python · AA-Turner · Jul 16, 2024
diff --git a/pyproject.toml b/pyproject.toml
@@ -29,6 +29,10 @@ classifiers = [
   "Topic :: Documentation",
   "Topic :: Software Development :: Documentation",
 ]
+dependencies = [
+  "httpx>=0.25",
+  'tomli>=2; python_version < "3.11"',
+]
 urls.Code = "https://github.com/python/python-docs-theme"
 urls.Download = "https://pypi.org/project/python-docs-theme/"
 urls.Homepage = "https://github.com/python/python-docs-theme/"

diff --git a/python_docs_theme/__init__.py b/python_docs_theme/__init__.py
@@ -2,16 +2,85 @@
 
 import hashlib
 import os
+import sys
 from functools import lru_cache
 from pathlib import Path
-from typing import Any
+from typing import Any, Literal
 
+import httpx
 import sphinx.application
 from sphinx.builders.html import StandaloneHTMLBuilder
 
+if sys.version_info[:2] >= (3, 11):
+    import tomllib
+else:
+    import tomli as tomllib
+
 THEME_PATH = Path(__file__).parent.resolve()
 
 
+def _version_label(
+    version_name: str,
+    status: Literal["feature", "prerelease", "bugfix", "security", "end-of-life"],
+) -> str:
+    if status == "feature":
+        return f"dev ({version_name})"
+    if status == "prerelease":
+        return f"pre ({version_name})"
+    if status in {"end-of-life", "security", "bugfix"}:
+        return version_name
+    msg = f"Unknown status: {status}"
+    raise ValueError(msg)
+
+
+def _builder_inited(app):
+    html_context = app.config.html_context
+    language = app.config.language
+    release = app.config.release
+    if app.config.html_theme != "python_docs_theme":
+        return
+
+    # Get the current branch statuses
+    releases = httpx.get(
+        "https://raw.githubusercontent.com/python/devguide/main/include/release-cycle.json",
+        timeout=30,
+    ).json()
+    # Get appropriate version labels
+    release_labels = {
+        name: _version_label(name, release["status"])
+        for name, release in releases.items()
+    }
+    # Update the current version to be the full release string
+    if (short_version := ".".join(release.split(".", 2)[:2])) in release_labels:
+        release_labels[short_version] = release
+
+    # Store the versions in the context as a sorted list of tuples
+    html_context["switchers_versions"] = sorted(
+        release_labels.items(),
+        key=lambda release_label: tuple(map(int, release_label[0].split("."))),
+        reverse=True,
+    )
+
+    # Get the languages from the docsbuild-scripts config
+    docsbuild_config = httpx.get(
+        "https://raw.githubusercontent.com/python/docsbuild-scripts/main/config.toml",
+        timeout=30,
+    ).text
+    # Convert language tags and extract language names
+    languages = [
+        (iso639_tag.replace("_", "-").lower(), section["name"])
+        for iso639_tag, section in tomllib.loads(docsbuild_config)["languages"].items()
+        if section.get("in_prod", True)
+    ]
+
+    # If we are working on a language that is not in the list, add it
+    if language and language not in dict(languages):
+        languages.append((language, language))
+
+    # Store the versions in the context as a sorted list of tuples
+    html_context["switchers_languages"] = sorted(languages)
+
+
 @lru_cache(maxsize=None)
 def _asset_hash(path: str) -> str:
     """Append a `?digest=` to an url based on the file content."""
@@ -56,6 +125,7 @@ def setup(app):
     current_dir = os.path.abspath(os.path.dirname(__file__))
     app.add_html_theme("python_docs_theme", current_dir)
 
+    app.connect("builder-inited", _builder_inited)
     app.connect("html-page-context", _html_page_context)
 
     return {

diff --git a/python_docs_theme/layout.html b/python_docs_theme/layout.html
@@ -17,8 +17,20 @@ <h3>{{ _('Navigation') }}</h3>
           <li><img src="{{ pathto('_static/' ~ theme_root_icon, 1) }}" alt="{{ theme_root_icon_alt_text }}" style="vertical-align: middle; margin-top: -1px"/></li>
           <li><a href="{{theme_root_url}}">{{theme_root_name}}</a>{{ reldelim1 }}</li>
           <li class="switchers">
-            <div class="language_switcher_placeholder"></div>
-            <div class="version_switcher_placeholder"></div>
+            <div class="language_switcher_placeholder">{% if switchers_languages %}
+                <select class="language">
+                {% for lang_code, lang_name in switchers_languages -%}
+                    <option value="{{ lang_code }}" {%- if lang_code == language %} selected="true" {%- endif %}>{{ lang_name }}</option>
+                {% endfor -%}
+                </select>
+            {% endif -%}</div>
+            <div class="version_switcher_placeholder">{% if switchers_versions %}
+                <select class="version-select">
+                {% for (version_name, version_title) in switchers_versions -%}
+                    <option value="{{ version_name }}" {%- if version_title == release %} selected="true" {%- endif %}>{{ version_title }}</option>
+                {% endfor -%}
+                </select>
+            {% endif %}</div>
           </li>
           <li>
               {% if theme_root_include_title %}
@@ -74,6 +86,7 @@ <h3>{{ _('Navigation') }}</h3>
     <link rel="shortcut icon" type="image/png" href="{{ pathto('_static/' ~ theme_root_icon, 1) }}" />
     {%- if builder != "htmlhelp" %}
         {%- if not embedded %}
+            <script type="text/javascript" src="{{ pathto('_static/switchers.js', 1) }}"></script>
             <script type="text/javascript" src="{{ pathto('_static/copybutton.js', 1) }}"></script>
             <script type="text/javascript" src="{{ pathto('_static/menu.js', 1) }}"></script>
             <script type="text/javascript" src="{{ pathto('_static/search-focus.js', 1) }}"></script>

diff --git a/python_docs_theme/static/switchers.js b/python_docs_theme/static/switchers.js
@@ -0,0 +1,131 @@
+'use strict';
+
+const _is_file_uri = (uri) => uri.startsWith('file://');
+
+const _IS_LOCAL = _is_file_uri(window.location.href);
+const _CONTENT_ROOT = document.documentElement.dataset.content_root;
+const _CURRENT_PREFIX = _IS_LOCAL
+  ? null
+  : new URL(_CONTENT_ROOT, window.location).pathname;
+const _CURRENT_RELEASE = DOCUMENTATION_OPTIONS.VERSION || '';
+const _CURRENT_VERSION = _CURRENT_RELEASE.split('.').slice(0, 2).join('.');
+const _CURRENT_LANGUAGE = DOCUMENTATION_OPTIONS.LANGUAGE?.toLowerCase() || 'en';
+
+/**
+ * Change the current page to the first existing URL in the list.
+ * @param {Array<string>} urls
+ * @private
+ */
+const _navigate_to_first_existing = async (urls) => {
+  // Navigate to the first existing URL of urls.
+  for (const url of urls) {
+    try {
+      const response = await fetch(url, { method: 'GET' })
+      if (response.ok) {
+        window.location.href = url;
+        return url;  // Avoid race conditions with multiple redirects
+      }
+    } catch(err) {
+      console.error(`Error in: ${url}`);
+      console.error(err)
+    }
+  }
+
+  // if all else fails, redirect to the d.p.o root
+  window.location.href = '/';
+};
+
+/**
+ * Navigate to the selected version.
+ * @param {Event} event
+ * @returns {Promise<void>}
+ */
+const on_version_switch = async (event) => {
+  if (_IS_LOCAL) return;
+
+  const selected_version = event.target.value;
+  // Special 'default' case for English.
+  const new_prefix =
+    _CURRENT_LANGUAGE === 'en'
+      ? `/${selected_version}/`
+      : `/${_CURRENT_LANGUAGE}/${selected_version}/`;
+  const new_prefix_en = `/${selected_version}/`;
+  if (_CURRENT_PREFIX !== new_prefix) {
+    // Try the following pages in order:
+    // 1. The current page in the current language with the new version
+    // 2. The current page in English with the new version
+    // 3. The documentation home in the current language with the new version
+    // 4. The documentation home in English with the new version
+    await _navigate_to_first_existing([
+      window.location.href.replace(_CURRENT_PREFIX, new_prefix),
+      window.location.href.replace(_CURRENT_PREFIX, new_prefix_en),
+      new_prefix,
+      new_prefix_en,
+    ]);
+  }
+};
+
+/**
+ * Navigate to the selected language.
+ * @param {Event} event
+ * @returns {Promise<void>}
+ */
+const on_language_switch = async (event) => {
+  if (_IS_LOCAL) return;
+
+  const selected_language = event.target.value;
+  // Special 'default' case for English.
+  const new_prefix =
+    selected_language === 'en'
+      ? `/${_CURRENT_VERSION}/`
+      : `/${selected_language}/${_CURRENT_VERSION}/`;
+  if (_CURRENT_PREFIX !== new_prefix) {
+    // Try the following pages in order:
+    // 1. The current page in the new language with the current version
+    // 2. The documentation home in the new language with the current version
+    await _navigate_to_first_existing([
+      window.location.href.replace(_CURRENT_PREFIX, new_prefix),
+      new_prefix,
+    ]);
+  }
+};
+
+/**
+ * Set up the version and language switchers.
+ * @returns {Promise<void>}
+ */
+const initialise_switchers = async () => {
+  try {
+    // Update the version select elements
+    document
+      .querySelectorAll('.version_switcher_placeholder select')
+        .forEach((select) => {
+          if (_IS_LOCAL) {
+            select.disabled = true;
+            select.title = 'Version switching is disabled in local builds';
+          }
+          select.addEventListener('change', on_version_switch);
+          select.parentElement.classList.remove('version_switcher_placeholder');
+        });
+
+    // Update the language select elements
+    document
+      .querySelectorAll('.language_switcher_placeholder select')
+        .forEach((select) => {
+          if (_IS_LOCAL) {
+            select.disabled = true;
+            select.title = 'Language switching is disabled in local builds';
+          }
+          select.addEventListener('change', on_language_switch);
+          select.parentElement.classList.remove('language_switcher_placeholder');
+        });
+  } catch (error) {
+    console.error(error);
+  }
+};
+
+if (document.readyState !== 'loading') {
+  initialise_switchers();
+} else {
+  document.addEventListener('DOMContentLoaded', initialise_switchers);
+}