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|
//! 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 super::GlobalsMap;
use genawaiter::rc::Gen;
use std::rc::Weak;
use crate::{
builtins::coerce_value_to_path,
generators::pin_generator,
observer::NoOpObserver,
value::{Builtin, Thunk},
vm::generators::{self, GenCo},
ErrorKind, SourceCode, Value,
};
async fn import_impl(
co: GenCo,
globals: Weak<GlobalsMap>,
source: SourceCode,
mut args: Vec<Value>,
) -> Result<Value, ErrorKind> {
// TODO(sterni): canon_path()?
let mut path = match coerce_value_to_path(&co, args.pop().unwrap()).await? {
Err(cek) => return Ok(Value::Catchable(Box::new(cek))),
Ok(path) => path,
};
if path.is_dir() {
path.push("default.nix");
}
if let Some(cached) = generators::request_import_cache_lookup(&co, path.clone()).await {
return Ok(cached);
}
let mut reader = generators::request_open_file(&co, path.clone()).await;
// We read to a String instead of a Vec<u8> because rnix only supports
// string source files.
let mut contents = String::new();
reader.read_to_string(&mut contents)?;
let parsed = rnix::ast::Root::parse(&contents);
let errors = parsed.errors();
let file = source.add_file(path.to_string_lossy().to_string(), contents.to_owned());
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()),
// 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"),
&source,
&file,
&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,
});
}
for warning in result.warnings {
generators::emit_warning(&co, warning).await;
}
// Compilation succeeded, we can construct a thunk from whatever it spat
// out and return that.
let res = Value::Thunk(Thunk::new_suspended(
result.lambda,
generators::request_span(&co).await,
));
generators::request_import_cache_put(&co, path, res.clone()).await;
Ok(res)
}
/// Constructs 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",
Some("Import the given file and return the Nix value it evaluates to"),
1,
move |args| {
Gen::new(|co| pin_generator(import_impl(co, globals.clone(), source.clone(), args)))
},
)
}
|
