Post: deprecate config files without sphinx or mkdocs configuration

Ref:

- readthedocs/readthedocs.org#10637
- readthedocs/readthedocs.org#11819

Author: stsewd

content/images/deprecated-config-file-without-sphinx-or-mkdocs-config.jpg

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+title: Deprecation of configuration files without Sphinx or MkDocs configuration
+date: December 16, 2024
+description: Announcing the deprecation of configuration files without Sphinx or MkDocs configuration.
+category: Changelog
+tags: deprecation, configuration-file
+authors: Santos Gallegos
+status: published
+image: /images/deprecated-config-file-without-sphinx-or-mkdocs-config.jpg
+image_credit: Photo by <a href="https://unsplash.com/@jernejgraj?utm_content=creditCopyText&utm_medium=referral&utm_source=unsplash">Jernej Graj</a> on <a href="https://unsplash.com/photos/photo-of-seashore-during-golden-hour-n44KHcbp1_E?utm_content=creditCopyText&utm_medium=referral&utm_source=unsplash">Unsplash</a>
+
+We are announcing the deprecation of configuration files that do not contain a explicit `sphinx` or `mkdocs` configuration.
+
+If your `.readthedocs.yaml` configuration file doesn't contain a `sphinx.configuration` or `mkdocs.configuration` key,
+make sure to add it. For example, for a Sphinx project, your configuration file should look like this:
+
+```yaml
+version: 2
+sphinx:
+  # Path to your Sphinx configuration file.
+  configuration: docs/conf.py
+```
+
+For a MkDocs project, your configuration file should look like this:
+
+```yaml
+version: 2
+mkdocs:
+  # Path to your MkDocs configuration file.
+  configuration: mkdocs.yml
+```
+
+We used to automatically try to find the configuration file for your project,
+but in order to make builds more explicit and predictable, we are deprecating this behavior.
+This will also allows us to better support projects that don't use Sphinx or MkDocs in the near future.
+
+Deprecation timeline
+--------------------
+
+- **Monday, January 6, 2024**: Temporarily disallow projects without an explicit Sphinx or MkDocs configuration for 12 hours, from 00:01 PST to 11:59 PST.
+- **Monday, January 20, 2025**:Temporarily disallow projects without an explicit Sphinx or MkDocs configuration for 24 hours, from 00:01 PST to 23:59 PST.
+- **Monday, February 3, 2025**: Permanently disallow projects without an explicit Sphinx or MkDocs configuration.