test(helpers): add tests for get with no/falsy receiver

packages/babel-helpers/test/fixtures/behavior/get-with-falsy-receiver/exec.js

@@ -0,0 +1,23 @@
+// ensure we test the helper implementation,
+// not built-in Reflect.get to which it defers
+delete Reflect;
+
+class Target {
+  get typeOf() {
+    return this === null ? "null" : typeof this;
+  }
+};
+
+// check that the 1st argument (target) *is not* used
+// in place of present but undefined 3rd argument (receiver)
+expect(HELPER_GET(new Target, "typeOf", undefined)).toBe("undefined");
+
+// because the helper replaces itself upon invocation,
+// check it again with nullish arguments
+expect(HELPER_GET(new Target, "typeOf", undefined)).toBe("undefined");
+expect(HELPER_GET(new Target, "typeOf", null)).toBe("null");
+
+// check other falsy types
+expect(HELPER_GET(new Target, "typeOf", false)).toBe("boolean");
+expect(HELPER_GET(new Target, "typeOf", 0)).toBe("number");
+expect(HELPER_GET(new Target, "typeOf", "")).toBe("string");

packages/babel-helpers/test/fixtures/behavior/get-with-falsy-receiver/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["./plugin"]
+}

packages/babel-helpers/test/fixtures/behavior/get-with-falsy-receiver/plugin.js

@@ -0,0 +1,12 @@
+module.exports = function() {
+  return {
+    visitor: {
+      Identifier(path) {
+        if (path.node.name === "HELPER_GET") {
+          const helper = this.addHelper("get");
+          path.replaceWith(helper);
+        }
+      },
+    },
+  };
+};

packages/babel-helpers/test/fixtures/behavior/get-without-receiver/exec.js

@@ -0,0 +1,17 @@
+// ensure we test the helper implementation,
+// not built-in Reflect.get to which it defers
+delete Reflect;
+
+class Target {
+  get receiver() {
+    return this;
+  }
+};
+
+// check that the 1st argument (target) *is* used
+// in place of missing 3rd argument (receiver)
+expect(HELPER_GET(new Target, "receiver")).toBeInstanceOf(Target);
+
+// because the helper replaces itself upon invocation,
+// check it again with the same arguments
+expect(HELPER_GET(new Target, "receiver")).toBeInstanceOf(Target);

packages/babel-helpers/test/fixtures/behavior/get-without-receiver/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["./plugin"]
+}

packages/babel-helpers/test/fixtures/behavior/get-without-receiver/plugin.js

@@ -0,0 +1,12 @@
+module.exports = function() {
+  return {
+    visitor: {
+      Identifier(path) {
+        if (path.node.name === "HELPER_GET") {
+          const helper = this.addHelper("get");
+          path.replaceWith(helper);
+        }
+      },
+    },
+  };
+};