[fix] interaction with autodoc plugin / sphinx-build in subprocess

To update changes to the doc strings (autodoc) in the source code in the HTML
output, the sphinx-build must not run in the same process as the server /
sphinx-build must run in a subprocess so that changed source code is
re-imported.

This issue was introduced in commit d57f117 / a commit without a PR & review.

Related: sphinx-doc#31 (comment)
Closes: sphinx-doc#148

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

sphinx_autobuild/build.py

@@ -2,9 +2,6 @@
 
 import subprocess
 
-# This isn't public API, but we want to avoid a subprocess call
-from sphinx.cmd.build import build_main
-
 from sphinx_autobuild.utils import show
 
 
@@ -32,12 +29,10 @@ def __call__(self, *, rebuild: bool = True):
             raise
 
         show(command=["sphinx-build"] + self.sphinx_args)
-
-        # NOTE:
-        # sphinx.cmd.build.build_main is not considered to be public API,
-        # but as this is a first-party project, we can cheat a little bit.
-        if return_code := build_main(self.sphinx_args):
-            print(f"Sphinx exited with exit code: {return_code}")
+        try:
+            subprocess.run(["sphinx-build"] + self.sphinx_args, check=True)
+        except subprocess.CalledProcessError as e:
+            print(f"Sphinx exited with exit code: {e.returncode}")
             print(
                 "The server will continue serving the build folder, but the contents "
                 "being served are no longer in sync with the documentation sources. "