Cache URL derivation during generation

Resolves #2386

Co-Authored-By: @ajesshope

CHANGELOG.md

@@ -12,6 +12,7 @@
 -   TypeDoc will now attempt to cache icons when `DefaultThemeRenderContext.icons` is overwritten by a custom theme.
     Note: To perform this optimization, TypeDoc relies on `DefaultThemeRenderContext.iconCache` being rendered within
     each page. TypeDoc does it in the `defaultLayout` template.
+-   Cache URL derivation during generation, #2386.
 
 ### Bug Fixes
 
@@ -24,6 +25,7 @@
 
 ### Thanks!
 
+-   @ajesshope
 -   @HemalPatil
 -   @hrueger
 -   @typhonrt

src/lib/output/components.ts

@@ -46,9 +46,12 @@ export abstract class ContextAwareRendererComponent extends RendererComponent {
         this.listenTo(this.owner, {
             [RendererEvent.BEGIN]: this.onBeginRenderer,
             [PageEvent.BEGIN]: this.onBeginPage,
+            [RendererEvent.END]: () => this.absoluteToRelativePathMap.clear(),
         });
     }
 
+    private absoluteToRelativePathMap = new Map<string, string>();
+
     /**
      * Transform the given absolute path into a relative path.
      *
@@ -59,7 +62,12 @@ export abstract class ContextAwareRendererComponent extends RendererComponent {
         if (this.urlPrefix.test(absolute)) {
             return absolute;
         } else {
-            return Path.posix.relative(this.location, absolute) || ".";
+            const key = `${this.location}:${absolute}`;
+            let path = this.absoluteToRelativePathMap.get(key);
+            if (path) return path;
+            path = Path.posix.relative(this.location, absolute) || ".";
+            this.absoluteToRelativePathMap.set(key, path);
+            return path;
         }
     }