docs/archive/2025-11-04-flake-migration.md


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# Flake Migration Complete

**Date:** November 4, 2025  
**Change:** Migrated from shell.nix to flake.nix

## What Changed

### Files Modified

1. **Created: grasp-audit/flake.nix**
   - Based on ../ngit/flake.nix
   - Uses rust-overlay for Rust toolchain
   - Includes devShell and package outputs
   - Properly configured with dependencies

2. **Removed: grasp-audit/shell.nix**
   - Old Nix shell configuration
   - Replaced by flake.nix

3. **Updated Documentation:**
   - grasp-audit/README.md
   - grasp-audit/QUICK_START.md
   - NEXT_SESSION_QUICKSTART.md
   - SMOKE_TEST_REPORT.md
   - FILES_CREATED.md

All references to `nix-shell` changed to `nix develop`.

## New Flake Configuration

```nix
{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    rust-overlay.url = "github:oxalica/rust-overlay";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = { nixpkgs, rust-overlay, flake-utils, ... }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        overlays = [ (import rust-overlay) ];
        pkgs = import nixpkgs { inherit system overlays; };
        manifest = pkgs.lib.importTOML ./Cargo.toml;
      in with pkgs; {
        devShells.default = mkShell {
          nativeBuildInputs = [
            rust-bin.stable.latest.default
            pkg-config
            gitlint
          ];
          buildInputs = [
            openssl
          ];
          shellHook = ''
            echo "🦀 GRASP Audit development environment loaded"
            # ... helpful messages ...
            export RUST_SRC_PATH=${pkgs.rustPlatform.rustLibSrc}
          '';
        };
        
        packages.default = pkgs.rustPlatform.buildRustPackage {
          pname = manifest.package.name;
          version = manifest.package.version;
          src = ./.;
          cargoLock = { lockFile = ./Cargo.lock; };
          buildInputs = [ openssl ];
          nativeBuildInputs = [ pkg-config ];
          doCheck = false;
        };
      });
}
```

## Flake Validation

```bash
$ cd grasp-audit && nix flake show
git+file:///persistent/dcdev/clones/ngit-grasp?dir=grasp-audit
├───devShells
│   ├───aarch64-darwin
│   │   └───default: omitted (use '--all-systems' to show)
│   ├───aarch64-linux
│   │   └───default: omitted (use '--all-systems' to show)
│   ├───x86_64-darwin
│   │   └───default: omitted (use '--all-systems' to show)
│   └───x86_64-linux
│       └───default: development environment 'nix-shell'
└───packages
    ├───aarch64-darwin
    │   └───default: omitted (use '--all-systems' to show)
    ├───aarch64-linux
    │   └───default: omitted (use '--all-systems' to show)
    ├───x86_64-darwin
    │   └───default: omitted (use '--all-systems' to show)
    └───x86_64-linux
        └───default: package 'grasp-audit-0.1.0'
```

✅ Flake is valid and provides:
- Dev shell for all major systems
- Package output for grasp-audit binary

## Usage

### Old Way (shell.nix)
```bash
cd grasp-audit
nix-shell
cargo build
```

### New Way (flake.nix)
```bash
cd grasp-audit
nix develop
cargo build
```

### Additional Flake Commands

```bash
# Show flake outputs
nix flake show

# Check flake validity
nix flake check

# Build the package directly
nix build

# Run without installing
nix run

# Update flake inputs
nix flake update
```

## Benefits of Flakes

1. **Reproducibility:** Locked inputs ensure consistent builds
2. **Multi-output:** Both dev shell and package in one file
3. **Standard:** Follows modern Nix best practices
4. **Composability:** Can be used as input to other flakes
5. **Better UX:** `nix develop` is clearer than `nix-shell`

## Updated Quick Start

```bash
# 1. Enter dev environment
cd grasp-audit
nix develop

# 2. Build
cargo build

# 3. Test
cargo test --lib

# 4. Run example
cargo run --example simple_audit
```

## Documentation Updates

All documentation has been updated to use `nix develop` instead of `nix-shell`:

- ✅ grasp-audit/README.md
- ✅ grasp-audit/QUICK_START.md
- ✅ NEXT_SESSION_QUICKSTART.md
- ✅ SMOKE_TEST_REPORT.md
- ✅ FILES_CREATED.md

## Next Steps

The flake is ready to use. Next session can:

1. **Enter dev environment:**
   ```bash
   cd grasp-audit
   nix develop
   ```

2. **Build and test:**
   ```bash
   cargo build
   cargo test --lib
   ```

3. **Continue with integration tests** (once relay is set up)

## Status

- ✅ Flake created and validated
- ✅ Documentation updated
- ✅ Old shell.nix removed
- ✅ Git tracking enabled
- 🚧 Dev environment ready (first run will download dependencies)
- 🚧 Build pending (waiting for nix develop to complete)

---

**Migration Complete:** shell.nix → flake.nix ✅