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keksAccountGUI/node_modulesOLD/eslint/lib/rules/yoda.js

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2019-08-11 18:48:02 +00:00
/**
* @fileoverview Rule to require or disallow yoda comparisons
* @author Nicholas C. Zakas
*/
"use strict";
//--------------------------------------------------------------------------
// Requirements
//--------------------------------------------------------------------------
const astUtils = require("../util/ast-utils");
//--------------------------------------------------------------------------
// Helpers
//--------------------------------------------------------------------------
/**
* Determines whether an operator is a comparison operator.
* @param {string} operator The operator to check.
* @returns {boolean} Whether or not it is a comparison operator.
*/
function isComparisonOperator(operator) {
return (/^(==|===|!=|!==|<|>|<=|>=)$/u).test(operator);
}
/**
* Determines whether an operator is an equality operator.
* @param {string} operator The operator to check.
* @returns {boolean} Whether or not it is an equality operator.
*/
function isEqualityOperator(operator) {
return (/^(==|===)$/u).test(operator);
}
/**
* Determines whether an operator is one used in a range test.
* Allowed operators are `<` and `<=`.
* @param {string} operator The operator to check.
* @returns {boolean} Whether the operator is used in range tests.
*/
function isRangeTestOperator(operator) {
return ["<", "<="].indexOf(operator) >= 0;
}
/**
* Determines whether a non-Literal node is a negative number that should be
* treated as if it were a single Literal node.
* @param {ASTNode} node Node to test.
* @returns {boolean} True if the node is a negative number that looks like a
* real literal and should be treated as such.
*/
function looksLikeLiteral(node) {
return (node.type === "UnaryExpression" &&
node.operator === "-" &&
node.prefix &&
node.argument.type === "Literal" &&
typeof node.argument.value === "number");
}
/**
* Attempts to derive a Literal node from nodes that are treated like literals.
* @param {ASTNode} node Node to normalize.
* @param {number} [defaultValue] The default value to be returned if the node
* is not a Literal.
* @returns {ASTNode} One of the following options.
* 1. The original node if the node is already a Literal
* 2. A normalized Literal node with the negative number as the value if the
* node represents a negative number literal.
* 3. The Literal node which has the `defaultValue` argument if it exists.
* 4. Otherwise `null`.
*/
function getNormalizedLiteral(node, defaultValue) {
if (node.type === "Literal") {
return node;
}
if (looksLikeLiteral(node)) {
return {
type: "Literal",
value: -node.argument.value,
raw: `-${node.argument.value}`
};
}
if (defaultValue) {
return {
type: "Literal",
value: defaultValue,
raw: String(defaultValue)
};
}
return null;
}
/**
* Checks whether two expressions reference the same value. For example:
* a = a
* a.b = a.b
* a[0] = a[0]
* a['b'] = a['b']
* @param {ASTNode} a Left side of the comparison.
* @param {ASTNode} b Right side of the comparison.
* @returns {boolean} True if both sides match and reference the same value.
*/
function same(a, b) {
if (a.type !== b.type) {
return false;
}
switch (a.type) {
case "Identifier":
return a.name === b.name;
case "Literal":
return a.value === b.value;
case "MemberExpression": {
const nameA = astUtils.getStaticPropertyName(a);
// x.y = x["y"]
if (nameA) {
return (
same(a.object, b.object) &&
nameA === astUtils.getStaticPropertyName(b)
);
}
/*
* x[0] = x[0]
* x[y] = x[y]
* x.y = x.y
*/
return (
a.computed === b.computed &&
same(a.object, b.object) &&
same(a.property, b.property)
);
}
case "ThisExpression":
return true;
default:
return false;
}
}
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
type: "suggestion",
docs: {
description: "require or disallow \"Yoda\" conditions",
category: "Best Practices",
recommended: false,
url: "https://eslint.org/docs/rules/yoda"
},
schema: [
{
enum: ["always", "never"]
},
{
type: "object",
properties: {
exceptRange: {
type: "boolean",
default: false
},
onlyEquality: {
type: "boolean",
default: false
}
},
additionalProperties: false
}
],
fixable: "code",
messages: {
expected: "Expected literal to be on the {{expectedSide}} side of {{operator}}."
}
},
create(context) {
// Default to "never" (!always) if no option
const always = (context.options[0] === "always");
const exceptRange = (context.options[1] && context.options[1].exceptRange);
const onlyEquality = (context.options[1] && context.options[1].onlyEquality);
const sourceCode = context.getSourceCode();
/**
* Determines whether node represents a range test.
* A range test is a "between" test like `(0 <= x && x < 1)` or an "outside"
* test like `(x < 0 || 1 <= x)`. It must be wrapped in parentheses, and
* both operators must be `<` or `<=`. Finally, the literal on the left side
* must be less than or equal to the literal on the right side so that the
* test makes any sense.
* @param {ASTNode} node LogicalExpression node to test.
* @returns {boolean} Whether node is a range test.
*/
function isRangeTest(node) {
const left = node.left,
right = node.right;
/**
* Determines whether node is of the form `0 <= x && x < 1`.
* @returns {boolean} Whether node is a "between" range test.
*/
function isBetweenTest() {
let leftLiteral, rightLiteral;
return (node.operator === "&&" &&
(leftLiteral = getNormalizedLiteral(left.left)) &&
(rightLiteral = getNormalizedLiteral(right.right, Number.POSITIVE_INFINITY)) &&
leftLiteral.value <= rightLiteral.value &&
same(left.right, right.left));
}
/**
* Determines whether node is of the form `x < 0 || 1 <= x`.
* @returns {boolean} Whether node is an "outside" range test.
*/
function isOutsideTest() {
let leftLiteral, rightLiteral;
return (node.operator === "||" &&
(leftLiteral = getNormalizedLiteral(left.right, Number.NEGATIVE_INFINITY)) &&
(rightLiteral = getNormalizedLiteral(right.left)) &&
leftLiteral.value <= rightLiteral.value &&
same(left.left, right.right));
}
/**
* Determines whether node is wrapped in parentheses.
* @returns {boolean} Whether node is preceded immediately by an open
* paren token and followed immediately by a close
* paren token.
*/
function isParenWrapped() {
return astUtils.isParenthesised(sourceCode, node);
}
return (node.type === "LogicalExpression" &&
left.type === "BinaryExpression" &&
right.type === "BinaryExpression" &&
isRangeTestOperator(left.operator) &&
isRangeTestOperator(right.operator) &&
(isBetweenTest() || isOutsideTest()) &&
isParenWrapped());
}
const OPERATOR_FLIP_MAP = {
"===": "===",
"!==": "!==",
"==": "==",
"!=": "!=",
"<": ">",
">": "<",
"<=": ">=",
">=": "<="
};
/**
* Returns a string representation of a BinaryExpression node with its sides/operator flipped around.
* @param {ASTNode} node The BinaryExpression node
* @returns {string} A string representation of the node with the sides and operator flipped
*/
function getFlippedString(node) {
const operatorToken = sourceCode.getFirstTokenBetween(node.left, node.right, token => token.value === node.operator);
const textBeforeOperator = sourceCode.getText().slice(sourceCode.getTokenBefore(operatorToken).range[1], operatorToken.range[0]);
const textAfterOperator = sourceCode.getText().slice(operatorToken.range[1], sourceCode.getTokenAfter(operatorToken).range[0]);
const leftText = sourceCode.getText().slice(node.range[0], sourceCode.getTokenBefore(operatorToken).range[1]);
const rightText = sourceCode.getText().slice(sourceCode.getTokenAfter(operatorToken).range[0], node.range[1]);
return rightText + textBeforeOperator + OPERATOR_FLIP_MAP[operatorToken.value] + textAfterOperator + leftText;
}
//--------------------------------------------------------------------------
// Public
//--------------------------------------------------------------------------
return {
BinaryExpression(node) {
const expectedLiteral = always ? node.left : node.right;
const expectedNonLiteral = always ? node.right : node.left;
// If `expectedLiteral` is not a literal, and `expectedNonLiteral` is a literal, raise an error.
if (
(expectedNonLiteral.type === "Literal" || looksLikeLiteral(expectedNonLiteral)) &&
!(expectedLiteral.type === "Literal" || looksLikeLiteral(expectedLiteral)) &&
!(!isEqualityOperator(node.operator) && onlyEquality) &&
isComparisonOperator(node.operator) &&
!(exceptRange && isRangeTest(context.getAncestors().pop()))
) {
context.report({
node,
messageId: "expected",
data: {
operator: node.operator,
expectedSide: always ? "left" : "right"
},
fix: fixer => fixer.replaceText(node, getFlippedString(node))
});
}
}
};
}
};