diff --git a/src/lib/exec.rs b/src/lib/exec.rs index 0dad8e5c6fd..7cca7d0d9cc 100644 --- a/src/lib/exec.rs +++ b/src/lib/exec.rs @@ -300,13 +300,12 @@ impl Executor for Interpreter { })) } ExprDef::BinOp(BinOp::Log(ref op), ref a, ref b) => { - let v_a = - from_value::(self.run(a)?).expect("Could not convert JS value to bool"); - let v_b = - from_value::(self.run(b)?).expect("Could not convert JS value to bool"); + // turn a `Value` into a `bool` + let to_bool = + |val| from_value::(val).expect("Could not convert JS value to bool"); Ok(match *op { - LogOp::And => to_value(v_a && v_b), - LogOp::Or => to_value(v_a || v_b), + LogOp::And => to_value(to_bool(self.run(a)?) && to_bool(self.run(b)?)), + LogOp::Or => to_value(to_bool(self.run(a)?) || to_bool(self.run(b)?)), }) } ExprDef::BinOp(BinOp::Assign(ref op), ref a, ref b) => match a.def { @@ -816,4 +815,67 @@ mod tests { "#; assert_eq!(exec(early_return), String::from("outer")); } + + #[test] + fn test_short_circuit_evaluation() { + // OR operation + assert_eq!(exec("true || true"), String::from("true")); + assert_eq!(exec("true || false"), String::from("true")); + assert_eq!(exec("false || true"), String::from("true")); + assert_eq!(exec("false || false"), String::from("false")); + + // the second operand must NOT be evaluated if the first one resolve to `true`. + let short_circuit_eval = r#" + function add_one(counter) { + counter.value += 1; + return true; + } + let counter = { value: 0 }; + let _ = add_one(counter) || add_one(counter); + counter.value + "#; + assert_eq!(exec(short_circuit_eval), String::from("1")); + + // the second operand must be evaluated if the first one resolve to `false`. + let short_circuit_eval = r#" + function add_one(counter) { + counter.value += 1; + return false; + } + let counter = { value: 0 }; + let _ = add_one(counter) || add_one(counter); + counter.value + "#; + assert_eq!(exec(short_circuit_eval), String::from("2")); + + // AND operation + assert_eq!(exec("true && true"), String::from("true")); + assert_eq!(exec("true && false"), String::from("false")); + assert_eq!(exec("false && true"), String::from("false")); + assert_eq!(exec("false && false"), String::from("false")); + + // the second operand must be evaluated if the first one resolve to `true`. + let short_circuit_eval = r#" + function add_one(counter) { + counter.value += 1; + return true; + } + let counter = { value: 0 }; + let _ = add_one(counter) && add_one(counter); + counter.value + "#; + assert_eq!(exec(short_circuit_eval), String::from("2")); + + // the second operand must NOT be evaluated if the first one resolve to `false`. + let short_circuit_eval = r#" + function add_one(counter) { + counter.value += 1; + return false; + } + let counter = { value: 0 }; + let _ = add_one(counter) && add_one(counter); + counter.value + "#; + assert_eq!(exec(short_circuit_eval), String::from("1")); + } }