chore: Update and improve nix devshell #1366

ThoFrank · 2025-11-14T17:26:59Z

Nix Development Environment Update

Nix flake inputs have been updated.
Switched to fenix to provide the rust toolchain instead of using the one provided by the nixpkgs repository (Think of it as equivalent to now using a rust toolchain provided by cargo instead of the one you would get via apt). Wich enabled the following point.
Running nix develop .#rust_minimum_version now sets up a development shell with the appropriate Minimum Supported Rust Version (MSRV) required by Tokio.
Added support for nix-direnv to allow the automatic loading of the default nix shell.

caspermeijn · 2025-11-21T14:58:21Z

.envrc

@@ -0,0 +1 @@
+use flake


Can you explain what this file does?

I explained it in the commit message:

Automatically enter nix shell via nix-direnv nix-direnv loads the nix devshell as soon as you enter the project directory (after allowing it once). [nix-direnv](https://github.com/nix-community/nix-direnv)

Basically it allows you to continue to use your system shell, but loads all the dependencies declared in the nix flake into your path. And does that automatically once you enter the prost repo directory and unload the nix shell once you exit.

I think it is super convenient. And it doesn't intrude on anybody who doesn't want to use nix-direnv

Sorry, but that doesn't have a place in this repo. I understand the flake files are useful for some people, but this is too niche.

caspermeijn · 2025-11-21T14:58:43Z

.gitignore

 Cargo.lock

-.DS_Store
+.direnv


Can you explain why this file needs to be ignored?

It's a directory created by nix-direnv and holds some caches. It's not recommended to be tracked by direnv.

Sorry, but that doesn't have a place in this repo. I understand the flake files are useful for some people, but this is too niche.

caspermeijn · 2025-11-21T15:02:00Z

flake.lock

        "owner": "NixOS",
        "repo": "nixpkgs",
-        "rev": "47e29c20abef74c45322eca25ca1550cdf5c3b50",
+        "rev": "91c9a64ce2a84e648d0cf9671274bb9c2fb9ba60",


Someone else also updated the nix files in #1307 . They have too many different changes in one PR, therefore it is not merged.

They had more changes to the lock file. Does it make sense to do that in this PR?

I have no knowledge about nix, so it is difficult for me to understand what happens here.

Nice hint! Thanks. I cherry picked @lalvesl commits as it is a lot nicer :)

Previously nix only had one input (nixpkgs). So updating the lock file resulted in a small diff. By including more inputs, updating these inputs will of course result in a bigger lock file and a bigger diff.

I'll add more info and explanations to the pr description soon.

…other develop rust_minimum_version for tests

- Add support for MSRV tokio with `nix develop .#rust_minimum_version`; - Update readme, with this nix command.

Flake lock file updates: • Updated input 'fenix': 'github:nix-community/fenix/70bb04a7de606a75ba0a2ee9d47b99802780b35d?narHash=sha256-0Xq5tZbvgZvxbbxv6kRHFuZE4Tq2za016NXh32nX0%2BQ%3D' (2025-07-10) → 'github:nix-community/fenix/2d8176c02f7be6d13578d24d5fd5049f1b46a4c5?narHash=sha256-FzUCFwXNjLnnZmVqYj/FjlBhUpat59SExflEaIGT62s%3D' (2025-11-27) • Updated input 'fenix/nixpkgs': 'github:nixos/nixpkgs/9807714d6944a957c2e036f84b0ff8caf9930bc0?narHash=sha256-LwWRsENAZJKUdD3SpLluwDmdXY9F45ZEgCb0X%2BxgOL0%3D' (2025-07-08) → 'github:nixos/nixpkgs/5ae3b07d8d6527c42f17c876e404993199144b6a?narHash=sha256-6eeL1YPcY1MV3DDStIDIdy/zZCDKgHdkCmsrLJFiZf0%3D' (2025-11-24) • Updated input 'fenix/rust-analyzer-src': 'github:rust-lang/rust-analyzer/6e3abe164b9036048dce1a3aa65a7e7e5200c0d3?narHash=sha256-USpVUdiWXDfPoh%2BagbvoBQaBhg3ZdKZgHXo/HikMfVo%3D' (2025-07-09) → 'github:rust-lang/rust-analyzer/71ddf07c1c75046df3bb496cf824de5c053d99ad?narHash=sha256-LfgFqvPz3C80VjaffSjy8lLyRWfbThhB7gE7IWXHjYU%3D' (2025-11-26) • Updated input 'nixpkgs': 'github:NixOS/nixpkgs/47e29c20abef74c45322eca25ca1550cdf5c3b50?narHash=sha256-fQ4k/hyQiH9RRPznztsA9kbcDajvwV1sRm01el6Sr3c%3D' (2024-12-31) → 'github:NixOS/nixpkgs/5c46f3bd98147c8d82366df95bbef2cab3a967ea?narHash=sha256-nXv6xb7cq%2BXpjBYIjWEGTLCqQetxJu6zvVlrqHMsCOA%3D' (2025-11-26)

nix-direnv loads the nix devshell as soon as you enter the project directory (after allowing it once). [nix-direnv](https://github.com/nix-community/nix-direnv)

Required for them to not be picked up by `cargo test`

caspermeijn

Do I understand correctly that the changes to flake.nix is just a rewrite using new language features?

I agree with the updated dependencies and updated readme. Just some nitpicks left.

caspermeijn · 2025-12-01T06:18:47Z

README.md

+
+This will drop you into a shell with all dependencies configured to build the entire project.
+
+If you want to use the minimum supported Rust version as required by Tokio [see MSRV](#msrv), run:


This is not true. Prost has its own MSRV, but applies the same policy. So this statement is incorrect.

caspermeijn · 2025-12-01T06:26:43Z

flake.nix

+        devShells."rust_minimum_version" =
+          let
+            rustpkgs = (fenix.packages.${system}.fromToolchainName {
+              name = "1.82";


Can you take this version number from Cargo.toml? Then it never has to be updated again.

caspermeijn · 2025-12-01T06:27:55Z

.envrc

@@ -0,0 +1 @@
+use flake


Sorry, but that doesn't have a place in this repo. I understand the flake files are useful for some people, but this is too niche.

caspermeijn · 2025-12-01T06:28:02Z

.gitignore

 Cargo.lock

-.DS_Store
+.direnv


Sorry, but that doesn't have a place in this repo. I understand the flake files are useful for some people, but this is too niche.

caspermeijn requested changes Nov 21, 2025

View reviewed changes

lalvesl and others added 6 commits November 27, 2025 13:27

ci-cd(flake.nix): change to use fenix rust version manager and add an…

d3204fa

…other develop rust_minimum_version for tests

chore(nix,readme):

2573b26

- Add support for MSRV tokio with `nix develop .#rust_minimum_version`; - Update readme, with this nix command.

Automatically enter nix shell via nix-direnv

2f2a927

nix-direnv loads the nix devshell as soon as you enter the project directory (after allowing it once). [nix-direnv](https://github.com/nix-community/nix-direnv)

Readme: Mark nix commands as bash code snippets

457c332

Required for them to not be picked up by `cargo test`

Bump MSRV to current MSRV in nix shell

17061ba

ThoFrank force-pushed the nix_care branch from 183bfaf to 17061ba Compare November 28, 2025 08:05

Make fenix.inputs.nixpkgs follow this flakes nixpkgs version

f8f79d4

caspermeijn requested changes Dec 1, 2025

View reviewed changes


		This will drop you into a shell with all dependencies configured to build the entire project.

		If you want to use the minimum supported Rust version as required by Tokio [see MSRV](#msrv), run:

chore: Update and improve nix devshell #1366

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chore: Update and improve nix devshell #1366

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ThoFrank commented Nov 14, 2025 •

edited

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