Config file: make sphinx or mkdocs configuration required for projects using Sphinx or MkDocs

[stsewd]

• This introduces a breaking change for users overriding the new (undocumented) jobs (create_environment, install, build.html and friends). This is, if they have overridden any of those jobs without explicitly declaring a Sphinx or MkDocs key, we will no longer run the sphinx/mkdocs commands, not their setup.
• This hardcodes the dates from Post: deprecate config files without sphinx or mkdocs configuration website#342 to through an error to users using the configuration file without an explicit sphinx/mkdocs configuration.

This allows for users to keep using the new overrides without worrying about sphinx/mkdocs, while giving enough time to old users to migrate their projects to give an explicit path.

Some notes

• We are allowing to use sphinx/mkdocs and probably other keys with build.commands, even if those keys don't affect the build in anything. Not really something that "interrupt" users in any way, but it can be missleading.
• A next step should be to not make python required at all, right now we still create a virtual environment. We probably want to create a virtual env only if python was provided in the list of build.tools.

---

• Ref: Post: deprecate config files without sphinx or mkdocs configuration website#342
• Closes Deprecation: stop auto-finding conf.py/mkdocs.yml from the repository #10637
• Closes Config: avoid default sphinx/mkdocs steps #11819
• Closes Build: don't run default steps if no sphinx or mkdocs #11810
• Closes Npm install support #11216

[ericholscher]

This looks great to me. It seems like we're unblocking ourselves for supporting build.jobs.build for other projects while doing the deprecation here?

[humitos]

I took a quick look at this code and it seems to be correct. However, I've tried running the Docusaurus example from #11810 and it still breaks with TypeError: sequence item 0: expected str instance, NoneType found when running create_environment. I understand that the job build.jobs.create_envronment should not be run at all in this case.

Adding the following chunk makes that example to work correctly:

diff --git a/readthedocs/doc_builder/director.py b/readthedocs/doc_builder/director.py
index ce93c967c..fab8ecfd6 100644
--- a/readthedocs/doc_builder/director.py
+++ b/readthedocs/doc_builder/director.py
@@ -307,6 +307,12 @@ class BuildDirector:
         if self.data.config.build.jobs.create_environment is not None:
             self.run_build_job("create_environment")
             return
+
+        # If the builder is generic, we have nothing to do here,
+        # as the commnads are provided by the user.
+        if self.data.config.doctype == GENERIC:
+            return
+
         self.language_environment.setup_base()
 
     # Install

I think we need to do something similar for those jobs we don't want to run when it's a GENERIC builder.

[humitos]

I implemented my previous comment in #11863.

[humitos]

Looks fine. This is ready to merge 👍🏼