vscode-extension--copy-words-to-clipboard/hover-words-to-copy/node_modules/eslint/lib/rules/no-implicit-coercion.js

/**
 * @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 = ["~", "!!", "+", "- -", "-", "*"];

/**
 * Checks whether or not a node is a double logical negating.
 * @param {ASTNode} node An UnaryExpression node to check.
 * @returns {boolean} Whether or not the node is a double logical negating.
 */
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) {
	if (node.operator !== "~") {
		return false;
	}
	const callNode = astUtils.skipChainExpression(node.argument);

	return (
		callNode.type === "CallExpression" &&
		astUtils.isSpecificMemberAccess(callNode.callee, null, INDEX_OF_PATTERN)
	);
}

/**
 * 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 given node logically represents multiplication by a fraction of `1`.
 * For example, `a * 1` in `a * 1 / b` is technically multiplication by `1`, but the
 * whole expression can be logically interpreted as `a * (1 / b)` rather than `(a * 1) / b`.
 * @param {BinaryExpression} node A BinaryExpression node to check.
 * @param {SourceCode} sourceCode The source code object.
 * @returns {boolean} Whether or not the node is a multiplying by a fraction of `1`.
 */
function isMultiplyByFractionOfOne(node, sourceCode) {
	return (
		node.type === "BinaryExpression" &&
		node.operator === "*" &&
		node.right.type === "Literal" &&
		node.right.value === 1 &&
		node.parent.type === "BinaryExpression" &&
		node.parent.operator === "/" &&
		node.parent.left === node &&
		!astUtils.isParenthesised(sourceCode, node)
	);
}

/**
 * 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 an expression evaluates to a string.
 * @param {ASTNode} node node that represents the expression to check.
 * @returns {boolean} Whether or not the expression evaluates to a string.
 */
function isStringType(node) {
	return (
		astUtils.isStringLiteral(node) ||
		(node.type === "CallExpression" &&
			node.callee.type === "Identifier" &&
			node.callee.name === "String")
	);
}

/**
 * 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) && !isStringType(node.right)) ||
			(isEmptyString(node.right) && !isStringType(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
//------------------------------------------------------------------------------

/** @type {import('../types').Rule.RuleModule} */
module.exports = {
	meta: {
		hasSuggestions: true,
		type: "suggestion",

		docs: {
			description: "Disallow shorthand type conversions",
			recommended: false,
			frozen: true,
			url: "https://eslint.org/docs/latest/rules/no-implicit-coercion",
		},

		fixable: "code",

		schema: [
			{
				type: "object",
				properties: {
					boolean: {
						type: "boolean",
					},
					number: {
						type: "boolean",
					},
					string: {
						type: "boolean",
					},
					disallowTemplateShorthand: {
						type: "boolean",
					},
					allow: {
						type: "array",
						items: {
							enum: ALLOWABLE_OPERATORS,
						},
						uniqueItems: true,
					},
				},
				additionalProperties: false,
			},
		],

		defaultOptions: [
			{
				allow: [],
				boolean: true,
				disallowTemplateShorthand: false,
				number: true,
				string: true,
			},
		],

		messages: {
			implicitCoercion:
				"Unexpected implicit coercion encountered. Use `{{recommendation}}` instead.",
			useRecommendation: "Use `{{recommendation}}` instead.",
		},
	},

	create(context) {
		const [options] = context.options;
		const sourceCode = context.sourceCode;

		/**
		 * 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} shouldSuggest Whether this report should offer a suggestion
		 * @param {bool} shouldFix Whether this report should fix the node
		 * @returns {void}
		 */
		function report(node, recommendation, shouldSuggest, shouldFix) {
			/**
			 * Fix function
			 * @param {RuleFixer} fixer The fixer to fix.
			 * @returns {Fix} The fix object.
			 */
			function fix(fixer) {
				const tokenBefore = sourceCode.getTokenBefore(node);

				if (
					tokenBefore?.range[1] === node.range[0] &&
					!astUtils.canTokensBeAdjacent(tokenBefore, recommendation)
				) {
					return fixer.replaceText(node, ` ${recommendation}`);
				}

				return fixer.replaceText(node, recommendation);
			}

			context.report({
				node,
				messageId: "implicitCoercion",
				data: { recommendation },
				fix(fixer) {
					if (!shouldFix) {
						return null;
					}

					return fix(fixer);
				},
				suggest: [
					{
						messageId: "useRecommendation",
						data: { recommendation },
						fix(fixer) {
							if (shouldFix || !shouldSuggest) {
								return null;
							}

							return fix(fixer);
						},
					},
				],
			});
		}

		return {
			UnaryExpression(node) {
				let operatorAllowed;

				// !!foo
				operatorAllowed = options.allow.includes("!!");
				if (
					!operatorAllowed &&
					options.boolean &&
					isDoubleLogicalNegating(node)
				) {
					const recommendation = `Boolean(${sourceCode.getText(node.argument.argument)})`;
					const variable = astUtils.getVariableByName(
						sourceCode.getScope(node),
						"Boolean",
					);
					const booleanExists = variable?.identifiers.length === 0;

					report(node, recommendation, true, booleanExists);
				}

				// ~foo.indexOf(bar)
				operatorAllowed = options.allow.includes("~");
				if (
					!operatorAllowed &&
					options.boolean &&
					isBinaryNegatingOfIndexOf(node)
				) {
					// `foo?.indexOf(bar) !== -1` will be true (== found) if the `foo` is nullish. So use `>= 0` in that case.
					const comparison =
						node.argument.type === "ChainExpression"
							? ">= 0"
							: "!== -1";
					const recommendation = `${sourceCode.getText(node.argument)} ${comparison}`;

					report(node, recommendation, false, false);
				}

				// +foo
				operatorAllowed = options.allow.includes("+");
				if (
					!operatorAllowed &&
					options.number &&
					node.operator === "+" &&
					!isNumeric(node.argument)
				) {
					const recommendation = `Number(${sourceCode.getText(node.argument)})`;

					report(node, recommendation, true, false);
				}

				// -(-foo)
				operatorAllowed = options.allow.includes("- -");
				if (
					!operatorAllowed &&
					options.number &&
					node.operator === "-" &&
					node.argument.type === "UnaryExpression" &&
					node.argument.operator === "-" &&
					!isNumeric(node.argument.argument)
				) {
					const recommendation = `Number(${sourceCode.getText(node.argument.argument)})`;

					report(node, recommendation, true, false);
				}
			},

			// Use `:exit` to prevent double reporting
			"BinaryExpression:exit"(node) {
				let operatorAllowed;

				// 1 * foo
				operatorAllowed = options.allow.includes("*");
				const nonNumericOperand =
					!operatorAllowed &&
					options.number &&
					isMultiplyByOne(node) &&
					!isMultiplyByFractionOfOne(node, sourceCode) &&
					getNonNumericOperand(node);

				if (nonNumericOperand) {
					const recommendation = `Number(${sourceCode.getText(nonNumericOperand)})`;

					report(node, recommendation, true, false);
				}

				// foo - 0
				operatorAllowed = options.allow.includes("-");
				if (
					!operatorAllowed &&
					options.number &&
					node.operator === "-" &&
					node.right.type === "Literal" &&
					node.right.value === 0 &&
					!isNumeric(node.left)
				) {
					const recommendation = `Number(${sourceCode.getText(node.left)})`;

					report(node, recommendation, true, false);
				}

				// "" + foo
				operatorAllowed = options.allow.includes("+");
				if (
					!operatorAllowed &&
					options.string &&
					isConcatWithEmptyString(node)
				) {
					const recommendation = `String(${sourceCode.getText(getNonEmptyOperand(node))})`;

					report(node, recommendation, true, false);
				}
			},

			AssignmentExpression(node) {
				// foo += ""
				const operatorAllowed = options.allow.includes("+");

				if (
					!operatorAllowed &&
					options.string &&
					isAppendEmptyString(node)
				) {
					const code = sourceCode.getText(getNonEmptyOperand(node));
					const recommendation = `${code} = String(${code})`;

					report(node, recommendation, true, false);
				}
			},

			TemplateLiteral(node) {
				if (!options.disallowTemplateShorthand) {
					return;
				}

				// tag`${foo}`
				if (node.parent.type === "TaggedTemplateExpression") {
					return;
				}

				// `` or `${foo}${bar}`
				if (node.expressions.length !== 1) {
					return;
				}

				//  `prefix${foo}`
				if (node.quasis[0].value.cooked !== "") {
					return;
				}

				//  `${foo}postfix`
				if (node.quasis[1].value.cooked !== "") {
					return;
				}

				// if the expression is already a string, then this isn't a coercion
				if (isStringType(node.expressions[0])) {
					return;
				}

				const code = sourceCode.getText(node.expressions[0]);
				const recommendation = `String(${code})`;

				report(node, recommendation, true, false);
			},
		};
	},
};