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use std::collections::HashMap;
use std::path::{Path, PathBuf};
use crate::error::ErrorBuilder;
use crate::error::{Error, ImportError};
use crate::semantics::{mkerr, Hir, HirKind, NameEnv};
use crate::syntax;
use crate::syntax::{BinOp, Expr, ExprKind, FilePath, ImportLocation, URL};
use crate::{Parsed, ParsedExpr, Resolved};
type Import = syntax::Import<Hir>;
/// A root from which to resolve relative imports.
#[derive(Debug, Clone, PartialEq, Eq)]
pub(crate) enum ImportRoot {
LocalDir(PathBuf),
}
type ImportCache = HashMap<Import, Hir>;
pub(crate) type ImportStack = Vec<Import>;
struct ResolveEnv {
cache: ImportCache,
stack: ImportStack,
}
impl ResolveEnv {
pub fn new() -> Self {
ResolveEnv {
cache: HashMap::new(),
stack: Vec::new(),
}
}
pub fn handle_import(
&mut self,
import: Import,
mut do_resolve: impl FnMut(&mut Self, &Import) -> Result<Hir, Error>,
) -> Result<Hir, Error> {
if self.stack.contains(&import) {
return Err(
ImportError::ImportCycle(self.stack.clone(), import).into()
);
}
Ok(match self.cache.get(&import) {
Some(expr) => expr.clone(),
None => {
// Push the current import on the stack
self.stack.push(import.clone());
// Resolve the import recursively
let expr = do_resolve(self, &import)?;
// Remove import from the stack.
self.stack.pop();
// Add the import to the cache
self.cache.insert(import, expr.clone());
expr
}
})
}
}
fn resolve_one_import(
env: &mut ResolveEnv,
import: &Import,
root: &ImportRoot,
) -> Result<Hir, Error> {
use self::ImportRoot::*;
use syntax::FilePrefix::*;
use syntax::ImportLocation::*;
let cwd = match root {
LocalDir(cwd) => cwd,
};
match &import.location {
Local(prefix, path) => {
let path_buf: PathBuf = path.file_path.iter().collect();
let path_buf = match prefix {
// TODO: fail gracefully
Parent => cwd.parent().unwrap().join(path_buf),
Here => cwd.join(path_buf),
_ => unimplemented!("{:?}", import),
};
Ok(load_import(env, &path_buf)?)
}
_ => unimplemented!("{:?}", import),
}
}
fn load_import(env: &mut ResolveEnv, f: &Path) -> Result<Hir, Error> {
let parsed = Parsed::parse_file(f)?;
Ok(resolve_with_env(env, parsed)?
.typecheck()?
.normalize()
.to_hir())
}
/// Traverse the expression, handling import alternatives and passing
/// found imports to the provided function.
fn traverse_resolve_expr(
name_env: &mut NameEnv,
expr: &Expr,
f: &mut impl FnMut(Import) -> Result<Hir, Error>,
) -> Result<Hir, Error> {
let kind = match expr.kind() {
ExprKind::Var(var) => match name_env.unlabel_var(&var) {
Some(v) => HirKind::Var(v),
None => mkerr(
ErrorBuilder::new(format!("unbound variable `{}`", var))
.span_err(expr.span(), "not found in this scope")
.format(),
)?,
},
ExprKind::BinOp(BinOp::ImportAlt, l, r) => {
return match traverse_resolve_expr(name_env, l, f) {
Ok(l) => Ok(l),
Err(_) => {
match traverse_resolve_expr(name_env, r, f) {
Ok(r) => Ok(r),
// TODO: keep track of the other error too
Err(e) => Err(e),
}
}
};
}
kind => {
let kind = kind.traverse_ref_maybe_binder(|l, e| {
if let Some(l) = l {
name_env.insert_mut(l);
}
let hir = traverse_resolve_expr(name_env, e, f)?;
if let Some(_) = l {
name_env.remove_mut();
}
Ok::<_, Error>(hir)
})?;
match kind {
ExprKind::Import(import) => f(import)?.kind().clone(),
kind => HirKind::Expr(kind),
}
}
};
Ok(Hir::new(kind, expr.span()))
}
fn resolve_with_env(
env: &mut ResolveEnv,
parsed: Parsed,
) -> Result<Resolved, Error> {
let Parsed(expr, root) = parsed;
let resolved =
traverse_resolve_expr(&mut NameEnv::new(), &expr, &mut |import| {
env.handle_import(import, |env, import| {
resolve_one_import(env, import, &root)
})
})?;
Ok(Resolved(resolved))
}
pub(crate) fn resolve(parsed: Parsed) -> Result<Resolved, Error> {
resolve_with_env(&mut ResolveEnv::new(), parsed)
}
pub(crate) fn skip_resolve(expr: &ParsedExpr) -> Result<Hir, Error> {
traverse_resolve_expr(&mut NameEnv::new(), expr, &mut |import| {
Err(ImportError::UnexpectedImport(import).into())
})
}
pub trait Canonicalize {
fn canonicalize(&self) -> Self;
}
impl Canonicalize for FilePath {
fn canonicalize(&self) -> FilePath {
let mut file_path = Vec::new();
let mut file_path_components = self.file_path.clone().into_iter();
loop {
let component = file_path_components.next();
match component.as_ref() {
// ───────────────────
// canonicalize(ε) = ε
None => break,
// canonicalize(directory₀) = directory₁
// ───────────────────────────────────────
// canonicalize(directory₀/.) = directory₁
Some(c) if c == "." => continue,
Some(c) if c == ".." => match file_path_components.next() {
// canonicalize(directory₀) = ε
// ────────────────────────────
// canonicalize(directory₀/..) = /..
None => file_path.push("..".to_string()),
// canonicalize(directory₀) = directory₁/..
// ──────────────────────────────────────────────
// canonicalize(directory₀/..) = directory₁/../..
Some(ref c) if c == ".." => {
file_path.push("..".to_string());
file_path.push("..".to_string());
}
// canonicalize(directory₀) = directory₁/component
// ─────────────────────────────────────────────── ; If "component" is not
// canonicalize(directory₀/..) = directory₁ ; ".."
Some(_) => continue,
},
// canonicalize(directory₀) = directory₁
// ───────────────────────────────────────────────────────── ; If no other
// canonicalize(directory₀/component) = directory₁/component ; rule matches
Some(c) => file_path.push(c.clone()),
}
}
FilePath { file_path }
}
}
impl<SE: Copy> Canonicalize for ImportLocation<SE> {
fn canonicalize(&self) -> ImportLocation<SE> {
match self {
ImportLocation::Local(prefix, file) => {
ImportLocation::Local(*prefix, file.canonicalize())
}
ImportLocation::Remote(url) => ImportLocation::Remote(URL {
scheme: url.scheme,
authority: url.authority.clone(),
path: url.path.canonicalize(),
query: url.query.clone(),
headers: url.headers.clone(),
}),
ImportLocation::Env(name) => ImportLocation::Env(name.to_string()),
ImportLocation::Missing => ImportLocation::Missing,
}
}
}
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