import * as Lint from 'tslint'; import { isPrefixUnaryExpression } from 'tsutils'; import * as ts from 'typescript'; // tslint:disable:no-unnecessary-type-assertion /** * A modified version of the no-magic-numbers rule that allows for magic numbers * when instantiating a BigNumber instance. * E.g We want to be able to write: * const amount = new BigNumber(5); * Original source: https://github.com/palantir/tslint/blob/42b058a6baa688f8be8558b277eb056c3ff79818/src/rules/noMagicNumbersRule.ts */ export class Rule extends Lint.Rules.AbstractRule { public static ALLOWED_NODES = new Set([ ts.SyntaxKind.ExportAssignment, ts.SyntaxKind.FirstAssignment, ts.SyntaxKind.LastAssignment, ts.SyntaxKind.PropertyAssignment, ts.SyntaxKind.ShorthandPropertyAssignment, ts.SyntaxKind.VariableDeclaration, ts.SyntaxKind.VariableDeclarationList, ts.SyntaxKind.EnumMember, ts.SyntaxKind.PropertyDeclaration, ts.SyntaxKind.Parameter, ]); public static DEFAULT_ALLOWED = [-1, 0, 1]; public apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] { const allowedNumbers = this.ruleArguments.length > 0 ? this.ruleArguments : Rule.DEFAULT_ALLOWED; return this.applyWithWalker( new CustomNoMagicNumbersWalker(sourceFile, this.ruleName, new Set(allowedNumbers.map(String))), ); } } // tslint:disable-next-line:max-classes-per-file class CustomNoMagicNumbersWalker extends Lint.AbstractWalker> { public static FAILURE_STRING = "'magic numbers' are not allowed"; private static _isNegativeNumberLiteral( node: ts.Node, ): node is ts.PrefixUnaryExpression & { operand: ts.NumericLiteral } { return ( isPrefixUnaryExpression(node) && node.operator === ts.SyntaxKind.MinusToken && node.operand.kind === ts.SyntaxKind.NumericLiteral ); } public walk(sourceFile: ts.SourceFile): void { const cb = (node: ts.Node): void => { if (node.kind === ts.SyntaxKind.NumericLiteral) { return this.checkNumericLiteral(node, (node as ts.NumericLiteral).text); } if (CustomNoMagicNumbersWalker._isNegativeNumberLiteral(node)) { return this.checkNumericLiteral(node, `-${(node.operand as ts.NumericLiteral).text}`); } return ts.forEachChild(node, cb); }; return ts.forEachChild(sourceFile, cb); } // tslint:disable:no-non-null-assertion // tslint:disable-next-line:underscore-private-and-protected private checkNumericLiteral(node: ts.Node, num: string): void { if (!Rule.ALLOWED_NODES.has(node.parent!.kind) && !this.options.has(num)) { if (node.parent!.kind === ts.SyntaxKind.NewExpression) { const className = (node.parent! as any).expression.escapedText; const BIG_NUMBER_NEW_EXPRESSION = 'BigNumber'; if (className === BIG_NUMBER_NEW_EXPRESSION) { return; // noop } } this.addFailureAtNode(node, CustomNoMagicNumbersWalker.FAILURE_STRING); } } // tslint:enable:no-non-null-assertion } // tslint:enable:no-unnecessary-type-assertion