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136 lines
4.2 KiB
136 lines
4.2 KiB
/**
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* @fileoverview Rule to flag blocks with no reason to exist
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* @author Brandon Mills
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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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/** @type {import('../shared/types').Rule} */
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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: "Disallow unnecessary nested blocks",
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recommended: false,
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url: "https://eslint.org/docs/latest/rules/no-lone-blocks"
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},
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schema: [],
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messages: {
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redundantBlock: "Block is redundant.",
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redundantNestedBlock: "Nested block is redundant."
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}
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},
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create(context) {
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// A stack of lone blocks to be checked for block-level bindings
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const loneBlocks = [];
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let ruleDef;
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const sourceCode = context.sourceCode;
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/**
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* Reports a node as invalid.
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* @param {ASTNode} node The node to be reported.
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* @returns {void}
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*/
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function report(node) {
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const messageId = node.parent.type === "BlockStatement" || node.parent.type === "StaticBlock"
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? "redundantNestedBlock"
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: "redundantBlock";
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context.report({
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node,
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messageId
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});
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}
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/**
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* Checks for any occurrence of a BlockStatement in a place where lists of statements can appear
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* @param {ASTNode} node The node to check
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* @returns {boolean} True if the node is a lone block.
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*/
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function isLoneBlock(node) {
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return node.parent.type === "BlockStatement" ||
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node.parent.type === "StaticBlock" ||
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node.parent.type === "Program" ||
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// Don't report blocks in switch cases if the block is the only statement of the case.
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node.parent.type === "SwitchCase" && !(node.parent.consequent[0] === node && node.parent.consequent.length === 1);
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}
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/**
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* Checks the enclosing block of the current node for block-level bindings,
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* and "marks it" as valid if any.
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* @param {ASTNode} node The current node to check.
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* @returns {void}
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*/
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function markLoneBlock(node) {
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if (loneBlocks.length === 0) {
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return;
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}
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const block = node.parent;
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if (loneBlocks[loneBlocks.length - 1] === block) {
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loneBlocks.pop();
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}
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}
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// Default rule definition: report all lone blocks
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ruleDef = {
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BlockStatement(node) {
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if (isLoneBlock(node)) {
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report(node);
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}
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}
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};
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// ES6: report blocks without block-level bindings, or that's only child of another block
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if (context.languageOptions.ecmaVersion >= 2015) {
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ruleDef = {
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BlockStatement(node) {
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if (isLoneBlock(node)) {
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loneBlocks.push(node);
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}
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},
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"BlockStatement:exit"(node) {
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if (loneBlocks.length > 0 && loneBlocks[loneBlocks.length - 1] === node) {
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loneBlocks.pop();
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report(node);
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} else if (
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(
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node.parent.type === "BlockStatement" ||
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node.parent.type === "StaticBlock"
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) &&
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node.parent.body.length === 1
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) {
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report(node);
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}
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}
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};
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ruleDef.VariableDeclaration = function(node) {
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if (node.kind === "let" || node.kind === "const") {
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markLoneBlock(node);
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}
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};
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ruleDef.FunctionDeclaration = function(node) {
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if (sourceCode.getScope(node).isStrict) {
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markLoneBlock(node);
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}
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};
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ruleDef.ClassDeclaration = markLoneBlock;
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}
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return ruleDef;
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}
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};
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