Repository: celery/celery

Issue:
ProxyLogger.write raises TypeError due to rstrip on a bytes instance.
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## Mandatory Debugging Information

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#### Related Issues

- [Created in PR #6838](https://github.com/celery/celery/pull/6838)

#### Possible Duplicates

- None

## Environment & Settings
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**Celery version**: 5.2.0
<!-- Include the output of celery -A proj report below -->
<details>
<summary><b><code>celery report</code> Output:</b></summary>
<p>

```
TypeError: a bytes-like object is required, not 'str'
  File "aspiredu/project/celery.py", line 43, in run_command
    sys.stdout.write(line)  # Write all output from the command
  File "celery/utils/log.py", line 227, in write
    data = data.rstrip('\n')
```

</p>
</details>

# Steps to Reproduce

## Required Dependencies
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* **Minimal Python Version**: 3.9.6
* **Minimal Celery Version**: 5.2
* **Minimal Kombu Version**: N/A or Unknown
* **Minimal Broker Version**: N/A or Unknown
* **Minimal Result Backend Version**: N/A or Unknown
* **Minimal OS and/or Kernel Version**: N/A or Unknown
* **Minimal Broker Client Version**: N/A or Unknown
* **Minimal Result Backend Client Version**: N/A or Unknown

### Python Packages
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<details>
<summary><b><code>pip freeze</code> Output:</b></summary>
<p>

```
scout_apm==2.23.3
```

</p>
</details>

### Other Dependencies
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N/A
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## Minimally Reproducible Test Case
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<details>
<p>

Add the following test to t.unit.app.test_log.test_default_logger

What's happening is that the logger is getting a data instance of type bytes, but can call rstrip with a `str` parameter which breaks.

```python
    @mock.restore_logging()
    def test_logging_proxy_bytes(self):
        logger = self.setup_logger(loglevel=logging.ERROR, logfile=None,
                                   root=False)

        with mock.wrap_logger(logger) as sio:
            p = LoggingProxy(logger, loglevel=logging.ERROR)
            p.close()
            p.write(b'foo')
            assert 'foo' not in str(sio.getvalue())
            p.closed = False
            p.write(b'\n')
            assert str(sio.getvalue()) == ''
            write_res = p.write(b'foo ')
            assert str(sio.getvalue()) == 'foo \n'
            assert write_res == 4
            p.flush()
            p.close()
            assert not p.isatty()

            with mock.stdouts() as (stdout, stderr):
                with in_sighandler():
                    p.write(b'foo')
                    assert stderr.getvalue()

```

</p>
</details>

# Expected Behavior
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Calling `ProxyLogger(logger).write(b'value')` should not break when a bytes instance is passed in.

# Actual Behavior
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A `TypeError: a bytes-like object is required, not 'str'` is raised.


I will be creating a PR as a follow-up to this issue.


Discussion:
Hey @tim-schilling :wave:,
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Resolving patch:
diff --git a/celery/utils/log.py b/celery/utils/log.py
--- a/celery/utils/log.py
+++ b/celery/utils/log.py
@@ -224,13 +224,13 @@ def write(self, data):
         if getattr(self._thread, 'recurse_protection', False):
             # Logger is logging back to this file, so stop recursing.
             return 0
-        data = data.rstrip('\n')
         if data and not self.closed:
             self._thread.recurse_protection = True
             try:
-                safe_data = safe_str(data)
-                self.logger.log(self.loglevel, safe_data)
-                return len(safe_data)
+                safe_data = safe_str(data).rstrip('\n')
+                if safe_data:
+                    self.logger.log(self.loglevel, safe_data)
+                    return len(safe_data)
             finally:
                 self._thread.recurse_protection = False
         return 0


Test patch:
diff --git a/t/unit/app/test_log.py b/t/unit/app/test_log.py
--- a/t/unit/app/test_log.py
+++ b/t/unit/app/test_log.py
@@ -286,6 +286,31 @@ def test_logging_proxy(self):
                     p.write('foo')
                     assert stderr.getvalue()
 
+    @mock.restore_logging()
+    def test_logging_proxy_bytes(self):
+        logger = self.setup_logger(loglevel=logging.ERROR, logfile=None,
+                                   root=False)
+
+        with mock.wrap_logger(logger) as sio:
+            p = LoggingProxy(logger, loglevel=logging.ERROR)
+            p.close()
+            p.write(b'foo')
+            assert 'foo' not in str(sio.getvalue())
+            p.closed = False
+            p.write(b'\n')
+            assert str(sio.getvalue()) == ''
+            write_res = p.write(b'foo ')
+            assert str(sio.getvalue()) == 'foo \n'
+            assert write_res == 4
+            p.flush()
+            p.close()
+            assert not p.isatty()
+
+            with mock.stdouts() as (stdout, stderr):
+                with in_sighandler():
+                    p.write(b'foo')
+                    assert stderr.getvalue()
+
     @mock.restore_logging()
     def test_logging_proxy_recurse_protection(self):
         logger = self.setup_logger(loglevel=logging.ERROR, logfile=None,