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evaluation.js
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evaluation.js
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import { parse } from "@babel/parser";
import _traverse from "../lib/index.js";
const traverse = _traverse.default || _traverse;
function getPath(code) {
const ast = parse(code);
let path;
traverse(ast, {
Program: function (_path) {
path = _path;
_path.stop();
},
});
return path;
}
function addDeoptTest(code, type, expectedType) {
it(type + " deopt: " + code, function () {
const visitor = {};
visitor[type] = function (path) {
const evaluate = path.evaluate();
expect(evaluate.confident).toBeFalsy();
expect(evaluate.deopt.type).toEqual(expectedType);
};
traverse(
parse(code, {
plugins: ["*"],
}),
visitor,
);
});
}
describe("evaluation", function () {
describe("evaluateTruthy", function () {
it("should work with null", function () {
expect(
getPath("false || a.length === 0;").get("body")[0].evaluateTruthy(),
).toBeUndefined();
});
it("should not mistake lack of confidence for falsy", function () {
expect(
getPath("foo || 'bar'").get("body")[0].evaluate().value,
).toBeUndefined();
});
});
it("should bail out on recursive evaluation", function () {
expect(
getPath("function fn(a) { var g = a ? 1 : 2, a = g * this.foo; }")
.get("body.0.body.body.0.declarations.1.init")
.evaluate().confident,
).toBe(false);
});
it("should short-circuit && and ||", function () {
expect(getPath("x === 'y' || 42").get("body")[0].evaluate().confident).toBe(
false,
);
expect(getPath("x === 'y' && 0").get("body")[0].evaluate().confident).toBe(
false,
);
expect(getPath("42 || x === 'y'").get("body")[0].evaluate().value).toBe(42);
expect(getPath("0 && x === 'y'").get("body")[0].evaluate().value).toBe(0);
});
it("should handle ??", function () {
expect(getPath("null ?? 42").get("body")[0].evaluate().value).toBe(42);
expect(getPath("void 0 ?? 42").get("body")[0].evaluate().value).toBe(42);
expect(getPath("0 ?? 42").get("body")[0].evaluate().value).toBe(0);
expect(getPath("x ?? 42").get("body")[0].evaluate().confident).toBe(false);
expect(getPath("42 ?? x === 'y'").get("body")[0].evaluate().value).toBe(42);
});
it("should work with repeated, indeterminate identifiers", function () {
expect(
getPath("var num = foo(); (num > 0 && num < 100);")
.get("body")[1]
.evaluateTruthy(),
).toBeUndefined();
});
it("should work with repeated, determinate identifiers", function () {
expect(
getPath("var num = 5; (num > 0 && num < 100);")
.get("body")[1]
.evaluateTruthy(),
).toBe(true);
});
it("should deopt when var is redeclared in the same scope", function () {
expect(
getPath("var x = 2; var y = x + 2; { var x = 3 }")
.get("body.1.declarations.0.init")
.evaluate().confident,
).toBe(false);
});
it("should evaluate template literals", function () {
expect(
getPath("var x = 8; var y = 1; var z = `value is ${x >>> y}`")
.get("body.2.declarations.0.init")
.evaluate().value,
).toBe("value is 4");
});
it("should evaluate member expressions", function () {
expect(
getPath("var x = 'foo'.length")
.get("body.0.declarations.0.init")
.evaluate().value,
).toBe(3);
expect(
getPath("var x = 'hello world'[6]")
.get("body.0.declarations.0.init")
.evaluate().value,
).toBe("w");
expect(
getPath("var length = 1; var x = 'abc'[length];")
.get("body.1.declarations.0.init")
.evaluate().value,
).toBe("b");
const member_expr = getPath(
"var x = Math.min(2,Math.max(3,4));var y = Math.random();",
);
const eval_member_expr = member_expr
.get("body.0.declarations.0.init")
.evaluate();
const eval_invalid_call = member_expr
.get("body.1.declarations.0.init")
.evaluate();
expect(eval_member_expr.value).toBe(2);
expect(eval_invalid_call.confident).toBe(false);
});
it("should not deopt vars in different scope", function () {
const input =
"var a = 5; function x() { var a = 5; var b = a + 1; } var b = a + 2";
expect(
getPath(input).get("body.1.body.body.1.declarations.0.init").evaluate()
.value,
).toBe(6);
expect(
getPath(input).get("body.2.declarations.0.init").evaluate().value,
).toBe(7);
});
it("should not deopt let/const inside blocks", function () {
expect(
getPath("let x = 5; { let x = 1; } let y = x + 5")
.get("body.2.declarations.0.init")
.evaluate().value,
).toBe(10);
const constExample =
"const d = true; if (d && true || false) { const d = false; d && 5; }";
expect(getPath(constExample).get("body.1.test").evaluate().value).toBe(
true,
);
expect(
getPath(constExample).get("body.1.consequent.body.1").evaluate().value,
).toBe(false);
const test_alternate = "var y = (3 < 4)? 3 + 4: 3 + 4;";
expect(
getPath(test_alternate)
.get("body.0.declarations.0.init.alternate")
.evaluate().value,
).toBe(7);
});
it("should deopt ids that are referenced before the bindings", function () {
expect(
getPath("let x = y + 5; let y = 5;")
.get("body.0.declarations.0.init")
.evaluate().confident,
).toBe(false);
expect(
getPath("if (typeof x === 'undefined') var x = {}")
.get("body.0.test")
.evaluate().confident,
).toBe(false);
});
it("should evaluate undefined, NaN and Infinity", () => {
expect(
getPath("undefined").get("body.0.expression").evaluate().confident,
).toBe(true);
expect(getPath("NaN").get("body.0.expression").evaluate().confident).toBe(
true,
);
expect(
getPath("Infinity").get("body.0.expression").evaluate().confident,
).toBe(true);
});
it("should deopt redefined primitives - undefined, NaN and Infinity", () => {
const eval_undef = getPath("let undefined; undefined;")
.get("body.1.expression")
.evaluate();
const eval_nan = getPath("let NaN; NaN;")
.get("body.1.expression")
.evaluate();
const eval_inf = getPath("let Infinity; Infinity;")
.get("body.1.expression")
.evaluate();
expect(eval_undef.confident).toBe(false);
expect(eval_nan.confident).toBe(false);
expect(eval_inf.confident).toBe(false);
expect(eval_undef.deopt.type).toBe("VariableDeclarator");
expect(eval_undef.deopt.parentPath.node.kind).toBe("let");
});
it("should work with String.raw", function () {
expect(getPath("String.raw`\\d`").get("body")[0].evaluate().value).toBe(
"\\d",
);
expect(
getPath("`${String.raw`\\d`}`").get("body")[0].evaluate().value,
).toBe("\\d");
});
it("sets deopt properly when not confident after evaluating multiple expressions", () => {
const ast = parse(`
const parts = [foo, bar];
console.log(parts.join('-'));
`);
let result;
traverse(ast, {
MemberExpression: {
enter(path) {
result = path.get("object").evaluate();
},
},
});
expect(result.confident).toBe(false);
expect(result.deopt.type).toBe("Identifier");
expect(result.deopt.node.name).toBe("foo");
});
it("sets deopt properly when confident after evaluating multiple expressions", () => {
const ast = parse(`
const foo = 'foo';
const bar = 'bar';
const parts = [foo, bar];
console.log(parts.join('-'))
`);
let result;
traverse(ast, {
MemberExpression: {
enter(path) {
result = path.get("object").evaluate();
},
},
});
expect(result.confident).toBe(true);
expect(result.deopt).toBeNull();
expect(result.value).toEqual(["foo", "bar"]);
});
addDeoptTest("({a:{b}})", "ObjectExpression", "Identifier");
addDeoptTest("({[a + 'b']: 1})", "ObjectExpression", "Identifier");
addDeoptTest("[{a}]", "ArrayExpression", "Identifier");
});