diff options
| -rw-r--r-- | dhall/src/imports.rs | 38 |
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)] |