polish: skip creating extra reference for safely re-used node (#10720)

* polish: skip creating extra reference for safely re-used node * reimplement using scope.maybeGenerateMemoised
babel · Nov 16, 2019 · 6c7f829 · 6c7f829 · williamgoodhew · Nov 20, 2019
1 parent d56911b
commit 6c7f829
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Showing 9 changed files with 26 additions and 11 deletions.
diff --git a/packages/babel-plugin-proposal-nullish-coalescing-operator/src/index.js b/packages/babel-plugin-proposal-nullish-coalescing-operator/src/index.js
@@ -16,14 +16,15 @@ export default declare((api, { loose = false }) => {
           return;
         }
 
-        const ref = scope.generateUidIdentifierBasedOnNode(node.left);
-        scope.push({ id: ref });
-
-        const assignment = t.assignmentExpression(
-          "=",
-          t.cloneNode(ref),
-          node.left,
-        );
+        let ref = scope.maybeGenerateMemoised(node.left);
+        let assignment;
+        // skip creating extra reference when `left` is static
+        if (ref === null) {
+          ref = node.left;
+          assignment = t.cloneNode(node.left);
+        } else {
+          assignment = t.assignmentExpression("=", ref, node.left);
+        }
 
         path.replaceWith(
           t.conditionalExpression(

diff --git a/...ullish-coalescing-operator/test/fixtures/nullish-coalescing/transform-in-default/input.js b/...ullish-coalescing-operator/test/fixtures/nullish-coalescing/transform-in-default/input.js
@@ -1 +1 @@
-function foo(foo, bar = foo ?? "bar") {}
+function foo(foo, qux = foo.bar ?? "qux") {}
diff --git a/...llish-coalescing-operator/test/fixtures/nullish-coalescing/transform-in-default/output.js b/...llish-coalescing-operator/test/fixtures/nullish-coalescing/transform-in-default/output.js
@@ -1,3 +1,3 @@
-function foo(foo, bar = (_foo = foo) !== null && _foo !== void 0 ? _foo : "bar") {
-  var _foo;
+function foo(foo, qux = (_foo$bar = foo.bar) !== null && _foo$bar !== void 0 ? _foo$bar : "qux") {
+  var _foo$bar;
 }
diff --git a/...scing-operator/test/fixtures/nullish-coalescing/transform-static-refs-in-default/input.js b/...scing-operator/test/fixtures/nullish-coalescing/transform-static-refs-in-default/input.js
@@ -0,0 +1 @@
+function foo(foo, bar = foo ?? "bar") {}
diff --git a/...g-operator/test/fixtures/nullish-coalescing/transform-static-refs-in-default/options.json b/...g-operator/test/fixtures/nullish-coalescing/transform-static-refs-in-default/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["proposal-nullish-coalescing-operator"]
+}
diff --git a/...cing-operator/test/fixtures/nullish-coalescing/transform-static-refs-in-default/output.js b/...cing-operator/test/fixtures/nullish-coalescing/transform-static-refs-in-default/output.js
@@ -0,0 +1 @@
+function foo(foo, bar = foo !== null && foo !== void 0 ? foo : "bar") {}
diff --git a/...cing-operator/test/fixtures/nullish-coalescing/transform-static-refs-in-function/input.js b/...cing-operator/test/fixtures/nullish-coalescing/transform-static-refs-in-function/input.js
@@ -0,0 +1,3 @@
+function foo() {
+  var foo = this ?? {};
+}
diff --git a/...-operator/test/fixtures/nullish-coalescing/transform-static-refs-in-function/options.json b/...-operator/test/fixtures/nullish-coalescing/transform-static-refs-in-function/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["proposal-nullish-coalescing-operator"]
+}
diff --git a/...ing-operator/test/fixtures/nullish-coalescing/transform-static-refs-in-function/output.js b/...ing-operator/test/fixtures/nullish-coalescing/transform-static-refs-in-function/output.js
@@ -0,0 +1,3 @@
+function foo() {
+  var foo = this !== null && this !== void 0 ? this : {};
+}