From 1e4e7eb17f93e84922ab58e87750556efa666621 Mon Sep 17 00:00:00 2001
From: matteozanoni <matteo.zanoni@energenius.it>
Date: Fri, 2 Feb 2024 10:18:40 +0100
Subject: [PATCH 1/3] Add optional `default_extra` param to formatter
 initializer.

This is used to specify extra parameters that are valid for all log
messages formatted with the formatter. It is usefull to avoid repeting
`extra={...}` in every log call.
---
 src/logfmter/formatter.py | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/logfmter/formatter.py b/src/logfmter/formatter.py
index f2e61d2..06c33f7 100644
--- a/src/logfmter/formatter.py
+++ b/src/logfmter/formatter.py
@@ -143,12 +143,18 @@ def __init__(
         self,
         keys: List[str] = ["at"],
         mapping: Dict[str, str] = {"at": "levelname"},
+        default_extra: Optional[Dict[str, str]] = None,
         datefmt: Optional[str] = None,
     ):
         self.keys = [self.normalize_key(key) for key in keys]
         self.mapping = {
             self.normalize_key(key): value for key, value in mapping.items()
         }
+        self.default_extra = (
+            {self.normalize_key(key): value for key, value in default_extra.items()}
+            if default_extra is not None
+            else {}
+        )
         self.datefmt = datefmt
 
     def format(self, record: logging.LogRecord) -> str:
@@ -163,6 +169,7 @@ def format(self, record: logging.LogRecord) -> str:
         else:
             params = {"msg": record.getMessage()}
 
+        params.update(self.default_extra)
         params.update(self.get_extra(record))
 
         tokens = []

From 7eb50e2fda890069d325f3681872db65cc2e124e Mon Sep 17 00:00:00 2001
From: Matteo Zanoni <56115369+matteo-zanoni@users.noreply.github.com>
Date: Fri, 1 Mar 2024 14:33:17 +0100
Subject: [PATCH 2/3] Update documentation regarding `default_extra`

The _old_ way described in the docs is now deprecated since the
`default_extra` parameter achieves the same outcome in a more clean and
explicit way.
---
 README.md | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/README.md b/README.md
index 0ed0d0a..30c022e 100644
--- a/README.md
+++ b/README.md
@@ -213,18 +213,13 @@ logging.error({"example": True}) # at=ERROR example=yes
 
 **Default Key/Value Pairs**
 
-Instead of providing key/value pairs at each log call, you can override
-the log record factory to provide defaults:
+Instead of providing key/value pairs at each log call, you can setup
+the formatter to provide defaults:
 
 ```py
-_record_factory = logging.getLogRecordFactory()
-
-def record_factory(*args, **kwargs):
-    record = _record_factory(*args, **kwargs)
-    record.trace_id = 123
-    return record
+from logfmter import Logfmter
 
-logging.setLogRecordFactory(record_factory)
+formatter = Logfmter(default_extra={"trace_id": 123})
 ```
 
 This will cause all logs to have the `trace_id=123` pair regardless of including

From c5cd08bc713277d28c39c54ac3cc2a1ea63e1f39 Mon Sep 17 00:00:00 2001
From: Matteo Zanoni <56115369+matteo-zanoni@users.noreply.github.com>
Date: Fri, 1 Mar 2024 14:50:03 +0100
Subject: [PATCH 3/3] add tests for default_extra

---
 tests/test_formatter.py | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/tests/test_formatter.py b/tests/test_formatter.py
index c646473..cbfa46c 100644
--- a/tests/test_formatter.py
+++ b/tests/test_formatter.py
@@ -266,3 +266,34 @@ def test_extra_keys(record):
     assert (
         Logfmter(keys=["at", "attr"]).format(record) == "at=INFO msg=alpha attr=value"
     )
+
+
+@pytest.mark.parametrize(
+    "default_extra,record,expected",
+    [
+        # When a parameter is present in the default_extra it should be emitted
+        (
+            {"extra1": "from_formatter"},
+            {"levelname": "INFO", "msg": "test"},
+            "at=INFO msg=test extra1=from_formatter",
+        ),
+        # When a parameter is present in the default_extra and also in the record
+        # the record value should take precedence
+        (
+            {"extra1": "from_formatter"},
+            {"levelname": "INFO", "extra1": "from_record", "msg": "test"},
+            "at=INFO msg=test extra1=from_record",
+        ),
+    ],
+)
+def test_format_default_extra(default_extra, record, expected):
+    """
+    If the `default_extra` parameter is specified in the formatter then all log
+    records must include such parameters.
+    """
+
+    # Generate a real `logging.LogRecord` from the provided dictionary.
+    record = logging.makeLogRecord(record)
+    formatter = Logfmter(keys=["at", "extra1"], default_extra=default_extra)
+
+    assert formatter.format(record) == expected