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fix: babel-traverse constant flag in bindings #13777

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fix: babel-traverse constant flag in bindings #13777

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11 changes: 11 additions & 0 deletions ...gin-transform-react-constant-elements/test/fixtures/constant-elements/for-loop-2/input.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
function render() {
const nodes = [];

for (let i = 0; i < 5; i++) {
const o = "foo";
const n = i;
nodes.push(<div>{n}</div>);
}

return nodes;
}
11 changes: 11 additions & 0 deletions ...in-transform-react-constant-elements/test/fixtures/constant-elements/for-loop-2/output.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
function render() {
const nodes = [];

for (let i = 0; i < 5; i++) {
const o = "foo";
const n = i;
nodes.push(<div>{n}</div>);
}

return nodes;
}
9 changes: 9 additions & 0 deletions ...gin-transform-react-constant-elements/test/fixtures/constant-elements/for-loop-3/input.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,9 @@
function render() {
const nodes = [];

for (const node of nodes) {
nodes.push(<div>{node}</div>);
}

return nodes;
}
9 changes: 9 additions & 0 deletions ...in-transform-react-constant-elements/test/fixtures/constant-elements/for-loop-3/output.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,9 @@
function render() {
const nodes = [];

for (const node of nodes) {
nodes.push(<div>{node}</div>);
}

return nodes;
}
10 changes: 10 additions & 0 deletions ...gin-transform-react-constant-elements/test/fixtures/constant-elements/for-loop-4/input.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
function render() {
const nodes = [];

for (const node of nodes) {
const n = node;
nodes.push(<div>{n}</div>);
}

return nodes;
}
10 changes: 10 additions & 0 deletions ...in-transform-react-constant-elements/test/fixtures/constant-elements/for-loop-4/output.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
function render() {
const nodes = [];

for (const node of nodes) {
const n = node;
nodes.push(<div>{n}</div>);
}

return nodes;
}
11 changes: 11 additions & 0 deletions ...gin-transform-react-constant-elements/test/fixtures/constant-elements/for-loop-5/input.js
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Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
function render() {
const nodes = [];

for (let i = 0; i < 5; i++) {
const o = "foo";
const n = i;
nodes.push(<div>{o}</div>);
}

return nodes;
}
11 changes: 11 additions & 0 deletions ...in-transform-react-constant-elements/test/fixtures/constant-elements/for-loop-5/output.js
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Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
function render() {
const nodes = [];

for (let i = 0; i < 5; i++) {
const o = "foo";
const n = i;
nodes.push(<div>{o}</div>);
}

return nodes;
}
7 changes: 7 additions & 0 deletions packages/babel-traverse/src/scope/binding.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -44,6 +44,13 @@ export default class Binding {
this.path = path;
this.kind = kind;

for (let node of path.getAncestry()) {
if (node.isLoop()) {
debugger;
this.constant = false;
}
}
Comment on lines +47 to +52
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  1. When node.isFunction() we can break the loop, since variables don't cross function boundaries: 
    for (;;) () => { var x };
    is constant.
  2. We only need to do this if we have a var, not for const or let
  3. We don't need to collect the whole ancestry, since we'll only use part of it (up to a function). We can do something like 
    let { parentPath } = path;
while (parentPath && !parentPath.isFunction()) {
  // ...
  ({ parentPath } = parentPath);
}


this.clearValue();
}

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23 changes: 23 additions & 0 deletions packages/babel-traverse/test/scope.js
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Original file line number Diff line number Diff line change
Expand Up @@ -361,6 +361,29 @@ describe("scope", () => {
expect(
getPath("var a = 1; var a = 2;").scope.getBinding("a").constant,
).toBe(false);
expect(
getPath("for (var n of ns) { var a = 1; }").scope.getBinding("a")
.constant,
).toBe(false);
expect(
getPath("for (var n in ns) { var a = 1; }").scope.getBinding("a")
.constant,
).toBe(false);
expect(
getPath("for (var i = 0; i < n; i++) { var a = 1; }").scope.getBinding(
"a",
).constant,
).toBe(false);
expect(
getPath("var i = 0; while (i != 1) { var a = 1; }").scope.getBinding(
"a",
).constant,
).toBe(false);
expect(
getPath("var i = 0; do { var a = 1; } while (i != 1)").scope.getBinding(
"a",
).constant,
).toBe(false);
});

it("purity", function () {
Expand Down