fix(script): do not hide failing scripts with constant output

CHANGELOG.md

@@ -9,6 +9,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Breaking
+- `custom/script` now doesn't hide failing script if it's output is not changing ([`#2636`](https://github.com/polybar/polybar/issues/2636)). Somewhat similar behaviour can be imitated with `format-fail`, if necessary.
 
 ## [3.6.1] - 2022-03-05
 ### Build

src/adapters/script_runner.cpp

@@ -106,8 +106,6 @@ script_runner::interval script_runner::run() {
   int fd = cmd.get_stdout(PIPE_READ);
   assert(fd != -1);
 
-  bool changed = false;
-
   bool got_output = false;
   while (!m_stopping && cmd.is_running() && !io_util::poll(fd, POLLHUP, 0)) {
     /**
@@ -115,7 +113,7 @@ script_runner::interval script_runner::run() {
      * down, we still need to continue polling.
      */
     if (io_util::poll_read(fd, 25) && !got_output) {
-      changed = set_output(cmd.readline());
+      set_output(cmd.readline());
       got_output = true;
     }
   }
@@ -127,10 +125,6 @@ script_runner::interval script_runner::run() {
 
   m_exit_status = cmd.wait();
 
-  if (!changed && m_exit_status != 0) {
-    clear_output();
-  }
-
   if (m_exit_status == 0) {
     return m_interval_success;
   } else {