From 1886a843a3e3f425f2ed68abc198d12d95dbf5fe Mon Sep 17 00:00:00 2001
From: Samuel Reed <samuel.trace.reed@gmail.com>
Date: Sat, 5 Nov 2016 11:15:57 -0500
Subject: [PATCH] feature: Support pure expressions in
 transform-react-constant-elements

---
 .../src/index.js                                      |  6 ++++++
 .../fixtures/constant-elements/pure-deopt/actual.js   |  5 +++++
 .../fixtures/constant-elements/pure-deopt/expected.js |  5 +++++
 .../constant-elements/pure-expression-2/actual.js     |  5 +++++
 .../constant-elements/pure-expression-2/expected.js   |  8 ++++++++
 .../constant-elements/pure-expression-3/actual.js     | 10 ++++++++++
 .../constant-elements/pure-expression-3/expected.js   | 10 ++++++++++
 .../constant-elements/pure-expression/actual.js       | 11 +++++++++++
 .../constant-elements/pure-expression/expected.js     |  8 ++++++++
 9 files changed, 68 insertions(+)
 create mode 100644 packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-deopt/actual.js
 create mode 100644 packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-deopt/expected.js
 create mode 100644 packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression-2/actual.js
 create mode 100644 packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression-2/expected.js
 create mode 100644 packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression-3/actual.js
 create mode 100644 packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression-3/expected.js
 create mode 100644 packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression/actual.js
 create mode 100644 packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression/expected.js

diff --git a/packages/babel-plugin-transform-react-constant-elements/src/index.js b/packages/babel-plugin-transform-react-constant-elements/src/index.js
index 9673af7c2683..2fe4ba8a6985 100644
--- a/packages/babel-plugin-transform-react-constant-elements/src/index.js
+++ b/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();
     }
   };
diff --git a/packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-deopt/actual.js b/packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-deopt/actual.js
new file mode 100644
index 000000000000..4df51832c7ce
--- /dev/null
+++ b/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 }} />;
+}
diff --git a/packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-deopt/expected.js b/packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-deopt/expected.js
new file mode 100644
index 000000000000..4df51832c7ce
--- /dev/null
+++ b/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 }} />;
+}
diff --git a/packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression-2/actual.js b/packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression-2/actual.js
new file mode 100644
index 000000000000..0acb75cfaf6a
--- /dev/null
+++ b/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} />;
+  };
+}
diff --git a/packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression-2/expected.js b/packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression-2/expected.js
new file mode 100644
index 000000000000..65df627806b2
--- /dev/null
+++ b/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;
+  };
+}
+
diff --git a/packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression-3/actual.js b/packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression-3/actual.js
new file mode 100644
index 000000000000..c6b89c77fd1a
--- /dev/null
+++ b/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} />
+    );
+  }
+});
+
diff --git a/packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression-3/expected.js b/packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression-3/expected.js
new file mode 100644
index 000000000000..e709176c4870
--- /dev/null
+++ b/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;
+  }
+});
+
diff --git a/packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression/actual.js b/packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression/actual.js
new file mode 100644
index 000000000000..5131c839899b
--- /dev/null
+++ b/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."
+      } />
+    );
+  }
+});
+
diff --git a/packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression/expected.js b/packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/pure-expression/expected.js
new file mode 100644
index 000000000000..a7afcb1d6edf
--- /dev/null
+++ b/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;
+  }
+});
+