Calling logfire.warn with a Django object raises exception

[joshbrooks]

Description

I'm calling logfire.warn on a Django "User" object with logfire.warn(request.user). What I'd expect is that I'd get the equivalent of calling str(request.user) in the log

In [2]: User.objects.first()
Out[2]: <User: eskola>

In [3]: str(User.objects.first())
Out[3]: 'eskola'

Instead, I get an exception as the serialization of the Django object is not supported

Feb 17 11:01:20 Caught an internal error in Logfire. Your code should still be running fine, just with less telemetry. This is just logging the internal error.
Feb 17 11:01:20 Traceback (most recent call last):
Feb 17 11:01:20   File "/var/www/education/env/lib/python3.12/site-packages/django/views/generic/base.py", line 143, in dispatch
Feb 17 11:01:20     return handler(request, *args, **kwargs)
Feb 17 11:01:20            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Feb 17 11:01:20   File "/var/www/education/source/gather/gather/surveydata/views.py", line 603, in put
Feb 17 11:01:20     couchdoc = self.create_couchdoc(request, rid=rid, uid=uid)
Feb 17 11:01:20                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Feb 17 11:01:20   File "/var/www/education/source/gather/gather/surveydata/views.py", line 564, in create_couchdoc
Feb 17 11:01:20     logfire.warn(request.user)
Feb 17 11:01:20   File "/var/www/education/env/lib/python3.12/site-packages/logfire/_internal/main.py", line 423, in warning
Feb 17 11:01:20     self.log('warn', msg_template, attributes, tags=_tags, exc_info=_exc_info)
Feb 17 11:01:20   File "/var/www/education/env/lib/python3.12/site-packages/logfire/_internal/main.py", line 681, in log
Feb 17 11:01:20     msg, extra_attrs, msg_template = logfire_format_with_magic(
Feb 17 11:01:20                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^
Feb 17 11:01:20   File "/var/www/education/env/lib/python3.12/site-packages/logfire/_internal/formatter.py", line 330, in logfire_format_with_magic
Feb 17 11:01:20     chunks, extra_attrs, new_template = chunks_formatter.chunks(
Feb 17 11:01:20                                         ^^^^^^^^^^^^^^^^^^^^^^^^
Feb 17 11:01:20   File "/var/www/education/env/lib/python3.12/site-packages/logfire/_internal/formatter.py", line 55, in chunks
Feb 17 11:01:20     chunks, extra_attrs = self._vformat_chunks(
Feb 17 11:01:20                           ^^^^^^^^^^^^^^^^^^^^^
Feb 17 11:01:20   File "/var/www/education/env/lib/python3.12/site-packages/logfire/_internal/formatter.py", line 228, in _vformat_chunks
Feb 17 11:01:20     for literal_text, field_name, format_spec, conversion in self.parse(format_string):
Feb 17 11:01:20                                                              ^^^^^^^^^^^^^^^^^^^^^^^^^
Feb 17 11:01:20   File "/usr/lib/python3.12/string.py", line 288, in parse
Feb 17 11:01:20     return _string.formatter_parser(format_string)
Feb 17 11:01:20            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Feb 17 11:01:20 TypeError: expected str, got SimpleLazyObject
Feb 17 11:01:20 Invalid type SimpleLazyObject for attribute 'logfire.msg_template' value. Expected one of ['bool', 'str', 'bytes', 'int', 'float'] or a sequence of those types
Feb 17 11:01:20 Invalid type SimpleLazyObject for attribute 'logfire.msg' value. Expected one of ['bool', 'str', 'bytes', 'int', 'float'] or a sequence of those types
Feb 17 11:01:20 Exception while exporting Span.
Feb 17 11:01:20 Traceback (most recent call last):
Feb 17 11:01:20   File "/var/www/education/env/lib/python3.12/site-packages/opentelemetry/sdk/trace/export/__init__.py", line 113, in on_end
Feb 17 11:01:20     self.span_exporter.export((span,))
Feb 17 11:01:20   File "/var/www/education/env/lib/python3.12/site-packages/logfire/_internal/exporters/console.py", line 94, in export
Feb 17 11:01:20     self._log_span(span)
Feb 17 11:01:20   File "/var/www/education/env/lib/python3.12/site-packages/logfire/_internal/exporters/console.py", line 373, in _log_span
Feb 17 11:01:20     self._print_span(span)
Feb 17 11:01:20   File "/var/www/education/env/lib/python3.12/site-packages/logfire/_internal/exporters/console.py", line 123, in _print_span
Feb 17 11:01:20     print(''.join(text for text, _style in parts), file=self._output)
Feb 17 11:01:20           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Feb 17 11:01:20 TypeError: sequence item 3: expected str instance, SimpleLazyObject found

Python, Logfire & OS Versions, related packages (not required)

logfire="3.5.3"
platform="Linux-6.8.0-52-generic-x86_64-with-glibc2.39"
python="3.12.3 (main, Jan 17 2025, 18:03:48) [GCC 13.3.0]"
[related_packages]
requests="2.31.0"
requests="2.32.3"
protobuf="4.21.12"
protobuf="5.29.3"
rich="13.7.1"
executing="2.2.0"
opentelemetry-api="1.30.0"
opentelemetry-exporter-otlp-proto-common="1.30.0"
opentelemetry-exporter-otlp-proto-http="1.30.0"
opentelemetry-instrumentation="0.51b0"
opentelemetry-instrumentation-django="0.51b0"
opentelemetry-instrumentation-wsgi="0.51b0"
opentelemetry-proto="1.30.0"
opentelemetry-sdk="1.30.0"
opentelemetry-semantic-conventions="0.51b0"
opentelemetry-util-http="0.51b0"

[alexmojaki]

The object can be serialized, but the first argument is always supposed to be a string with the message/template, e.g. logfire.warn(f'Problem with {request.user}') . Even logfire.warn(123) gives the same error.

We should at least produce a clearer error. Not sure if we should try to make this 'just work'.