feat(challenge-parser): add feedback to mc questions (#51942)

tools/challenge-parser/parser/plugins/utils/before-heading.js

@@ -0,0 +1,21 @@
+const find = require('unist-util-find');
+const findAllBefore = require('unist-util-find-all-before');
+
+function getAllBefore(tree, marker) {
+  const start = find(tree, {
+    type: 'heading',
+    children: [
+      {
+        type: 'text',
+        value: marker
+      }
+    ]
+  });
+
+  if (!start) return [];
+
+  // reverse because it goes up the tree backwards and adds nodes in that order
+  return findAllBefore(tree, start).reverse();
+}
+
+module.exports = getAllBefore;

tools/challenge-parser/parser/plugins/utils/before-heading.test.js

@@ -0,0 +1,24 @@
+const isArray = require('lodash/isArray');
+const simpleAst = require('../../__fixtures__/ast-simple.json');
+const getAllBefore = require('./before-heading');
+
+describe('before-headings', () => {
+  it('should return an array', () => {
+    expect.assertions(1);
+    const actual = getAllBefore(simpleAst, '--hints--');
+    expect(isArray(actual)).toBe(true);
+  });
+
+  it('should return an empty array if the marker is not present', () => {
+    expect.assertions(2);
+    const actual = getAllBefore(simpleAst, '--not-a-marker--');
+    expect(isArray(actual)).toBe(true);
+    expect(actual.length).toBe(0);
+  });
+
+  it('should include the whole AST before the marker', () => {
+    expect.assertions(1);
+    const actual = getAllBefore(simpleAst, '--hints--');
+    expect(actual).toHaveLength(6);
+  });
+});