feat: optional chaing

packages/babel-plugin-transform-optional-chaining/.npmignore

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+src
+test
+*.log

packages/babel-plugin-transform-optional-chaining/README.md

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+# babel-plugin-transform-optional-chaining

packages/babel-plugin-transform-optional-chaining/package.json

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+{
+  "name": "babel-plugin-transform-optional-chaining",
+  "version": "7.0.0-alpha.7",
+  "description": "",
+  "repository": "https://github.com/babel/babel/tree/master/packages/babel-plugin-transform-optional-chaining",
+  "license": "MIT",
+  "main": "lib/index.js",
+  "dependencies": {
+    "babel-traverse": "7.0.0-alpha.7",
+    "babel-types": "7.0.0-alpha.7",
+    "babel-template": "7.0.0-alpha.7",
+    "lodash": "^4.2.0"
+  },
+  "keywords": [
+    "babel-plugin"
+  ],
+  "devDependencies": {
+    "babel-helper-plugin-test-runner": "7.0.0-alpha.7"
+  }
+}

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

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+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();
+        }
+      },
+    },
+  };
+}

packages/babel-plugin-transform-optional-chaining/test/fixtures/general/member-access/actual.js

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+foo?.bar

packages/babel-plugin-transform-optional-chaining/test/fixtures/general/member-access/expected.js

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+typeof foo !== "undefined" && foo !== null ? foo.bar : null;

packages/babel-plugin-transform-optional-chaining/test/fixtures/general/nested-member-access/actual.js

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+foo?.bar?.vroum

packages/babel-plugin-transform-optional-chaining/test/fixtures/general/nested-member-access/expected.js

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+typeof (typeof foo !== "undefined" && foo !== null ? foo.bar : null) !== "undefined" && (typeof foo !== "undefined" && foo !== null ? foo.bar : null) !== null ? foo.bar.vroum : null;

packages/babel-plugin-transform-optional-chaining/test/fixtures/general/options.json

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+{
+  "plugins": ["transform-optional-chaining"]
+}

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

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+import runner from "babel-helper-plugin-test-runner";
+
+runner(__dirname);