fix: Nix flake by webbrain-one · Pull Request #108 · avelino/mcp

webbrain-one · 2026-08-13T07:02:32Z

Closes #18

Enables installing and running mcp via `nix run github:avelino/mcp`. Facilitates integration into NixOS and home-manager configurations. Closes avelino#18

qodo-code-review · 2026-08-13T07:03:28Z

< 8000 /tr>

PR Summary by Qodo

Add Nix flake to build/run mcp via nix

⚙️ Configuration changes ✨ Enhancement 🕐 Less than 10 minutes

AI Description

• Add Nix flake outputs for package, app, and dev shell.
• Enable nix run github:avelino/mcp for reproducible installs.
• Provide Rust toolchain devShell for NixOS/home-manager workflows.

Diagram

graph TD
  A["flake.nix"] --> B["flake-utils"] --> C["eachDefaultSystem"] --> D["nixpkgs"] --> E["buildRustPackage"] --> F["packages.default"]
  C --> G["apps.default"]
  C --> H["devShells.default"]
  F --> G

High-Level Assessment

The following are alternative approaches to this PR:

1. Use crane for Rust builds

➕ Often better incremental builds and caching in CI
➕ First-class patterns for Rust workspaces and dependency-only builds
➖ Adds a new flake input and slightly more setup complexity
➖ May be overkill for a single-crate CLI

2. Use naersk instead of buildRustPackage

➕ Simple configuration and commonly used for Rust flakes
➕ Can avoid some buildRustPackage-specific quirks
➖ Extra dependency and less aligned with nixpkgs standard packaging
➖ May require additional tuning for reproducibility across toolchains

Recommendation: The current approach (nixpkgs rustPlatform.buildRustPackage + Cargo.lock) is the most standard and easiest to maintain for a Rust CLI. Consider switching to crane only if CI build times/caching become a priority or if the project evolves into a workspace with more complex dependency management.

Files changed (1) +42 / -0

Other (1) +42 / -0

flake.nixIntroduce Nix flake for building, running, and developing mcp +42/-0

Introduce Nix flake for building, running, and developing mcp

• Adds a flake that imports nixpkgs and uses flake-utils to generate per-system outputs. Defines a default Rust package build from Cargo.toml/Cargo.lock, an app entrypoint for 'nix run', and a dev shell with common Rust tooling.

flake.nix

Copilot

Pull request overview

Adds a Nix flake to let Nix/NixOS users build and run mcp via standard flake workflows (e.g., nix run), addressing the packaging gap described in Issue #18.

Changes:

Introduces flake.nix with buildRustPackage packaging for the Rust CLI.
Defines a default app entry for nix run and a Rust-focused development shell.

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+  outputs = { self, nixpkgs, utils }:
+    utils.eachDefaultSystem (system:


+          cargoLock = {
+            lockFile = ./Cargo.lock;
+            allowBuiltinFetchGit = true;
+          };


qodo-code-review · 2026-08-13T07:07:25Z

Code Review by Qodo

🐞 Bugs (2) 📘 Rule violations (0) 📜 Skill insights (0)

1. No flake.lock pinning 🐞 Bug ☼ Reliability

Description

The flake declares nixpkgs/flake-utils as floating GitHub references, but there is no commit
8000
ted
flake.lock, so different users/CI runs can resolve different nixpkgs revisions over time and get
inconsistent builds. This undermines the main reproducibility benefit of introducing a flake.

Code

flake.nix[R4-7]

+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+    utils.url = "github:numtide/flake-utils";
+  };

Evidence

The flake inputs are explicitly set to moving GitHub references; without a lock file, these inputs
are not pinned to a specific revision.

flake.nix[4-7]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

### Issue description
`flake.nix` uses floating GitHub inputs (e.g., `nixos-unstable`) but the repo does not include a committed `flake.lock`, making the flake evaluation non-deterministic across time/machines.

### Issue Context
Nix flakes rely on `flake.lock` to pin exact revisions of each input. Without it, the input versions are resolved at evaluation time and can change without any repo changes.

### Fix Focus Areas
- flake.lock[1-999999]

### Suggested fix
1. Run `nix flake lock` (or `nix flake update` if you intend to refresh inputs).
2. Commit the generated `flake.lock` file.

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

2. Unneeded fetchGit fallback 🐞 Bug ⚙ Maintainability

Description

cargoLock.allowBuiltinFetchGit = true enables a fallback mechanism intended for git-based Cargo
dependencies, but for registry-sourced dependencies it provides no benefit and adds avoidable
configuration surface. Keeping it disabled unless required helps preserve stricter/reproducible
fetch behavior.

Code

flake.nix[R23-26]

+          cargoLock = {
+            lockFile = ./Cargo.lock;
+            allowBuiltinFetchGit = true;
+          };

Evidence

The PR explicitly enables allowBuiltinFetchGit. The lockfile contains registry-sourced packages
(example), which do not require this git fallback.

flake.nix[23-26]
Cargo.lock[208-213]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

### Issue description
`cargoLock.allowBuiltinFetchGit = true` is enabled in the flake. This setting is generally only needed when your `Cargo.lock` contains git dependencies that you are not pinning via `outputHashes`.

### Issue Context
The current lockfile includes registry-sourced packages (example shown in citations). If you don’t have git dependencies, leaving this enabled is unnecessary.

### Fix Focus Areas
- flake.nix[23-26]

### Suggested fix
- Remove `allowBuiltinFetchGit = true;`.
- If you do have git dependencies that require special handling, prefer adding explicit `outputHashes` (and optionally add a short comment documenting which dependency requires it).

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

Context

✅ Compliance rules (platform): 28 rules

Review mode: ⚖️ Balanced: This adds runtime build, packaging, app, and development-shell configuration; it is localized but behaviorally significant and not eligible for lite or skip.

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qodo-code-review · 2026-08-13T07:07:26Z

+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+    utils.url = "github:numtide/flake-utils";
+  };


1. No flake.lock pinning 🐞 Bug ☼ Reliability

The flake declares nixpkgs/flake-utils as floating GitHub references, but there is no committed flake.lock, so different u 8000 sers/CI runs can resolve different nixpkgs revisions over time and get inconsistent builds. This undermines the main reproducibility benefit of introducing a flake.

Agent Prompt

### Issue description `flake.nix` uses floating GitHub inputs (e.g., `nixos-unstable`) but the repo does not include a committed `flake.lock`, making the flake evaluation non-deterministic across time/machines. ### Issue Context Nix flakes rely on `flake.lock` to pin exact revisions of each input. Without it, the input versions are resolved at evaluation time and can change without any repo changes. ### Fix Focus Areas - flake.lock[1-999999] ### Suggested fix 1. Run `nix flake lock` (or `nix flake update` if you intend to refresh inputs). 2. Commit the generated `flake.lock` file.

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

qodo-code-review · 2026-08-13T07:07:27Z

+          cargoLock = {
+            lockFile = ./Cargo.lock;
+            allowBuiltinFetchGit = true;
+          };


2. Unneeded fetchgit fallback 🐞 Bug ⚙ Maintainability

cargoLock.allowBuiltinFetchGit = true enables a fallback mechanism intended for git-based Cargo dependencies, but for registry-sourced dependencies it provides no benefit and adds avoidable configuration surface. Keeping it disabled unless required helps preserve stricter/reproducible fetch behavior.

Agent Prompt

### Issue description `cargoLock.allowBuiltinFetchGit = true` is enabled in the flake. This setting is generally only needed when your `Cargo.lock` contains git dependencies that you are not pinning via `outputHashes`. ### Issue Context The current lockfile includes registry-sourced packages (example shown in citations). If you don’t have git dependencies, leaving this enabled is unnecessary. ### Fix Focus Areas - flake.nix[23-26] ### Suggested fix - Remove `allowBuiltinFetchGit = true;`. - If you do have git dependencies that require special handling, prefer adding explicit `outputHashes` (and optionally add a short comment documenting which dependency requires it).

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

qodo-code-review · 2026-08-13T07:08:18Z

Qodo Fixer

✅ Merged (0) · ☑ Fixed (0)

Process

No fixes were applied (no_fixes_applied)

avelino · 2026-10-07T13:34:15Z

Thanks for adding this, and sorry for the slow reply. Happy to have Nix support. A few small things before merging: could you commit the flake.lock so builds are reproducible, drop defaultPackage (packages.default already covers it), and add a short install line to the README, something like nix run github:avelino/mcp? Then it's good to go.

Add Nix flake

cd9de21

Enables installing and running mcp via `nix run github:avelino/mcp`. Facilitates integration into NixOS and home-manager configurations. Closes avelino#18

Copilot AI lite review requested due to automatic review settings August 13, 2026 07:02

webbrain-one mentioned this pull request Aug 13, 2026

Nix flake #18

Closed

Copilot started reviewing on behalf of webbrain-one August 13, 2026 07:03

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qodo-code-review Bot added the 🕐 Less than 10 minutes label Aug 13, 2026

Copilot AI reviewed Aug 13, 2026

View reviewed changes

Comment thread flake.nix

Comment on lines +9 to +10

outputs = { self, nixpkgs, utils }:

utils.eachDefaultSystem (system:

Comment thread flake.nix

Comment on lines +23 to +26

cargoLock = {

lockFile = ./Cargo.lock;

allowBuiltinFetchGit = true;

};

qodo-code-review Bot reviewed Aug 13, 2026

View reviewed changes

avelino merged commit 30456e4 into avelino:main Oct 13, 2026
1 check passed

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fix: Nix flake - #108

fix: Nix flake#108
avelino merged 1 commit into
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		outputs = { self, nixpkgs, utils }:
		utils.eachDefaultSystem (system:

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