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fix: account for different scopes during path evaluation #831

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May 13, 2018
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53 changes: 41 additions & 12 deletions packages/babel-helper-evaluate-path/src/index.js
Original file line number Diff line number Diff line change
@@ -1,7 +1,9 @@
"use strict";

const t = require("@babel/types");

module.exports = function evaluate(path, { tdz = false } = {}) {
if (!tdz) {
if (!tdz && !path.isReferencedIdentifier()) {
return baseEvaluate(path);
}

Expand Down Expand Up @@ -63,7 +65,21 @@ function evaluateIdentifier(path) {
const binding = path.scope.getBinding(node.name);

if (!binding) {
return deopt(path);
const { name } = node;
if (!name) {
return deopt(path);
}

switch (name) {
case "undefined":
return { confident: true, value: undefined };
case "NaN":
return { confident: true, value: NaN };
case "Infinity":
return { confident: true, value: Infinity };
default:
return deopt(path);
}
}

if (binding.constantViolations.length > 0) {
Expand Down Expand Up @@ -105,24 +121,39 @@ function evaluateBasedOnControlFlow(binding, refPath) {
if (binding.kind === "var") {
// early-exit
const declaration = binding.path.parentPath;

if (
declaration.parentPath.isIfStatement() ||
declaration.parentPath.isLoop() ||
declaration.parentPath.isSwitchCase()
t.isIfStatement(declaration.parentPath) ||
t.isLoop(declaration.parentPath) ||
t.isSwitchCase(declaration.parentPath)
) {
if (declaration.parentPath.removed) {
return { confident: true, value: void 0 };
}
return { shouldDeopt: true };
}

const fnParent = (
binding.path.scope.getFunctionParent() ||
binding.path.scope.getProgramParent()
).path;

let blockParent = binding.path.scope.getBlockParent().path;
const fnParent = binding.path.getFunctionParent();

if (blockParent === fnParent) {
if (!fnParent.isProgram()) blockParent = blockParent.get("body");
if (blockParent === fnParent && !fnParent.isProgram()) {
blockParent = blockParent.get("body");
}

// detect Usage Outside Init Scope
if (!blockParent.get("body").some(stmt => stmt.isAncestor(refPath))) {
return { shouldDeopt: true };
const blockBody = blockParent.get("body");

if (
Array.isArray(blockBody) &&
!blockBody.some(stmt => stmt.isAncestor(refPath))
) {
return {
shouldDeopt: true
};
}

// Detect usage before init
Expand All @@ -143,8 +174,6 @@ function evaluateBasedOnControlFlow(binding, refPath) {
) {
return { confident: true, value: void 0 };
}

return { shouldDeopt: true };
}
} else if (binding.kind === "let" || binding.kind === "const") {
// binding.path is the declarator
Expand Down
Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
function foo(v) {
if (v) ;
console.log("hello", v);
if (v) var w = 10;
if (w) console.log("hello", v);
}
Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,11 @@ const { markEvalScopes, hasEval } = require("babel-helper-mark-eval-scopes");
const removeUseStrict = require("./remove-use-strict");
const evaluate = require("babel-helper-evaluate-path");

function evaluateTruthy(path) {
const res = evaluate(path);
if (res.confident) return !!res.value;
}

function prevSiblings(path) {
const parentPath = path.parentPath;
const siblings = [];
Expand Down Expand Up @@ -548,7 +553,7 @@ module.exports = ({ types: t, traverse }) => {

ConditionalExpression(path) {
const { node } = path;
const evaluateTest = path.get("test").evaluateTruthy();
const evaluateTest = evaluateTruthy(path.get("test"));
if (evaluateTest === true) {
path.replaceWith(node.consequent);
} else if (evaluateTest === false) {
Expand Down Expand Up @@ -977,6 +982,7 @@ module.exports = ({ types: t, traverse }) => {
path.traverse({
VariableDeclaration(varPath) {
if (!varPath.isVariableDeclaration({ kind: "var" })) return;

if (!isSameFunctionScope(varPath, path)) return;

for (const decl of varPath.node.declarations) {
Expand Down
14 changes: 10 additions & 4 deletions packages/babel-plugin-minify-guarded-expressions/src/index.js
Original file line number Diff line number Diff line change
@@ -1,4 +1,10 @@
"use strict";
const evaluate = require("babel-helper-evaluate-path");

function evaluateTruthy(path) {
const res = evaluate(path);
if (res.confident) return !!res.value;
}

module.exports = function({ types: t }) {
const flipExpressions = require("babel-helper-flip-expressions")(t);
Expand Down Expand Up @@ -28,28 +34,28 @@ module.exports = function({ types: t }) {
const shouldBail = !path.parentPath.isExpressionStatement();

if (node.operator === "&&") {
const leftTruthy = left.evaluateTruthy();
const leftTruthy = evaluateTruthy(left);
if (leftTruthy === false) {
// Short-circuit
path.replaceWith(node.left);
} else if (leftTruthy === true && left.isPure()) {
path.replaceWith(node.right);
} else if (
right.evaluateTruthy() === false &&
evaluateTruthy(right) === false &&
right.isPure() &&
!shouldBail
) {
path.replaceWith(node.left);
}
} else if (node.operator === "||") {
const leftTruthy = left.evaluateTruthy();
const leftTruthy = evaluateTruthy(left);
if (leftTruthy === false && left.isPure()) {
path.replaceWith(node.right);
} else if (leftTruthy === true) {
// Short-circuit
path.replaceWith(node.left);
} else if (
right.evaluateTruthy() === false &&
evaluateTruthy(right) === false &&
right.isPure() &&
!shouldBail
) {
Expand Down
3 changes: 2 additions & 1 deletion packages/babel-plugin-minify-simplify/src/helpers.js
Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
"use strict";

const VOID_0 = t => t.unaryExpression("void", t.numericLiteral(0), true);
const evaluate = require("babel-helper-evaluate-path");

// Types as Symbols - for comparing types
const types = {};
Expand Down Expand Up @@ -39,7 +40,7 @@ const isPatternMatchesPath = t =>
return patternValue(inputPath);
}
if (isNodeOfType(t, inputPath.node, patternValue)) return true;
const evalResult = inputPath.evaluate();
const evalResult = evaluate(inputPath);
if (!evalResult.confident || !inputPath.isPure()) return false;
return evalResult.value === patternValue;
};
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -2,13 +2,14 @@

const h = require("./helpers");
const PatternMatch = require("./pattern-match");
const evaluate = require("babel-helper-evaluate-path");

module.exports = t => {
const OP_AND = input => input === "&&";
const OP_OR = input => input === "||";

function simplifyPatterns(path) {
// cache of path.evaluate()
// cache of evaluate(path)
const evaluateMemo = new Map();

const TRUTHY = input => {
Expand All @@ -22,7 +23,7 @@ module.exports = t => {
return true;
}
}
const evalResult = input.evaluate();
const evalResult = evaluate(input);
evaluateMemo.set(input, evalResult);
return evalResult.confident && input.isPure() && evalResult.value;
};
Expand All @@ -35,7 +36,7 @@ module.exports = t => {
return true;
}
}
const evalResult = input.evaluate();
const evalResult = evaluate(input);
evaluateMemo.set(input, evalResult);
return evalResult.confident && input.isPure() && !evalResult.value;
};
Expand Down Expand Up @@ -67,7 +68,7 @@ module.exports = t => {
if (evaluateMemo.has(left)) {
value = evaluateMemo.get(left).value;
} else {
value = left.evaluate().value;
value = evaluate(left).value;
}
path.replaceWith(result.value(t.valueToNode(value), right.node));
}
Expand Down
15 changes: 15 additions & 0 deletions packages/babel-preset-minify/__tests__/preset-tests.js
Original file line number Diff line number Diff line change
Expand Up @@ -177,4 +177,19 @@ describe("preset", () => {
}
`
);

thePlugin(
"should fix issue#810 declaration inside different scope",
`
if (false) {
var bar = true;
}
if (bar) {
alert('bug!');
}
`,
`
var bar;
`
);
});