083fc1dbe5
This is necessary because builtins.compareVersions compares versions in a subtly not-quite-but-still-lexicographical way: `pre` for example can have an effect if it is post-fixed: `2.3 < 2.3pre`. This is a violation of the rule that in a lexicographical ordering, the longer string is considered greater if they are otherwise equal. builtins.compareVersion is comparing lexicographically though, if you do the following transformation beforehand: 2.3 --split--> [ "2" "3" ] --append--> [ "2" "3" "" ] 2.3pre --split--> [ "2" "3" "pre" ] --append--> [ "2" "3" "pre" "" ] Comparing the transformed version is then done lexicographically: 2.3 < 2.3.0pre since [ "2" "3" "" ] < [ "2" "3" "0" "pre" ] Here, the `pre` rule never comes into effect because no comparison on it happens, instead we use the longer string rule of a lexicographical comparison. In the C++ codebase, the reason for this behavior is that the iterator-esque construct they use always yields the empty string before it exposes it has been fully consumed. This is probably intentional to support the postfixed `pre` which is, for example, used by NixOS versions (e.g. unstable post 22.05 is 22.11-pre). We replicate this behavior using the `Chain` iterator in `VersionPartsIter::new_for_cmp`. Change-Id: I021c69aa27b0b7deb949dffe50ed18b6de3a7b1f Reviewed-on: https://cl.tvl.fyi/c/depot/+/6720 Tested-by: BuildkiteCI Reviewed-by: tazjin <tazjin@tvl.su> |
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| .. | ||
| benches | ||
| docs | ||
| proptest-regressions/value | ||
| src | ||
| tests | ||
| .envrc | ||
| .gitignore | ||
| .skip-subtree | ||
| Cargo.lock | ||
| Cargo.toml | ||
| default.nix | ||
| README.md | ||
| shell.nix | ||
Tvix Evaluator
This project implements an interpreter for the Nix programming language. You can experiment with an online version of the evaluator: tvixbolt.
The interpreter aims to be compatible with nixpkgs, on the
foundation of Nix 2.3.
Important note: The evaluator is not yet feature-complete, and while the core mechanisms (compiler, runtime, ...) have stabilised somewhat, a lot of components are still changing rapidly.
Please contact TVL with any questions you might have.
Building the evaluator
If you are in a full checkout of the TVL depot, you can simply run mg build in this directory (or mg build //tvix/eval from anywhere in
the repo).
Important note: We only use and test Nix builds of our software against Nix 2.3. There are a variety of bugs and subtle problems in newer Nix versions which we do not have the bandwidth to address, builds in newer Nix versions may or may not work.
The evaluator can also be built with standard Rust tooling (i.e.
cargo build).
If you would like to clone only the evaluator and build it directly with Rust tooling, you can do:
git clone https://code.tvl.fyi/depot.git:/tvix/eval.git tvix-eval
cd tvix-eval && cargo build
Nix test suite
C++ Nix implements a language test suite in the form of Nix source code files, and their expected output. The coverage of this test suite is not complete, but we intend to be compatible with it.
We have ported the test suite to Tvix, but do not run it by default as we are not yet compatible with it.
You can run the test suite by enabling the nix_tests feature in
Cargo:
cargo test --features nix_tests
rnix-parser
Tvix is written in memory of jD91mZM2, the author of rnix-parser who sadly passed away.
Tvix makes heavy use of rnix-parser in its bytecode compiler. The parser is now maintained by Nix community members.