History

Vincent Ambo 8724d2fff8 fix(tvix/eval): use top-level span for `force_with_output` When forcing thunks in `force_with_output`, the call stack of the VM is actually empty (as the calls are synthetic and no longer part of the evaluation of the top-level expression). This means that Tvix crashed when constructing error spans for the `fallible` macro, as the assumption of there being an enclosing span was violated. To work around this, we instead pass the span for the whole top-level expression to force_for_output and set this as the span for the enclosing error chain. Existing output logic will already avoid printing the entire expression as an error span. This fixes b/213. Change-Id: I93978e0deaf5bcb0f47a6fa95b3f5bebef5bad4c Reviewed-on: https://cl.tvl.fyi/c/depot/+/7052 Autosubmit: tazjin <tazjin@tvl.su> Tested-by: BuildkiteCI Reviewed-by: grfn <grfn@gws.fyi>		2022-10-22 17:01:41 +00:00
..
benches	refactor(tvix/eval): use Clap for arg+env parsing	2022-09-18 22:08:43 +00:00
docs	fix(tvix/eval): bring foldl' strictness in line with C++ Nix	2022-10-15 14:12:23 +00:00
proptest-regressions/value	test(tvix/eval): Add tests for the Eq laws of Value	2022-09-18 17:57:09 +00:00
src	fix(tvix/eval): use top-level span for `force_with_output`	2022-10-22 17:01:41 +00:00
tests	feat(tvix/eval): Allow adding strings to paths	2022-10-10 20:23:41 +00:00
.envrc	chore(tvix/eval): add simple .envrc / shell.nix	2022-09-17 17:31:08 +00:00
.gitignore	feat(tvix/eval): check in generated project skeleton	2022-08-12 12:34:29 +00:00
.skip-subtree	feat(tvix/tests): check in Nix' language test suite	2022-08-24 21:25:41 +00:00
Cargo.lock	feat(tvix/eval): add an AST pretty-printing module	2022-10-16 12:26:56 +00:00
Cargo.toml	test(tvix/eval): enable nix_tests by default	2022-10-20 02:28:38 +00:00
default.nix	test(tvix): nix-planned test verification using C++ Nix 2.3 and 2.11	2022-10-20 02:28:38 +00:00
README.md	docs(tvix/eval): explain where to find the site-specific `mg` tool	2022-10-13 18:41:02 +00:00
shell.nix	chore(tvix/eval): add rustfmt to the shell	2022-09-18 23:19:54 +00:00

README.md

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). The mg command is found in /tools/magrathea.

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.