refactor: Move extension entrypoint from ext.py to __init__.py

Then it can be consistency with other sphinxnotes projects.

docs/conf.py

@@ -152,7 +152,7 @@
 # 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('../src/sphinxnotes'))
-extensions.append('snippet.ext')
+extensions.append('snippet')
 
 # DOG FOOD CONFIGURATION START
 

src/sphinxnotes/snippet/__init__.py

@@ -0,0 +1,36 @@
+"""
+sphinxnotes.snippet
+~~~~~~~~~~~~~~~~~~~
+
+Sphinx extension entrypoint.
+
+:copyright: Copyright 2024 Shengyu Zhang
+:license: BSD, see LICENSE for details.
+"""
+
+
+def setup(app):
+    # **WARNING**: We don't import these packages globally, because the current
+    # package (sphinxnotes.snippet) is always resloved when importing
+    # sphinxnotes.snippet.*. If we import packages here, eventually we will
+    # load a lot of packages from the Sphinx. It will seriously **SLOW DOWN**
+    # the startup time of our CLI tool (sphinxnotes.snippet.cli).
+    #
+    # .. seealso:: https://github.com/sphinx-notes/snippet/pull/31
+    from .ext import (
+        SnippetBuilder,
+        on_config_inited,
+        on_env_get_outdated,
+        on_doctree_resolved,
+        on_builder_finished,
+    )
+
+    app.add_builder(SnippetBuilder)
+
+    app.add_config_value('snippet_config', {}, '')
+    app.add_config_value('snippet_patterns', {'*': ['.*']}, '')
+
+    app.connect('config-inited', on_config_inited)
+    app.connect('env-get-outdated', on_env_get_outdated)
+    app.connect('doctree-resolved', on_doctree_resolved)
+    app.connect('build-finished', on_builder_finished)

src/sphinxnotes/snippet/ext.py

@@ -1,10 +1,10 @@
 """
-sphinxnotes.ext.snippet
+sphinxnotes.snippet.ext
 ~~~~~~~~~~~~~~~~~~~~~~~
 
-Sphinx extension for sphinxnotes.snippet.
+Sphinx extension implementation, but the entrypoint is located at __init__.py.
 
-:copyright: Copyright 2021 Shengyu Zhang
+:copyright: Copyright 2024 Shengyu Zhang
 :license: BSD, see LICENSE for details.
 """
 
@@ -206,15 +206,3 @@ def _format_modified_time(timestamp: float) -> str:
     """Return an RFC 3339 formatted string representing the given timestamp."""
     seconds, fraction = divmod(timestamp, 1)
     return time.strftime('%Y-%m-%d %H:%M:%S', time.gmtime(seconds)) + f'.{fraction:.3f}'
-
-
-def setup(app: Sphinx):
-    app.add_builder(SnippetBuilder)
-
-    app.add_config_value('snippet_config', {}, '')
-    app.add_config_value('snippet_patterns', {'*': ['.*']}, '')
-
-    app.connect('config-inited', on_config_inited)
-    app.connect('env-get-outdated', on_env_get_outdated)
-    app.connect('doctree-resolved', on_doctree_resolved)
-    app.connect('build-finished', on_builder_finished)