From f38707484de2557666a46a20e0dd5a36ac198d64 Mon Sep 17 00:00:00 2001
From: Zach Leatherman <zachleat@users.noreply.github.com>
Date: Fri, 13 Dec 2024 16:44:48 -0600
Subject: [PATCH] Adds keep and replace options to eleventy:optional attribute.
 #259

---
 src/image-attrs-to-posthtml-node.js | 12 ++++++++++--
 src/transform-plugin.js             | 24 +++++++++++++++++++-----
 2 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/src/image-attrs-to-posthtml-node.js b/src/image-attrs-to-posthtml-node.js
index 7c92110..bd4cfa4 100644
--- a/src/image-attrs-to-posthtml-node.js
+++ b/src/image-attrs-to-posthtml-node.js
@@ -83,8 +83,16 @@ function isIgnored(node) {
   return node?.attrs && node?.attrs?.[ATTR.IGNORE] !== undefined;
 }
 
-function isOptional(node) {
-  return node?.attrs && node?.attrs?.[ATTR.OPTIONAL] !== undefined;
+function isOptional(node, comparisonValue) {
+  let attrValue = node?.attrs && node?.attrs?.[ATTR.OPTIONAL];
+  if(attrValue !== undefined) {
+    // if comparisonValue is not specified, return true
+    if(comparisonValue === undefined) {
+      return true;
+    }
+    return attrValue === comparisonValue;
+  }
+  return false;
 }
 
 function getOutputDirectory(node) {
diff --git a/src/transform-plugin.js b/src/transform-plugin.js
index 4c86fcf..83e02a5 100644
--- a/src/transform-plugin.js
+++ b/src/transform-plugin.js
@@ -58,13 +58,27 @@ function transformTag(context, node, opts) {
 
     Object.assign(node, obj);
   }, (error) => {
-    if(!isOptional(node) && opts.failOnError) {
-      return Promise.reject(error);
+    if(isOptional(node) || !opts.failOnError) {
+      if(isOptional(node, "keep")) {
+        // leave as-is, likely 404 when a user visits the page
+      } else if(isOptional(node, "replace")) {
+        // transparent png
+        node.attrs.src = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mNgYAAAAAMAASsJTYQAAAAASUVORK5CYII=";
+      } else if(isOptional(node)) {
+        // delete node
+        delete node.tag;
+        delete node.attrs;
+
+        return Promise.resolve();
+      }
+
+      // optional or don’t fail on error
+      cleanTag(node);
+
+      return Promise.resolve();
     }
 
-    cleanTag(node);
-
-    return Promise.resolve();
+    return Promise.reject(error);
   });
 }