feat: share original content with post-transforms

Author: nvlang

src/base/Sveltex.ts

@@ -444,7 +444,7 @@ export class Sveltex<
             // Apply the post-transformers
             html = applyTransformations(
                 html,
-                frontmatter ?? {},
+                { ...(frontmatter ?? {}), original: content },
                 markdownHandler.configuration.transformers.post,
             );
             /* eslint-enable @typescript-eslint/no-unnecessary-condition */

src/handlers/CodeHandler.ts

@@ -141,7 +141,7 @@ export class CodeHandler<B extends CodeBackend> extends Handler<
             if (transformers.post) {
                 processed = applyTransformations(
                     processed,
-                    mergedOpts,
+                    { ...mergedOpts, original: code },
                     transformers.post,
                 );
             }

src/handlers/MathHandler.ts

@@ -42,21 +42,21 @@ export class MathHandler<B extends MathBackend> extends Handler<
             await this.handleCss();
 
             // Apply pre-transformers
-            tex = applyTransformations(
+            const pretransformed = applyTransformations(
                 tex,
                 { inline: options?.inline !== false },
                 this._configuration.transformers.pre,
             );
 
             const res = await super.process(
-                tex,
+                pretransformed,
                 options ?? ({} as MathProcessOptions<B>),
             );
 
             // Apply post-transformers
             res.processed = applyTransformations(
                 res.processed,
-                { inline: options?.inline !== false },
+                { inline: options?.inline !== false, original: tex },
                 this._configuration.transformers.post,
             );
 

src/handlers/VerbatimHandler.ts

@@ -261,7 +261,11 @@ export class VerbatimHandler<C extends CodeBackend> extends Handler<
                 typeAssert(is<FullVerbEnvConfigNoop>(config));
             }
 
-            processed = applyTransformations(processed, options, post);
+            processed = applyTransformations(
+                processed,
+                { ...options, original: innerContent },
+                post,
+            );
 
             // If `component !== 'none'`, wrap the processed content in the
             // output tag, so that `processed` now stores the _outer_ content.

src/types/handlers/Handler.ts

@@ -56,7 +56,19 @@ export interface Transformers<Options extends object> {
      * - 2-tuple: `transformed = content.replaceAll(...transformation)`
      * - Function: `transformed = transformation(content, opts)`
      */
-    post?: Transformer<Options> | Transformer<Options>[] | undefined | null;
+    post?:
+        | Transformer<Options & WithOriginal>
+        | Transformer<Options & WithOriginal>[]
+        | undefined
+        | null;
+}
+
+interface WithOriginal {
+    /**
+     * The original content that was passed to the backend for processing. This
+     * is before pre-transformations were applied, too.
+     */
+    original: string;
 }
 
 /**