Fix broken links with structure-dir router

Resolves #2928

Author: Gerrit0

CHANGELOG.md

@@ -20,6 +20,7 @@ title: Changelog
 - When printing entry point globs which fail to match any paths, TypeDoc will no longer normalize the glob, #2918.
 - Inlining types can now handle more type variants, #2920.
 - Fixed behavior of `externalSymbolLinkMappings` option when URL is set to `#`, #2921.
+- Fixed broken links within module pages when structure-dir router was used, #2928.
 - API: `toString` on types containing index signatures now behave correctly, #2917.
 
 ## v0.28.1 (2025-03-20)

src/lib/output/router.ts

@@ -221,6 +221,19 @@ export abstract class BaseRouter implements Router {
             // an own document.
             from = from.parent as RouterTarget;
         }
+
+        let toPage = to;
+        while (!this.hasOwnDocument(toPage)) {
+            toPage = toPage.parent as RouterTarget;
+        }
+
+        // We unfortunately have to special case ProjectReflection as it is
+        // the model used twice for rendering. This should be changed in a
+        // future version to remove this hackery.
+        if (from === toPage && !(to instanceof ProjectReflection)) {
+            return to === toPage ? "" : `#${this.getAnchor(to)}`;
+        }
+
         const fromUrl = this.getFullUrl(from);
         const toUrl = this.getFullUrl(to);
         let equal = true;
@@ -237,13 +250,15 @@ export abstract class BaseRouter implements Router {
             }
         }
 
-        if (equal && !(to instanceof ProjectReflection)) {
-            if (fromUrl === toUrl) {
-                return "";
-            }
-            return `#${this.getAnchor(to)}`;
+        // If equal is still set, we're going to a page either in
+        // the same directory as this page, or a lower directory,
+        // don't bother going up directories just to come back down.
+        if (equal) {
+            return toUrl.substring(start);
         }
 
+        // Otherwise, go up until we get to the common directory
+        // and then back down to the target path.
         return "../".repeat(slashes) + toUrl.substring(start);
     }
 

src/test/output/router.test.ts

@@ -330,6 +330,16 @@ describe("StructureDirRouter", () => {
             ),
             "../../Foo/#codegeneration",
         );
+
+        equal(
+            router.relativeUrl(
+                query(project, "Nested"),
+                query(project, "Nested.refl"),
+            ),
+            "refl/",
+        );
+
+        equal(router.relativeUrl(query(project, "Nested.refl"), query(project, "Nested")), "../");
     });
 });