--- /dev/null
+/**
+ * @fileoverview A rule to disallow the type conversions with shorter notations.
+ * @author Toru Nagashima
+ */
+
+"use strict";
+
+const astUtils = require("./utils/ast-utils");
+
+//------------------------------------------------------------------------------
+// Helpers
+//------------------------------------------------------------------------------
+
+const INDEX_OF_PATTERN = /^(?:i|lastI)ndexOf$/u;
+const ALLOWABLE_OPERATORS = ["~", "!!", "+", "*"];
+
+/**
+ * Parses and normalizes an option object.
+ * @param {Object} options An option object to parse.
+ * @returns {Object} The parsed and normalized option object.
+ */
+function parseOptions(options) {
+ return {
+ boolean: "boolean" in options ? options.boolean : true,
+ number: "number" in options ? options.number : true,
+ string: "string" in options ? options.string : true,
+ allow: options.allow || []
+ };
+}
+
+/**
+ * Checks whether or not a node is a double logical nigating.
+ * @param {ASTNode} node An UnaryExpression node to check.
+ * @returns {boolean} Whether or not the node is a double logical nigating.
+ */
+function isDoubleLogicalNegating(node) {
+ return (
+ node.operator === "!" &&
+ node.argument.type === "UnaryExpression" &&
+ node.argument.operator === "!"
+ );
+}
+
+/**
+ * Checks whether or not a node is a binary negating of `.indexOf()` method calling.
+ * @param {ASTNode} node An UnaryExpression node to check.
+ * @returns {boolean} Whether or not the node is a binary negating of `.indexOf()` method calling.
+ */
+function isBinaryNegatingOfIndexOf(node) {
+ return (
+ node.operator === "~" &&
+ node.argument.type === "CallExpression" &&
+ node.argument.callee.type === "MemberExpression" &&
+ node.argument.callee.property.type === "Identifier" &&
+ INDEX_OF_PATTERN.test(node.argument.callee.property.name)
+ );
+}
+
+/**
+ * Checks whether or not a node is a multiplying by one.
+ * @param {BinaryExpression} node A BinaryExpression node to check.
+ * @returns {boolean} Whether or not the node is a multiplying by one.
+ */
+function isMultiplyByOne(node) {
+ return node.operator === "*" && (
+ node.left.type === "Literal" && node.left.value === 1 ||
+ node.right.type === "Literal" && node.right.value === 1
+ );
+}
+
+/**
+ * Checks whether the result of a node is numeric or not
+ * @param {ASTNode} node The node to test
+ * @returns {boolean} true if the node is a number literal or a `Number()`, `parseInt` or `parseFloat` call
+ */
+function isNumeric(node) {
+ return (
+ node.type === "Literal" && typeof node.value === "number" ||
+ node.type === "CallExpression" && (
+ node.callee.name === "Number" ||
+ node.callee.name === "parseInt" ||
+ node.callee.name === "parseFloat"
+ )
+ );
+}
+
+/**
+ * Returns the first non-numeric operand in a BinaryExpression. Designed to be
+ * used from bottom to up since it walks up the BinaryExpression trees using
+ * node.parent to find the result.
+ * @param {BinaryExpression} node The BinaryExpression node to be walked up on
+ * @returns {ASTNode|null} The first non-numeric item in the BinaryExpression tree or null
+ */
+function getNonNumericOperand(node) {
+ const left = node.left,
+ right = node.right;
+
+ if (right.type !== "BinaryExpression" && !isNumeric(right)) {
+ return right;
+ }
+
+ if (left.type !== "BinaryExpression" && !isNumeric(left)) {
+ return left;
+ }
+
+ return null;
+}
+
+/**
+ * Checks whether a node is an empty string literal or not.
+ * @param {ASTNode} node The node to check.
+ * @returns {boolean} Whether or not the passed in node is an
+ * empty string literal or not.
+ */
+function isEmptyString(node) {
+ return astUtils.isStringLiteral(node) && (node.value === "" || (node.type === "TemplateLiteral" && node.quasis.length === 1 && node.quasis[0].value.cooked === ""));
+}
+
+/**
+ * Checks whether or not a node is a concatenating with an empty string.
+ * @param {ASTNode} node A BinaryExpression node to check.
+ * @returns {boolean} Whether or not the node is a concatenating with an empty string.
+ */
+function isConcatWithEmptyString(node) {
+ return node.operator === "+" && (
+ (isEmptyString(node.left) && !astUtils.isStringLiteral(node.right)) ||
+ (isEmptyString(node.right) && !astUtils.isStringLiteral(node.left))
+ );
+}
+
+/**
+ * Checks whether or not a node is appended with an empty string.
+ * @param {ASTNode} node An AssignmentExpression node to check.
+ * @returns {boolean} Whether or not the node is appended with an empty string.
+ */
+function isAppendEmptyString(node) {
+ return node.operator === "+=" && isEmptyString(node.right);
+}
+
+/**
+ * Returns the operand that is not an empty string from a flagged BinaryExpression.
+ * @param {ASTNode} node The flagged BinaryExpression node to check.
+ * @returns {ASTNode} The operand that is not an empty string from a flagged BinaryExpression.
+ */
+function getNonEmptyOperand(node) {
+ return isEmptyString(node.left) ? node.right : node.left;
+}
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+ meta: {
+ type: "suggestion",
+
+ docs: {
+ description: "disallow shorthand type conversions",
+ category: "Best Practices",
+ recommended: false,
+ url: "https://eslint.org/docs/rules/no-implicit-coercion"
+ },
+
+ fixable: "code",
+
+ schema: [{
+ type: "object",
+ properties: {
+ boolean: {
+ type: "boolean",
+ default: true
+ },
+ number: {
+ type: "boolean",
+ default: true
+ },
+ string: {
+ type: "boolean",
+ default: true
+ },
+ allow: {
+ type: "array",
+ items: {
+ enum: ALLOWABLE_OPERATORS
+ },
+ uniqueItems: true
+ }
+ },
+ additionalProperties: false
+ }]
+ },
+
+ create(context) {
+ const options = parseOptions(context.options[0] || {});
+ const sourceCode = context.getSourceCode();
+
+ /**
+ * Reports an error and autofixes the node
+ * @param {ASTNode} node An ast node to report the error on.
+ * @param {string} recommendation The recommended code for the issue
+ * @param {bool} shouldFix Whether this report should fix the node
+ * @returns {void}
+ */
+ function report(node, recommendation, shouldFix) {
+ context.report({
+ node,
+ message: "use `{{recommendation}}` instead.",
+ data: {
+ recommendation
+ },
+ fix(fixer) {
+ if (!shouldFix) {
+ return null;
+ }
+
+ const tokenBefore = sourceCode.getTokenBefore(node);
+
+ if (
+ tokenBefore &&
+ tokenBefore.range[1] === node.range[0] &&
+ !astUtils.canTokensBeAdjacent(tokenBefore, recommendation)
+ ) {
+ return fixer.replaceText(node, ` ${recommendation}`);
+ }
+ return fixer.replaceText(node, recommendation);
+ }
+ });
+ }
+
+ return {
+ UnaryExpression(node) {
+ let operatorAllowed;
+
+ // !!foo
+ operatorAllowed = options.allow.indexOf("!!") >= 0;
+ if (!operatorAllowed && options.boolean && isDoubleLogicalNegating(node)) {
+ const recommendation = `Boolean(${sourceCode.getText(node.argument.argument)})`;
+
+ report(node, recommendation, true);
+ }
+
+ // ~foo.indexOf(bar)
+ operatorAllowed = options.allow.indexOf("~") >= 0;
+ if (!operatorAllowed && options.boolean && isBinaryNegatingOfIndexOf(node)) {
+ const recommendation = `${sourceCode.getText(node.argument)} !== -1`;
+
+ report(node, recommendation, false);
+ }
+
+ // +foo
+ operatorAllowed = options.allow.indexOf("+") >= 0;
+ if (!operatorAllowed && options.number && node.operator === "+" && !isNumeric(node.argument)) {
+ const recommendation = `Number(${sourceCode.getText(node.argument)})`;
+
+ report(node, recommendation, true);
+ }
+ },
+
+ // Use `:exit` to prevent double reporting
+ "BinaryExpression:exit"(node) {
+ let operatorAllowed;
+
+ // 1 * foo
+ operatorAllowed = options.allow.indexOf("*") >= 0;
+ const nonNumericOperand = !operatorAllowed && options.number && isMultiplyByOne(node) && getNonNumericOperand(node);
+
+ if (nonNumericOperand) {
+ const recommendation = `Number(${sourceCode.getText(nonNumericOperand)})`;
+
+ report(node, recommendation, true);
+ }
+
+ // "" + foo
+ operatorAllowed = options.allow.indexOf("+") >= 0;
+ if (!operatorAllowed && options.string && isConcatWithEmptyString(node)) {
+ const recommendation = `String(${sourceCode.getText(getNonEmptyOperand(node))})`;
+
+ report(node, recommendation, true);
+ }
+ },
+
+ AssignmentExpression(node) {
+
+ // foo += ""
+ const operatorAllowed = options.allow.indexOf("+") >= 0;
+
+ if (!operatorAllowed && options.string && isAppendEmptyString(node)) {
+ const code = sourceCode.getText(getNonEmptyOperand(node));
+ const recommendation = `${code} = String(${code})`;
+
+ report(node, recommendation, true);
+ }
+ }
+ };
+ }
+};
projects / dotfiles / .git / blobdiff