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/**
* @fileoverview Rule to flag trailing underscores in variable declarations.
* @author Matt DuVall <http://www.mattduvall.com>
*/
"use strict";
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
docs: {
description: "disallow dangling underscores in identifiers",
category: "Stylistic Issues",
recommended: false
},
schema: [
{
type: "object",
properties: {
allow: {
type: "array",
items: {
type: "string"
}
},
allowAfterThis: {
type: "boolean"
},
allowAfterSuper: {
type: "boolean"
},
enforceInMethodNames: {
type: "boolean"
}
},
additionalProperties: false
}
]
},
create(context) {
const options = context.options[0] || {};
const ALLOWED_VARIABLES = options.allow ? options.allow : [];
const allowAfterThis = typeof options.allowAfterThis !== "undefined" ? options.allowAfterThis : false;
const allowAfterSuper = typeof options.allowAfterSuper !== "undefined" ? options.allowAfterSuper : false;
const enforceInMethodNames = typeof options.enforceInMethodNames !== "undefined" ? options.enforceInMethodNames : false;
//-------------------------------------------------------------------------
// Helpers
//-------------------------------------------------------------------------
/**
* Check if identifier is present inside the allowed option
* @param {string} identifier name of the node
* @returns {boolean} true if its is present
* @private
*/
function isAllowed(identifier) {
return ALLOWED_VARIABLES.some(ident => ident === identifier);
}
/**
* Check if identifier has a underscore at the end
* @param {ASTNode} identifier node to evaluate
* @returns {boolean} true if its is present
* @private
*/
function hasTrailingUnderscore(identifier) {
const len = identifier.length;
return identifier !== "_" && (identifier[0] === "_" || identifier[len - 1] === "_");
}
/**
* Check if identifier is a special case member expression
* @param {ASTNode} identifier node to evaluate
* @returns {boolean} true if its is a special case
* @private
*/
function isSpecialCaseIdentifierForMemberExpression(identifier) {
return identifier === "__proto__";
}
/**
* Check if identifier is a special case variable expression
* @param {ASTNode} identifier node to evaluate
* @returns {boolean} true if its is a special case
* @private
*/
function isSpecialCaseIdentifierInVariableExpression(identifier) {
// Checks for the underscore library usage here
return identifier === "_";
}
/**
* Check if function has a underscore at the end
* @param {ASTNode} node node to evaluate
* @returns {void}
* @private
*/
function checkForTrailingUnderscoreInFunctionDeclaration(node) {
if (node.id) {
const identifier = node.id.name;
if (typeof identifier !== "undefined" && hasTrailingUnderscore(identifier) && !isAllowed(identifier)) {
context.report({
node,
message: "Unexpected dangling '_' in '{{identifier}}'.",
data: {
identifier
}
});
}
}
}
/**
* Check if variable expression has a underscore at the end
* @param {ASTNode} node node to evaluate
* @returns {void}
* @private
*/
function checkForTrailingUnderscoreInVariableExpression(node) {
const identifier = node.id.name;
if (typeof identifier !== "undefined" && hasTrailingUnderscore(identifier) &&
!isSpecialCaseIdentifierInVariableExpression(identifier) && !isAllowed(identifier)) {
context.report({
node,
message: "Unexpected dangling '_' in '{{identifier}}'.",
data: {
identifier
}
});
}
}
/**
* Check if member expression has a underscore at the end
* @param {ASTNode} node node to evaluate
* @returns {void}
* @private
*/
function checkForTrailingUnderscoreInMemberExpression(node) {
const identifier = node.property.name,
isMemberOfThis = node.object.type === "ThisExpression",
isMemberOfSuper = node.object.type === "Super";
if (typeof identifier !== "undefined" && hasTrailingUnderscore(identifier) &&
!(isMemberOfThis && allowAfterThis) &&
!(isMemberOfSuper && allowAfterSuper) &&
!isSpecialCaseIdentifierForMemberExpression(identifier) && !isAllowed(identifier)) {
context.report({
node,
message: "Unexpected dangling '_' in '{{identifier}}'.",
data: {
identifier
}
});
}
}
/**
* Check if method declaration or method property has a underscore at the end
* @param {ASTNode} node node to evaluate
* @returns {void}
* @private
*/
function checkForTrailingUnderscoreInMethod(node) {
const identifier = node.key.name;
const isMethod = node.type === "MethodDefinition" || node.type === "Property" && node.method;
if (typeof identifier !== "undefined" && enforceInMethodNames && isMethod && hasTrailingUnderscore(identifier)) {
context.report({
node,
message: "Unexpected dangling '_' in '{{identifier}}'.",
data: {
identifier
}
});
}
}
//--------------------------------------------------------------------------
// Public API
//--------------------------------------------------------------------------
return {
FunctionDeclaration: checkForTrailingUnderscoreInFunctionDeclaration,
VariableDeclarator: checkForTrailingUnderscoreInVariableExpression,
MemberExpression: checkForTrailingUnderscoreInMemberExpression,
MethodDefinition: checkForTrailingUnderscoreInMethod,
Property: checkForTrailingUnderscoreInMethod
};
}
};
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