feature: Support pure expressions in transform-react-constant-elements

packages/babel-plugin-transform-react-constant-elements/src/index.js

@@ -19,6 +19,12 @@ export default function () {
         return;
       }
 
+      // Expressions are okay, but not if there is a mutable object involved.
+      // TODO would be great if we could evaluate, because [] + 1 is technically fine
+      if (path.isPure() && !path.isObjectExpression()) {
+        return;
+      }
+
       if (!path.isImmutable()) stop();
     }
   };

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-deopt/actual.js

@@ -0,0 +1,5 @@
+// https://github.com/facebook/react/issues/3226
+// Not safe to reuse because it is mutable
+function render() {
+  return <div style={{ width: 100 }} />;
+}

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-deopt/expected.js

@@ -0,0 +1,5 @@
+// https://github.com/facebook/react/issues/3226
+// Not safe to reuse because it is mutable
+function render() {
+  return <div style={{ width: 100 }} />;
+}

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression-2/actual.js

@@ -0,0 +1,5 @@
+function render(offset) {
+  return function () {
+    return <div tabIndex={offset + 1} />;
+  };
+}

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression-2/expected.js

@@ -0,0 +1,8 @@
+function render(offset) {
+  var _ref = <div tabIndex={offset + 1} />;
+
+  return function () {
+    return _ref;
+  };
+}
+

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression-3/actual.js

@@ -0,0 +1,10 @@
+const OFFSET = 3;
+
+var Foo = React.createClass({
+  render: function () {
+    return (
+      <div tabIndex={OFFSET + 1} />
+    );
+  }
+});
+

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression-3/expected.js

@@ -0,0 +1,10 @@
+const OFFSET = 3;
+
+var _ref = <div tabIndex={OFFSET + 1} />;
+
+var Foo = React.createClass({
+  render: function () {
+    return _ref;
+  }
+});
+

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression/actual.js

@@ -0,0 +1,11 @@
+var Foo = React.createClass({
+  render: function () {
+    return (
+      <div data-text={
+        "Some text, " +
+        "and some more too."
+      } />
+    );
+  }
+});
+

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression/expected.js

@@ -0,0 +1,8 @@
+var _ref = <div data-text={"Some text, " + "and some more too."} />;
+
+var Foo = React.createClass({
+  render: function () {
+    return _ref;
+  }
+});
+