Road to Nimble 1.0.0

[jmgomez]

Nimble 1.0.0 Overview

The new Nimble 1.0.0 introduces a SAT-based design with a brand-new greenfield code path, reducing complexity and improving maintainability.
local dependency resolution will be the new default.

Key Changes

• No Nim required initially – Resolves the Nim version from compilation.nim; no VM fallback for Nim itself.
• Centralized, upfront resolution – Solves dependencies globally at the start, replacing the legacy greedy approach.
• Single-pass by default – Uses a declarative parser for most cases; falls back to the VM parser (with the resolved Nim) only for tricky packages or require statements inside control flow.
• Local dependencies by default – Ensures predictable behavior and avoids global pollution.
• Ensure compatibility with fallback – Guarantees backward compatibility with existing projects.
• Lay the groundwork for a new choosenim alternative – Provides the foundation for future Nim version management improvements.
• Improve speed – Declarative parser is faster than the VM parser, along with faster Nim selection and other optimizations.
• Introduce “prefer” for Nim – Uses the system Nim version if possible, selecting older dependency versions when needed.
  Example: If system Nim is 2.0 but the latest package B requires 2.2, Nimble will choose an earlier package B that works with 2.0.
• Normalize dependencies – Resolves package URLs to names before solving so different URLs for the same package aren’t treated as separate dependencies.

Milestones

• Implement upfront SATPass (main goal; required major refactor)
• Remove requirement for Nim at startup
• Make local dependencies the default
• Improve speed
  • Add benchmarks
  • Optimize code paths
  • Enable parallel downloads
  • Expand cache
• Ensure full backward compatibility with legacy flag (preserves old behavior)
• Implement dependency normalization
• Add prefer system Nim feature
• Support file paths for local requires
• Improve nimble develop workflow
• Add Nim version management (e.g. nimble install nim@2.0.8)
• Complete miscellaneous tasks:
  • Update `nimble dump
  • nimble update nimble
  • Battle test Nim selection
• Triage issue tracker

Postponed to next version (1.2.x)

• Complete declarative parser (missing platform selection for when) PR already done: Adds support some when expressions in the declarative parser. #1457 (likely will require changes though)
• Lazy Tagged Versions Mechanism (Lazy Tagged Versions Mechanism #1478)