/
no-unnecessary-qualifier.ts
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/
no-unnecessary-qualifier.ts
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import {
AST_NODE_TYPES,
TSESTree,
} from '@typescript-eslint/experimental-utils';
import ts from 'typescript';
import * as tsutils from 'tsutils';
import * as util from '../util';
export default util.createRule({
name: 'no-unnecessary-qualifier',
meta: {
docs: {
category: 'Best Practices',
description: 'Warns when a namespace qualifier is unnecessary',
recommended: false,
requiresTypeChecking: true,
},
fixable: 'code',
messages: {
unnecessaryQualifier:
"Qualifier is unnecessary since '{{ name }}' is in scope.",
},
schema: [],
type: 'suggestion',
},
defaultOptions: [],
create(context) {
const namespacesInScope: ts.Node[] = [];
let currentFailedNamespaceExpression: TSESTree.Node | null = null;
const parserServices = util.getParserServices(context);
const esTreeNodeToTSNodeMap = parserServices.esTreeNodeToTSNodeMap;
const program = parserServices.program;
const checker = program.getTypeChecker();
const sourceCode = context.getSourceCode();
function tryGetAliasedSymbol(
symbol: ts.Symbol,
checker: ts.TypeChecker,
): ts.Symbol | null {
return tsutils.isSymbolFlagSet(symbol, ts.SymbolFlags.Alias)
? checker.getAliasedSymbol(symbol)
: null;
}
function symbolIsNamespaceInScope(symbol: ts.Symbol): boolean {
const symbolDeclarations = symbol.getDeclarations() ?? [];
if (
symbolDeclarations.some(decl =>
namespacesInScope.some(ns => ns === decl),
)
) {
return true;
}
const alias = tryGetAliasedSymbol(symbol, checker);
return alias !== null && symbolIsNamespaceInScope(alias);
}
function getSymbolInScope(
node: ts.Node,
flags: ts.SymbolFlags,
name: string,
): ts.Symbol | undefined {
// TODO:PERF `getSymbolsInScope` gets a long list. Is there a better way?
const scope = checker.getSymbolsInScope(node, flags);
return scope.find(scopeSymbol => scopeSymbol.name === name);
}
function symbolsAreEqual(accessed: ts.Symbol, inScope: ts.Symbol): boolean {
return accessed === checker.getExportSymbolOfSymbol(inScope);
}
function qualifierIsUnnecessary(
qualifier: TSESTree.Node,
name: TSESTree.Identifier,
): boolean {
const tsQualifier = esTreeNodeToTSNodeMap.get(qualifier);
const tsName = esTreeNodeToTSNodeMap.get(name);
const namespaceSymbol = checker.getSymbolAtLocation(tsQualifier);
if (
typeof namespaceSymbol === 'undefined' ||
!symbolIsNamespaceInScope(namespaceSymbol)
) {
return false;
}
const accessedSymbol = checker.getSymbolAtLocation(tsName);
if (typeof accessedSymbol === 'undefined') {
return false;
}
// If the symbol in scope is different, the qualifier is necessary.
const fromScope = getSymbolInScope(
tsQualifier,
accessedSymbol.flags,
sourceCode.getText(name),
);
return (
typeof fromScope === 'undefined' ||
symbolsAreEqual(accessedSymbol, fromScope)
);
}
function visitNamespaceAccess(
node: TSESTree.Node,
qualifier: TSESTree.Node,
name: TSESTree.Identifier,
): void {
// Only look for nested qualifier errors if we didn't already fail on the outer qualifier.
if (
!currentFailedNamespaceExpression &&
qualifierIsUnnecessary(qualifier, name)
) {
currentFailedNamespaceExpression = node;
context.report({
node: qualifier,
messageId: 'unnecessaryQualifier',
data: {
name: sourceCode.getText(name),
},
fix(fixer) {
return fixer.removeRange([qualifier.range[0], name.range[0]]);
},
});
}
}
function enterDeclaration(node: TSESTree.Node): void {
namespacesInScope.push(esTreeNodeToTSNodeMap.get(node));
}
function exitDeclaration(): void {
namespacesInScope.pop();
}
function resetCurrentNamespaceExpression(node: TSESTree.Node): void {
if (node === currentFailedNamespaceExpression) {
currentFailedNamespaceExpression = null;
}
}
function isPropertyAccessExpression(
node: TSESTree.Node,
): node is TSESTree.MemberExpression {
return node.type === AST_NODE_TYPES.MemberExpression && !node.computed;
}
function isEntityNameExpression(node: TSESTree.Node): boolean {
return (
node.type === AST_NODE_TYPES.Identifier ||
(isPropertyAccessExpression(node) &&
isEntityNameExpression(node.object))
);
}
return {
TSModuleDeclaration: enterDeclaration,
TSEnumDeclaration: enterDeclaration,
'ExportNamedDeclaration[declaration.type="TSModuleDeclaration"]': enterDeclaration,
'ExportNamedDeclaration[declaration.type="TSEnumDeclaration"]': enterDeclaration,
'TSModuleDeclaration:exit': exitDeclaration,
'TSEnumDeclaration:exit': exitDeclaration,
'ExportNamedDeclaration[declaration.type="TSModuleDeclaration"]:exit': exitDeclaration,
'ExportNamedDeclaration[declaration.type="TSEnumDeclaration"]:exit': exitDeclaration,
TSQualifiedName(node: TSESTree.TSQualifiedName): void {
visitNamespaceAccess(node, node.left, node.right);
},
'MemberExpression[computed=false]': function(
node: TSESTree.MemberExpression,
): void {
const property = node.property as TSESTree.Identifier;
if (isEntityNameExpression(node.object)) {
visitNamespaceAccess(node, node.object, property);
}
},
'TSQualifiedName:exit': resetCurrentNamespaceExpression,
'MemberExpression:exit': resetCurrentNamespaceExpression,
};
},
});