From 4b183be2254b48645959a494821c00ada98e5947 Mon Sep 17 00:00:00 2001
From: Lars Wirzenius <liw@liw.fi>
Date: Fri, 4 Aug 2017 18:01:02 +0300
Subject: Add: log object massager

---
 slog/slog.py       |  7 +++++++
 slog/slog_tests.py | 20 +++++++++++++++++++-
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/slog/slog.py b/slog/slog.py
index 81d2c61..b3725dd 100644
--- a/slog/slog.py
+++ b/slog/slog.py
@@ -46,6 +46,7 @@ class StructuredLog:
         self._msg_counter = slog.Counter()
         self._context = {}
         self._writers = []
+        self._massagers = []
 
     def close(self):
         for writer, _ in self._writers:
@@ -55,6 +56,9 @@ class StructuredLog:
     def add_log_writer(self, writer, filter_rule):
         self._writers.append((writer, filter_rule))
 
+    def add_log_massager(self, massager):
+        self._massagers.append(massager)
+
     def set_context(self, new_context):
         thread_id = self._get_thread_id()
         self._context[thread_id] = new_context
@@ -73,6 +77,9 @@ class StructuredLog:
             log_obj[key] = self._convert_value(value)
 
         self._add_extra_fields(log_obj, exc_info)
+        for massager in self._massagers:
+            log_obj = massager(log_obj)
+
         for writer, filter_rule in self._writers:
             if filter_rule.allow(log_obj):
                 writer.write(log_obj)
diff --git a/slog/slog_tests.py b/slog/slog_tests.py
index cc18f15..04f1cf4 100644
--- a/slog/slog_tests.py
+++ b/slog/slog_tests.py
@@ -187,7 +187,7 @@ class StructuredLogTests(unittest.TestCase):
         self.assertEqual(objs[0]['dikt'], dikt)
 
     def test_logs_to_two_files(self):
-        filename1 = os.path.join(self.tempdir, 'slog1XS')
+        filename1 = os.path.join(self.tempdir, 'slog1')
         writer1 = slog.FileSlogWriter()
         writer1.set_filename(filename1)
 
@@ -205,6 +205,24 @@ class StructuredLogTests(unittest.TestCase):
 
         self.assertEqual(objs1, objs2)
 
+    def test_massages_log_objects(self):
+
+        def add_foo(log_obj):
+            log_obj['foo'] = 'this is foo'
+            return log_obj
+
+        filename = os.path.join(self.tempdir, 'slog.log')
+        writer = slog.FileSlogWriter()
+        writer.set_filename(filename)
+
+        log = slog.StructuredLog()
+        log.add_log_writer(writer, slog.FilterAllow())
+        log.add_log_massager(add_foo)
+
+        log.log('test', msg_text='hello')
+        objs = self.read_log_entries(writer)
+        self.assertEqual(objs[0]['foo'], 'this is foo')
+
 
 class FileSlogWriterTests(unittest.TestCase):
 
-- 
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