improve dash import test

see #1143

Author: alexcjohnson

Diff for: .circleci/config.yml

@@ -122,7 +122,7 @@ jobs:
           command: |
               . venv/bin/activate && pip install --no-cache-dir --upgrade -e . --progress-bar off && mkdir packages
               cd dash-renderer && renderer build && python setup.py sdist && mv dist/* ../packages/ && cd ..
-              git clone --depth 1 https://github.com/plotly/dash-core-components.git
+              git clone --depth 1 -b import-test https://github.com/plotly/dash-core-components.git
               cd dash-core-components && npm ci && npm run build && python setup.py sdist && mv dist/* ../packages/  && cd ..
               ls -la packages
       - persist_to_workspace:

Diff for: dash/__init__.py

@@ -1,7 +1,11 @@
-from .dash import Dash, no_update  # noqa: F401
-from . import dependencies  # noqa: F401
-from . import development  # noqa: F401
-from . import exceptions  # noqa: F401
-from . import resources  # noqa: F401
-from .version import __version__  # noqa: F401
-from ._callback_context import callback_context  # noqa: F401
+# pylint: disable=C0413
+# __plotly_dash is for the "make sure you don't have a dash.py" check
+# must come before any other imports.
+__plotly_dash = True
+from .dash import Dash, no_update  # noqa: F401,E402
+from . import dependencies  # noqa: F401,E402
+from . import development  # noqa: F401,E402
+from . import exceptions  # noqa: F401,E402
+from . import resources  # noqa: F401,E402
+from .version import __version__  # noqa: F401,E402
+from ._callback_context import callback_context  # noqa: F401,E402

Diff for: package.json

@@ -22,6 +22,7 @@
     "private::test.unit-dash": "pytest tests/unit",
     "private::test.unit-renderer": "cd dash-renderer && npm run test",
     "private::test.integration-dash": "TESTFILES=$(circleci tests glob \"tests/integration/**/test_*.py\" | circleci tests split --split-by=timings) && pytest --headless --nopercyfinalize --junitxml=test-reports/junit_intg.xml ${TESTFILES}",
+    "private::test.integration-dash-import": "cd tests/integration/dash && python dash_import_test.py",
     "format": "run-s private::format.*",
     "initialize": "run-s private::initialize.*",
     "lint": "run-s private::lint.*",

Diff for: tests/integration/dash/dash_import_test.py

@@ -0,0 +1,15 @@
+# NOTE: this is NOT a pytest test. Just run it as a regular Python script.
+# pytest does some magic that makes the issue we're trying to test disappear.
+
+import types
+import os
+
+import dash
+
+assert isinstance(dash, types.ModuleType), "dash can be imported"
+
+this_dir = os.path.dirname(__file__)
+with open(os.path.join(this_dir, "../../../dash/version.py")) as fp:
+    assert dash.__version__ in fp.read(), "version is consistent"
+
+assert getattr(dash, "Dash").__name__ == "Dash", "access to main Dash class is valid"

Diff for: tests/integration/dash/org.py

@@ -0,0 +1,3 @@
+# used implicitly by dash_import_test
+# to test https://github.com/plotly/dash/issues/1143
+import dash_core_components as dcc  # noqa: F401