Do not show announcement banner if announcement contents are empty (pydata#1703)

* Do not show announcement banner if announcement contents are empty

Also add documentation about updating and removing announcement banners.

* dedent

* Apply suggestions from code review

---------

Co-authored-by: Daniel McCloy <[email protected]>

Author: 2 people

docs/user_guide/announcements.rst

@@ -41,6 +41,15 @@ For example, the following configuration tells the theme to load the ``custom-te
       "announcement": "https://github.com/pydata/pydata-sphinx-theme/raw/main/docs/_templates/custom-template.html",
    }
 
+Update or remove announcement banner
+------------------------------------
+
+To update or remove the announcement banner, you can change the value of
+``html_theme_options["announcement"]`` in your ``conf.py`` or you can edit the
+contents of the ``custom-template.html`` file directly. For example, if you have a
+temporary announcement that you want to remove without rebuilding your
+documentation pages, you can use an empty ``custom-template.html`` file and the
+banner will be hidden.
 
 .. _version-warning-banners:
 

src/pydata_sphinx_theme/theme/pydata_sphinx_theme/sections/announcement.html

@@ -7,6 +7,10 @@
 fetch("{{ theme_announcement }}")
   .then(res => {return res.text();})
   .then(data => {
+    if (data.length === 0) {
+      console.log("[PST]: Empty announcement at: {{ theme_announcement }}");
+      return;
+    }
     div = document.querySelector(".bd-header-announcement");
     div.classList.add(...{{ header_classes | tojson }});
     div.innerHTML = `<div class="bd-header-announcement__content">${data}</div>`;