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import * as Lint from 'tslint';
import { isPrefixUnaryExpression } from 'tsutils';
import * as ts from 'typescript';
/**
* 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>([
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<Set<string>> {
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
}
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