os.environ not passed through Flask test_client() after Flask app been wrapped by wrap_wsgi_app()

[shianyow]

Expected Behavior

ID1 before test_client(): 123
ID2 before test_client(): 456
APPLICATION_ID after test_client(): testbed-test
ID1 after test_client(): 123
ID2 after test_client(): 456
APPLICATION_ID after test_client(): testbed-test

Actual Behavior

ID1 before test_client(): 123
ID2 before test_client(): 456
APPLICATION_ID after test_client(): testbed-test
ID1 after test_client(): 123
ID2 after test_client():
APPLICATION_ID after test_client():

Steps to Reproduce the Problem

1. Run the following code with Python 3

from flask import Flask
from google.appengine.api import wrap_wsgi_app
from google.appengine.ext import testbed
import os


os.environ['ID1'] = "123"
app = Flask(__name__)
app.wsgi_app = wrap_wsgi_app(app.wsgi_app)
os.environ['ID2'] = "456"


@app.route('/')
def hello():
    print("ID1 after test_client(): %s" % os.environ.get("ID1", ""))
    print("ID2 after test_client(): %s" % os.environ.get("ID2", ""))
    print("APPLICATION_ID after test_client(): %s" % os.environ.get("APPLICATION_ID", ""))
    return "OK"


t = testbed.Testbed()
t.activate()
t.setup_env()

print("ID1 before test_client(): %s" % os.environ.get("ID1", ""))
print("ID2 before test_client(): %s" % os.environ.get("ID2", ""))
print("APPLICATION_ID after test_client(): %s" % os.environ.get("APPLICATION_ID", ""))

app.test_client().get('/')

Specifications

• Version: appengine-python-standard 1.0.0
• Platform: Python 3.9

[SADA-Sam]

As far as I can tell, to fix this, you have to call testbed.activate before wrap_wsgi_app.
wrap_wsgi_app creates a copy of the os.envrion that will not (and, as is, can not) be patched by the testbed, so the testbed has to be activated first, so that environment is set up before wrap_wsgi_app copies it.

I wrote an analysis of this issue I encountered here.
#54 (comment)