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2024-07-05 r/8345 feat(tvix/eval): Allow passing in an env to evaluationAspen Smith1-0/+1
Allow passing in a top-level env, a map from name to value, to evaluation. The intent is to support bound identifiers in the REPL just like upstream nix does. Getting this working involves mucking around a bit with internals - most notably, locals now only optionally have a Span (since locals don't have an easy span we can use) - and getting that working requires propagating some minor hacks to places where we currently *need* a span (and which would require too much changing now to make spans optional; my guess is that that would essentially end up making spans optional throughout the codebase). Also, some extra care has to be taken to close out the scope in the case that we do pass in an env, to avoid breaking our assumptions about the size of the stack when we return from the toplevel Change-Id: Ie475b2d3dfc72ccbf298d2a3ea28c63ac877d653 Reviewed-on: https://cl.tvl.fyi/c/depot/+/11953 Tested-by: BuildkiteCI Autosubmit: aspen <root@gws.fyi> Reviewed-by: flokli <flokli@flokli.de>
2024-04-09 r/7882 fix(tvix): Avoid buffering file into memory in builtins.hashFileConnor Brewster1-4/+5
Right now `builtins.hashFile` always reads the entire file into memory before hashing, which is not ideal for large files. This replaces `read_to_string` with `open_file` which allows calculating the hash of the file without buffering it entirely into memory. Other callers can continue to buffer into memory if they choose, but they still use the `open_file` VM request and then call `read_to_string` or `read_to_end` on the `std::io::Reader`. Fixes b/380 Change-Id: Ifa1c8324bcee8f751604b0b449feab875c632fda Reviewed-on: https://cl.tvl.fyi/c/depot/+/11236 Reviewed-by: flokli <flokli@flokli.de> Tested-by: BuildkiteCI
2024-02-20 r/7571 refactor(tvix/eval): add SourceCode directly into error typesVincent Ambo1-1/+2
With this change it's no longer necessary to track the SourceCode struct separately from the evaluation for error reporting: It's just stored directly in the errors. This also ends up resolving an issue in compiler::bindings, where we cloned the Arc containing file references way too often. In fact those clones probably compensate for all additional SourceCode clones during error construction now. Change-Id: Ice93bf161e61f8ea3d48103435e20c53e6aa8c3a Reviewed-on: https://cl.tvl.fyi/c/depot/+/10986 Reviewed-by: flokli <flokli@flokli.de> Tested-by: BuildkiteCI
2024-02-13 r/7508 feat(tvix/eval): Box Value::CatchableAspen Smith1-1/+1
This is now the only enum variant for Value that is larger than 8 bytes (it's 16 bytes), so boxing it (especially since it's not perf-critical) allows us to get the Value size down to only 16 bytes! Change-Id: I98598e2b762944448bef982e8ff7da6d6683c4aa Reviewed-on: https://cl.tvl.fyi/c/depot/+/10798 Tested-by: BuildkiteCI Reviewed-by: raitobezarius <tvl@lahfa.xyz> Autosubmit: aspen <root@gws.fyi>
2024-01-31 r/7460 fix(tvix): Represent strings as byte arraysAspen Smith1-2/+3
C++ nix uses C-style zero-terminated char pointers to represent strings internally - however, up to this point, tvix has used Rust `String` and `str` for string values. Since those are required to be valid utf-8, we haven't been able to properly represent all the string values that Nix supports. To fix that, this change converts the internal representation of the NixString struct from `Box<str>` to `BString`, from the `bstr` crate - this is a wrapper around a `Vec<u8>` with extra functions for treating that byte vector as a "morally string-like" value, which is basically exactly what we need. Since this changes a pretty fundamental assumption about a pretty core type, there are a *lot* of changes in a lot of places to make this work, but I've tried to keep the general philosophy and intent of most of the code in most places intact. Most notably, there's nothing that's been done to make the derivation stuff in //tvix/glue work with non-utf8 strings everywhere, instead opting to just convert to String/str when passing things into that - there *might* be something to be done there, but I don't know what the rules should be and I don't want to figure them out in this change. To deal with OS-native paths in a way that also works in WASM for tvixbolt, this also adds a dependency on the "os_str_bytes" crate. Fixes: b/189 Fixes: b/337 Change-Id: I5e6eb29c62f47dd91af954f5e12bfc3d186f5526 Reviewed-on: https://cl.tvl.fyi/c/depot/+/10200 Reviewed-by: tazjin <tazjin@tvl.su> Reviewed-by: flokli <flokli@flokli.de> Reviewed-by: sterni <sternenseemann@systemli.org> Autosubmit: aspen <root@gws.fyi> Tested-by: BuildkiteCI
2023-09-24 r/6650 fix(tvix/eval): fix b/281 by adding Value::CatchableAdam Joseph1-6/+6
This commit makes catchable errors a variant of Value. The main downside of this approach is that we lose the ability to use Rust's `?` syntax for propagating catchable errors. Change-Id: Ibe89438d8a70dcec29e016df692b5bf88a5cad13 Reviewed-on: https://cl.tvl.fyi/c/depot/+/9289 Reviewed-by: tazjin <tazjin@tvl.su> Autosubmit: Adam Joseph <adam@westernsemico.com> Tested-by: BuildkiteCI
2023-06-21 r/6341 fix(tvix/eval): use realpaths for import cachesterni1-0/+1
I've noticed this behavior when writing the admittedly cursed test case included in this CL. Alternatively we could use some sort of machinery using `builtins.trace`, but I don't think we capture stderr anywhere. I've elected to put this into the eval cache itself while C++ Nix does it in builtins.import already, namely via `realisePath`. We don't have an equivalent for this yet, since we don't support any kind of IfD, but we could revise that later. In any case, it seems good to encapsulate `ImportCache` in this way, as it'll also allow using file hashes as identifiers, for example. C++ Nix also does our equivalent of canon_path in `builtins.import` which we still don't, but I suspect it hardly makes a difference. Change-Id: I05004737ca2458a4c67359d9e7d9a2f2154a0a0f Reviewed-on: https://cl.tvl.fyi/c/depot/+/8839 Autosubmit: sterni <sternenseemann@systemli.org> Reviewed-by: tazjin <tazjin@tvl.su> Tested-by: BuildkiteCI
2023-03-13 r/5983 fix(tvix/eval): emit warnings from builtins.import againVincent Ambo1-4/+3
Wires up generator logic to emit warnings that already have spans attached again. Change-Id: I9f878cec3b9d4f6f7819e7c71bab7ae70bd3f08b Reviewed-on: https://cl.tvl.fyi/c/depot/+/8224 Tested-by: BuildkiteCI Reviewed-by: raitobezarius <tvl@lahfa.xyz>
2023-03-13 r/5964 refactor(tvix/eval): flatten call stack of VM using generatorsVincent Ambo1-76/+88
Warning: This is probably the biggest refactor in tvix-eval history, so far. This replaces all instances of trampolines and recursion during evaluation of the VM loop with generators. A generator is an asynchronous function that can be suspended to yield a message (in our case, vm::generators::GeneratorRequest) and receive a response (vm::generators::GeneratorResponsee). The `genawaiter` crate provides an interpreter for generators that can drive their execution and lets us move control flow between the VM and suspended generators. To do this, massive changes have occured basically everywhere in the code. On a high-level: 1. The VM is now organised around a frame stack. A frame is either a call frame (execution of Tvix bytecode) or a generator frame (a running or suspended generator). The VM has an outer loop that pops a frame off the frame stack, and then enters an inner loop either driving the execution of the bytecode or the execution of a generator. Both types of frames have several branches that can result in the frame re-enqueuing itself, and enqueuing some other work (in the form of a different frame) on top of itself. The VM will eventually resume the frame when everything "above" it has been suspended. In this way, the VM's new frame stack takes over much of the work that was previously achieved by recursion. 2. All methods previously taking a VM have been refactored into async functions that instead emit/receive generator messages for communication with the VM. Notably, this includes *all* builtins. This has had some other effects: - Some test have been removed or commented out, either because they tested code that was mostly already dead (nix_eq) or because they now require generator scaffolding which we do not have in place for tests (yet). - Because generator functions are technically async (though no async IO is involved), we lose the ability to use much of the Rust standard library e.g. in builtins. This has led to many algorithms being unrolled into iterative versions instead of iterator combinations, and things like sorting had to be implemented from scratch. - Many call sites that previously saw a `Result<..., ErrorKind>` bubble up now only see the result value, as the error handling is encapsulated within the generator loop. This reduces number of places inside of builtin implementations where error context can be attached to calls that can fail. Currently what we gain in this tradeoff is significantly more detailed span information (which we still need to bubble up, this commit does not change the error display). We'll need to do some analysis later of how useful the errors turn out to be and potentially introduce some methods for attaching context to a generator frame again. This change is very difficult to do in stages, as it is very much an "all or nothing" change that affects huge parts of the codebase. I've tried to isolate changes that can be isolated into the parent CLs of this one, but this change is still quite difficult to wrap one's mind and I'm available to discuss it and explain things to any reviewer. Fixes: b/238, b/237, b/251 and potentially others. Change-Id: I39244163ff5bbecd169fe7b274df19262b515699 Reviewed-on: https://cl.tvl.fyi/c/depot/+/8104 Reviewed-by: raitobezarius <tvl@lahfa.xyz> Reviewed-by: Adam Joseph <adam@westernsemico.com> Tested-by: BuildkiteCI
2023-01-04 r/5581 refactor(tvix/eval): streamline construction of globals/builtinsVincent Ambo1-0/+105
Previously the construction of globals (a compiler-only concept) and builtins (a (now) user-facing API) was intermingled between multiple different modules, and kind of difficult to understand. The complexity of this had grown in large part due to the implementation of `builtins.import`, which required the notorious "knot-tying" trick using Rc::new_cyclic (see cl/7097) for constructing the set of globals. As part of the new `Evaluation` API users should have the ability to bring their own builtins, and control explicitly whether or not impure builtins are available (regardless of whether they're compiled in or not). To streamline the construction and allow the new API features to work, this commit restructures things by making these changes: 1. The `tvix_eval::builtins` module is now only responsible for exporting sets of builtins. It no longer has any knowledge of whether or not certain sets (e.g. only pure, or pure+impure) are enabled, and it has no control over which builtins are globally available (this is now handled in the compiler). 2. The compiler module is now responsible for both constructing the final attribute set of builtins from the set of builtins supplied by a user, as well as for populating its globals (that is identifiers which are available at the top-level scope). 3. The `Evaluation` API now carries a `builtins` field which is populated with the pure builtins by default, and can be extended by users. 4. The `import` feature has been moved into the compiler, as a special case. In general, builtins no longer have the ability to reference the "fix point" of the globals set. This should not change any functionality, and in fact preserves minor differences between Tvix/Nix that we already had (such as `builtins.builtins` not existing). Change-Id: Icdf5dd50eb81eb9260d89269d6e08b1e67811a2c Reviewed-on: https://cl.tvl.fyi/c/depot/+/7738 Reviewed-by: sterni <sternenseemann@systemli.org> Autosubmit: tazjin <tazjin@tvl.su> Tested-by: BuildkiteCI Reviewed-by: flokli <flokli@flokli.de>