fix(logging): fix issue with dd.* properties not getting injected onto logging records [backport 3.10] (#13929)

Backport 265f660 from #13924 to 3.10.

Resolves: #13892

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- The change includes or references documentation updates if necessary
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[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist
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Co-authored-by: brettlangdon <[email protected]>

Author: github-actions[bot]

ddtrace/contrib/internal/logging/patch.py

@@ -54,7 +54,7 @@ def __init__(self, trace_id: int, span_id: int, service: str, version: str, env:
 def _w_makeRecord(func, instance, args, kwargs):
     # Get the LogRecord instance for this log
     record = func(*args, **kwargs)
-    if config._logs_injection != LogInjectionState.ENABLED:
+    if config._logs_injection == LogInjectionState.DISABLED:
         # log injection is opt-in for non-structured logging
         return record
     record.__dict__.update(ddtrace.tracer.get_log_correlation_context())

releasenotes/notes/fix-log-injection-structured-logs-7157452b11e8e0a4.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    logging: Fix issue when ``dd.*`` properties were not injected onto logging records unless ``DD_LOGS_ENABLED=true`` env var was set (default value is ``structured``).
+    This issue causes problems for non-structured loggers which set their own format string instead of having ``ddtrace`` set the logging format string for you.

tests/contrib/logging/test_logging.py

@@ -1,5 +1,6 @@
 from io import StringIO
 import logging
+import os
 
 import pytest
 import wrapt
@@ -299,3 +300,29 @@ def test_log_strformat_style_format(self):
                 assert not hasattr(record, "dd")
                 assert getattr(record, LOG_ATTR_TRACE_ID) == "{:032x}".format(span.trace_id)
                 assert getattr(record, LOG_ATTR_SPAN_ID) == str(span.span_id)
+
+
+@pytest.mark.parametrize("dd_logs_enabled", ["true", "false", "structured"])
+def test_manual_log_formatter_injection(dd_logs_enabled: str, run_python_code_in_subprocess):
+    code = """
+import ddtrace.auto
+
+import logging
+
+format_string = (
+    "%(message)s - dd.service=%(dd.service)s dd.version=%(dd.version)s dd.env=%(dd.env)s"
+    " dd.trace_id=%(dd.trace_id)s dd.span_id=%(dd.span_id)s"
+)
+
+log = logging.getLogger()
+logging.basicConfig(level=logging.INFO, format=format_string)
+log.info("Hello!")
+    """
+
+    env = os.environ.copy()
+    env["DD_LOGS_ENABLED"] = dd_logs_enabled
+    stdout, stderr, status, _ = run_python_code_in_subprocess(code, env=env)
+    assert status == 0, stderr
+
+    assert stdout == b"", stderr
+    assert stderr == b"Hello! - dd.service=ddtrace_subprocess_dir dd.version= dd.env= dd.trace_id=0 dd.span_id=0\n"