Restrict swup transitions to same-directory links

Use directory comparison in ignoreVisit instead of CSS selector
filtering. This correctly handles both absolute and relative links:

- Same-directory links get smooth swup transitions (sidebar stays valid)
- Cross-directory links trigger full page reloads (sidebar updates)
- Same-page links with .html mismatch are recognized as self-links

The broader linkSelector now accepts all non-external, non-anchor links,
while ignoreVisit does the smart filtering with JS logic.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: garazdawi

assets/js/swup.js

@@ -19,18 +19,32 @@ const maybeMetaRedirect = (visit, {page}) => {
   }
 }
 
+/**
+ * Checks if a navigation should be ignored by swup.
+ * Returns true for same-page links and cross-directory links.
+ * Same-directory links get smooth swup transitions.
+ */
+export function shouldIgnoreVisit (url, currentPathname) {
+  const path = url.split('#')[0]
+  // Ignore same-page links (with or without .html mismatch).
+  if (path === currentPathname ||
+      path === currentPathname + '.html' ||
+      path + '.html' === currentPathname) { return true }
+  // Only use swup for links within the same directory (same app).
+  // Cross-directory links need a full reload to update the sidebar.
+  const currentDir = currentPathname.substring(0, currentPathname.lastIndexOf('/') + 1)
+  const targetDir = path.substring(0, path.lastIndexOf('/') + 1)
+  return targetDir !== currentDir
+}
+
 window.addEventListener('DOMContentLoaded', emitExdocLoaded)
 
 if (!isEmbedded && window.location.protocol !== 'file:') {
   new Swup({
     animationSelector: false,
     containers: ['#main'],
-    ignoreVisit: (url) => {
-      const path = url.split('#')[0]
-      return path === window.location.pathname ||
-            path === window.location.pathname + '.html'
-    },
-    linkSelector: 'a[href]:not([href^="/"]):not([href^="http"])[href$=".html"]',
+    ignoreVisit: (url) => shouldIgnoreVisit(url, window.location.pathname),
+    linkSelector: 'a[href]:not([href^="http"]):not([href^="#"])',
     hooks: {
       'page:load': maybeMetaRedirect,
       'page:view': emitExdocLoaded

assets/test/swup.spec.js

@@ -0,0 +1,53 @@
+import { shouldIgnoreVisit } from '../js/swup'
+
+describe('shouldIgnoreVisit', () => {
+  describe('same-page detection', () => {
+    it('ignores exact same path', () => {
+      expect(shouldIgnoreVisit('/doc/apps/stdlib/gen_server.html', '/doc/apps/stdlib/gen_server.html')).toBe(true)
+    })
+
+    it('ignores same path with hash', () => {
+      expect(shouldIgnoreVisit('/doc/apps/stdlib/gen_server.html#start_link/3', '/doc/apps/stdlib/gen_server.html')).toBe(true)
+    })
+
+    it('ignores extensionless URL matching .html page', () => {
+      expect(shouldIgnoreVisit('/doc/apps/stdlib/gen_server', '/doc/apps/stdlib/gen_server.html')).toBe(true)
+    })
+
+    it('ignores .html URL matching extensionless page', () => {
+      expect(shouldIgnoreVisit('/doc/apps/stdlib/gen_server.html', '/doc/apps/stdlib/gen_server')).toBe(true)
+    })
+  })
+
+  describe('same-directory links (use swup)', () => {
+    it('allows .html links in same directory', () => {
+      expect(shouldIgnoreVisit('/doc/apps/stdlib/lists.html', '/doc/apps/stdlib/gen_server.html')).toBe(false)
+    })
+
+    it('allows extensionless links in same directory', () => {
+      expect(shouldIgnoreVisit('/doc/apps/stdlib/lists', '/doc/apps/stdlib/gen_server')).toBe(false)
+    })
+
+    it('allows extensionless link from .html page', () => {
+      expect(shouldIgnoreVisit('/doc/apps/stdlib/lists', '/doc/apps/stdlib/gen_server.html')).toBe(false)
+    })
+
+    it('allows .html link from extensionless page', () => {
+      expect(shouldIgnoreVisit('/doc/apps/stdlib/lists.html', '/doc/apps/stdlib/gen_server')).toBe(false)
+    })
+  })
+
+  describe('cross-directory links (full reload)', () => {
+    it('ignores cross-app links', () => {
+      expect(shouldIgnoreVisit('/doc/apps/kernel/file.html', '/doc/apps/stdlib/gen_server.html')).toBe(true)
+    })
+
+    it('ignores cross-app extensionless links', () => {
+      expect(shouldIgnoreVisit('/doc/apps/kernel/file', '/doc/apps/stdlib/gen_server')).toBe(true)
+    })
+
+    it('ignores links to system docs from app docs', () => {
+      expect(shouldIgnoreVisit('/doc/system/design_principles', '/doc/apps/stdlib/gen_server')).toBe(true)
+    })
+  })
+})