1 files changed, 47 insertions, 0 deletions
diff --git a/dev/lib/handlebars/src/handlebars.ts b/dev/lib/handlebars/src/handlebars.ts
new file mode 100644
index 00000000..358d1b73
--- /dev/null
+++ b/dev/lib/handlebars/src/handlebars.ts
@@ -0,0 +1,47 @@
+/*
+ * Elasticsearch B.V licenses this file to you under the MIT License.
+ * See `packages/kbn-handlebars/LICENSE` for more information.
+ */
+
+// The handlebars module uses `export =`, so we should technically use `import Handlebars = require('handlebars')`, but Babel will not allow this:
+// https://www.typescriptlang.org/docs/handbook/modules.html#export--and-import--require
+import Handlebars = require('handlebars');
+
+import type { CompileOptions, RuntimeOptions, TemplateDelegate } from './types';
+import { ElasticHandlebarsVisitor } from './visitor';
+
+const originalCreate = Handlebars.create;
+
+export { Handlebars };
+
+/**
+ * Creates an isolated Handlebars environment.
+ *
+ * Each environment has its own helpers.
+ * This is only necessary for use cases that demand distinct helpers.
+ * Most use cases can use the root Handlebars environment directly.
+ *
+ * @returns A sandboxed/scoped version of the @kbn/handlebars module
+ */
+Handlebars.create = function (): typeof Handlebars {
+  const SandboxedHandlebars = originalCreate.call(Handlebars) as typeof Handlebars;
+  // When creating new Handlebars environments, ensure the custom compileAST function is present in the new environment as well
+  SandboxedHandlebars.compileAST = Handlebars.compileAST;
+  return SandboxedHandlebars;
+};
+
+Handlebars.compileAST = function (
+  input: string | hbs.AST.Program,
+  options?: CompileOptions
+): TemplateDelegate {
+  if (input == null || (typeof input !== 'string' && input.type !== 'Program')) {
+    throw new Handlebars.Exception(
+      `You must pass a string or Handlebars AST to Handlebars.compileAST. You passed ${input}`
+    );
+  }
+
+  // If `Handlebars.compileAST` is reassigned, `this` will be undefined.
+  const visitor = new ElasticHandlebarsVisitor(this ?? Handlebars, input, options);
+
+  return (context: any, runtimeOptions?: RuntimeOptions) => visitor.render(context, runtimeOptions);
+};