Add backwards-compatible logging for GCF Python 3.7

src/functions_framework/__init__.py

@@ -65,6 +65,17 @@ def __init__(
         self.data = data
 
 
+class _LoggingHandler(object):
+    """Logging replacement for stdout and stderr in GCF Python 3.7."""
+
+    def __init__(self, level):
+        self.level = level
+
+    def write(self, out):
+        if out.rstrip() != "":
+            self.level(out.rstrip())
+
+
 def _http_view_func_wrapper(function, request):
     def view_func(path):
         return function(request._get_current_object())
@@ -221,6 +232,19 @@ def handle_none(rv):
 
         app.make_response = handle_none
 
+        # Handle log severity backwards compatibility
+        import logging  # isort:skip
+        from google.cloud.logging_v2.handlers.container_engine import (  # isort:skip
+            ContainerEngineHandler,
+        )
+
+        handler = ContainerEngineHandler()
+        cloud_logger = logging.getLogger()
+        cloud_logger.setLevel(logging.DEBUG)
+        cloud_logger.addHandler(handler)
+        sys.stdout = _LoggingHandler(logging.info)
+        sys.stderr = _LoggingHandler(logging.warning)
+
     # Extract the target function from the source file
     if not hasattr(source_module, target):
         raise MissingTargetException(

tests/test_functions.py

@@ -495,6 +495,39 @@ def test_legacy_function_check_env(monkeypatch):
     assert resp.data.decode("utf-8") == target
 
 
+def test_legacy_function_log_severity(monkeypatch, capsys):
+    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": "stdout"})
+    captured = capsys.readouterr().err
+    assert resp.status_code == 200
+    assert '"severity": "INFO"' in captured
+
+    resp = client.post("/", json={"mode": "stderr"})
+    captured = capsys.readouterr().err
+    assert resp.status_code == 200
+    assert '"severity": "WARNING"' in captured
+
+    resp = client.post("/", json={"mode": "loginfo"})
+    captured = capsys.readouterr().err
+    assert resp.status_code == 200
+    assert '"severity": "INFO"' in captured
+
+    resp = client.post("/", json={"mode": "logwarn"})
+    captured = capsys.readouterr().err
+    assert resp.status_code == 200
+    assert '"severity": "WARNING"' in captured
+
+    resp = client.post("/", json={"mode": "logerr"})
+    captured = capsys.readouterr().err
+    assert resp.status_code == 200
+    assert '"severity": "ERROR"' 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 +1,47 @@
+# 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")
+    return name

tox.ini

@@ -5,6 +5,7 @@ envlist = py{35,36,37,38,39}-{ubuntu-latest,macos-latest,windows-latest},lint
 usedevelop = true
 deps =
     docker
+    google-cloud-logging
     pytest-cov
     pytest-integration
     pretend