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Diffstat (limited to 'tools/node_modules/eslint/lib/rules/no-self-assign.js')
| -rw-r--r-- | tools/node_modules/eslint/lib/rules/no-self-assign.js | 214 |
1 files changed, 214 insertions, 0 deletions
diff --git a/tools/node_modules/eslint/lib/rules/no-self-assign.js b/tools/node_modules/eslint/lib/rules/no-self-assign.js new file mode 100644 index 0000000000..48b922d46b --- /dev/null +++ b/tools/node_modules/eslint/lib/rules/no-self-assign.js @@ -0,0 +1,214 @@ +/** + * @fileoverview Rule to disallow assignments where both sides are exactly the same + * @author Toru Nagashima + */ + +"use strict"; + +//------------------------------------------------------------------------------ +// Requirements +//------------------------------------------------------------------------------ + +const astUtils = require("../ast-utils"); + +//------------------------------------------------------------------------------ +// Helpers +//------------------------------------------------------------------------------ + +const SPACES = /\s+/g; + +/** + * Checks whether the property of 2 given member expression nodes are the same + * property or not. + * + * @param {ASTNode} left - A member expression node to check. + * @param {ASTNode} right - Another member expression node to check. + * @returns {boolean} `true` if the member expressions have the same property. + */ +function isSameProperty(left, right) { + if (left.property.type === "Identifier" && + left.property.type === right.property.type && + left.property.name === right.property.name && + left.computed === right.computed + ) { + return true; + } + + const lname = astUtils.getStaticPropertyName(left); + const rname = astUtils.getStaticPropertyName(right); + + return lname !== null && lname === rname; +} + +/** + * Checks whether 2 given member expression nodes are the reference to the same + * property or not. + * + * @param {ASTNode} left - A member expression node to check. + * @param {ASTNode} right - Another member expression node to check. + * @returns {boolean} `true` if the member expressions are the reference to the + * same property or not. + */ +function isSameMember(left, right) { + if (!isSameProperty(left, right)) { + return false; + } + + const lobj = left.object; + const robj = right.object; + + if (lobj.type !== robj.type) { + return false; + } + if (lobj.type === "MemberExpression") { + return isSameMember(lobj, robj); + } + return lobj.type === "Identifier" && lobj.name === robj.name; +} + +/** + * Traverses 2 Pattern nodes in parallel, then reports self-assignments. + * + * @param {ASTNode|null} left - A left node to traverse. This is a Pattern or + * a Property. + * @param {ASTNode|null} right - A right node to traverse. This is a Pattern or + * a Property. + * @param {boolean} props - The flag to check member expressions as well. + * @param {Function} report - A callback function to report. + * @returns {void} + */ +function eachSelfAssignment(left, right, props, report) { + if (!left || !right) { + + // do nothing + } else if ( + left.type === "Identifier" && + right.type === "Identifier" && + left.name === right.name + ) { + report(right); + } else if ( + left.type === "ArrayPattern" && + right.type === "ArrayExpression" + ) { + const end = Math.min(left.elements.length, right.elements.length); + + for (let i = 0; i < end; ++i) { + const rightElement = right.elements[i]; + + eachSelfAssignment(left.elements[i], rightElement, props, report); + + // After a spread element, those indices are unknown. + if (rightElement && rightElement.type === "SpreadElement") { + break; + } + } + } else if ( + left.type === "RestElement" && + right.type === "SpreadElement" + ) { + eachSelfAssignment(left.argument, right.argument, props, report); + } else if ( + left.type === "ObjectPattern" && + right.type === "ObjectExpression" && + right.properties.length >= 1 + ) { + + /* + * Gets the index of the last spread property. + * It's possible to overwrite properties followed by it. + */ + let startJ = 0; + + for (let i = right.properties.length - 1; i >= 0; --i) { + if (right.properties[i].type === "ExperimentalSpreadProperty") { + startJ = i + 1; + break; + } + } + + for (let i = 0; i < left.properties.length; ++i) { + for (let j = startJ; j < right.properties.length; ++j) { + eachSelfAssignment( + left.properties[i], + right.properties[j], + props, + report + ); + } + } + } else if ( + left.type === "Property" && + right.type === "Property" && + !left.computed && + !right.computed && + right.kind === "init" && + !right.method && + left.key.name === right.key.name + ) { + eachSelfAssignment(left.value, right.value, props, report); + } else if ( + props && + left.type === "MemberExpression" && + right.type === "MemberExpression" && + isSameMember(left, right) + ) { + report(right); + } +} + +//------------------------------------------------------------------------------ +// Rule Definition +//------------------------------------------------------------------------------ + +module.exports = { + meta: { + docs: { + description: "disallow assignments where both sides are exactly the same", + category: "Best Practices", + recommended: true + }, + + schema: [ + { + type: "object", + properties: { + props: { + type: "boolean" + } + }, + additionalProperties: false + } + ] + }, + + create(context) { + const sourceCode = context.getSourceCode(); + const options = context.options[0]; + const props = Boolean(options && options.props); + + /** + * Reports a given node as self assignments. + * + * @param {ASTNode} node - A node to report. This is an Identifier node. + * @returns {void} + */ + function report(node) { + context.report({ + node, + message: "'{{name}}' is assigned to itself.", + data: { + name: sourceCode.getText(node).replace(SPACES, "") + } + }); + } + + return { + AssignmentExpression(node) { + if (node.operator === "=") { + eachSelfAssignment(node.left, node.right, props, report); + } + } + }; + } +}; |