Add backwards-compatible logging for GCF Python 3.7

conftest.py

@@ -12,7 +12,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import logging
 import os
+import sys
+
+from importlib import reload
 
 import pytest
 
@@ -26,3 +30,15 @@ def isolate_environment():
     finally:
         os.environ.clear()
         os.environ.update(_environ)
+
+
+@pytest.fixture(scope="function", autouse=True)
+def isolate_logging():
+    "Ensure any changes to logging are isolated to individual tests" ""
+    try:
+        yield
+    finally:
+        sys.stdout = sys.__stdout__
+        sys.stderr = sys.__stderr__
+        logging.shutdown()
+        reload(logging)

src/functions_framework/__init__.py

@@ -14,6 +14,7 @@
 
 import functools
 import importlib.util
+import io
 import json
 import os.path
 import pathlib
@@ -65,6 +66,19 @@ def __init__(
         self.data = data
 
 
+class _LoggingHandler(io.TextIOWrapper):
+    """Logging replacement for stdout and stderr in GCF Python 3.7."""
+
+    def __init__(self, level, stderr=sys.stderr):
+        io.TextIOWrapper.__init__(self, io.StringIO(), encoding=stderr.encoding)
+        self.level = level
+        self.stderr = stderr
+
+    def write(self, out):
+        payload = dict(severity=self.level, message=out.rstrip("\n"))
+        return self.stderr.write(json.dumps(payload) + "\n")
+
+
 def _http_view_func_wrapper(function, request):
     def view_func(path):
         return function(request._get_current_object())
@@ -221,6 +235,17 @@ def handle_none(rv):
 
         app.make_response = handle_none
 
+        # Handle log severity backwards compatibility
+        import logging  # isort:skip
+
+        logging.info = _LoggingHandler("INFO", sys.stderr).write
+        logging.warn = _LoggingHandler("ERROR", sys.stderr).write
+        logging.warning = _LoggingHandler("ERROR", sys.stderr).write
+        logging.error = _LoggingHandler("ERROR", sys.stderr).write
+        logging.critical = _LoggingHandler("ERROR", sys.stderr).write
+        sys.stdout = _LoggingHandler("INFO", sys.stderr)
+        sys.stderr = _LoggingHandler("ERROR", sys.stderr)
+
     # Extract the target function from the source file
     if not hasattr(source_module, target):
         raise MissingTargetException(

tests/test_functions.py

@@ -16,6 +16,7 @@
 import os
 import pathlib
 import re
+import sys
 import time
 
 import pretend
@@ -495,6 +496,30 @@ def test_legacy_function_check_env(monkeypatch):
     assert resp.data.decode("utf-8") == target
 
 
+@pytest.mark.parametrize(
+    "mode, expected",
+    [
+        ("loginfo", '"severity": "INFO"'),
+        ("logwarn", '"severity": "ERROR"'),
+        ("logerr", '"severity": "ERROR"'),
+        ("logcrit", '"severity": "ERROR"'),
+        ("stdout", '"severity": "INFO"'),
+        ("stderr", '"severity": "ERROR"'),
+    ],
+)
+def test_legacy_function_log_severity(monkeypatch, capfd, mode, expected):
+    source = TEST_FUNCTIONS_DIR / "http_check_severity" / "main.py"
+    target = "function"
+
+    monkeypatch.setenv("ENTRY_POINT", target)
+
+    client = create_app(target, source).test_client()
+    resp = client.post("/", json={"mode": mode})
+    captured = capfd.readouterr().err
+    assert resp.status_code == 200
+    assert expected in captured
+
+
 def test_legacy_function_returns_none(monkeypatch):
     source = TEST_FUNCTIONS_DIR / "returns_none" / "main.py"
     target = "function"

tests/test_functions/http_check_severity/main.py

@@ -0,0 +1,49 @@
+# Copyright 2020 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Function used in Worker tests of legacy GCF Python 3.7 logging."""
+import logging
+import os
+import sys
+
+X_GOOGLE_FUNCTION_NAME = "gcf-function"
+X_GOOGLE_ENTRY_POINT = "function"
+HOME = "/tmp"
+
+
+def function(request):
+    """Test function which logs to the appropriate output.
+
+    Args:
+      request: The HTTP request which triggered this function. Must contain name
+        of the requested output in the 'mode' field in JSON document
+        in request body.
+
+    Returns:
+      Value of the mode.
+    """
+    name = request.get_json().get("mode")
+    if name == "stdout":
+        print("log")
+    elif name == "stderr":
+        print("log", file=sys.stderr)
+    elif name == "loginfo":
+        logging.info("log")
+    elif name == "logwarn":
+        logging.warning("log")
+    elif name == "logerr":
+        logging.error("log")
+    elif name == "logcrit":
+        logging.critical("log")
+    return name