diff options
Diffstat (limited to 'tools/node_modules/eslint/lib/rules/yoda.js')
-rw-r--r-- | tools/node_modules/eslint/lib/rules/yoda.js | 310 |
1 files changed, 310 insertions, 0 deletions
diff --git a/tools/node_modules/eslint/lib/rules/yoda.js b/tools/node_modules/eslint/lib/rules/yoda.js new file mode 100644 index 0000000000..2ccb61f73a --- /dev/null +++ b/tools/node_modules/eslint/lib/rules/yoda.js @@ -0,0 +1,310 @@ +/** + * @fileoverview Rule to require or disallow yoda comparisons + * @author Nicholas C. Zakas + */ +"use strict"; + +//-------------------------------------------------------------------------- +// Requirements +//-------------------------------------------------------------------------- + +const astUtils = require("../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 (/^(==|===|!=|!==|<|>|<=|>=)$/).test(operator); +} + +/** + * Determines whether an operator is an equality operator. + * @param {string} operator The operator to check. + * @returns {boolean} Whether or not it is an equality operator. + */ +function isEqualityOperator(operator) { + return (/^(==|===)$/).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: { + docs: { + description: "require or disallow \"Yoda\" conditions", + category: "Best Practices", + recommended: false + }, + + schema: [ + { + enum: ["always", "never"] + }, + { + type: "object", + properties: { + exceptRange: { + type: "boolean" + }, + onlyEquality: { + type: "boolean" + } + }, + additionalProperties: false + } + ], + + fixable: "code" + }, + + 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, + message: "Expected literal to be on the {{expectedSide}} side of {{operator}}.", + data: { + operator: node.operator, + expectedSide: always ? "left" : "right" + }, + fix: fixer => fixer.replaceText(node, getFlippedString(node)) + }); + } + + } + }; + + } +}; |