Fix Read the Docs build for v2 documentation

Update .readthedocs.yaml to install from pyproject.toml extras instead of
missing requirements-dev.txt. Add mock imports in conf.py so autodoc works
without the native snap7 C library. Use sphinx_rtd_theme for consistent
styling.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: gijzelaerr

.readthedocs.yaml

@@ -12,4 +12,7 @@ sphinx:
 
 python:
   install:
-    - requirements: requirements-dev.txt
+    - method: pip
+      path: .
+      extra_requirements:
+        - doc

doc/conf.py

@@ -11,14 +11,21 @@
 
 import sys
 from pathlib import Path
+from unittest.mock import MagicMock
 
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 # sys.path.insert(0, os.path.abspath('.'))
 sys.path.insert(0, str(Path("..").resolve()))
 
-import snap7  # noqa: E402
+# Mock the snap7 C library loading for Read the Docs builds where the native
+# library is not available.
+try:
+    import snap7  # noqa: E402
+except (RuntimeError, OSError):
+    snap7 = MagicMock()  # type: ignore[misc]
+    snap7.__version__ = "2.1.0"
 
 # -- General configuration -----------------------------------------------------
 
@@ -29,6 +36,10 @@
 # coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
 extensions = ["sphinx.ext.autodoc", "sphinx.ext.coverage", "sphinx.ext.viewcode", "sphinx.ext.napoleon"]
 
+# Mock modules that depend on the native snap7 C library, so autodoc works
+# on Read the Docs where the library is not available.
+autodoc_mock_imports = ["snap7.common", "snap7.protocol"]
+
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ["_templates"]
 
@@ -93,7 +104,7 @@
 
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
-html_theme = "default"
+html_theme = "sphinx_rtd_theme"
 
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the