152 lines
4.9 KiB
JavaScript
152 lines
4.9 KiB
JavaScript
/**
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* @fileoverview Rule to enforce consistent naming of "this" context variables
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* @author Raphael Pigulla
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*/
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"use strict";
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
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module.exports = {
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meta: {
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type: "suggestion",
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docs: {
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description: "enforce consistent naming when capturing the current execution context",
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category: "Stylistic Issues",
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recommended: false,
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url: "https://eslint.org/docs/rules/consistent-this"
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},
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schema: {
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type: "array",
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items: {
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type: "string",
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minLength: 1
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},
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uniqueItems: true
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},
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messages: {
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aliasNotAssignedToThis: "Designated alias '{{name}}' is not assigned to 'this'.",
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unexpectedAlias: "Unexpected alias '{{name}}' for 'this'."
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}
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},
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create(context) {
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let aliases = [];
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if (context.options.length === 0) {
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aliases.push("that");
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} else {
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aliases = context.options;
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}
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/**
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* Reports that a variable declarator or assignment expression is assigning
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* a non-'this' value to the specified alias.
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* @param {ASTNode} node The assigning node.
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* @param {string} name the name of the alias that was incorrectly used.
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* @returns {void}
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*/
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function reportBadAssignment(node, name) {
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context.report({ node, messageId: "aliasNotAssignedToThis", data: { name } });
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}
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/**
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* Checks that an assignment to an identifier only assigns 'this' to the
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* appropriate alias, and the alias is only assigned to 'this'.
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* @param {ASTNode} node The assigning node.
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* @param {Identifier} name The name of the variable assigned to.
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* @param {Expression} value The value of the assignment.
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* @returns {void}
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*/
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function checkAssignment(node, name, value) {
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const isThis = value.type === "ThisExpression";
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if (aliases.indexOf(name) !== -1) {
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if (!isThis || node.operator && node.operator !== "=") {
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reportBadAssignment(node, name);
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}
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} else if (isThis) {
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context.report({ node, messageId: "unexpectedAlias", data: { name } });
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}
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}
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/**
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* Ensures that a variable declaration of the alias in a program or function
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* is assigned to the correct value.
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* @param {string} alias alias the check the assignment of.
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* @param {Object} scope scope of the current code we are checking.
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* @private
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* @returns {void}
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*/
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function checkWasAssigned(alias, scope) {
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const variable = scope.set.get(alias);
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if (!variable) {
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return;
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}
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if (variable.defs.some(def => def.node.type === "VariableDeclarator" &&
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def.node.init !== null)) {
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return;
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}
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/*
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* The alias has been declared and not assigned: check it was
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* assigned later in the same scope.
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*/
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if (!variable.references.some(reference => {
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const write = reference.writeExpr;
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return (
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reference.from === scope &&
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write && write.type === "ThisExpression" &&
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write.parent.operator === "="
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);
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})) {
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variable.defs.map(def => def.node).forEach(node => {
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reportBadAssignment(node, alias);
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});
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}
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}
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/**
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* Check each alias to ensure that is was assigned to the correct value.
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* @returns {void}
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*/
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function ensureWasAssigned() {
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const scope = context.getScope();
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aliases.forEach(alias => {
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checkWasAssigned(alias, scope);
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});
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}
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return {
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"Program:exit": ensureWasAssigned,
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"FunctionExpression:exit": ensureWasAssigned,
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"FunctionDeclaration:exit": ensureWasAssigned,
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VariableDeclarator(node) {
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const id = node.id;
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const isDestructuring =
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id.type === "ArrayPattern" || id.type === "ObjectPattern";
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if (node.init !== null && !isDestructuring) {
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checkAssignment(node, id.name, node.init);
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}
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},
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AssignmentExpression(node) {
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if (node.left.type === "Identifier") {
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checkAssignment(node, node.left.name, node.right);
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}
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}
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};
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}
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};
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