Allow pulumi.export calls from unit tests (#4670)

The previous attempt to allow this didn't actually allow it, so this is
take two. As part of the previous attempt, I thought after tweaking the
test I had observed the test failing, and then succeeding after making
the product changes, but I must have been mistaken.

It turns out that our existing mocks tests weren't running at all
because of a missing `__init__.py` file. Once the missing `__init__.py`
is added, the tests run, but other tests ("test mode" tests) fail
because the code that creates the mocks and resources will run during
test discovery, and setting the mocks modifies global state.

To address the test issue, I've moved the mocks tests into their own
`test_with_mocks` package that can be run separately from other tests.

And addressed the original issue, by creating a root Stack resource if
one isn't already present when the mocks are set.

CHANGELOG.md

@@ -12,6 +12,9 @@ CHANGELOG
 - Fix a Regression in .NET unit testing.
  [#4656](https://github.com/pulumi/pulumi/pull/4656)
 
+- Allow `pulumi.export` calls from Python unit tests.
+  [#4670](https://github.com/pulumi/pulumi/pull/4670)
+
 ## 2.2.1 (2020-05-13)
 - Add new brew target to fix homebrew builds
  [#4633](https://github.com/pulumi/pulumi/pull/4633)
@@ -82,9 +85,6 @@ CHANGELOG
 - Increase the MaxCallRecvMsgSize for all RPC calls. 
   [#4455](https://github.com/pulumi/pulumi/pull/4455)
 
-- Allow `pulumi.export` calls from Python unit tests.
-  [#4518](https://github.com/pulumi/pulumi/pull/4518)
-
 ## 2.0.0 (2020-04-16)
 
 - CLI behavior change.  Commands in non-interactive mode (i.e. when `pulumi` has its output piped to

sdk/python/Makefile

@@ -41,6 +41,7 @@ install:: install_package install_plugin
 test_fast:: build
 	pipenv run pip install ./env/src
 	pipenv run python -m unittest discover -s lib/test -v
+	pipenv run python -m unittest discover -s lib/test_with_mocks -v
 
 test_all:: test_fast
 

sdk/python/lib/pulumi/runtime/mocks.py

@@ -23,10 +23,10 @@ from typing import Optional, Awaitable, Tuple, Union, Any, TYPE_CHECKING
 import grpc
 from google.protobuf import empty_pb2
 from . import rpc
-from .settings import Settings, configure, get_stack, get_project
+from .settings import Settings, configure, get_stack, get_project, get_root_resource
 from .sync_await import _sync_await
 from ..runtime.proto import engine_pb2, engine_pb2_grpc, provider_pb2, resource_pb2, resource_pb2_grpc
-from ..runtime.stack import _run_test
+from ..runtime.stack import Stack, run_pulumi_func
 from ..output import Output
 
 if TYPE_CHECKING:
@@ -35,7 +35,7 @@ if TYPE_CHECKING:
 
 def test(fn):
     def wrapper(*args, **kwargs):
-        _sync_await(_run_test(lambda: _sync_await(Output.from_input(fn(*args, **kwargs)).future())))
+        _sync_await(run_pulumi_func(lambda: _sync_await(Output.from_input(fn(*args, **kwargs)).future())))
     return wrapper
 
 class Mocks(ABC):
@@ -159,3 +159,7 @@ def set_mocks(mocks: Mocks,
                         dry_run=preview,
                         test_mode_enabled=True)
     configure(settings)
+
+    # Ensure a new root stack resource has been initialized.
+    if get_root_resource() is None:
+        Stack(lambda: None)

sdk/python/lib/pulumi/runtime/stack.py

@@ -80,15 +80,6 @@ async def run_in_stack(func: Callable):
     """
     await run_pulumi_func(lambda: Stack(func))
 
-async def _run_test(func: Callable):
-    """
-    Run the given function after ensuring a new stack resource has been initialized. This is meant
-    for internal runtime use only.
-    """
-    if get_root_resource() is None:
-        Stack(lambda: None)
-
-    await run_pulumi_func(func)
 
 @known_types.stack
 class Stack(ComponentResource):

sdk/python/lib/test/langhost/testing_with_mocks/.gitignore

@@ -1 +0,0 @@
-venv

sdk/python/lib/test_with_mocks/__init__.py

@@ -12,4 +12,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import resources
+"""
+The Pulumi SDK test package for testing with mocks.
+"""
+
+# The mocks tests are in their own `test_with_mocks` package so they can be run separately
+# from other tests in the `test` package. Otherwise, if the mocks tests were in the same
+# package as other tests, the code that initializes the mocks and test resources would run
+# during test discovery and impact the behavior of other tests due to modifying global state.

sdk/python/lib/test_with_mocks/resources.py

@@ -30,5 +30,6 @@ myinstance = Instance("instance",
                       value=pulumi.Output.secret("secret_value"))
 invoke_result = do_invoke()
 
+pulumi.export("hello", "world")
 pulumi.export("outprop", mycomponent.outprop)
 pulumi.export("public_ip", myinstance.public_ip)