feat: optional chaing

packages/babel-plugin-transform-optional-chaining/src/index.js

@@ -0,0 +1,64 @@
+import createTemplate from "babel-template";
+import traverse from "babel-traverse";
+
+const nullOrUndefinedCheck = createTemplate(`
+  typeof CHECK !== "undefined" && CHECK !== null
+    ? NEXT
+    : null
+`);
+
+function isOptional(path) {
+  return path.node.optional === true;
+}
+
+const nullOrUndefinedCheckVisitor = {
+  noScope: true,
+
+  Identifier(path, replacements) {
+    if (path.node.name in replacements) {
+      path.replaceInline(replacements[path.node.name]);
+    }
+  },
+};
+
+function createCheck(node, object) {
+
+  const template = nullOrUndefinedCheck();
+
+  traverse(template, nullOrUndefinedCheckVisitor, null, {
+    CHECK: object,
+    NEXT: node,
+  });
+
+  return template;
+}
+
+export default function ({ types: t }) {
+
+  return {
+    visitor: {
+      MemberExpression(path) {
+
+        if (isOptional(path)) {
+          let { object } = path.node;
+
+          while (
+            t.isMemberExpression(object)
+            && isOptional({ node: object })
+          ) {
+            object = createCheck(
+              object,
+              object.object
+            );
+          }
+
+          path.replaceWith(
+            createCheck(path.node, object)
+          );
+
+          path.stop();
+        }
+      },
+    },
+  };
+}