collectUnusedVariables.js
24.2 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
"use strict";
var __createBinding = (this && this.__createBinding) || (Object.create ? (function(o, m, k, k2) {
if (k2 === undefined) k2 = k;
Object.defineProperty(o, k2, { enumerable: true, get: function() { return m[k]; } });
}) : (function(o, m, k, k2) {
if (k2 === undefined) k2 = k;
o[k2] = m[k];
}));
var __setModuleDefault = (this && this.__setModuleDefault) || (Object.create ? (function(o, v) {
Object.defineProperty(o, "default", { enumerable: true, value: v });
}) : function(o, v) {
o["default"] = v;
});
var __importStar = (this && this.__importStar) || function (mod) {
if (mod && mod.__esModule) return mod;
var result = {};
if (mod != null) for (var k in mod) if (k !== "default" && Object.prototype.hasOwnProperty.call(mod, k)) __createBinding(result, mod, k);
__setModuleDefault(result, mod);
return result;
};
var __classPrivateFieldSet = (this && this.__classPrivateFieldSet) || function (receiver, privateMap, value) {
if (!privateMap.has(receiver)) {
throw new TypeError("attempted to set private field on non-instance");
}
privateMap.set(receiver, value);
return value;
};
var __classPrivateFieldGet = (this && this.__classPrivateFieldGet) || function (receiver, privateMap) {
if (!privateMap.has(receiver)) {
throw new TypeError("attempted to get private field on non-instance");
}
return privateMap.get(receiver);
};
var _scopeManager;
Object.defineProperty(exports, "__esModule", { value: true });
exports.collectUnusedVariables = void 0;
const experimental_utils_1 = require("@typescript-eslint/experimental-utils");
const scope_manager_1 = require("@typescript-eslint/scope-manager");
const Visitor_1 = require("@typescript-eslint/scope-manager/dist/referencer/Visitor");
const util = __importStar(require("."));
class UnusedVarsVisitor extends Visitor_1.Visitor {
// readonly #unusedVariables = new Set<TSESLint.Scope.Variable>();
constructor(context) {
super({
visitChildrenEvenIfSelectorExists: true,
});
_scopeManager.set(this, void 0);
//#endregion HELPERS
//#region VISITORS
// NOTE - This is a simple visitor - meaning it does not support selectors
this.ClassDeclaration = this.visitClass;
this.ClassExpression = this.visitClass;
this.FunctionDeclaration = this.visitFunction;
this.FunctionExpression = this.visitFunction;
this.MethodDefinition = this.visitSetter;
this.Property = this.visitSetter;
this.TSCallSignatureDeclaration = this.visitFunctionTypeSignature;
this.TSConstructorType = this.visitFunctionTypeSignature;
this.TSConstructSignatureDeclaration = this.visitFunctionTypeSignature;
this.TSDeclareFunction = this.visitFunctionTypeSignature;
this.TSEmptyBodyFunctionExpression = this.visitFunctionTypeSignature;
this.TSFunctionType = this.visitFunctionTypeSignature;
this.TSMethodSignature = this.visitFunctionTypeSignature;
__classPrivateFieldSet(this, _scopeManager, util.nullThrows(context.getSourceCode().scopeManager, 'Missing required scope manager'));
}
static collectUnusedVariables(context) {
const program = context.getSourceCode().ast;
const cached = this.RESULTS_CACHE.get(program);
if (cached) {
return cached;
}
const visitor = new this(context);
visitor.visit(program);
const unusedVars = visitor.collectUnusedVariables(visitor.getScope(program));
this.RESULTS_CACHE.set(program, unusedVars);
return unusedVars;
}
collectUnusedVariables(scope, unusedVariables = new Set()) {
for (const variable of scope.variables) {
if (
// skip function expression names,
scope.functionExpressionScope ||
// variables marked with markVariableAsUsed(),
variable.eslintUsed ||
// implicit lib variables (from @typescript-eslint/scope-manager),
variable instanceof scope_manager_1.ImplicitLibVariable ||
// basic exported variables
isExported(variable) ||
// variables implicitly exported via a merged declaration
isMergableExported(variable) ||
// used variables
isUsedVariable(variable)) {
continue;
}
unusedVariables.add(variable);
}
for (const childScope of scope.childScopes) {
this.collectUnusedVariables(childScope, unusedVariables);
}
return unusedVariables;
}
//#region HELPERS
getScope(currentNode) {
// On Program node, get the outermost scope to avoid return Node.js special function scope or ES modules scope.
const inner = currentNode.type !== experimental_utils_1.AST_NODE_TYPES.Program;
let node = currentNode;
while (node) {
const scope = __classPrivateFieldGet(this, _scopeManager).acquire(node, inner);
if (scope) {
if (scope.type === 'function-expression-name') {
return scope.childScopes[0];
}
return scope;
}
node = node.parent;
}
return __classPrivateFieldGet(this, _scopeManager).scopes[0];
}
markVariableAsUsed(variableOrIdentifierOrName, parent) {
if (typeof variableOrIdentifierOrName !== 'string' &&
!('type' in variableOrIdentifierOrName)) {
variableOrIdentifierOrName.eslintUsed = true;
return;
}
let name;
let node;
if (typeof variableOrIdentifierOrName === 'string') {
name = variableOrIdentifierOrName;
node = parent;
}
else {
name = variableOrIdentifierOrName.name;
node = variableOrIdentifierOrName;
}
let currentScope = this.getScope(node);
while (currentScope) {
const variable = currentScope.variables.find(scopeVar => scopeVar.name === name);
if (variable) {
variable.eslintUsed = true;
return;
}
currentScope = currentScope.upper;
}
}
visitClass(node) {
// skip a variable of class itself name in the class scope
const scope = this.getScope(node);
for (const variable of scope.variables) {
if (variable.identifiers[0] === scope.block.id) {
this.markVariableAsUsed(variable);
return;
}
}
}
visitFunction(node) {
const scope = this.getScope(node);
// skip implicit "arguments" variable
const variable = scope.set.get('arguments');
if ((variable === null || variable === void 0 ? void 0 : variable.defs.length) === 0) {
this.markVariableAsUsed(variable);
}
}
visitFunctionTypeSignature(node) {
// function type signature params create variables because they can be referenced within the signature,
// but they obviously aren't unused variables for the purposes of this rule.
for (const param of node.params) {
this.visitPattern(param, name => {
this.markVariableAsUsed(name);
});
}
}
visitSetter(node) {
if (node.kind === 'set') {
// ignore setter parameters because they're syntactically required to exist
for (const param of node.value.params) {
this.visitPattern(param, id => {
this.markVariableAsUsed(id);
});
}
}
}
ForInStatement(node) {
/**
* (Brad Zacher): I hate that this has to exist.
* But it is required for compat with the base ESLint rule.
*
* In 2015, ESLint decided to add an exception for these two specific cases
* ```
* for (var key in object) return;
*
* var key;
* for (key in object) return;
* ```
*
* I disagree with it, but what are you going to do...
*
* https://github.com/eslint/eslint/issues/2342
*/
let idOrVariable;
if (node.left.type === experimental_utils_1.AST_NODE_TYPES.VariableDeclaration) {
const variable = __classPrivateFieldGet(this, _scopeManager).getDeclaredVariables(node.left)[0];
if (!variable) {
return;
}
idOrVariable = variable;
}
if (node.left.type === experimental_utils_1.AST_NODE_TYPES.Identifier) {
idOrVariable = node.left;
}
if (idOrVariable == null) {
return;
}
let body = node.body;
if (node.body.type === experimental_utils_1.AST_NODE_TYPES.BlockStatement) {
if (node.body.body.length !== 1) {
return;
}
body = node.body.body[0];
}
if (body.type !== experimental_utils_1.AST_NODE_TYPES.ReturnStatement) {
return;
}
this.markVariableAsUsed(idOrVariable);
}
Identifier(node) {
const scope = this.getScope(node);
if (scope.type === experimental_utils_1.TSESLint.Scope.ScopeType.function &&
node.name === 'this') {
// this parameters should always be considered used as they're pseudo-parameters
if ('params' in scope.block && scope.block.params.includes(node)) {
this.markVariableAsUsed(node);
}
}
}
TSEnumDeclaration(node) {
// enum members create variables because they can be referenced within the enum,
// but they obviously aren't unused variables for the purposes of this rule.
const scope = this.getScope(node);
for (const variable of scope.variables) {
this.markVariableAsUsed(variable);
}
}
TSMappedType(node) {
// mapped types create a variable for their type name, but it's not necessary to reference it,
// so we shouldn't consider it as unused for the purpose of this rule.
this.markVariableAsUsed(node.typeParameter.name);
}
TSModuleDeclaration(node) {
// global augmentation can be in any file, and they do not need exports
if (node.global === true) {
this.markVariableAsUsed('global', node.parent);
}
}
TSParameterProperty(node) {
let identifier = null;
switch (node.parameter.type) {
case experimental_utils_1.AST_NODE_TYPES.AssignmentPattern:
if (node.parameter.left.type === experimental_utils_1.AST_NODE_TYPES.Identifier) {
identifier = node.parameter.left;
}
break;
case experimental_utils_1.AST_NODE_TYPES.Identifier:
identifier = node.parameter;
break;
}
if (identifier) {
this.markVariableAsUsed(identifier);
}
}
}
_scopeManager = new WeakMap();
UnusedVarsVisitor.RESULTS_CACHE = new WeakMap();
//#region private helpers
/**
* Checks the position of given nodes.
* @param inner A node which is expected as inside.
* @param outer A node which is expected as outside.
* @returns `true` if the `inner` node exists in the `outer` node.
*/
function isInside(inner, outer) {
return inner.range[0] >= outer.range[0] && inner.range[1] <= outer.range[1];
}
/**
* Determine if an identifier is referencing an enclosing name.
* This only applies to declarations that create their own scope (modules, functions, classes)
* @param ref The reference to check.
* @param nodes The candidate function nodes.
* @returns True if it's a self-reference, false if not.
*/
function isSelfReference(ref, nodes) {
let scope = ref.from;
while (scope) {
if (nodes.has(scope.block)) {
return true;
}
scope = scope.upper;
}
return false;
}
const MERGABLE_TYPES = new Set([
experimental_utils_1.AST_NODE_TYPES.TSInterfaceDeclaration,
experimental_utils_1.AST_NODE_TYPES.TSTypeAliasDeclaration,
experimental_utils_1.AST_NODE_TYPES.TSModuleDeclaration,
experimental_utils_1.AST_NODE_TYPES.ClassDeclaration,
experimental_utils_1.AST_NODE_TYPES.FunctionDeclaration,
]);
/**
* Determine if the variable is directly exported
* @param variable the variable to check
* @param target the type of node that is expected to be exported
*/
function isMergableExported(variable) {
var _a, _b;
// If all of the merged things are of the same type, TS will error if not all of them are exported - so we only need to find one
for (const def of variable.defs) {
// parameters can never be exported.
// their `node` prop points to the function decl, which can be exported
// so we need to special case them
if (def.type === experimental_utils_1.TSESLint.Scope.DefinitionType.Parameter) {
continue;
}
if ((MERGABLE_TYPES.has(def.node.type) &&
((_a = def.node.parent) === null || _a === void 0 ? void 0 : _a.type) === experimental_utils_1.AST_NODE_TYPES.ExportNamedDeclaration) ||
((_b = def.node.parent) === null || _b === void 0 ? void 0 : _b.type) === experimental_utils_1.AST_NODE_TYPES.ExportDefaultDeclaration) {
return true;
}
}
return false;
}
/**
* Determines if a given variable is being exported from a module.
* @param variable eslint-scope variable object.
* @returns True if the variable is exported, false if not.
*/
function isExported(variable) {
const definition = variable.defs[0];
if (definition) {
let node = definition.node;
if (node.type === experimental_utils_1.AST_NODE_TYPES.VariableDeclarator) {
node = node.parent;
}
else if (definition.type === experimental_utils_1.TSESLint.Scope.DefinitionType.Parameter) {
return false;
}
return node.parent.type.indexOf('Export') === 0;
}
return false;
}
/**
* Determines if the variable is used.
* @param variable The variable to check.
* @returns True if the variable is used
*/
function isUsedVariable(variable) {
/**
* Gets a list of function definitions for a specified variable.
* @param variable eslint-scope variable object.
* @returns Function nodes.
*/
function getFunctionDefinitions(variable) {
const functionDefinitions = new Set();
variable.defs.forEach(def => {
var _a, _b;
// FunctionDeclarations
if (def.type === experimental_utils_1.TSESLint.Scope.DefinitionType.FunctionName) {
functionDefinitions.add(def.node);
}
// FunctionExpressions
if (def.type === experimental_utils_1.TSESLint.Scope.DefinitionType.Variable &&
(((_a = def.node.init) === null || _a === void 0 ? void 0 : _a.type) === experimental_utils_1.AST_NODE_TYPES.FunctionExpression ||
((_b = def.node.init) === null || _b === void 0 ? void 0 : _b.type) === experimental_utils_1.AST_NODE_TYPES.ArrowFunctionExpression)) {
functionDefinitions.add(def.node.init);
}
});
return functionDefinitions;
}
function getTypeDeclarations(variable) {
const nodes = new Set();
variable.defs.forEach(def => {
if (def.node.type === experimental_utils_1.AST_NODE_TYPES.TSInterfaceDeclaration ||
def.node.type === experimental_utils_1.AST_NODE_TYPES.TSTypeAliasDeclaration) {
nodes.add(def.node);
}
});
return nodes;
}
function getModuleDeclarations(variable) {
const nodes = new Set();
variable.defs.forEach(def => {
if (def.node.type === experimental_utils_1.AST_NODE_TYPES.TSModuleDeclaration) {
nodes.add(def.node);
}
});
return nodes;
}
/**
* Checks if the ref is contained within one of the given nodes
*/
function isInsideOneOf(ref, nodes) {
for (const node of nodes) {
if (isInside(ref.identifier, node)) {
return true;
}
}
return false;
}
/**
* If a given reference is left-hand side of an assignment, this gets
* the right-hand side node of the assignment.
*
* In the following cases, this returns null.
*
* - The reference is not the LHS of an assignment expression.
* - The reference is inside of a loop.
* - The reference is inside of a function scope which is different from
* the declaration.
* @param ref A reference to check.
* @param prevRhsNode The previous RHS node.
* @returns The RHS node or null.
*/
function getRhsNode(ref, prevRhsNode) {
/**
* Checks whether the given node is in a loop or not.
* @param node The node to check.
* @returns `true` if the node is in a loop.
*/
function isInLoop(node) {
let currentNode = node;
while (currentNode) {
if (util.isFunction(currentNode)) {
break;
}
if (util.isLoop(currentNode)) {
return true;
}
currentNode = currentNode.parent;
}
return false;
}
const id = ref.identifier;
const parent = id.parent;
const grandparent = parent.parent;
const refScope = ref.from.variableScope;
const varScope = ref.resolved.scope.variableScope;
const canBeUsedLater = refScope !== varScope || isInLoop(id);
/*
* Inherits the previous node if this reference is in the node.
* This is for `a = a + a`-like code.
*/
if (prevRhsNode && isInside(id, prevRhsNode)) {
return prevRhsNode;
}
if (parent.type === experimental_utils_1.AST_NODE_TYPES.AssignmentExpression &&
grandparent.type === experimental_utils_1.AST_NODE_TYPES.ExpressionStatement &&
id === parent.left &&
!canBeUsedLater) {
return parent.right;
}
return null;
}
/**
* Checks whether a given reference is a read to update itself or not.
* @param ref A reference to check.
* @param rhsNode The RHS node of the previous assignment.
* @returns The reference is a read to update itself.
*/
function isReadForItself(ref, rhsNode) {
/**
* Checks whether a given Identifier node exists inside of a function node which can be used later.
*
* "can be used later" means:
* - the function is assigned to a variable.
* - the function is bound to a property and the object can be used later.
* - the function is bound as an argument of a function call.
*
* If a reference exists in a function which can be used later, the reference is read when the function is called.
* @param id An Identifier node to check.
* @param rhsNode The RHS node of the previous assignment.
* @returns `true` if the `id` node exists inside of a function node which can be used later.
*/
function isInsideOfStorableFunction(id, rhsNode) {
/**
* Finds a function node from ancestors of a node.
* @param node A start node to find.
* @returns A found function node.
*/
function getUpperFunction(node) {
let currentNode = node;
while (currentNode) {
if (util.isFunction(currentNode)) {
return currentNode;
}
currentNode = currentNode.parent;
}
return null;
}
/**
* Checks whether a given function node is stored to somewhere or not.
* If the function node is stored, the function can be used later.
* @param funcNode A function node to check.
* @param rhsNode The RHS node of the previous assignment.
* @returns `true` if under the following conditions:
* - the funcNode is assigned to a variable.
* - the funcNode is bound as an argument of a function call.
* - the function is bound to a property and the object satisfies above conditions.
*/
function isStorableFunction(funcNode, rhsNode) {
let node = funcNode;
let parent = funcNode.parent;
while (parent && isInside(parent, rhsNode)) {
switch (parent.type) {
case experimental_utils_1.AST_NODE_TYPES.SequenceExpression:
if (parent.expressions[parent.expressions.length - 1] !== node) {
return false;
}
break;
case experimental_utils_1.AST_NODE_TYPES.CallExpression:
case experimental_utils_1.AST_NODE_TYPES.NewExpression:
return parent.callee !== node;
case experimental_utils_1.AST_NODE_TYPES.AssignmentExpression:
case experimental_utils_1.AST_NODE_TYPES.TaggedTemplateExpression:
case experimental_utils_1.AST_NODE_TYPES.YieldExpression:
return true;
default:
if (parent.type.endsWith('Statement') ||
parent.type.endsWith('Declaration')) {
/*
* If it encountered statements, this is a complex pattern.
* Since analyzing complex patterns is hard, this returns `true` to avoid false positive.
*/
return true;
}
}
node = parent;
parent = parent.parent;
}
return false;
}
const funcNode = getUpperFunction(id);
return (!!funcNode &&
isInside(funcNode, rhsNode) &&
isStorableFunction(funcNode, rhsNode));
}
const id = ref.identifier;
const parent = id.parent;
const grandparent = parent.parent;
return (ref.isRead() && // in RHS of an assignment for itself. e.g. `a = a + 1`
// self update. e.g. `a += 1`, `a++`
((parent.type === experimental_utils_1.AST_NODE_TYPES.AssignmentExpression &&
grandparent.type === experimental_utils_1.AST_NODE_TYPES.ExpressionStatement &&
parent.left === id) ||
(parent.type === experimental_utils_1.AST_NODE_TYPES.UpdateExpression &&
grandparent.type === experimental_utils_1.AST_NODE_TYPES.ExpressionStatement) ||
(!!rhsNode &&
isInside(id, rhsNode) &&
!isInsideOfStorableFunction(id, rhsNode))));
}
const functionNodes = getFunctionDefinitions(variable);
const isFunctionDefinition = functionNodes.size > 0;
const typeDeclNodes = getTypeDeclarations(variable);
const isTypeDecl = typeDeclNodes.size > 0;
const moduleDeclNodes = getModuleDeclarations(variable);
const isModuleDecl = moduleDeclNodes.size > 0;
let rhsNode = null;
return variable.references.some(ref => {
const forItself = isReadForItself(ref, rhsNode);
rhsNode = getRhsNode(ref, rhsNode);
return (ref.isRead() &&
!forItself &&
!(isFunctionDefinition && isSelfReference(ref, functionNodes)) &&
!(isTypeDecl && isInsideOneOf(ref, typeDeclNodes)) &&
!(isModuleDecl && isSelfReference(ref, moduleDeclNodes)));
});
}
//#endregion private helpers
/**
* Collects the set of unused variables for a given context.
*
* Due to complexity, this does not take into consideration:
* - variables within declaration files
* - variables within ambient module declarations
*/
function collectUnusedVariables(context) {
return UnusedVarsVisitor.collectUnusedVariables(context);
}
exports.collectUnusedVariables = collectUnusedVariables;
//# sourceMappingURL=collectUnusedVariables.js.map