diff options
Diffstat (limited to 'tvix/eval/src/compiler')
| -rw-r--r-- | tvix/eval/src/compiler/import.rs | 105 | ||||
| -rw-r--r-- | tvix/eval/src/compiler/mod.rs | 103 |
2 files changed, 187 insertions, 21 deletions
diff --git a/tvix/eval/src/compiler/import.rs b/tvix/eval/src/compiler/import.rs new file mode 100644 index 0000000000..3a8847f2cb --- /dev/null +++ b/tvix/eval/src/compiler/import.rs @@ -0,0 +1,105 @@ +//! This module implements the Nix language's `import` feature, which +//! is exposed as a builtin in the Nix language. +//! +//! This is not a typical builtin, as it needs access to internal +//! compiler and VM state (such as the [`crate::SourceCode`] +//! instance, or observers). + +use std::rc::Weak; + +use crate::{ + observer::NoOpObserver, + value::{Builtin, BuiltinArgument, Thunk}, + vm::VM, + ErrorKind, SourceCode, Value, +}; + +use super::GlobalsMap; +use crate::builtins::coerce_value_to_path; + +/// Constructs and inserts the `import` builtin. This builtin is special in that +/// it needs to capture the [crate::SourceCode] structure to correctly track +/// source code locations while invoking a compiler. +// TODO: need to be able to pass through a CompilationObserver, too. +// TODO: can the `SourceCode` come from the compiler? +pub(super) fn builtins_import(globals: &Weak<GlobalsMap>, source: SourceCode) -> Builtin { + // This (very cheap, once-per-compiler-startup) clone exists + // solely in order to keep the borrow checker happy. It + // resolves the tension between the requirements of + // Rc::new_cyclic() and Builtin::new() + let globals = globals.clone(); + + Builtin::new( + "import", + &[BuiltinArgument { + strict: true, + name: "path", + }], + None, + move |mut args: Vec<Value>, vm: &mut VM| { + let mut path = coerce_value_to_path(&args.pop().unwrap(), vm)?; + if path.is_dir() { + path.push("default.nix"); + } + + let current_span = vm.current_light_span(); + + if let Some(cached) = vm.import_cache.get(&path) { + return Ok(cached.clone()); + } + + let contents = vm.io().read_to_string(path.clone())?; + + let parsed = rnix::ast::Root::parse(&contents); + let errors = parsed.errors(); + + let file = source.add_file(path.to_string_lossy().to_string(), contents); + + if !errors.is_empty() { + return Err(ErrorKind::ImportParseError { + path, + file, + errors: errors.to_vec(), + }); + } + + let result = crate::compiler::compile( + &parsed.tree().expr().unwrap(), + Some(path.clone()), + file, + // The VM must ensure that a strong reference to the + // globals outlives any self-references (which are + // weak) embedded within the globals. If the + // expect() below panics, it means that did not + // happen. + globals + .upgrade() + .expect("globals dropped while still in use"), + &mut NoOpObserver::default(), + ) + .map_err(|err| ErrorKind::ImportCompilerError { + path: path.clone(), + errors: vec![err], + })?; + + if !result.errors.is_empty() { + return Err(ErrorKind::ImportCompilerError { + path, + errors: result.errors, + }); + } + + // Compilation succeeded, we can construct a thunk from whatever it spat + // out and return that. + let res = Value::Thunk(Thunk::new_suspended(result.lambda, current_span)); + + vm.import_cache.insert(path, res.clone()); + + for warning in result.warnings { + vm.push_warning(warning); + } + + Ok(res) + }, + ) +} diff --git a/tvix/eval/src/compiler/mod.rs b/tvix/eval/src/compiler/mod.rs index 12fd269c2f..4a44f95691 100644 --- a/tvix/eval/src/compiler/mod.rs +++ b/tvix/eval/src/compiler/mod.rs @@ -14,6 +14,7 @@ //! mistakes early during development. mod bindings; +mod import; mod scope; use codemap::Span; @@ -30,8 +31,9 @@ use crate::observer::CompilerObserver; use crate::opcode::{CodeIdx, Count, JumpOffset, OpCode, UpvalueIdx}; use crate::spans::LightSpan; use crate::spans::ToSpan; -use crate::value::{Closure, Formals, Lambda, Thunk, Value}; +use crate::value::{Closure, Formals, Lambda, NixAttrs, Thunk, Value}; use crate::warnings::{EvalWarning, WarningKind}; +use crate::SourceCode; use self::scope::{LocalIdx, LocalPosition, Scope, Upvalue, UpvalueKind}; @@ -73,17 +75,38 @@ impl LambdaCtx { } } +/// The type of a global as used inside of the compiler. Differs from +/// Nix's own notion of "builtins" in that it can emit arbitrary code. +/// Nix's builtins are wrapped inside of this type. +pub type Global = Rc<dyn Fn(&mut Compiler, Span)>; + /// The map of globally available functions that should implicitly /// be resolvable in the global scope. -pub type GlobalsMap = HashMap<&'static str, Rc<dyn Fn(&mut Compiler, Span)>>; - -/// Functions with this type are used to construct a -/// self-referential `builtins` object; it takes a weak reference to -/// its own result, similar to how nixpkgs' overlays work. -/// Rc::new_cyclic() is what "ties the knot". The heap allocation -/// (Box) and vtable (dyn) do not impair runtime or compile-time -/// performance; they exist only during compiler startup. -pub type GlobalsMapFunc = Box<dyn FnOnce(&Weak<GlobalsMap>) -> GlobalsMap>; +type GlobalsMap = HashMap<&'static str, Rc<dyn Fn(&mut Compiler, Span)>>; + +/// Set of builtins that (if they exist) should be made available in +/// the global scope, meaning that they can be accessed not just +/// through `builtins.<name>`, but directly as `<name>`. This is not +/// configurable, it is based on what Nix 2.3 exposed. +const GLOBAL_BUILTINS: &'static [&'static str] = &[ + "abort", + "baseNameOf", + "derivation", + "derivationStrict", + "dirOf", + "fetchGit", + "fetchMercurial", + "fetchTarball", + "fromTOML", + "import", + "isNull", + "map", + "placeholder", + "removeAttrs", + "scopedImport", + "throw", + "toString", +]; pub struct Compiler<'observer> { contexts: Vec<LambdaCtx>, @@ -1183,19 +1206,57 @@ fn optimise_tail_call(chunk: &mut Chunk) { } } -/// Prepare the full set of globals from additional globals supplied -/// by the caller of the compiler, as well as the built-in globals -/// that are always part of the language. This also "ties the knot" -/// required in order for import to have a reference cycle back to -/// the globals. +/// Prepare the full set of globals available in evaluated code. These +/// are constructed from the set of builtins supplied by the caller, +/// which are made available globally under the `builtins` identifier. +/// +/// A subset of builtins (specified by [`GLOBAL_BUILTINS`]) is +/// available globally *iff* they are set. /// -/// Note that all builtin functions are *not* considered part of the -/// language in this sense and MUST be supplied as additional global -/// values, including the `builtins` set itself. -pub fn prepare_globals(additional: GlobalsMapFunc) -> Rc<GlobalsMap> { - Rc::new_cyclic(Box::new(|weak: &Weak<GlobalsMap>| { - let mut globals = additional(weak); +/// Optionally adds the `import` feature if desired by the caller. +pub fn prepare_globals( + builtins: Vec<(&'static str, Value)>, + source: SourceCode, + enable_import: bool, +) -> Rc<GlobalsMap> { + Rc::new_cyclic(Box::new(move |weak: &Weak<GlobalsMap>| { + // First step is to construct the builtins themselves as + // `NixAttrs`. + let mut builtins_under_construction: HashMap<&'static str, Value> = + HashMap::from_iter(builtins.into_iter()); + + // At this point, optionally insert `import` if enabled. To + // "tie the knot" of `import` needing the full set of globals + // to instantiate its compiler, the `Weak` reference is passed + // here. + if enable_import { + let import = Value::Builtin(import::builtins_import(weak, source)); + builtins_under_construction.insert("import", import); + } + + // Next, the actual map of globals is constructed and + // populated with (copies) of the values that should be + // available in the global scope (see [`GLOBAL_BUILTINS`]). + let mut globals: GlobalsMap = HashMap::new(); + + for global in GLOBAL_BUILTINS { + if let Some(builtin) = builtins_under_construction.get(global).cloned() { + let global_builtin: Global = + Rc::new(move |c, s| c.emit_constant(builtin.clone(), &s)); + globals.insert(global, global_builtin); + } + } + + // This is followed by the actual `builtins` attribute set + // being constructed and inserted in the global scope. + let builtins_set = + Value::attrs(NixAttrs::from_iter(builtins_under_construction.into_iter())); + globals.insert( + "builtins", + Rc::new(move |c, s| c.emit_constant(builtins_set.clone(), &s)), + ); + // Finally insert the compiler-internal "magic" builtins for top-level values. globals.insert( "true", Rc::new(|compiler, span| { |