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Diffstat (limited to 'tools/node_modules/eslint/lib/rules/vars-on-top.js')
-rw-r--r-- | tools/node_modules/eslint/lib/rules/vars-on-top.js | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/tools/node_modules/eslint/lib/rules/vars-on-top.js b/tools/node_modules/eslint/lib/rules/vars-on-top.js new file mode 100644 index 0000000000..f74db905b1 --- /dev/null +++ b/tools/node_modules/eslint/lib/rules/vars-on-top.js @@ -0,0 +1,149 @@ +/** + * @fileoverview Rule to enforce var declarations are only at the top of a function. + * @author Danny Fritz + * @author Gyandeep Singh + */ +"use strict"; + +//------------------------------------------------------------------------------ +// Rule Definition +//------------------------------------------------------------------------------ + +module.exports = { + meta: { + docs: { + description: "require `var` declarations be placed at the top of their containing scope", + category: "Best Practices", + recommended: false + }, + + schema: [] + }, + + create(context) { + const errorMessage = "All 'var' declarations must be at the top of the function scope."; + + //-------------------------------------------------------------------------- + // Helpers + //-------------------------------------------------------------------------- + + /** + * @param {ASTNode} node - any node + * @returns {boolean} whether the given node structurally represents a directive + */ + function looksLikeDirective(node) { + return node.type === "ExpressionStatement" && + node.expression.type === "Literal" && typeof node.expression.value === "string"; + } + + /** + * Check to see if its a ES6 import declaration + * @param {ASTNode} node - any node + * @returns {boolean} whether the given node represents a import declaration + */ + function looksLikeImport(node) { + return node.type === "ImportDeclaration" || node.type === "ImportSpecifier" || + node.type === "ImportDefaultSpecifier" || node.type === "ImportNamespaceSpecifier"; + } + + /** + * Checks whether a given node is a variable declaration or not. + * + * @param {ASTNode} node - any node + * @returns {boolean} `true` if the node is a variable declaration. + */ + function isVariableDeclaration(node) { + return ( + node.type === "VariableDeclaration" || + ( + node.type === "ExportNamedDeclaration" && + node.declaration && + node.declaration.type === "VariableDeclaration" + ) + ); + } + + /** + * Checks whether this variable is on top of the block body + * @param {ASTNode} node - The node to check + * @param {ASTNode[]} statements - collection of ASTNodes for the parent node block + * @returns {boolean} True if var is on top otherwise false + */ + function isVarOnTop(node, statements) { + const l = statements.length; + let i = 0; + + // skip over directives + for (; i < l; ++i) { + if (!looksLikeDirective(statements[i]) && !looksLikeImport(statements[i])) { + break; + } + } + + for (; i < l; ++i) { + if (!isVariableDeclaration(statements[i])) { + return false; + } + if (statements[i] === node) { + return true; + } + } + + return false; + } + + /** + * Checks whether variable is on top at the global level + * @param {ASTNode} node - The node to check + * @param {ASTNode} parent - Parent of the node + * @returns {void} + */ + function globalVarCheck(node, parent) { + if (!isVarOnTop(node, parent.body)) { + context.report({ node, message: errorMessage }); + } + } + + /** + * Checks whether variable is on top at functional block scope level + * @param {ASTNode} node - The node to check + * @param {ASTNode} parent - Parent of the node + * @param {ASTNode} grandParent - Parent of the node's parent + * @returns {void} + */ + function blockScopeVarCheck(node, parent, grandParent) { + if (!(/Function/.test(grandParent.type) && + parent.type === "BlockStatement" && + isVarOnTop(node, parent.body))) { + context.report({ node, message: errorMessage }); + } + } + + //-------------------------------------------------------------------------- + // Public API + //-------------------------------------------------------------------------- + + return { + VariableDeclaration(node) { + const ancestors = context.getAncestors(); + let parent = ancestors.pop(); + let grandParent = ancestors.pop(); + + if (node.kind === "var") { // check variable is `var` type and not `let` or `const` + if (parent.type === "ExportNamedDeclaration") { + node = parent; + parent = grandParent; + grandParent = ancestors.pop(); + } + + if (parent.type === "Program") { // That means its a global variable + globalVarCheck(node, parent); + } else { + blockScopeVarCheck(node, parent, grandParent); + } + } + } + }; + + } +}; |