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Diffstat (limited to 'tools/node_modules/eslint/lib/rules/no-useless-concat.js')
-rw-r--r-- | tools/node_modules/eslint/lib/rules/no-useless-concat.js | 108 |
1 files changed, 108 insertions, 0 deletions
diff --git a/tools/node_modules/eslint/lib/rules/no-useless-concat.js b/tools/node_modules/eslint/lib/rules/no-useless-concat.js new file mode 100644 index 0000000000..e42781fee7 --- /dev/null +++ b/tools/node_modules/eslint/lib/rules/no-useless-concat.js @@ -0,0 +1,108 @@ +/** + * @fileoverview disallow unncessary concatenation of template strings + * @author Henry Zhu + */ +"use strict"; + +//------------------------------------------------------------------------------ +// Requirements +//------------------------------------------------------------------------------ + +const astUtils = require("../ast-utils"); + +//------------------------------------------------------------------------------ +// Helpers +//------------------------------------------------------------------------------ + +/** + * Checks whether or not a given node is a concatenation. + * @param {ASTNode} node - A node to check. + * @returns {boolean} `true` if the node is a concatenation. + */ +function isConcatenation(node) { + return node.type === "BinaryExpression" && node.operator === "+"; +} + +/** + * Checks if the given token is a `+` token or not. + * @param {Token} token - The token to check. + * @returns {boolean} `true` if the token is a `+` token. + */ +function isConcatOperatorToken(token) { + return token.value === "+" && token.type === "Punctuator"; +} + +/** + * Get's the right most node on the left side of a BinaryExpression with + operator. + * @param {ASTNode} node - A BinaryExpression node to check. + * @returns {ASTNode} node + */ +function getLeft(node) { + let left = node.left; + + while (isConcatenation(left)) { + left = left.right; + } + return left; +} + +/** + * Get's the left most node on the right side of a BinaryExpression with + operator. + * @param {ASTNode} node - A BinaryExpression node to check. + * @returns {ASTNode} node + */ +function getRight(node) { + let right = node.right; + + while (isConcatenation(right)) { + right = right.left; + } + return right; +} + +//------------------------------------------------------------------------------ +// Rule Definition +//------------------------------------------------------------------------------ + +module.exports = { + meta: { + docs: { + description: "disallow unnecessary concatenation of literals or template literals", + category: "Best Practices", + recommended: false + }, + + schema: [] + }, + + create(context) { + const sourceCode = context.getSourceCode(); + + return { + BinaryExpression(node) { + + // check if not concatenation + if (node.operator !== "+") { + return; + } + + // account for the `foo + "a" + "b"` case + const left = getLeft(node); + const right = getRight(node); + + if (astUtils.isStringLiteral(left) && + astUtils.isStringLiteral(right) && + astUtils.isTokenOnSameLine(left, right) + ) { + const operatorToken = sourceCode.getFirstTokenBetween(left, right, isConcatOperatorToken); + + context.report({ + node, + loc: operatorToken.loc.start, + message: "Unexpected string concatenation of literals." + }); + } + } + }; + } +}; |