Don't pin the rust compiler used to build wasmtime

[bryceberger]

This allows building with nixpkgs versions that do not provide specifically rust_1_89.

Motivation

I pin nixpkgs in my config, then set determinate.inputs.nixpkgs.follows = "nixpkgs". The nixpkgs I have pinned does not provide rust_1_89.

Context

Added in #309, specifically d049bf3. I don't see any specific reasoning in the PR for pinning the compiler version.

Upstream nixpkgs just uses bare rustPlatform: https://github.com/NixOS/nixpkgs/blob/18451d41a40765408adb9f3f20e76c151fdfa307/pkgs/by-name/wa/wasmtime/package.nix

Summary by CodeRabbit

• Chores
  • Updated the build configuration toolchain for improved compatibility and maintainability.

[coderabbitai]

📝 Walkthrough

Walkthrough

Updated the Nix package derivation in packaging/wasmtime.nix to directly reference rustPlatform.buildRustPackage instead of accessing it through the rust_1_89.packages.stable path, streamlining the module import chain.

Changes

Cohort / File(s)	Summary
Nix Package Configuration packaging/wasmtime.nix	Simplified rustPlatform reference by replacing nested rust_1_89.packages.stable.rustPlatform.buildRustPackage with direct rustPlatform.buildRustPackage call, reducing import path depth.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰 The rabbit hops with glee,
Simplifying paths wild and free,
No more nested calls to trace,
rustPlatform shines in its rightful place!
Less is more, we all agree! 🌟

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically summarizes the main change: removing the pinned Rust compiler version (rust_1_89) from the wasmtime build configuration, which directly corresponds to the changeset that replaces rust_1_89.packages.stable.rustPlatform with rustPlatform.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[cole-h]

LGTM, but I review-requested Eelco to see if there was a specific reason.

[cole-h]

Ah, that's why:

wasmtime> error: rustc 1.86.0 is not supported by the following packages:
wasmtime>   cranelift-assembler-x64@0.127.2 requires rustc 1.89.0
wasmtime>   cranelift-assembler-x64@0.127.2 requires rustc 1.89.0
wasmtime>   cranelift-assembler-x64@0.127.2 requires rustc 1.89.0
wasmtime>   cranelift-assembler-x64-meta@0.127.2 requires rustc 1.89.0
wasmtime>   cranelift-bforest@0.127.2 requires rustc 1.89.0
wasmtime>   cranelift-bitset@0.127.2 requires rustc 1.89.0
wasmtime>   cranelift-bitset@0.127.2 requires rustc 1.89.0
wasmtime>   cranelift-codegen@0.127.2 requires rustc 1.89.0
wasmtime>   cranelift-codegen@0.127.2 requires rustc 1.89.0
wasmtime>   cranelift-codegen@0.127.2 requires rustc 1.89.0
wasmtime>   cranelift-codegen-meta@0.127.2 requires rustc 1.89.0
wasmtime>   cranelift-codegen-shared@0.127.2 requires rustc 1.89.0
wasmtime>   cranelift-codegen-shared@0.127.2 requires rustc 1.89.0
wasmtime>   cranelift-control@0.127.2 requires rustc 1.89.0
wasmtime>   cranelift-entity@0.127.2 requires rustc 1.89.0
wasmtime>   cranelift-frontend@0.127.2 requires rustc 1.89.0
wasmtime>   cranelift-isle@0.127.2 requires rustc 1.89.0
wasmtime>   cranelift-isle@0.127.2 requires rustc 1.89.0
wasmtime>   cranelift-isle@0.127.2 requires rustc 1.89.0
wasmtime>   cranelift-native@0.127.2 requires rustc 1.89.0
wasmtime>   cranelift-srcgen@0.127.2 requires rustc 1.89.0
wasmtime>   pulley-interpreter@40.0.2 requires rustc 1.89.0
wasmtime>   pulley-interpreter@40.0.2 requires rustc 1.89.0
wasmtime>   pulley-macros@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-c-api@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-c-api-impl@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-c-api-impl@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-c-api-impl@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-environ@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-internal-c-api-macros@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-internal-component-macro@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-internal-component-macro@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-internal-component-macro@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-internal-component-util@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-internal-component-util@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-internal-cranelift@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-internal-fiber@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-internal-fiber@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-internal-fiber@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-internal-jit-icache-coherence@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-internal-math@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-internal-slab@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-internal-unwinder@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-internal-unwinder@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-internal-unwinder@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-internal-versioned-export-macros@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-internal-wit-bindgen@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-wasi@40.0.2 requires rustc 1.89.0
wasmtime>   wasmtime-wasi-io@40.0.2 requires rustc 1.89.0
wasmtime>   wiggle@40.0.2 requires rustc 1.89.0
wasmtime>   wiggle-generate@40.0.2 requires rustc 1.89.0
wasmtime>   wiggle-macro@40.0.2 requires rustc 1.89.0
wasmtime>   wiggle-macro@40.0.2 requires rustc 1.89.0
wasmtime>   wiggle-macro@40.0.2 requires rustc 1.89.0

So it looks like we do need to specify 1.89... Maybe there's some niceness we can do so that it works for both of us. (I'll look in the morning.)

[bryceberger]

Ah, it was pinned to a newer version. I'll admit I just unpinned it and verified it started building... 😓

One possible solution is to update the nixpkgs pin from 25.05 to 25.11, but there may be other reasons not to do that.

If you do want to update the pin to 25.11, I made a branch with the changes I think are required at https://github.com/bryceberger/detnix/tree/nixpkgs-25.11 (permalink: https://github.com/bryceberger/detnix/commits/56fb7a232690c2bd30542587e6f2423c09782bed). Not sure if they're all the right changes, will leave that to someone with more knowledge. Just kept poking things until nix flake check worked on my machine.

[RossComputerGuy]

I think this could definitely help fix some of the issues I saw in #323. I think the way we can get around bumping nixpkgs is by using crane. I think that would be more beneficial, especially for #323.