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Diffstat (limited to 'tools/node_modules/eslint/lib/rules/no-extra-boolean-cast.js')
-rw-r--r-- | tools/node_modules/eslint/lib/rules/no-extra-boolean-cast.js | 122 |
1 files changed, 122 insertions, 0 deletions
diff --git a/tools/node_modules/eslint/lib/rules/no-extra-boolean-cast.js b/tools/node_modules/eslint/lib/rules/no-extra-boolean-cast.js new file mode 100644 index 0000000000..47ca7e22fe --- /dev/null +++ b/tools/node_modules/eslint/lib/rules/no-extra-boolean-cast.js @@ -0,0 +1,122 @@ +/** + * @fileoverview Rule to flag unnecessary double negation in Boolean contexts + * @author Brandon Mills + */ + +"use strict"; + +//------------------------------------------------------------------------------ +// Requirements +//------------------------------------------------------------------------------ + +const astUtils = require("../ast-utils"); + +//------------------------------------------------------------------------------ +// Rule Definition +//------------------------------------------------------------------------------ + +module.exports = { + meta: { + docs: { + description: "disallow unnecessary boolean casts", + category: "Possible Errors", + recommended: true + }, + + schema: [], + + fixable: "code" + }, + + create(context) { + const sourceCode = context.getSourceCode(); + + // Node types which have a test which will coerce values to booleans. + const BOOLEAN_NODE_TYPES = [ + "IfStatement", + "DoWhileStatement", + "WhileStatement", + "ConditionalExpression", + "ForStatement" + ]; + + /** + * Check if a node is in a context where its value would be coerced to a boolean at runtime. + * + * @param {Object} node The node + * @param {Object} parent Its parent + * @returns {boolean} If it is in a boolean context + */ + function isInBooleanContext(node, parent) { + return ( + (BOOLEAN_NODE_TYPES.indexOf(parent.type) !== -1 && + node === parent.test) || + + // !<bool> + (parent.type === "UnaryExpression" && + parent.operator === "!") + ); + } + + + return { + UnaryExpression(node) { + const ancestors = context.getAncestors(), + parent = ancestors.pop(), + grandparent = ancestors.pop(); + + // Exit early if it's guaranteed not to match + if (node.operator !== "!" || + parent.type !== "UnaryExpression" || + parent.operator !== "!") { + return; + } + + if (isInBooleanContext(parent, grandparent) || + + // Boolean(<bool>) and new Boolean(<bool>) + ((grandparent.type === "CallExpression" || grandparent.type === "NewExpression") && + grandparent.callee.type === "Identifier" && + grandparent.callee.name === "Boolean") + ) { + context.report({ + node, + message: "Redundant double negation.", + fix: fixer => fixer.replaceText(parent, sourceCode.getText(node.argument)) + }); + } + }, + CallExpression(node) { + const parent = node.parent; + + if (node.callee.type !== "Identifier" || node.callee.name !== "Boolean") { + return; + } + + if (isInBooleanContext(node, parent)) { + context.report({ + node, + message: "Redundant Boolean call.", + fix: fixer => { + if (!node.arguments.length) { + return fixer.replaceText(parent, "true"); + } + + if (node.arguments.length > 1 || node.arguments[0].type === "SpreadElement") { + return null; + } + + const argument = node.arguments[0]; + + if (astUtils.getPrecedence(argument) < astUtils.getPrecedence(node.parent)) { + return fixer.replaceText(node, `(${sourceCode.getText(argument)})`); + } + return fixer.replaceText(node, sourceCode.getText(argument)); + } + }); + } + } + }; + + } +}; |