Fix a test failure caused by an internal docutils open() call

[kurtmckee]

docutils 0.22 introduced an RST stylesheet feature that must be able to open files during RST-to-HTML rendering.

The original design of the test_cli_explicit_format test patched pathlib.Path.open() so it would always return the same open file instance...which was always closed on first use. This caused a failure when docutils tried to open minimal.css:

ValueError: I/O operation on closed file.

This change introduces a more complex mocking strategy that documents and meets the current technical requirements.

When combined with #328, the full test suite will now pass.

Note

It may be worthwhile to consider using the pyfakefs plugin, and pytest's capsys, to simplify some of the mocking and patching used in the test suite.

[kurtmckee]

Hello @miketheman, I hope you're well! I was wondering if you could take a look at this PR -- and a couple of others -- that address lint and test suite failures?

For example, this PR fixes new CI failures; #328 addresses lint failures; and both of these issues were found when CI ran on #327.

Thanks for your time, and have a great weekend!

[miketheman]

Hey @kurtmckee ! Thanks for looking into it.

This definitely is an odd smell, but I think there might be a simpler solution here, by copying the input to a temp file, using builtin fixture tmp_path. Something like:

-def test_cli_explicit_format(input_file):
+def test_cli_explicit_format(input_file, tmp_path):
     fmt = input_file.suffix.lstrip(".")
-    with input_file.open() as fp, \
-            mock.patch("pathlib.Path.open", return_value=fp), \
-            mock.patch("builtins.print") as print_:
-        main(["-f", fmt, "no-file.invalid"])
+
+    temp_input = tmp_path / "no-file.invalid"
+    temp_input.write_text(input_file.read_text())
+
+    with mock.patch("builtins.print") as print_:
+        main(["-f", fmt, str(temp_input)])

What do you think?

[kurtmckee]

Works for me! I had been under the impression that it was undesirable to write a temporary file so I tried to stick with that assumed goal. Much easier this way!

I've updated the PR to match your suggestion. Type annotation linting will fail; that's addressed in #328.

[miketheman]

Thanks for working through this, @kurtmckee !