feat(nix): expose openspec as a consumable overlay

[jmuchovej]

Refactor the flake so the package derivation is defined once, in overlays.default, and every other output consumes it. Previously the derivation lived inline in packages.default, so anyone who wanted openspec in their own package set had to copy the derivation rather than import it.

What changed:

• Add overlays.default, a standard final: _prev: overlay that exposes pkgs.openspec. The derivation is written against final, so downstream overlay composition and overrideAttrs behave as expected.
• Route packages.{default,openspec} through the overlay via a pkgsFor helper (import nixpkgs { overlays = [ self.overlays.default ]; }), so the flake's own package resolves exactly as a consumer's would. No more duplicated build definition.
• Refresh the nixpkgs pin in flake.lock.

apps and devShells are unchanged in behaviour.

Usage — a downstream flake:

nixpkgs.overlays = [ openspec.overlays.default ];
# -> pkgs.openspec

or devenv, via devenv.yaml:

inputs:
  openspec:
    url: github:Fission-AI/OpenSpec
    overlays:
      - default

Summary by CodeRabbit

• Refactor
  • Improved the Nix flake build configuration for the OpenSpec package.
  • Standardized package builds across supported systems through the default overlay.
  • Preserved existing build behavior and package metadata.

[coderabbitai]

📝 Walkthrough

Walkthrough

The flake refactors per-system package generation around a default overlay. pkgsFor imports nixpkgs with that overlay, and package outputs expose the resulting openspec derivation as both default and openspec.

Changes

Flake package wiring

Layer / File(s)	Summary
Overlay-backed package outputs flake.nix	Per-system nixpkgs imports apply self.overlays.default, which defines the openspec derivation; package outputs now expose pkgs.openspec under both default and openspec.

Estimated code review effort: 2 (Simple) | ~10 minutes

Suggested reviewers: tabishb, clay-good, tabishb

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: exposing openspec through a consumable Nix overlay.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

🧹 Nitpick comments (1)

flake.nix (1)

51-56: 🩺 Stability & Availability | 🔵 Trivial | ⚡ Quick win

Plan a pnpm/fetcher migration for this derivation.

pnpm_9 is EOL and being phased out in Nixpkgs, while this flake is on nixos-unstable and still uses pnpm_9 plus fetchPnpmDeps with fetcherVersion = 3. Update the build/dev/dependency-fetching path to a supported pnpm version such as pnpm_11 and use fetcherVersion = 4, regenerating the pnpmDeps hash accordingly.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@flake.nix` around lines 51 - 56, Update the derivation’s pnpm
dependency-fetching and build/development configuration from pnpm_9 to a
supported version such as pnpm_11, change fetchPnpmDeps to fetcherVersion 4, and
regenerate the pnpmDeps hash for the new fetcher output. Ensure all related pnpm
references use the same supported version.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@flake.nix`:
- Around line 51-56: Update the derivation’s pnpm dependency-fetching and
build/development configuration from pnpm_9 to a supported version such as
pnpm_11, change fetchPnpmDeps to fetcherVersion 4, and regenerate the pnpmDeps
hash for the new fetcher output. Ensure all related pnpm references use the same
supported version.

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ℹ️ Review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 19d4171 and bc4abb4.

📒 Files selected for processing (1)

• flake.nix