/
no-shadow.ts
441 lines (392 loc) · 12.6 KB
/
no-shadow.ts
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import {
TSESTree,
TSESLint,
AST_NODE_TYPES,
} from '@typescript-eslint/experimental-utils';
import { ScopeType } from '@typescript-eslint/scope-manager';
import * as util from '../util';
type MessageIds = 'noShadow';
type Options = [
{
allow?: string[];
builtinGlobals?: boolean;
hoist?: 'all' | 'functions' | 'never';
ignoreTypeValueShadow?: boolean;
ignoreFunctionTypeParameterNameValueShadow?: boolean;
},
];
export default util.createRule<Options, MessageIds>({
name: 'no-shadow',
meta: {
type: 'suggestion',
docs: {
description:
'Disallow variable declarations from shadowing variables declared in the outer scope',
category: 'Variables',
recommended: false,
extendsBaseRule: true,
},
schema: [
{
type: 'object',
properties: {
builtinGlobals: {
type: 'boolean',
},
hoist: {
enum: ['all', 'functions', 'never'],
},
allow: {
type: 'array',
items: {
type: 'string',
},
},
ignoreTypeValueShadow: {
type: 'boolean',
},
ignoreFunctionTypeParameterNameValueShadow: {
type: 'boolean',
},
},
additionalProperties: false,
},
],
messages: {
noShadow: "'{{name}}' is already declared in the upper scope.",
},
},
defaultOptions: [
{
allow: [],
builtinGlobals: false,
hoist: 'functions',
ignoreTypeValueShadow: true,
ignoreFunctionTypeParameterNameValueShadow: true,
},
],
create(context, [options]) {
/**
* Check if a scope is a TypeScript module augmenting the global namespace.
*/
function isGlobalAugmentation(scope: TSESLint.Scope.Scope): boolean {
return (
(scope.type === ScopeType.tsModule && !!scope.block.global) ||
(!!scope.upper && isGlobalAugmentation(scope.upper))
);
}
/**
* Check if variable is a `this` parameter.
*/
function isThisParam(variable: TSESLint.Scope.Variable): boolean {
return variable.defs[0].type === 'Parameter' && variable.name === 'this';
}
function isTypeValueShadow(
variable: TSESLint.Scope.Variable,
shadowed: TSESLint.Scope.Variable,
): boolean {
if (options.ignoreTypeValueShadow !== true) {
return false;
}
if (!('isValueVariable' in variable)) {
// this shouldn't happen...
return false;
}
const isShadowedValue =
'isValueVariable' in shadowed ? shadowed.isValueVariable : true;
return variable.isValueVariable !== isShadowedValue;
}
function isFunctionTypeParameterNameValueShadow(
variable: TSESLint.Scope.Variable,
shadowed: TSESLint.Scope.Variable,
): boolean {
if (options.ignoreFunctionTypeParameterNameValueShadow !== true) {
return false;
}
if (!('isValueVariable' in variable)) {
// this shouldn't happen...
return false;
}
const isShadowedValue =
'isValueVariable' in shadowed ? shadowed.isValueVariable : true;
if (!isShadowedValue) {
return false;
}
const id = variable.identifiers[0];
return util.isFunctionType(id.parent);
}
function isGenericOfStaticMethod(
variable: TSESLint.Scope.Variable,
): boolean {
if (!('isTypeVariable' in variable)) {
// this shouldn't happen...
return false;
}
if (!variable.isTypeVariable) {
return false;
}
if (variable.identifiers.length === 0) {
return false;
}
const typeParameter = variable.identifiers[0].parent;
if (typeParameter?.type !== AST_NODE_TYPES.TSTypeParameter) {
return false;
}
const typeParameterDecl = typeParameter.parent;
if (
typeParameterDecl?.type !== AST_NODE_TYPES.TSTypeParameterDeclaration
) {
return false;
}
const functionExpr = typeParameterDecl.parent;
if (
!functionExpr ||
(functionExpr.type !== AST_NODE_TYPES.FunctionExpression &&
functionExpr.type !== AST_NODE_TYPES.TSEmptyBodyFunctionExpression)
) {
return false;
}
const methodDefinition = functionExpr.parent;
if (methodDefinition?.type !== AST_NODE_TYPES.MethodDefinition) {
return false;
}
return methodDefinition.static;
}
function isGenericOfClassDecl(variable: TSESLint.Scope.Variable): boolean {
if (!('isTypeVariable' in variable)) {
// this shouldn't happen...
return false;
}
if (!variable.isTypeVariable) {
return false;
}
if (variable.identifiers.length === 0) {
return false;
}
const typeParameter = variable.identifiers[0].parent;
if (typeParameter?.type !== AST_NODE_TYPES.TSTypeParameter) {
return false;
}
const typeParameterDecl = typeParameter.parent;
if (
typeParameterDecl?.type !== AST_NODE_TYPES.TSTypeParameterDeclaration
) {
return false;
}
const classDecl = typeParameterDecl.parent;
return classDecl?.type === AST_NODE_TYPES.ClassDeclaration;
}
function isGenericOfAStaticMethodShadow(
variable: TSESLint.Scope.Variable,
shadowed: TSESLint.Scope.Variable,
): boolean {
return (
isGenericOfStaticMethod(variable) && isGenericOfClassDecl(shadowed)
);
}
/**
* Check if variable name is allowed.
* @param variable The variable to check.
* @returns Whether or not the variable name is allowed.
*/
function isAllowed(variable: TSESLint.Scope.Variable): boolean {
return options.allow!.indexOf(variable.name) !== -1;
}
/**
* Checks if a variable of the class name in the class scope of ClassDeclaration.
*
* ClassDeclaration creates two variables of its name into its outer scope and its class scope.
* So we should ignore the variable in the class scope.
* @param variable The variable to check.
* @returns Whether or not the variable of the class name in the class scope of ClassDeclaration.
*/
function isDuplicatedClassNameVariable(
variable: TSESLint.Scope.Variable,
): boolean {
const block = variable.scope.block;
return (
block.type === AST_NODE_TYPES.ClassDeclaration &&
block.id === variable.identifiers[0]
);
}
/**
* Checks if a variable of the class name in the class scope of TSEnumDeclaration.
*
* TSEnumDeclaration creates two variables of its name into its outer scope and its class scope.
* So we should ignore the variable in the class scope.
* @param variable The variable to check.
* @returns Whether or not the variable of the class name in the class scope of TSEnumDeclaration.
*/
function isDuplicatedEnumNameVariable(
variable: TSESLint.Scope.Variable,
): boolean {
const block = variable.scope.block;
return (
block.type === AST_NODE_TYPES.TSEnumDeclaration &&
block.id === variable.identifiers[0]
);
}
/**
* Checks if a variable is inside the initializer of scopeVar.
*
* To avoid reporting at declarations such as `var a = function a() {};`.
* But it should report `var a = function(a) {};` or `var a = function() { function a() {} };`.
* @param variable The variable to check.
* @param scopeVar The scope variable to look for.
* @returns Whether or not the variable is inside initializer of scopeVar.
*/
function isOnInitializer(
variable: TSESLint.Scope.Variable,
scopeVar: TSESLint.Scope.Variable,
): boolean {
const outerScope = scopeVar.scope;
const outerDef = scopeVar.defs[0];
const outer = outerDef?.parent?.range;
const innerScope = variable.scope;
const innerDef = variable.defs[0];
const inner = innerDef?.name.range;
return !!(
outer &&
inner &&
outer[0] < inner[0] &&
inner[1] < outer[1] &&
((innerDef.type === 'FunctionName' &&
innerDef.node.type === AST_NODE_TYPES.FunctionExpression) ||
innerDef.node.type === AST_NODE_TYPES.ClassExpression) &&
outerScope === innerScope.upper
);
}
/**
* Get a range of a variable's identifier node.
* @param variable The variable to get.
* @returns The range of the variable's identifier node.
*/
function getNameRange(
variable: TSESLint.Scope.Variable,
): TSESTree.Range | undefined {
const def = variable.defs[0];
return def?.name.range;
}
/**
* Checks if a variable is in TDZ of scopeVar.
* @param variable The variable to check.
* @param scopeVar The variable of TDZ.
* @returns Whether or not the variable is in TDZ of scopeVar.
*/
function isInTdz(
variable: TSESLint.Scope.Variable,
scopeVar: TSESLint.Scope.Variable,
): boolean {
const outerDef = scopeVar.defs[0];
const inner = getNameRange(variable);
const outer = getNameRange(scopeVar);
return !!(
inner &&
outer &&
inner[1] < outer[0] &&
// Excepts FunctionDeclaration if is {"hoist":"function"}.
(options.hoist !== 'functions' ||
!outerDef ||
outerDef.node.type !== AST_NODE_TYPES.FunctionDeclaration)
);
}
/**
* Finds the variable by a given name in a given scope and its upper scopes.
* @param initScope A scope to start find.
* @param name A variable name to find.
* @returns A found variable or `null`.
*/
function getVariableByName(
initScope: TSESLint.Scope.Scope | null,
name: string,
): TSESLint.Scope.Variable | null {
let scope = initScope;
while (scope) {
const variable = scope.set.get(name);
if (variable) {
return variable;
}
scope = scope.upper;
}
return null;
}
/**
* Checks the current context for shadowed variables.
* @param {Scope} scope Fixme
*/
function checkForShadows(scope: TSESLint.Scope.Scope): void {
// ignore global augmentation
if (isGlobalAugmentation(scope)) {
return;
}
const variables = scope.variables;
for (const variable of variables) {
// ignore "arguments"
if (variable.identifiers.length === 0) {
continue;
}
// this params are pseudo-params that cannot be shadowed
if (isThisParam(variable)) {
continue;
}
// ignore variables of a class name in the class scope of ClassDeclaration
if (isDuplicatedClassNameVariable(variable)) {
continue;
}
// ignore variables of a class name in the class scope of ClassDeclaration
if (isDuplicatedEnumNameVariable(variable)) {
continue;
}
// ignore configured allowed names
if (isAllowed(variable)) {
continue;
}
// Gets shadowed variable.
const shadowed = getVariableByName(scope.upper, variable.name);
if (!shadowed) {
continue;
}
// ignore type value variable shadowing if configured
if (isTypeValueShadow(variable, shadowed)) {
continue;
}
// ignore function type parameter name shadowing if configured
if (isFunctionTypeParameterNameValueShadow(variable, shadowed)) {
continue;
}
// ignore static class method generic shadowing class generic
// this is impossible for the scope analyser to understand
// so we have to handle this manually in this rule
if (isGenericOfAStaticMethodShadow(variable, shadowed)) {
continue;
}
const isESLintGlobal = 'writeable' in shadowed;
if (
(shadowed.identifiers.length > 0 ||
(options.builtinGlobals && isESLintGlobal)) &&
!isOnInitializer(variable, shadowed) &&
!(options.hoist !== 'all' && isInTdz(variable, shadowed))
) {
context.report({
node: variable.identifiers[0],
messageId: 'noShadow',
data: {
name: variable.name,
},
});
}
}
}
return {
'Program:exit'(): void {
const globalScope = context.getScope();
const stack = globalScope.childScopes.slice();
while (stack.length) {
const scope = stack.pop()!;
stack.push(...scope.childScopes);
checkForShadows(scope);
}
},
};
},
});