experiments: Cursor rule for Cursor

Project Context

The current codebase enforces strict type safety, accessibility standards, and consistent code quality for JavaScript/TypeScript projects using Biome's lightning-fast formatter and linter.

Key Principles

• Strictly speak in English
• Never produce in code non-English text
• Zero configuration required
• Subsecond performance
• Maximum type safety
• AI-friendly code generation

Before Writing Code

1. Analyze existing patterns in the codebase
2. Consider edge cases and error scenarios
3. Follow the rules below strictly
4. Validate accessibility requirements

Rules

Terminal & Package Manager

• Always use Bun as the package manager.
• Always use cd <absolute/path/to/directory> to change the current working directory.
• Never use cd without an absolute path.
• When working on CLI commands, you can check their performance by running Measure-Command { bun dler tsc --verbose }.

Code Complexity and Quality

• Don't add _ prefix to disable unused variable, when this variable is really unused (just use e.g. } catch { instead of } catch (_error) {)
• Don't use consecutive spaces in regular expression literals.
• Don't use the arguments object.
• Don't use primitive type aliases or misleading types.
• Don't use the comma operator.
• Don't use empty type parameters in type aliases and interfaces.
• Don't write functions that exceed a given Cognitive Complexity score.
• Don't nest describe() blocks too deeply in test files.
• Don't use unnecessary boolean casts.
• Don't use unnecessary callbacks with flatMap.
• Use for...of statements instead of Array.forEach.
• Don't create classes that only have static members (like a static namespace).
• Don't use this and super in static contexts.
• Don't use unnecessary catch clauses.
• Don't use unnecessary constructors.
• Don't use unnecessary continue statements.
• Don't export empty modules that don't change anything.
• Don't use unnecessary escape sequences in regular expression literals.
• Don't use unnecessary labels.
• Don't use unnecessary nested block statements.
• Don't rename imports, exports, and destructured assignments to the same name.
• Don't use unnecessary string or template literal concatenation.
• Don't use String.raw in template literals when there are no escape sequences.
• Don't use useless case statements in switch statements.
• Don't use ternary operators when simpler alternatives exist.
• Don't use useless this aliasing.
• Don't use any or unknown as type constraints.
• Don't initialize variables to undefined.
• Don't use the void operators (they're not familiar).
• Use arrow functions instead of function expressions.
• Use Date.now() to get milliseconds since the Unix Epoch.
• Use .flatMap() instead of map().flat() when possible.
• Use literal property access instead of computed property access.
• Don't use parseInt() or Number.parseInt() when binary, octal, or hexadecimal literals work.
• Use concise optional chaining instead of chained logical expressions.
• Use regular expression literals instead of the RegExp constructor when possible.
• Don't use number literal object member names that aren't base 10 or use underscore separators.
• Remove redundant terms from logical expressions.
• Use while loops instead of for loops when you don't need initializer and update expressions.
• Don't reassign const variables.
• Don't use constant expressions in conditions.
• Don't use Math.min and Math.max to clamp values when the result is constant.
• Don't return a value from a constructor.
• Don't use empty character classes in regular expression literals.
• Don't use empty destructuring patterns.
• Don't call global object properties as functions.
• Don't declare functions and vars that are accessible outside their block.
• Make sure builtins are correctly instantiated.
• Don't use super() incorrectly inside classes. Also check that super() is called in classes that extend other constructors.
• Don't use variables and function parameters before they're declared.
• Don't use 8 and 9 escape sequences in string literals.
• Don't use literal numbers that lose precision.