdout_callback, stderr_callback, done_callback, exit_callback)
+function spawn.with_line_callback(cmd, callbacks)
+    local stdout_callback, stderr_callback, done_callback, exit_callback =
+        callbacks.stdout, callbacks.stderr, callbacks.output_done, callbacks.exit
     local have_stdout, have_stderr = stdout_callback ~= nil, stderr_callback ~= nil
     local pid, sn_id, stdin, stdout, stderr = capi.awesome.spawn(cmd,
             false, false, have_stdout, have_stderr, exit_callback)

tests/test-spawn.lua

@@ -9,43 +9,51 @@ local steps = {
   function(count)
     if count == 1 then
       local steps_yay = 0
-      spawn.with_line_callback("echo yay", function(line)
+      spawn.with_line_callback("echo yay", {
+          stdout = function(line)
               assert(line == "yay", "line == '" .. tostring(line) .. "'")
               assert(steps_yay == 0)
               steps_yay = steps_yay + 1
-      end, nil, function()
+          end,
+          output_done = function()
               assert(steps_yay == 1)
               steps_yay = steps_yay + 1
               spawns_done = spawns_done + 1
-      end, function(reason, code)
+          end,
+          exit = function(reason, code)
               assert(reason == "exit")
               assert(exit_yay == nil)
               assert(code == 0)
               exit_yay = code
-      end)
+          end
+      })
 
       local steps_count = 0
       local err_count = 0
-      spawn.with_line_callback({ "sh", "-c", "printf line1\\\\nline2\\\\nline3 ; echo err >&2 ; exit 42" },
+      spawn.with_line_callback({ "sh", "-c", "printf line1\\\\nline2\\\\nline3 ; echo err >&2 ; exit 42" }, {
-      function(line)
+          stdout = function(line)
               assert(steps_count < 3)
               steps_count = steps_count + 1
               assert(line == "line" .. steps_count, "line == '" .. tostring(line) .. "'")
-      end, function(line)
+          end,
+          stderr = function(line)
               assert(err_count == 0)
               err_count = err_count + 1
               assert(line == "err", "line == '" .. tostring(line) .. "'")
-      end, function()
+          end,
+          output_done = function()
               assert(steps_count == 3)
               assert(err_count == 1)
               steps_count = steps_count + 1
               spawns_done = spawns_done + 1
-      end, function(reason, code)
+          end,
+          exit = function(reason, code)
               assert(reason == "exit")
               assert(exit_snd == nil)
               assert(code == 42)
               exit_snd = code
-      end)
+          end
+      })
     end
     if spawns_done == 2 then
       assert(exit_yay == 0)