2 * @fileoverview A rule to control the use of single variable declarations.
3 * @author Ian Christian Myers
8 //------------------------------------------------------------------------------
10 //------------------------------------------------------------------------------
12 const astUtils = require("./utils/ast-utils");
14 //------------------------------------------------------------------------------
16 //------------------------------------------------------------------------------
19 * Determines whether the given node is in a statement list.
20 * @param {ASTNode} node node to check
21 * @returns {boolean} `true` if the given node is in a statement list
23 function isInStatementList(node) {
24 return astUtils.STATEMENT_LIST_PARENTS.has(node.parent.type);
27 //------------------------------------------------------------------------------
29 //------------------------------------------------------------------------------
36 description: "enforce variables to be declared either together or separately in functions",
37 category: "Stylistic Issues",
39 url: "https://eslint.org/docs/rules/one-var"
48 enum: ["always", "never", "consecutive"]
57 enum: ["always", "never", "consecutive"]
60 enum: ["always", "never", "consecutive"]
63 enum: ["always", "never", "consecutive"]
66 additionalProperties: false
72 enum: ["always", "never", "consecutive"]
75 enum: ["always", "never", "consecutive"]
78 additionalProperties: false
85 combineUninitialized: "Combine this with the previous '{{type}}' statement with uninitialized variables.",
86 combineInitialized: "Combine this with the previous '{{type}}' statement with initialized variables.",
87 splitUninitialized: "Split uninitialized '{{type}}' declarations into multiple statements.",
88 splitInitialized: "Split initialized '{{type}}' declarations into multiple statements.",
89 splitRequires: "Split requires to be separated into a single block.",
90 combine: "Combine this with the previous '{{type}}' statement.",
91 split: "Split '{{type}}' declarations into multiple statements."
96 const MODE_ALWAYS = "always";
97 const MODE_NEVER = "never";
98 const MODE_CONSECUTIVE = "consecutive";
99 const mode = context.options[0] || MODE_ALWAYS;
103 if (typeof mode === "string") { // simple options configuration with just a string
104 options.var = { uninitialized: mode, initialized: mode };
105 options.let = { uninitialized: mode, initialized: mode };
106 options.const = { uninitialized: mode, initialized: mode };
107 } else if (typeof mode === "object") { // options configuration is an object
108 options.separateRequires = !!mode.separateRequires;
109 options.var = { uninitialized: mode.var, initialized: mode.var };
110 options.let = { uninitialized: mode.let, initialized: mode.let };
111 options.const = { uninitialized: mode.const, initialized: mode.const };
112 if (Object.prototype.hasOwnProperty.call(mode, "uninitialized")) {
113 options.var.uninitialized = mode.uninitialized;
114 options.let.uninitialized = mode.uninitialized;
115 options.const.uninitialized = mode.uninitialized;
117 if (Object.prototype.hasOwnProperty.call(mode, "initialized")) {
118 options.var.initialized = mode.initialized;
119 options.let.initialized = mode.initialized;
120 options.const.initialized = mode.initialized;
124 const sourceCode = context.getSourceCode();
126 //--------------------------------------------------------------------------
128 //--------------------------------------------------------------------------
130 const functionStack = [];
131 const blockStack = [];
134 * Increments the blockStack counter.
138 function startBlock() {
140 let: { initialized: false, uninitialized: false },
141 const: { initialized: false, uninitialized: false }
146 * Increments the functionStack counter.
150 function startFunction() {
151 functionStack.push({ initialized: false, uninitialized: false });
156 * Decrements the blockStack counter.
160 function endBlock() {
165 * Decrements the functionStack counter.
169 function endFunction() {
175 * Check if a variable declaration is a require.
176 * @param {ASTNode} decl variable declaration Node
177 * @returns {bool} if decl is a require, return true; else return false.
180 function isRequire(decl) {
181 return decl.init && decl.init.type === "CallExpression" && decl.init.callee.name === "require";
185 * Records whether initialized/uninitialized/required variables are defined in current scope.
186 * @param {string} statementType node.kind, one of: "var", "let", or "const"
187 * @param {ASTNode[]} declarations List of declarations
188 * @param {Object} currentScope The scope being investigated
192 function recordTypes(statementType, declarations, currentScope) {
193 for (let i = 0; i < declarations.length; i++) {
194 if (declarations[i].init === null) {
195 if (options[statementType] && options[statementType].uninitialized === MODE_ALWAYS) {
196 currentScope.uninitialized = true;
199 if (options[statementType] && options[statementType].initialized === MODE_ALWAYS) {
200 if (options.separateRequires && isRequire(declarations[i])) {
201 currentScope.required = true;
203 currentScope.initialized = true;
211 * Determines the current scope (function or block)
212 * @param {string} statementType node.kind, one of: "var", "let", or "const"
213 * @returns {Object} The scope associated with statementType
215 function getCurrentScope(statementType) {
218 if (statementType === "var") {
219 currentScope = functionStack[functionStack.length - 1];
220 } else if (statementType === "let") {
221 currentScope = blockStack[blockStack.length - 1].let;
222 } else if (statementType === "const") {
223 currentScope = blockStack[blockStack.length - 1].const;
229 * Counts the number of initialized and uninitialized declarations in a list of declarations
230 * @param {ASTNode[]} declarations List of declarations
231 * @returns {Object} Counts of 'uninitialized' and 'initialized' declarations
234 function countDeclarations(declarations) {
235 const counts = { uninitialized: 0, initialized: 0 };
237 for (let i = 0; i < declarations.length; i++) {
238 if (declarations[i].init === null) {
239 counts.uninitialized++;
241 counts.initialized++;
248 * Determines if there is more than one var statement in the current scope.
249 * @param {string} statementType node.kind, one of: "var", "let", or "const"
250 * @param {ASTNode[]} declarations List of declarations
251 * @returns {boolean} Returns true if it is the first var declaration, false if not.
254 function hasOnlyOneStatement(statementType, declarations) {
256 const declarationCounts = countDeclarations(declarations);
257 const currentOptions = options[statementType] || {};
258 const currentScope = getCurrentScope(statementType);
259 const hasRequires = declarations.some(isRequire);
261 if (currentOptions.uninitialized === MODE_ALWAYS && currentOptions.initialized === MODE_ALWAYS) {
262 if (currentScope.uninitialized || currentScope.initialized) {
269 if (declarationCounts.uninitialized > 0) {
270 if (currentOptions.uninitialized === MODE_ALWAYS && currentScope.uninitialized) {
274 if (declarationCounts.initialized > 0) {
275 if (currentOptions.initialized === MODE_ALWAYS && currentScope.initialized) {
281 if (currentScope.required && hasRequires) {
284 recordTypes(statementType, declarations, currentScope);
289 * Fixer to join VariableDeclaration's into a single declaration
290 * @param {VariableDeclarator[]} declarations The `VariableDeclaration` to join
291 * @returns {Function} The fixer function
293 function joinDeclarations(declarations) {
294 const declaration = declarations[0];
295 const body = Array.isArray(declaration.parent.parent.body) ? declaration.parent.parent.body : [];
296 const currentIndex = body.findIndex(node => node.range[0] === declaration.parent.range[0]);
297 const previousNode = body[currentIndex - 1];
300 const type = sourceCode.getTokenBefore(declaration);
301 const prevSemi = sourceCode.getTokenBefore(type);
304 if (previousNode && previousNode.kind === sourceCode.getText(type)) {
305 if (prevSemi.value === ";") {
306 res.push(fixer.replaceText(prevSemi, ","));
308 res.push(fixer.insertTextAfter(prevSemi, ","));
310 res.push(fixer.replaceText(type, ""));
318 * Fixer to split a VariableDeclaration into individual declarations
319 * @param {VariableDeclaration} declaration The `VariableDeclaration` to split
320 * @returns {Function|null} The fixer function
322 function splitDeclarations(declaration) {
323 const { parent } = declaration;
325 // don't autofix code such as: if (foo) var x, y;
326 if (!isInStatementList(parent.type === "ExportNamedDeclaration" ? parent : declaration)) {
330 return fixer => declaration.declarations.map(declarator => {
331 const tokenAfterDeclarator = sourceCode.getTokenAfter(declarator);
333 if (tokenAfterDeclarator === null) {
337 const afterComma = sourceCode.getTokenAfter(tokenAfterDeclarator, { includeComments: true });
339 if (tokenAfterDeclarator.value !== ",") {
343 const exportPlacement = declaration.parent.type === "ExportNamedDeclaration" ? "export " : "";
347 * tokenAfterDeclarator ^^ afterComma
349 if (afterComma.range[0] === tokenAfterDeclarator.range[1]) {
350 return fixer.replaceText(tokenAfterDeclarator, `; ${exportPlacement}${declaration.kind} `);
355 * tokenAfterDeclarator ^
360 afterComma.loc.start.line > tokenAfterDeclarator.loc.end.line ||
361 afterComma.type === "Line" ||
362 afterComma.type === "Block"
364 let lastComment = afterComma;
366 while (lastComment.type === "Line" || lastComment.type === "Block") {
367 lastComment = sourceCode.getTokenAfter(lastComment, { includeComments: true });
370 return fixer.replaceTextRange(
371 [tokenAfterDeclarator.range[0], lastComment.range[0]],
372 `;${sourceCode.text.slice(tokenAfterDeclarator.range[1], lastComment.range[0])}${exportPlacement}${declaration.kind} `
376 return fixer.replaceText(tokenAfterDeclarator, `; ${exportPlacement}${declaration.kind}`);
381 * Checks a given VariableDeclaration node for errors.
382 * @param {ASTNode} node The VariableDeclaration node to check
386 function checkVariableDeclaration(node) {
387 const parent = node.parent;
388 const type = node.kind;
390 if (!options[type]) {
394 const declarations = node.declarations;
395 const declarationCounts = countDeclarations(declarations);
396 const mixedRequires = declarations.some(isRequire) && !declarations.every(isRequire);
398 if (options[type].initialized === MODE_ALWAYS) {
399 if (options.separateRequires && mixedRequires) {
402 messageId: "splitRequires"
408 const nodeIndex = (parent.body && parent.body.length > 0 && parent.body.indexOf(node)) || 0;
411 const previousNode = parent.body[nodeIndex - 1];
412 const isPreviousNodeDeclaration = previousNode.type === "VariableDeclaration";
413 const declarationsWithPrevious = declarations.concat(previousNode.declarations || []);
416 isPreviousNodeDeclaration &&
417 previousNode.kind === type &&
418 !(declarationsWithPrevious.some(isRequire) && !declarationsWithPrevious.every(isRequire))
420 const previousDeclCounts = countDeclarations(previousNode.declarations);
422 if (options[type].initialized === MODE_CONSECUTIVE && options[type].uninitialized === MODE_CONSECUTIVE) {
425 messageId: "combine",
429 fix: joinDeclarations(declarations)
431 } else if (options[type].initialized === MODE_CONSECUTIVE && declarationCounts.initialized > 0 && previousDeclCounts.initialized > 0) {
434 messageId: "combineInitialized",
438 fix: joinDeclarations(declarations)
440 } else if (options[type].uninitialized === MODE_CONSECUTIVE &&
441 declarationCounts.uninitialized > 0 &&
442 previousDeclCounts.uninitialized > 0) {
445 messageId: "combineUninitialized",
449 fix: joinDeclarations(declarations)
456 if (!hasOnlyOneStatement(type, declarations)) {
457 if (options[type].initialized === MODE_ALWAYS && options[type].uninitialized === MODE_ALWAYS) {
460 messageId: "combine",
464 fix: joinDeclarations(declarations)
467 if (options[type].initialized === MODE_ALWAYS && declarationCounts.initialized > 0) {
470 messageId: "combineInitialized",
474 fix: joinDeclarations(declarations)
477 if (options[type].uninitialized === MODE_ALWAYS && declarationCounts.uninitialized > 0) {
478 if (node.parent.left === node && (node.parent.type === "ForInStatement" || node.parent.type === "ForOfStatement")) {
483 messageId: "combineUninitialized",
487 fix: joinDeclarations(declarations)
494 if (parent.type !== "ForStatement" || parent.init !== node) {
495 const totalDeclarations = declarationCounts.uninitialized + declarationCounts.initialized;
497 if (totalDeclarations > 1) {
498 if (options[type].initialized === MODE_NEVER && options[type].uninitialized === MODE_NEVER) {
500 // both initialized and uninitialized
507 fix: splitDeclarations(node)
509 } else if (options[type].initialized === MODE_NEVER && declarationCounts.initialized > 0) {
514 messageId: "splitInitialized",
518 fix: splitDeclarations(node)
520 } else if (options[type].uninitialized === MODE_NEVER && declarationCounts.uninitialized > 0) {
525 messageId: "splitUninitialized",
529 fix: splitDeclarations(node)
536 //--------------------------------------------------------------------------
538 //--------------------------------------------------------------------------
541 Program: startFunction,
542 FunctionDeclaration: startFunction,
543 FunctionExpression: startFunction,
544 ArrowFunctionExpression: startFunction,
545 BlockStatement: startBlock,
546 ForStatement: startBlock,
547 ForInStatement: startBlock,
548 ForOfStatement: startBlock,
549 SwitchStatement: startBlock,
550 VariableDeclaration: checkVariableDeclaration,
551 "ForStatement:exit": endBlock,
552 "ForOfStatement:exit": endBlock,
553 "ForInStatement:exit": endBlock,
554 "SwitchStatement:exit": endBlock,
555 "BlockStatement:exit": endBlock,
556 "Program:exit": endFunction,
557 "FunctionDeclaration:exit": endFunction,
558 "FunctionExpression:exit": endFunction,
559 "ArrowFunctionExpression:exit": endFunction