fix: swallow BrokenPipeError in Printer.write

honcho/printer.py

@@ -58,7 +58,13 @@ def write(self, message):
                 prefix = '{time} {name}| '.format(time=time_formatted, name=name)
                 if self.colour and self._colours_supported and message.colour:
                     prefix = _colour_string(message.colour, prefix)
-            print(prefix + line, file=self.output, flush=True)
+            try:
+                print(prefix + line, file=self.output, flush=True)
+            except BrokenPipeError:
+                # Consumer of a pipe closed early (e.g. `honcho start | head`).
+                # Swallow so the manager can still terminate child processes
+                # instead of aborting mid-loop (issue #255).
+                return
 
 
 def _ansi(code):

tests/test_printer.py

@@ -130,3 +130,16 @@ def test_write_flushes_output(self):
         p = Printer(output=out, prefix=False)
         p.write(fake_message("paranoid android\n"))
         assert out.flushcount == 1
+
+
+    def test_write_broken_pipe_is_swallowed(self):
+        class BrokenPipeOutput(FakeOutput):
+            def write(self, data):
+                raise BrokenPipeError()
+
+        out = BrokenPipeOutput()
+        p = Printer(output=out, prefix=False)
+        # Must not raise — manager loop relies on write being safe when the
+        # downstream pipe has gone away (#255).
+        p.write(fake_message("still here\n"))
+