fix: Always assign DEFAULT_CATEGORY

PR #3589 tied category assignment to `CATEGORY_SAVE_AS`, so disabling
category pages also removed article categories and broke `{category}`
in URL patterns (#3596). PR #3597 restored folder-based categories, but
articles outside a subfolder still lost `DEFAULT_CATEGORY`. This change
assigns it again, so `CATEGORY_SAVE_AS` only controls whether category
pages are generated. Setting `DEFAULT_CATEGORY = None` is now the
documented way to have no categories.

This also stops the Simple and NotMyIdea themes from linking to category
pages that don't exist.

docs/settings.rst

@@ -65,6 +65,10 @@ Basic settings
 
    The default category to fall back on. The default is ``"misc"``.
 
+   To publish articles without any category, set ``DEFAULT_CATEGORY = None``
+   and ``USE_FOLDER_AS_CATEGORY = False``. Articles will then only have a
+   category if one is specified in their metadata.
+
 .. data:: DISPLAY_PAGES_ON_MENU
 
    Whether to display pages on the menu of the template. Templates may or may
@@ -590,6 +594,8 @@ This would save your articles into something like
 .. data:: CATEGORY_SAVE_AS
 
    The location to save a category. The default is ``"category/{slug}.html"``.
+   Set this to ``""`` to disable category pages. Articles still keep their
+   categories, which can be used in URL patterns such as ``ARTICLE_SAVE_AS``.
 
 .. data:: TAG_URL
 

pelican/readers.py

@@ -82,9 +82,9 @@ def ensure_metadata_list(text):
 
 def _process_if_nonempty(processor, name, settings):
     """Removes extra whitespace from name and applies a metadata processor.
-    If name is empty or all whitespace, returns _DISCARD instead.
+    If name is None, empty, or all whitespace, returns _DISCARD instead.
     """
-    name = name.strip()
+    name = (name or "").strip()
     return processor(name, settings) if name else _DISCARD
 
 
@@ -746,7 +746,7 @@ def default_metadata(settings=None, process=None):
             if process:
                 value = process(name, value)
             metadata[name] = value
-        if "DEFAULT_CATEGORY" in settings and settings.get("CATEGORY_SAVE_AS"):
+        if "DEFAULT_CATEGORY" in settings:
             value = settings["DEFAULT_CATEGORY"]
             if process:
                 value = process("category", value)

pelican/tests/test_generators.py

@@ -405,7 +405,7 @@ class TestArticlesGenerator(unittest.TestCase):
             settings = get_settings(PATH=content_dir)
             settings["CACHE_PATH"] = self.temp_cache
             settings["USE_FOLDER_AS_CATEGORY"] = False
-            settings["CATEGORY_SAVE_AS"] = None  # No default category fallback
+            settings["DEFAULT_CATEGORY"] = None  # No default category fallback
             context = get_context(settings)
 
             generator = ArticlesGenerator(

pelican/tests/test_readers.py

@@ -161,16 +161,44 @@ class DefaultReaderTest(ReaderTest):
                 )
 
     def test_path_metadata_categories(self):
+        """Ensure folder names become categories even when category pages are
+        disabled, so {category} still works in URL patterns."""
         nested_content_path = os.path.join(CUR_DIR, "nested_content")
-        r = readers.Readers(
-            settings=get_settings(USE_FOLDER_AS_CATEGORY=True, CATEGORY_SAVE_AS=None)
-        )
-        mainpage = r.read_file(base_path=nested_content_path, path="maindir/maindir.md")
-        self.assertDictHasSubset(mainpage.metadata, {"category": "maindir"})
-        subpage = r.read_file(
-            base_path=nested_content_path, path="maindir/subdir/subdir.md"
-        )
-        self.assertDictHasSubset(subpage.metadata, {"category": "subdir"})
+        for category_save_as in ("", None, False):
+            with self.subTest(CATEGORY_SAVE_AS=category_save_as):
+                r = readers.Readers(
+                    settings=get_settings(
+                        USE_FOLDER_AS_CATEGORY=True, CATEGORY_SAVE_AS=category_save_as
+                    )
+                )
+                mainpage = r.read_file(
+                    base_path=nested_content_path, path="maindir/maindir.md"
+                )
+                self.assertDictHasSubset(mainpage.metadata, {"category": "maindir"})
+                subpage = r.read_file(
+                    base_path=nested_content_path, path="maindir/subdir/subdir.md"
+                )
+                self.assertDictHasSubset(subpage.metadata, {"category": "subdir"})
+
+    def test_default_category_when_category_pages_disabled(self):
+        for category_save_as in ("", None, False):
+            with self.subTest(CATEGORY_SAVE_AS=category_save_as):
+                page = self.read_file(
+                    path="article.rst",
+                    DEFAULT_CATEGORY="misc",
+                    CATEGORY_SAVE_AS=category_save_as,
+                )
+                self.assertEqual(page.metadata["category"], "misc")
+
+    def test_empty_default_category_omits_category(self):
+        for default_category in ("", None):
+            with self.subTest(DEFAULT_CATEGORY=default_category):
+                page = self.read_file(
+                    path="article.rst",
+                    DEFAULT_CATEGORY=default_category,
+                    USE_FOLDER_AS_CATEGORY=False,
+                )
+                self.assertNotIn("category", page.metadata)
 
 
 class RstReaderTest(ReaderTest):

pelican/tests/test_theme.py

@@ -134,8 +134,8 @@ class TestTemplateInheritance(LoggedTestCase):
         self.assertIn("New footer", content)
 
     def test_disabled_categories_no_links(self):
-        """When CATEGORY_SAVE_AS is empty, articles without an explicit
-        category should not get a default category or show category links."""
+        """When DEFAULT_CATEGORY is empty, articles without an explicit
+        category should not show a category."""
 
         # Create an article without a Category metadata line
         content_dir = mkdtemp(prefix="pelican_test_content.")
@@ -155,6 +155,8 @@ class TestTemplateInheritance(LoggedTestCase):
                     "OUTPUT_PATH": self.temp_output,
                     "CACHE_PATH": self.temp_cache,
                     "SITEURL": "http://example.com",
+                    "DEFAULT_CATEGORY": "",
+                    "USE_FOLDER_AS_CATEGORY": False,
                     "CATEGORY_SAVE_AS": None,
                     "CATEGORY_URL": None,
                     "CATEGORIES_SAVE_AS": None,
@@ -171,6 +173,45 @@ class TestTemplateInheritance(LoggedTestCase):
         finally:
             rmtree(content_dir)
 
+    def test_disabled_category_pages_no_links(self):
+        """When CATEGORY_SAVE_AS is empty, articles keep their category, but
+        themes should not link to category pages that are not generated."""
+
+        content_dir = mkdtemp(prefix="pelican_test_content.")
+        os.makedirs(os.path.join(content_dir, "blog"))
+        with open(os.path.join(content_dir, "blog", "in_blog.md"), "w") as f:
+            f.write("Title: In Blog\nDate: 2024-01-01\n\nArticle in a folder.\n")
+
+        try:
+            for theme in ("simple", "notmyidea"):
+                with self.subTest(theme=theme):
+                    settings = read_settings(
+                        path=None,
+                        override={
+                            "THEME": theme,
+                            "PATH": content_dir,
+                            "OUTPUT_PATH": self.temp_output,
+                            "CACHE_PATH": self.temp_cache,
+                            "SITEURL": "http://example.com",
+                            "ARTICLE_SAVE_AS": "{category}/{slug}.html",
+                            "CATEGORY_SAVE_AS": False,
+                            "CATEGORIES_SAVE_AS": False,
+                        },
+                    )
+
+                    pelican = Pelican(settings=settings)
+                    mute(True)(pelican.run)()
+
+                    with open(
+                        os.path.join(self.temp_output, "blog", "in-blog.html")
+                    ) as f:
+                        content = f.read()
+
+                    self.assertIn("blog", content)
+                    self.assertNotIn("/category/", content)
+        finally:
+            rmtree(content_dir)
+
     def test_category_and_tag_feed_titles_use_slug(self):
         """Feed link titles on category/tag pages should have unique titles."""
 

pelican/themes/notmyidea/templates/article_infos.html

@@ -16,7 +16,9 @@
                         {% endfor %}
                 </address>
         {% endif %}
-        <p>In <a href="{{ SITEURL }}/{{ article.category.url }}">{{ article.category }}</a>.</p>
+        {% if article.category %}
+                <p>In {% if CATEGORY_SAVE_AS %}<a href="{{ SITEURL }}/{{ article.category.url }}">{{ article.category }}</a>{% else %}{{ article.category }}{% endif %}.</p>
+        {% endif %}
         {% include 'taglist.html' %}
         {% import 'translations.html' as translations with context %}
         {{ translations.translations_for(article) }}

pelican/themes/notmyidea/templates/base.html

@@ -30,7 +30,7 @@
                                                 <li{% if pg == page %} class="active"{% endif %}><a href="{{ SITEURL }}/{{ pg.url }}">{{ pg.title }}</a></li>
                                         {% endfor %}
                                 {% endif %}
-                                {% if DISPLAY_CATEGORIES_ON_MENU -%}
+                                {% if DISPLAY_CATEGORIES_ON_MENU and CATEGORY_SAVE_AS -%}
                                         {% for cat, null in categories %}
                                                 <li{% if cat == category %} class="active"{% endif %}><a href="{{ SITEURL }}/{{ cat.url }}">{{ cat }}</a></li>
                                         {% endfor %}

pelican/themes/simple/templates/article.html

@@ -49,7 +49,12 @@
       {% endif %}
       {% if article.category %}
         <p>
-          Category: <a href="{{ SITEURL }}/{{ article.category.url }}">{{ article.category }}</a>
+          Category:
+          {% if CATEGORY_SAVE_AS %}
+            <a href="{{ SITEURL }}/{{ article.category.url }}">{{ article.category }}</a>
+          {% else %}
+            {{ article.category }}
+          {% endif %}
         </p>
       {% endif %}
       {% if article.tags %}

pelican/themes/simple/templates/base.html

@@ -58,7 +58,7 @@
                 <li><a href="{{ SITEURL }}/{{ p.url }}" {% if p==page %} aria-current="page" {% endif %}>{{ p.title }}</a></li>
               {% endfor %}
             {% endif %}
-            {% if DISPLAY_CATEGORIES_ON_MENU %}
+            {% if DISPLAY_CATEGORIES_ON_MENU and CATEGORY_SAVE_AS %}
               {% for cat, null in categories %}
                 <li><a href="{{ SITEURL }}/{{ cat.url }}" {% if cat==category %} aria-current="page" {% endif %}>{{ cat}}</a></li>
               {% endfor %}