fix: remove up to the fence indentation from each content line

src/Tokenizer.ts

@@ -68,11 +68,9 @@ function indentCodeCompensation(raw: string, text: string, rules: Rules) {
 
       const [indentInNode] = matchIndentInNode;
 
-      if (indentInNode.length >= indentToCode.length) {
-        return node.slice(indentToCode.length);
-      }
-
-      return node;
+      // Up to the fence's own indentation is removed from each line, so a line
+      // indented less than the fence loses whatever indentation it has.
+      return node.slice(Math.min(indentInNode.length, indentToCode.length));
     })
     .join('\n');
 }

test/unit/marked.test.js

@@ -22,6 +22,18 @@ describe('marked unit', () => {
     });
   });
 
+  describe('fenced code block indentation', () => {
+    it('should remove up to the fence indentation from each line', () => {
+      const md = '   ```\n   aaa\n    aaa\n  aaa\n   ```\n';
+      assert.strictEqual(marked.parse(md), '<pre><code>aaa\n aaa\naaa\n</code></pre>\n');
+    });
+
+    it('should leave lines indented more than the fence with the remainder', () => {
+      const md = '  ```\n      aaa\n  ```\n';
+      assert.strictEqual(marked.parse(md), '<pre><code>    aaa\n</code></pre>\n');
+    });
+  });
+
   describe('changeDefaults', () => {
     it('should change global defaults', async() => {
       const { defaults, setOptions } = await import('../../lib/marked.esm.js');