d5ec9a0c6f
Use bolt.tvix.dev everywhere. Change-Id: Ifebbea60058418c12cde20a2a3879a8a7f5f830c Reviewed-on: https://cl.tvl.fyi/c/depot/+/11022 Reviewed-by: flokli <flokli@flokli.de> Autosubmit: flokli <flokli@flokli.de> Tested-by: BuildkiteCI Reviewed-by: tazjin <tazjin@tvl.su>
92 lines
3.6 KiB
Markdown
92 lines
3.6 KiB
Markdown
Tvix Evaluator
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==============
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This project implements an interpreter for the Nix programming
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language. You can experiment with an online version of the evaluator:
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[tvixbolt][].
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The interpreter aims to be compatible with `nixpkgs`, on the
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foundation of Nix 2.3.
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**Important note:** The evaluator is not yet feature-complete, and
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while the core mechanisms (compiler, runtime, ...) have stabilised
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somewhat, a lot of components are still changing rapidly.
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Please contact [TVL](https://tvl.fyi) with any questions you might
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have.
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## Building tvix-eval
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Please check the `README.md` one level up for instructions on how to build this.
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The evaluator itself can also be built with standard Rust tooling (i.e. `cargo
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build`).
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If you would like to clone **only** the evaluator and build it
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directly with Rust tooling, you can do:
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```bash
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git clone https://code.tvl.fyi/depot.git:/tvix/eval.git tvix-eval
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cd tvix-eval && cargo build
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```
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## Tests
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Tvix currently has three language test suites for tvix-eval:
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* `nix_tests` and `tvix_tests` are based on the same mechanism
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borrowed from the C++ Nix implementation. They consist of
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Nix files as well as expected output (if applicable).
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The test cases are split into four categories:
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`eval-okay` (evaluates successfully with the expected output),
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`eval-fail` (fails to evaluate, no expected output),
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`parse-okay` (expression parses successfully, no expected output)
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and `parse-fail` (expression fails to parse, no expected output).
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Tvix currently ignores the last two types of test cases, since
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it doesn't implement its own parser.
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Both test suites have a `notyetpassing` directory. All test cases
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in here test behavior that is not yet supported by Tvix. They are
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considered to be expected failures, so you can't forget to move
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them into the test suite proper when fixing the incompatibility.
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Additionally, separate targets in the depot pipeline, under
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`//tvix/verify-lang-tests`, check both test suites (including
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`notyetpassing` directories) against
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C++ Nix 2.3 and the default C++ Nix version in nixpkgs.
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This way we can prevent accidentally introducing test cases
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for behavior that C++ Nix doesn't exhibit.
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* `nix_tests` has the test cases from C++ Nix's language test
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suite and is sporadically updated by manually syncing the
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directories. The `notyetpassing` directory shows how far
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it is until we pass it completely.
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* `tvix_tests` contains test cases written by the Tvix contributors.
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Some more or less duplicate test cases contained in `nix_tests`,
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but many cover relevant behavior that isn't by `nix_tests`.
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Consequently, it'd be nice to eventually merge the two test
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suites into a jointly maintained, common Nix language test suite.
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It also has a `notyetpassing` directory for missing behavior
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that is discovered while working on Tvix and isn't covered by the
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`nix_tests` suite.
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* `nix_oracle` can evaluate Nix expressions in Tvix and compare the
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result against C++ Nix (2.3) directly. Eventually it should gain
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the ability to property test generated Nix expressions.
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An additional feature is that it can evaluate expressions without
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`--strict`, so thunking behavior can be verified more easily.
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## rnix-parser
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Tvix is written in memory of jD91mZM2, the author of [rnix-parser][]
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who sadly [passed away][rip].
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Tvix makes heavy use of rnix-parser in its bytecode compiler. The
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parser is now maintained by Nix community members.
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[rnix-parser]: https://github.com/nix-community/rnix-parser
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[rip]: https://www.redox-os.org/news/open-source-mental-health/
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[tvixbolt]: https://bolt.tvix.dev/
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