45 lines
2 KiB
TypeScript
45 lines
2 KiB
TypeScript
import * as Lint from "tslint/lib/lint";
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import * as ts from "typescript";
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export class Rule extends Lint.Rules.AbstractRule {
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public static POSTFIX_FAILURE_STRING = "Don't use '++' or '--' postfix operators outside statements or for loops.";
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public static PREFIX_FAILURE_STRING = "Don't use '++' or '--' prefix operators.";
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public apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
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return this.applyWithWalker(new IncrementDecrementWalker(sourceFile, this.getOptions()));
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}
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}
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class IncrementDecrementWalker extends Lint.RuleWalker {
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visitPostfixUnaryExpression(node: ts.PostfixUnaryExpression) {
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super.visitPostfixUnaryExpression(node);
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if (node.operator === ts.SyntaxKind.PlusPlusToken || node.operator == ts.SyntaxKind.MinusMinusToken) {
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this.visitIncrementDecrement(node);
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}
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}
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visitPrefixUnaryExpression(node: ts.PrefixUnaryExpression) {
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super.visitPrefixUnaryExpression(node);
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if (node.operator === ts.SyntaxKind.PlusPlusToken || node.operator == ts.SyntaxKind.MinusMinusToken) {
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this.addFailure(this.createFailure(node.getStart(), node.getWidth(), Rule.PREFIX_FAILURE_STRING));
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}
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}
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visitIncrementDecrement(node: ts.UnaryExpression) {
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if (node.parent && (
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// Can be a statement
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node.parent.kind === ts.SyntaxKind.ExpressionStatement ||
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// Can be directly in a for-statement
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node.parent.kind === ts.SyntaxKind.ForStatement ||
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// Can be in a comma operator in a for statement (`for (let a = 0, b = 10; a < b; a++, b--)`)
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node.parent.kind === ts.SyntaxKind.BinaryExpression &&
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(<ts.BinaryExpression>node.parent).operatorToken.kind === ts.SyntaxKind.CommaToken &&
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node.parent.parent.kind === ts.SyntaxKind.ForStatement)) {
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return;
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}
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this.addFailure(this.createFailure(node.getStart(), node.getWidth(), Rule.POSTFIX_FAILURE_STRING));
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}
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}
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