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Track using violations #1

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merged 2 commits into from
Oct 31, 2016
Merged

Track using violations #1

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06c4195
Track using violations
jridgewell Oct 27, 2016
712922a
Find the function's function's references
jridgewell Oct 29, 2016
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84 changes: 76 additions & 8 deletions ...in-transform-remove-undefined/__tests__/babel-plugin-remove-undefined-if-possible-test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -55,18 +55,13 @@ describe("remove-undefined-if-possible-plugin", () => {
expect(transform(source)).toBe(expected);
});

it("should remove nested var-assignments if not referenced before", () => {
it("idk what this is", () => {
const source = unpad(`
function foo() {
a = 3;
var { a: aa, b: bb } = undefined;
}`);
const expected = unpad(`
function foo() {
a = 3;
var { a: aa, b: bb };
}`);
expect(transform(source)).toBe(expected);
expect(transform(source)).toBe(source);
});

it("should remove let-assignments in inner blocks", () => {
Expand All @@ -88,11 +83,25 @@ describe("remove-undefined-if-possible-plugin", () => {
expect(transform(source)).toBe(source);
});

it("should not remove var-assignments in loops", () => {
it("should remove var-assignments in loops", () => {
const source = unpad(`
for (var a = undefined;;) {
var b = undefined;
}`);
const expected = unpad(`
for (var a;;) {
var b;
}`);
expect(transform(source)).toBe(expected);
});

it("should not remove var-assignments in loops 2", () => {
const source = unpad(`
for (var a;;) {
var b = undefined;
console.log(b);
b = 3;
}`);
expect(transform(source)).toBe(source);
});

Expand All @@ -113,4 +122,63 @@ describe("remove-undefined-if-possible-plugin", () => {
}`);
expect(transform(source)).toBe(source);
});

it("should not remove ...", () => {
const source = unpad(`
function foo() {
bar();
var x = undefined;
console.log(x);
function bar() {
x = 3;
}
}`);
expect(transform(source)).toBe(source);
});

it("should remove ...", () => {
const source = unpad(`
function foo() {
var x = undefined;
bar();
console.log(x);
function bar() {
x = 3;
}
}`);
const expected = unpad(`
function foo() {
var x;
bar();
console.log(x);
function bar() {
x = 3;
}
}`);
expect(transform(source)).toBe(expected);
});

it("should remove ...", () => {
const source = unpad(`
foo();
function foo() {
var x = undefined;
bar();
console.log(x);
function bar() {
x = 3;
}
}`);
const expected = unpad(`
foo();
function foo() {
var x;
bar();
console.log(x);
function bar() {
x = 3;
}
}`);
expect(transform(source)).toBe(expected);
});
});
85 changes: 50 additions & 35 deletions packages/babel-plugin-transform-remove-undefined/src/index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -8,15 +8,16 @@ function removeRvalIfUndefined(declaratorPath) {
}
}

function areAllBindingsNotSeen(declaratorPath, seenNames, t) {
const id = declaratorPath.node.id;
const names = t.getBindingIdentifiers(id);
for (const name in names) {
if (seenNames.has(name)) {
return false;
}
}
return true;
function getLoopParent(path, scopeParent) {
const parent = path.findParent((p) => p.isLoop() || p === scopeParent);
// don't traverse higher than the function the var is defined in.
return parent === scopeParent ? null : parent;
}

function getFunctionParent(path, scopeParent) {
const parent = path.findParent((p) => p.isFunction());
// don't traverse higher than the function the var is defined in.
return parent === scopeParent ? null : parent;
}

module.exports = function({ types: t }) {
Expand All @@ -25,27 +26,6 @@ module.exports = function({ types: t }) {
return {
name: "remove-undefined-if-possible",
visitor: {
Program: {
enter() {
names = new Set();
functionNesting = 0;
},
exit() {
names = null;
functionNesting = 0;
},
},
Function: {
enter() {
functionNesting++;
},
exit() {
functionNesting--;
},
},
Identifier(path) {
names.add(path.node.name);
},
ReturnStatement(path) {
if (path.node.argument !== null) {
const rval = path.get("argument")
Expand All @@ -55,6 +35,7 @@ module.exports = function({ types: t }) {
}
}
},

VariableDeclaration(path) {
switch (path.node.kind) {
case "const":
Expand All @@ -65,12 +46,46 @@ module.exports = function({ types: t }) {
}
break;
case "var":
if (functionNesting === 0) {
// ignore global vars
break;
}
const { node, scope } = path;
for (const declarator of path.get("declarations")) {
if (areAllBindingsNotSeen(declarator, names, t)) {
const binding = scope.getBinding(declarator.node.id.name);
if (!binding) {
continue;
}

const { start } = node;
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@shinew shinew Oct 27, 2016 •
edited
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I think the start and end attributes won't work for nodes that are runtime-generated: https://astexplorer.net/#/Pl6ASeZRlL. This is still probably better than any other way of determining relative ordering though, if we add some existence checks for these attributes for safety.

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Ah, I thought doing a #replaceWith auto-inherited the location. Looks like you have to t.inherits(newNode, oldNode) in order to get that.

const scopeParent = declarator.getFunctionParent();

const violation = binding.constantViolations.some(v => {
const violationStart = v.node.start;
if (violationStart < start) {
return true;
}

for (let func = getFunctionParent(v, scopeParent); func; func = getFunctionParent(func, scopeParent)) {
const id = func.node.id;
const binding = id && scope.getBinding(id.name);

if (!binding) {
continue;
}

const funcViolation = binding.referencePaths.some((p) => {
return p.node.start < start;
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@shinew shinew Oct 27, 2016 •
edited
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Would this fail for references through multiple levels of indirection?

e.g.

function foo() {
  bar();
  var a = undefined;
  console.log(a);
  function bar() {
    g();
  }
  function g() {
    a = 4;
  }
}

We cannot remove the = undefined in this case. As I understand this, it only checks for 1 level of referencing.

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That'll be easy enough to add.

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Done, but it's unoptimized.

});
if (funcViolation) {
return true;
}
}

for (let loop = getLoopParent(declarator, scopeParent); loop; loop = getLoopParent(loop, scopeParent)) {
if (loop.node.end > violationStart) {
return true;
}
}
});

if (!violation) {
removeRvalIfUndefined(declarator);
}
}
Expand Down