Introduce/document VALIDATE_PYPROJECT_NO_NETWORK (#34)

README.rst

@@ -111,15 +111,19 @@ To do so, don't forget to add it to your `virtual environment`_ or specify it as
    ``packaging`` and ``trove-classifiers`` will be automatically pulled as
    dependencies. ``tomli`` is a lightweight parser for TOML, while
    ``packaging`` and ``trove-classifiers`` are used to validate aspects of `PEP
-   621`_
+   621`_.
 
    If you are only interested in using the Python API and wants to keep the
-   depedependencies minimal, you can also install ``validate-pyproject``
+   dependencies minimal, you can also install ``validate-pyproject``
    (without the ``[all]`` extra dependencies group).
+
    If you don't install ``trove-classifiers``, ``validate-pyproject`` will
-   perform a weaker validation. On the other hand, if ``validate-pyproject``
-   cannot find a copy of ``packaging`` in your environment, the validation will
-   fail.
+   try to download a list of valid classifiers directly from PyPI
+   (to prevent that, set the environment variable
+   ``NO_NETWORK`` or ``VALIDATE_PYPROJECT_NO_NETWORK``).
+
+   On the other hand, if ``validate-pyproject`` cannot find a copy of
+   ``packaging`` in your environment, the validation will fail.
 
 More details about ``validate-pyproject`` and its Python API can be found in
 `our docs`_, which includes a description of the `used JSON schemas`_,

src/validate_pyproject/formats.py

@@ -139,7 +139,7 @@ def __call__(self, value: str) -> bool:
         if self.downloaded is False:
             return True
 
-        if os.getenv("NO_NETWORK"):
+        if os.getenv("NO_NETWORK") or os.getenv("VALIDATE_PYPROJECT_NO_NETWORK"):
             self.downloaded = False
             msg = (
                 "Install ``trove-classifiers`` to ensure proper validation. "

tests/test_formats.py

@@ -346,8 +346,11 @@ def test_valid_download_only_once(self, monkeypatch):
             assert validator(classifier) is True
         downloader.assert_called_once()
 
-    def test_always_valid_with_no_network(self, monkeypatch):
-        monkeypatch.setenv("NO_NETWORK", "1")
+    @pytest.mark.parametrize(
+        "no_network", ("NO_NETWORK", "VALIDATE_PYPROJECT_NO_NETWORK")
+    )
+    def test_always_valid_with_no_network(self, monkeypatch, no_network):
+        monkeypatch.setenv(no_network, "1")
         validator = formats._TroveClassifier()
         assert validator("Made Up :: Classifier") is True
         assert not validator.downloaded

tests/test_vendoring.py

@@ -11,3 +11,8 @@ def test_api(tmp_path):
 def test_cli(tmp_path):
     with pytest.warns(DeprecationWarning, match="will be removed"):
         cli.run(["-O", str(tmp_path)])
+
+
+def test_main(tmp_path):
+    with pytest.warns(DeprecationWarning, match="will be removed"):
+        cli.main(["-O", str(tmp_path)])