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[DCE] Fix removal of ArrayPattern #622

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merged 1 commit into from
Jul 8, 2017
Merged

[DCE] Fix removal of ArrayPattern #622

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22 changes: 22 additions & 0 deletions packages/babel-plugin-minify-dead-code-elimination/__tests__/dead-code-elimination-test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2426,4 +2426,26 @@ describe("dce-plugin", () => {
}
`
);

thePlugin(
"should bail out for Array and Object Pattern - fix issue#617",
`
function foo(arr) {
let [a, b] = arr;
console.log(a);
}
`
);

thePlugin(
"should bail out for Array and Object Pattern - fix issue#617",
`
function foo() {
return getPromise().then(arr => {
let { a, b } = arr;
console.log(a);
});
}
`
);
});
32 changes: 20 additions & 12 deletions packages/babel-plugin-minify-dead-code-elimination/src/index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -228,21 +228,29 @@ module.exports = ({ types: t, traverse }) => {
continue;
}

if (
binding.path.isVariableDeclarator() &&
binding.path.node.init &&
!scope.isPure(binding.path.node.init) &&
binding.path.parentPath.node.declarations
) {
if (binding.path.parentPath.node.declarations.length !== 1) {
continue;
}
// Bail out for ArrayPattern and ObjectPattern
if (binding.path.isVariableDeclarator()) {
if (!binding.path.get("id").isIdentifier()) {
// deopt for object and array pattern
continue;
}

binding.path.parentPath.replaceWith(binding.path.node.init);
// if declarator has some impure init expression
// var x = foo();
// => foo();
if (
binding.path.node.init &&
!scope.isPure(binding.path.node.init) &&
binding.path.parentPath.node.declarations
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I'm currently getting the error Cannot read property 'declarations' of null here. Doing steps to reproduce is a lot of work (big repo). So I thought I would take a wild stab in the dark and ask if you could see that it would in any way make sense to add a guard here for if binding.path.parentPath.node is null? If that doesn't make sense I apologise for wasting your time...

) {
// binding path has more than one declarations
if (binding.path.parentPath.node.declarations.length !== 1) {
continue;
}
binding.path.parentPath.replaceWith(binding.path.node.init);
} else {
updateReferences(binding.path, this);
removeOrVoid(binding.path);
}
} else {
updateReferences(binding.path, this);
removeOrVoid(binding.path);
Expand Down Expand Up @@ -403,7 +411,7 @@ module.exports = ({ types: t, traverse }) => {
}
}
}
}
} // end-for-of
}
},

Expand Down