Type-Level Package Manager in TypeScript

Imagine a world where your package manager operates entirely at the type level in TypeScript. This challenge asks you to build a system that can declare package dependencies and resolve them using only TypeScript's type system, ensuring compile-time safety and correctness. This is useful for understanding advanced type manipulation and for scenarios where static analysis of dependencies is paramount.

Problem Description

You need to create a type-level system in TypeScript that simulates a package manager. This system should allow you to:

1. Define Packages: Represent individual packages with their own unique names.
2. Declare Dependencies: Define relationships where one package depends on another.
3. Resolve Dependencies: Given a target package, infer its entire dependency tree, including transitive dependencies.
4. Detect Circular Dependencies: Identify and report (via a specific type error) any circular dependencies within the declared package graph.

Key Requirements:

• All package definitions, dependency declarations, and dependency resolution must be handled within TypeScript's type system.
• The system should be extensible to define any number of packages and dependencies.
• A mechanism must be in place to indicate a successful resolution (e.g., by inferring the list of all dependencies).
• A mechanism must be in place to indicate a circular dependency error.

Expected Behavior:

• When a package with no dependencies is requested, the system should resolve to an empty list (or a specific marker for "no dependencies").
• When a package with direct dependencies is requested, the system should resolve to a list containing its direct dependencies.
• When a package with transitive dependencies is requested, the system should resolve to a list containing all direct and indirect dependencies.
• If a circular dependency is detected, the type system should produce a clear error, ideally with a message indicating the cycle.

Edge Cases:

• Packages with no dependencies.
• Packages with complex, multi-level dependency trees.
• Circular dependencies.
• Packages that are depended upon by multiple other packages.

Examples

Example 1: Simple Dependency

Let's define three packages: A, B, and C. A depends on B. B depends on C. C has no dependencies.

// Package definitions
type PackageA = { name: 'A' };
type PackageB = { name: 'B' };
type PackageC = { name: 'C' };

// Dependency declarations (conceptual - we'll implement this with types)
// A -> B
// B -> C

// How would we represent this and resolve dependencies for 'A'?

// Expected resolution for 'A': ['B', 'C'] (order might not be strictly enforced at type level,
// but the presence of dependencies is key)

Example 2: Transitive Dependencies

Consider packages X, Y, Z, and W. X depends on Y. Y depends on Z. Z depends on W. W has no dependencies.

// Package definitions
type PackageX = { name: 'X' };
type PackageY = { name: 'Y' };
type PackageZ = { name: 'Z' };
type PackageW = { name: 'W' };

// Dependency declarations (conceptual)
// X -> Y
// Y -> Z
// Z -> W

// Expected resolution for 'X': ['Y', 'Z', 'W']

Example 3: Circular Dependency

Consider packages P and Q. P depends on Q. Q depends on P.

// Package definitions
type PackageP = { name: 'P' };
type PackageQ = { name: 'Q' };

// Dependency declarations (conceptual)
// P -> Q
// Q -> P

// Expected behavior: A type error indicating a circular dependency.
// e.g., "Circular dependency detected: P -> Q -> P"

Constraints

• The solution must use only TypeScript's type system. No runtime code execution for dependency resolution.
• The names of packages should be unique string literals (e.g., 'A', 'B').
• The output of a successful dependency resolution should be a tuple of package names.
• Circular dependency detection should manifest as a compile-time error.
• The system should be able to handle at least 10 distinct packages and a dependency graph of depth up to 10.

Notes

• This challenge requires a deep understanding of advanced TypeScript features like conditional types, recursive type definitions, mapped types, and variadic tuple types.
• You'll likely need helper types to manage the state of your dependency resolution (e.g., keeping track of visited packages to detect cycles).
• Consider how you will represent the package graph itself within the types. You might need a way to map package names to their direct dependencies.
• The exact form of the error message for circular dependencies can be flexible, as long as it clearly indicates the problem. A union type with a specific literal string is a common approach.
• Think about how to represent the "list" of dependencies. Variadic tuple types are a good candidate for this.