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