✨ NEW: add version switcher

docs/_static/switcher.json

@@ -0,0 +1,51 @@
+[
+  {
+    "name": "v0.7.1 (stable)",
+    "version": "0.7.1"
+  },
+  {
+    "version": "0.7.0"
+  },
+  {
+    "version": "0.6.3"
+  },
+  {
+    "version": "0.6.2"
+  },
+  {
+    "version": "0.6.1"
+  },
+  {
+    "version": "0.6.0"
+  },
+  {
+    "version": "0.5.2"
+  },
+  {
+    "version": "0.5.1"
+  },
+  {
+    "version": "0.5.0"
+  },
+  {
+    "version": "0.4.3"
+  },
+  {
+    "version": "0.4.2"
+  },
+  {
+    "version": "0.4.1"
+  },
+  {
+    "version": "0.4.0"
+  },
+  {
+    "version": "0.3.2"
+  },
+  {
+    "version": "0.3.1"
+  },
+  {
+    "version": "0.3.0"
+  }
+]

docs/conf.py

@@ -24,7 +24,8 @@
 
 import pydata_sphinx_theme
 
-version = pydata_sphinx_theme.__version__.replace("dev0", "")
+release = pydata_sphinx_theme.__version__
+version = release.replace("dev0", "")
 
 # -- General configuration ---------------------------------------------------
 
@@ -96,8 +97,14 @@
     # "navbar_align": "left",  # [left, content, right] For testing that the navbar items align properly
     # "navbar_start": ["navbar-logo", "navbar-version"],
     # "navbar_center": ["navbar-nav", "navbar-version"],  # Just for testing
-    # "navbar_end": ["navbar-icon-links", "navbar-version"]  # Just for testing
+    "navbar_end": ["version-switcher", "navbar-icon-links"],
     # "footer_items": ["copyright", "sphinx-version", ""]
+    "switcher": {
+        # "json_url": "/_static/switcher.json",
+        "json_url": "https://pydata-sphinx-theme.readthedocs.io/en/latest/_static/switcher.json",
+        "url_template": "https://pydata-sphinx-theme.readthedocs.io/en/v{version}/",
+        "version_match": version,
+    },
 }
 
 

docs/user_guide/configuring.rst

@@ -277,6 +277,198 @@ at the bottom. You can hide these buttons with the following configuration:
    }
 
 
+Add a dropdown to switch between docs versions
+==============================================
+
+You can add a button to your site that allows users to
+switch between versions of your documentation. The links in the version
+switcher will differ depending on which page of the docs is being viewed. For
+example, on the page ``https://mysite.org/en/v2.0/changelog.html``, the
+switcher links will go to ``changelog.html`` in the other versions of your
+docs. When clicked, the switcher will check for the existence of that page, and
+if it doesn't exist, redirect to the homepage of that docs version instead.
+
+The switcher requires the following configuration steps:
+
+1. Add a JSON file containing a list of the documentation versions that the
+   switcher should show on each page.
+
+2. Add a configuration dictionary called ``switcher`` to the
+   ``html_theme_options`` dict in ``conf.py``. ``switcher`` should have 3 keys:
+
+   - ``json_url``: the persistent location of the JSON file described above.
+   - ``url_template``: a template string used to generate the correct URLs for
+     the different documentation versions.
+   - ``version_match``: a string stating the version of the documentation that
+     is currently being browsed.
+
+3. Specify where to place the switcher in your page layout. For example, add
+   the ``"version-switcher"`` template to one of the layout lists in
+   ``html_theme_options`` (e.g., ``navbar_end``, ``footer_items``, etc).
+
+Below is a more in-depth description of each of these configuration steps.
+
+
+Add a JSON file to define your switcher's versions
+--------------------------------------------------
+
+First, write a JSON file stating which versions of your docs will be listed in
+the switcher's dropdown menu. That file should contain a list of entries that
+each have one or two fields:
+
+- ``version``: a version string. This will be inserted into
+  ``switcher['url_template']`` to create the links to other docs versions, and
+  also checked against ``switcher['version_match']`` to provide styling to the
+  switcher.
+- ``name``: an optional name to display in the switcher dropdown instead of the
+  version string (e.g., "latest", "stable", "dev", etc).
+
+Here is an example JSON file:
+
+.. code:: json
+
+    [
+        {
+            "name": "v2.1 (stable)",
+            "version": "2.1"
+        },
+        {
+            "version": "2.0"
+        },
+        {
+            "version": "1.0"
+        },
+    ]
+
+See the discussion of ``switcher['json_url']`` (below) for options of where to
+save the JSON file.
+
+
+Configure ``switcher['json_url']``
+----------------------------------
+
+The JSON file needs to be at a stable, persistent, fully-resolved URL (i.e.,
+not specified as a path relative to the sphinx root of the current doc build).
+Each version of your documentation should point to the same URL, so that as new
+versions are added to the JSON file all the older versions of the docs will
+gain switcher dropdown entries linking to the new versions. This could be done
+a few different ways:
+
+- The location could be one that is always associated with the most recent
+  documentation build (i.e., if your docs server aliases "latest" to the most
+  recent version, it could point to a location in the build tree of version
+  "latest"). For example:
+
+  .. code:: python
+
+      html_theme_options = {
+          ...,
+          "switcher": {
+              "json_url": "https://mysite.org/en/latest/_static/switcher.json",
+          }
+      }
+
+  In this case the JSON is versioned alongside the rest of the docs pages but
+  only the most recent version is ever loaded (even by older versions of the
+  docs).
+
+- The JSON could be saved in a folder that is listed under your site's
+  ``html_static_path`` configuration. See `the Sphinx static path documentation
+  <https://www.sphinx-doc.org/en/master/usage/configuration.html#confval-html_static_path>`_
+  for more information.
+
+- The JSON could be stored outside the doc build trees. This probably means it
+  would be outside the software repo, and would require you to add new version
+  entries to the JSON file manually as part of your release process. Example:
+
+  .. code:: python
+
+      html_theme_options = {
+          ...,
+          "switcher": {
+              "json_url": "https://mysite.org/switcher.json",
+          }
+      }
+
+
+Configure ``switcher['url_template']``
+--------------------------------------
+
+The switcher's links to other versions of your docs are made by combining the
+*version strings* from the JSON file with a *template string* you provide in
+``switcher['url_template']``. The template string must contain a placeholder
+``{version}`` and otherwise be a fully-resolved URL. For example:
+
+.. code:: python
+
+    html_theme_options = {
+        ...,
+        "switcher": {
+            "url_template": "https://mysite.org/en/version-{version}/",
+        }
+    }
+
+The example above will result in a link to
+``https://mysite.org/en/version-1.0/`` for the JSON entry for version
+``"1.0"``.
+
+
+Configure ``switcher['version_match']``
+---------------------------------------
+
+This configuration value tells the switcher what docs version is currently
+being viewed, and is used to style the switcher (i.e., to highlight the current
+docs version in the switcher's dropdown menu, and to change the text displayed
+on the switcher button).
+
+Typically you can re-use one of the sphinx variables ``version``
+or ``release`` as the value of ``switcher['version_match']``; which one you use
+depends on how granular your docs versioning is. See
+`the Sphinx "project info" documentation
+<https://www.sphinx-doc.org/en/master/usage/configuration.html#project-information>`__
+for more information). Example:
+
+.. code:: python
+
+    version = my_package_name.__version__.replace("dev0", "")  # may differ
+    html_theme_options = {
+        ...,
+        "switcher": {
+            "version_match": version,
+        }
+    }
+
+
+Specify where to display the switcher
+-------------------------------------
+
+Finally, tell the theme where on your site's pages you want the switcher to
+appear. There are many choices here: you can add ``"version-switcher"`` to one
+of the locations in ``html_theme_options`` (e.g., ``navbar_end``,
+``footer_items``, etc). For example:
+
+.. code:: python
+
+   html_theme_options = {
+      ...,
+      "navbar_end": ["version-switcher"]
+   }
+
+
+Alternatively, you could override one of the other templates to include the
+version switcher in a sidebar. For example, you could define
+``_templates/sidebar-nav-bs.html`` as:
+
+.. code:: jinja
+
+    {%- include 'version-switcher.html' -%}
+    {{ super() }}
+
+to insert a version switcher at the top of the left sidebar, while still
+keeping the default navigation below it. See :doc:`sections` for more
+information.
+
+
 Add an Edit this Page button
 ============================
 

docs/user_guide/sections.rst

@@ -118,6 +118,7 @@ will be named accordingly).
 - ``sidebar-ethical-ads.html``
 - ``sidebar-nav-bs.html``
 - ``sphinx-version.html``
+- ``version-switcher.html``
 
 Add your own HTML templates to theme sections
 =============================================

src/pydata_sphinx_theme/theme/pydata_sphinx_theme/_templates/version-switcher.html

@@ -0,0 +1,79 @@
+<div class="dropdown" id="version_switcher">
+    <button type="button" class="btn btn-primary btn-sm navbar-btn dropdown-toggle" id="version_switcher_button" data-toggle="dropdown">
+        {{ theme_switcher.get('version_match') }}  <!-- this text may get changed later by javascript -->
+        <span class="caret"></span>
+    </button>
+    <div id="version_switcher_menu" class="dropdown-menu list-group-flush py-0" aria-labelledby="version_switcher_button">
+    <!-- dropdown will be populated by javascript on page load -->
+    </div>
+</div>
+
+<!-- NOTE: this JS must live here (not in our global JS file) because it relies
+     on being processed by Jinja before it is run (specifically for replacing
+     variables {{ pagename }} and {{ theme_switcher }}.
+-->
+
+<script type="text/javascript">
+// Construct the target URL from the JSON components
+function buildURL(entry) {
+    var template = "{{ theme_switcher.get('url_template') }}";  // supplied by jinja
+    template = template.replace("{version}", entry.version);
+    return template;
+}
+
+// Check if corresponding page path exists in other version of docs
+// and, if so, go there instead of the homepage of the other docs version
+function checkPageExistsAndRedirect(event) {
+    const currentFilePath = "{{ pagename }}.html",
+          tryUrl = event.target.getAttribute("href");
+    let otherDocsHomepage = tryUrl.replace(currentFilePath, "");
+    $.ajax({
+        type: 'HEAD',
+        url: tryUrl,
+        // if the page exists, go there
+        success: function() {
+            location.href = tryUrl;
+        }
+    }).fail(function() {
+        location.href = otherDocsHomepage;
+    });
+    // this prevents the browser from following the href of the clicked node
+    // (which is fine because this function takes care of redirecting)
+    return false;
+}
+
+// Populate the version switcher from the JSON config file
+(function () {
+    $.getJSON("{{ theme_switcher.get('json_url') }}", function(data, textStatus, jqXHR) {
+        const currentFilePath = "{{ pagename }}.html";
+        // create links to the corresponding page in the other docs versions
+        $.each(data, function(index, entry) {
+            // if no custom name specified (e.g., "latest"), use version string
+            if (!("name" in entry)) {
+                entry.name = entry.version;
+            }
+            // create the node
+            const node = document.createElement("a");
+            node.setAttribute("class", "list-group-item list-group-item-action py-1");
+            node.textContent = `${entry.name}`;
+            // get the base URL for that doc version, add the current page's
+            // path to it, and set as `href`
+            entry.url = buildURL(entry);
+            node.setAttribute("href", `${entry.url}${currentFilePath}`);
+            // on click, AJAX calls will check if the linked page exists before
+            // trying to redirect, and if not, will redirect to the homepage
+            // for that version of the docs.
+            node.onclick = checkPageExistsAndRedirect;
+            $("#version_switcher_menu").append(node);
+            // replace dropdown button text with the preferred display name of
+            // this version, rather than using sphinx's {{ version }} variable.
+            // also highlight the dropdown entry for the currently-viewed
+            // version's entry
+            if (entry.version == "{{ theme_switcher.get('version_match') }}") {
+                node.classList.add("active");
+                $("#version_switcher_button").text(entry.name);
+            }
+        });
+    });
+})();
+</script>

src/pydata_sphinx_theme/theme/pydata_sphinx_theme/theme.conf

@@ -32,3 +32,4 @@ navbar_center = navbar-nav.html
 navbar_end = navbar-icon-links.html
 footer_items = copyright.html, sphinx-version.html
 page_sidebar_items = page-toc.html, edit-this-page.html
+switcher =