test262/harness/typeCoercion.js

// Copyright (C) 2017 Josh Wolfe. All rights reserved.
// This code is governed by the BSD license found in the LICENSE file.
/*---
description: |
    Functions to help generate test cases for testing type coercion abstract
    operations like ToNumber.
---*/

function testCoercibleToIntegerZero(test) {
  testCoercibleToNumberZero(test);

  testCoercibleToIntegerFromInteger(0, test);

  // NaN -> +0
  testCoercibleToNumberNan(test);

  // When toString() returns a string that parses to NaN:
  test({});
  test([]);
}

function testCoercibleToIntegerOne(test) {
  testCoercibleToNumberOne(test);

  testCoercibleToIntegerFromInteger(1, test);

  // When toString() returns "1"
  test([1]);
  test(["1"]);
}

function testCoercibleToNumberZero(test) {
  function testPrimitiveValue(value) {
    test(value);
    // ToPrimitive
    testPrimitiveWrappers(value, "number", test);
  }

  testPrimitiveValue(null);
  testPrimitiveValue(false);
  testPrimitiveValue(0);
  testPrimitiveValue("0");
}

function testCoercibleToNumberNan(test) {
  function testPrimitiveValue(value) {
    test(value);
    // ToPrimitive
    testPrimitiveWrappers(value, "number", test);
  }

  testPrimitiveValue(undefined);
  testPrimitiveValue(NaN);
  testPrimitiveValue("");
  testPrimitiveValue("foo");
  testPrimitiveValue("true");
}

function testCoercibleToNumberOne(test) {
  function testPrimitiveValue(value) {
    test(value);
    // ToPrimitive
    testPrimitiveWrappers(value, "number", test);
  }

  testPrimitiveValue(true);
  testPrimitiveValue(1);
  testPrimitiveValue("1");
}

function testCoercibleToIntegerFromInteger(nominalInteger, test) {
  assert(Number.isInteger(nominalInteger));

  function testPrimitiveValue(value) {
    test(value);
    // ToPrimitive
    testPrimitiveWrappers(value, "number", test);

    // Non-primitive values that coerce to the nominal integer:
    // toString() returns a string that parsers to a primitive value.
    test([value]);
  }

  function testPrimitiveNumber(number) {
    testPrimitiveValue(number);
    // ToNumber: String -> Number
    testPrimitiveValue(number.toString());
  }

  testPrimitiveNumber(nominalInteger);

  // ToInteger: floor(abs(number))
  if (nominalInteger >= 0) {
    testPrimitiveNumber(nominalInteger + 0.9);
  }
  if (nominalInteger <= 0) {
    testPrimitiveNumber(nominalInteger - 0.9);
  }
}

function testPrimitiveWrappers(primitiveValue, hint, test) {
  if (primitiveValue != null) {
    // null and undefined result in {} rather than a proper wrapper,
    // so skip this case for those values.
    test(Object(primitiveValue));
  }

  testCoercibleToPrimitiveWithMethod(hint, function() {
    return primitiveValue;
  }, test);
}

function testCoercibleToPrimitiveWithMethod(hint, method, test) {
  var methodNames;
  if (hint === "number") {
    methodNames = ["valueOf", "toString"];
  } else if (hint === "string") {
    methodNames = ["toString", "valueOf"];
  } else {
    throw new Test262Error();
  }
  // precedence order
  test({
    [Symbol.toPrimitive]: method,
    [methodNames[0]]: function() { throw new Test262Error(); },
    [methodNames[1]]: function() { throw new Test262Error(); },
  });
  test({
    [methodNames[0]]: method,
    [methodNames[1]]: function() { throw new Test262Error(); },
  });
  if (hint === "number") {
    // The default valueOf returns an object, which is unsuitable.
    // The default toString returns a String, which is suitable.
    // Therefore this test only works for valueOf falling back to toString.
    test({
      // this is toString:
      [methodNames[1]]: method,
    });
  }

  // GetMethod: if func is undefined or null, return undefined.
  test({
    [Symbol.toPrimitive]: undefined,
    [methodNames[0]]: method,
    [methodNames[1]]: method,
  });
  test({
    [Symbol.toPrimitive]: null,
    [methodNames[0]]: method,
    [methodNames[1]]: method,
  });

  // if methodNames[0] is not callable, fallback to methodNames[1]
  test({
    [methodNames[0]]: null,
    [methodNames[1]]: method,
  });
  test({
    [methodNames[0]]: 1,
    [methodNames[1]]: method,
  });
  test({
    [methodNames[0]]: {},
    [methodNames[1]]: method,
  });

  // if methodNames[0] returns an object, fallback to methodNames[1]
  test({
    [methodNames[0]]: function() { return {}; },
    [methodNames[1]]: method,
  });
  test({
    [methodNames[0]]: function() { return Object(1); },
    [methodNames[1]]: method,
  });
}

function testNotCoercibleToInteger(test) {
  // ToInteger only throws from ToNumber.
  return testNotCoercibleToNumber(test);
}
function testNotCoercibleToNumber(test) {
  function testPrimitiveValue(value) {
    test(TypeError, value);
    // ToPrimitive
    testPrimitiveWrappers(value, "number", function(value) {
      test(TypeError, value);
    });
  }

  // ToNumber: Symbol -> TypeError
  testPrimitiveValue(Symbol("1"));

  if (typeof BigInt !== "undefined") {
    // ToNumber: BigInt -> TypeError
    testPrimitiveValue(BigInt(0));
  }

  // ToPrimitive
  testNotCoercibleToPrimitive("number", test);
}

function testNotCoercibleToPrimitive(hint, test) {
  function MyError() {}

  // ToPrimitive: input[@@toPrimitive] is not callable (and non-null)
  test(TypeError, {[Symbol.toPrimitive]: 1});
  test(TypeError, {[Symbol.toPrimitive]: {}});

  // ToPrimitive: input[@@toPrimitive] returns object
  test(TypeError, {[Symbol.toPrimitive]: function() { return Object(1); }});
  test(TypeError, {[Symbol.toPrimitive]: function() { return {}; }});

  // ToPrimitive: input[@@toPrimitive] throws
  test(MyError, {[Symbol.toPrimitive]: function() { throw new MyError(); }});

  // OrdinaryToPrimitive: method throws
  testCoercibleToPrimitiveWithMethod(hint, function() {
    throw new MyError();
  }, function(value) {
    test(MyError, value);
  });

  // OrdinaryToPrimitive: both methods are unsuitable
  function testUnsuitableMethod(method) {
    test(TypeError, {valueOf:method, toString:method});
  }
  // not callable:
  testUnsuitableMethod(null);
  testUnsuitableMethod(1);
  testUnsuitableMethod({});
  // returns object:
  testUnsuitableMethod(function() { return Object(1); });
  testUnsuitableMethod(function() { return {}; });
}

function testCoercibleToString(test) {
  function testPrimitiveValue(value, expectedString) {
    test(value, expectedString);
    // ToPrimitive
    testPrimitiveWrappers(value, "string", function(value) {
      test(value, expectedString);
    });
  }

  testPrimitiveValue(undefined, "undefined");
  testPrimitiveValue(null, "null");
  testPrimitiveValue(true, "true");
  testPrimitiveValue(false, "false");
  testPrimitiveValue(0, "0");
  testPrimitiveValue(-0, "0");
  testPrimitiveValue(Infinity, "Infinity");
  testPrimitiveValue(-Infinity, "-Infinity");
  testPrimitiveValue(123.456, "123.456");
  testPrimitiveValue(-123.456, "-123.456");
  testPrimitiveValue("", "");
  testPrimitiveValue("foo", "foo");

  if (typeof BigInt !== "undefined") {
    // BigInt -> TypeError
    testPrimitiveValue(BigInt(0), "0");
  }

  // toString of a few objects
  test([], "");
  test(["foo", "bar"], "foo,bar");
  test({}, "[object Object]");
}

function testNotCoercibleToString(test) {
  function testPrimitiveValue(value) {
    test(TypeError, value);
    // ToPrimitive
    testPrimitiveWrappers(value, "string", function(value) {
      test(TypeError, value);
    });
  }

  // Symbol -> TypeError
  testPrimitiveValue(Symbol("1"));

  // ToPrimitive
  testNotCoercibleToPrimitive("string", test);
}