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-rw-r--r--dhall/src/imports.rs38
1 files changed, 32 insertions, 6 deletions
diff --git a/dhall/src/imports.rs b/dhall/src/imports.rs
index 20affc4..b6dd80b 100644
--- a/dhall/src/imports.rs
+++ b/dhall/src/imports.rs
@@ -11,6 +11,7 @@ use std::path::PathBuf;
pub enum ImportError {
Recursive(Import, Box<Error>),
UnexpectedImport(Import),
+ ImportCycle(ImportStack, Import),
}
/// A root from which to resolve relative imports.
@@ -21,10 +22,13 @@ pub enum ImportRoot {
type ImportCache = HashMap<Import, Normalized<'static>>;
+type ImportStack = Vec<Import>;
+
fn resolve_import(
import: &Import,
root: &ImportRoot,
import_cache: &mut ImportCache,
+ import_stack: &ImportStack,
) -> Result<Normalized<'static>, ImportError> {
use self::ImportRoot::*;
use dhall_core::FilePrefix::*;
@@ -40,7 +44,7 @@ fn resolve_import(
Here => cwd.join(path),
_ => unimplemented!("{:?}", import),
};
- Ok(load_import(&path, import_cache).map_err(|e| {
+ Ok(load_import(&path, import_cache, import_stack).map_err(|e| {
ImportError::Recursive(import.clone(), Box::new(e))
})?)
}
@@ -51,22 +55,44 @@ fn resolve_import(
fn load_import(
f: &Path,
import_cache: &mut ImportCache,
+ import_stack: &ImportStack,
) -> Result<Normalized<'static>, Error> {
- Ok(do_resolve_expr(Parsed::parse_file(f)?, import_cache)?
- .typecheck()?
- .normalize())
+ Ok(
+ do_resolve_expr(Parsed::parse_file(f)?, import_cache, import_stack)?
+ .typecheck()?
+ .normalize(),
+ )
}
fn do_resolve_expr<'a>(
Parsed(expr, root): Parsed<'a>,
import_cache: &mut ImportCache,
+ import_stack: &ImportStack,
) -> Result<Resolved<'a>, ImportError> {
let resolve =
|import: &Import| -> Result<Normalized<'static>, ImportError> {
+ if import_stack.contains(import) {
+ return Err(ImportError::ImportCycle(
+ import_stack.clone(),
+ import.clone(),
+ ));
+ }
match import_cache.get(import) {
Some(expr) => Ok(expr.clone()),
None => {
- let expr = resolve_import(import, &root, import_cache)?;
+ // Copy the import stack and push the current import
+ let mut import_stack = import_stack.clone();
+ import_stack.push(import.clone());
+
+ // Resolve the import recursively
+ let expr = resolve_import(
+ import,
+ &root,
+ import_cache,
+ &import_stack,
+ )?;
+
+ // Add the import to the cache
import_cache.insert(import.clone(), expr.clone());
Ok(expr)
}
@@ -112,7 +138,7 @@ impl<'a> Parsed<'a> {
}
pub fn resolve(self) -> Result<Resolved<'a>, ImportError> {
- crate::imports::do_resolve_expr(self, &mut HashMap::new())
+ crate::imports::do_resolve_expr(self, &mut HashMap::new(), &Vec::new())
}
#[allow(dead_code)]