consistent-this.js
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/**
* @fileoverview Rule to enforce consistent naming of "this" context variables
* @author Raphael Pigulla
* @copyright 2015 Timothy Jones. All rights reserved.
* @copyright 2015 David Aurelio. All rights reserved.
*/
"use strict";
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = function(context) {
var alias = context.options[0];
/**
* Reports that a variable declarator or assignment expression is assigning
* a non-'this' value to the specified alias.
* @param {ASTNode} node - The assigning node.
* @returns {void}
*/
function reportBadAssignment(node) {
context.report(node,
"Designated alias '{{alias}}' is not assigned to 'this'.",
{ alias: alias });
}
/**
* Checks that an assignment to an identifier only assigns 'this' to the
* appropriate alias, and the alias is only assigned to 'this'.
* @param {ASTNode} node - The assigning node.
* @param {Identifier} name - The name of the variable assigned to.
* @param {Expression} value - The value of the assignment.
* @returns {void}
*/
function checkAssignment(node, name, value) {
var isThis = value.type === "ThisExpression";
if (name === alias) {
if (!isThis || node.operator && node.operator !== "=") {
reportBadAssignment(node);
}
} else if (isThis) {
context.report(node,
"Unexpected alias '{{name}}' for 'this'.", { name: name });
}
}
/**
* Ensures that a variable declaration of the alias in a program or function
* is assigned to the correct value.
* @returns {void}
*/
function ensureWasAssigned() {
var scope = context.getScope();
var variable = scope.set.get(alias);
if (!variable) {
return;
}
if (variable.defs.some(function(def) {
return def.node.type === "VariableDeclarator" &&
def.node.init !== null;
})) {
return;
}
var lookup = (variable.references.length === 0 && scope.type === "global") ? scope : variable;
// The alias has been declared and not assigned: check it was
// assigned later in the same scope.
if (!lookup.references.some(function(reference) {
var write = reference.writeExpr;
if (reference.from === scope &&
write && write.type === "ThisExpression" &&
write.parent.operator === "=") {
return true;
}
})) {
variable.defs.map(function(def) {
return def.node;
}).forEach(reportBadAssignment);
}
}
return {
"Program:exit": ensureWasAssigned,
"FunctionExpression:exit": ensureWasAssigned,
"FunctionDeclaration:exit": ensureWasAssigned,
"VariableDeclarator": function(node) {
var id = node.id;
var isDestructuring =
id.type === "ArrayPattern" || id.type === "ObjectPattern";
if (node.init !== null && !isDestructuring) {
checkAssignment(node, id.name, node.init);
}
},
"AssignmentExpression": function(node) {
if (node.left.type === "Identifier") {
checkAssignment(node, node.left.name, node.right);
}
}
};
};
module.exports.schema = [
{
"type": "string"
}
];