diff options
Diffstat (limited to 'tvix/eval/src/builtins/mod.rs')
| -rw-r--r-- | tvix/eval/src/builtins/mod.rs | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/tvix/eval/src/builtins/mod.rs b/tvix/eval/src/builtins/mod.rs index 048c8867a717..8973a25927ed 100644 --- a/tvix/eval/src/builtins/mod.rs +++ b/tvix/eval/src/builtins/mod.rs @@ -692,6 +692,86 @@ mod pure_builtins { Ok(Value::attrs(NixAttrs::from_iter(elements))) } + #[builtin("appendContext")] + #[allow(non_snake_case)] + async fn builtin_appendContext( + co: GenCo, + origin: Value, + added_context: Value, + ) -> Result<Value, ErrorKind> { + // `appendContext` is a "grow" context function. + // It cannot remove a context element, neither replace a piece of its contents. + // + // Growing context is always a safe operation, there's no loss of dependency tracking + // information. + // + // This is why this operation is not prefixed by `unsafe` and is deemed *safe*. + // Nonetheless, it is possible to craft nonsensical context elements referring + // to inexistent derivations, output paths or output names. + // + // In Nix, those nonsensical context elements are partially mitigated by checking + // that various parameters are indeed syntatically valid store paths in the context, i.e. + // starting with the same prefix as `builtins.storeDir`, or ending with `.drv`. + // In addition, if writing to the store is possible (evaluator not in read-only mode), Nix + // will realize some paths and ensures they are present in the store. + // + // In this implementation, we do none of that, no syntax checks, no realization. + // The next `TODO` are the checks that Nix implements. + let mut ctx_elements: HashSet<NixContextElement> = HashSet::new(); + let span = generators::request_span(&co).await; + let origin = origin + .coerce_to_string( + co, + CoercionKind { + strong: true, + import_paths: true, + }, + span, + ) + .await?; + let mut origin = origin.to_contextful_str()?; + + let added_context = added_context.to_attrs()?; + for (context_key, context_element) in added_context.into_iter() { + // Invariant checks: + // - TODO: context_key must be a syntactically valid store path. + // - Perform a deep force `context_element`. + let context_element = context_element.to_attrs()?; + if let Some(path) = context_element.select("path") { + if path.as_bool()? { + ctx_elements.insert(NixContextElement::Plain(context_key.to_string())); + } + } + if let Some(all_outputs) = context_element.select("allOutputs") { + if all_outputs.as_bool()? { + // TODO: check if `context_key` is a derivation path. + // This may require realization. + ctx_elements.insert(NixContextElement::Derivation(context_key.to_string())); + } + } + if let Some(some_outputs) = context_element.select("outputs") { + let some_outputs = some_outputs.to_list()?; + // TODO: check if `context_key` is a derivation path. + // This may require realization. + for output in some_outputs.into_iter() { + let output = output.to_str()?; + ctx_elements.insert(NixContextElement::Single { + derivation: context_key.to_string(), + name: output.to_string(), + }); + } + } + } + + if let Some(origin_ctx) = origin.context_mut() { + // FUTUREWORK(performance): avoid this clone + // and extend in-place. + *origin_ctx = origin_ctx.clone().join(&mut ctx_elements.into()); + } + + Ok(origin.into()) + } + #[builtin("hashString")] #[allow(non_snake_case)] async fn builtin_hashString(co: GenCo, algo: Value, s: Value) -> Result<Value, ErrorKind> { |