2 files changed, 75 insertions, 5 deletions

diff --git a/dhall/src/phase/binary.rs b/dhall/src/phase/binary.rs
index 16e7ce9..3c45e81 100644
--- a/dhall/src/phase/binary.rs
+++ b/dhall/src/phase/binary.rs
@@ -6,7 +6,7 @@ use std::vec;
 use dhall_syntax::map::DupTreeMap;
 use dhall_syntax::{
     rc, Expr, ExprF, FilePrefix, Hash, Import, ImportLocation, ImportMode,
-    Integer, InterpolatedText, Label, Natural, Scheme, URL, V, File
+    Integer, InterpolatedText, Label, Natural, Scheme, URL, V, FilePath
 };
 
 use crate::error::{DecodeError, EncodeError};
@@ -279,7 +279,7 @@ fn cbor_value_to_dhall(data: &cbor::Value) -> Result<DecodedExpr, DecodeError> {
                                 "import/remote/query".to_owned(),
                             ))?,
                         };
-                        let file_path: Vec<_> = rest
+                        let file_path = rest
                             .map(|s| match s.as_string() {
                                 Some(s) => Ok(s.clone()),
                                 None => Err(DecodeError::WrongFormatError(
@@ -287,7 +287,7 @@ fn cbor_value_to_dhall(data: &cbor::Value) -> Result<DecodedExpr, DecodeError> {
                                 )),
                             })
                             .collect::<Result<_, _>>()?;
-                        let path = File { file_path };
+                        let path = FilePath { file_path };
                         ImportLocation::Remote(URL {
                             scheme,
                             authority,
@@ -306,7 +306,7 @@ fn cbor_value_to_dhall(data: &cbor::Value) -> Result<DecodedExpr, DecodeError> {
                                 "import/local/prefix".to_owned(),
                             ))?,
                         };
-                        let file_path: Vec<_> = rest
+                        let file_path = rest
                             .map(|s| match s.as_string() {
                                 Some(s) => Ok(s.clone()),
                                 None => Err(DecodeError::WrongFormatError(
@@ -314,7 +314,7 @@ fn cbor_value_to_dhall(data: &cbor::Value) -> Result<DecodedExpr, DecodeError> {
                                 )),
                             })
                             .collect::<Result<_, _>>()?;
-                        let path = File { file_path };
+                        let path = FilePath { file_path };
                         ImportLocation::Local(prefix, path)
                     }
                     6 => {
diff --git a/dhall/src/phase/resolve.rs b/dhall/src/phase/resolve.rs
index 5bde68a..54a0f27 100644
--- a/dhall/src/phase/resolve.rs
+++ b/dhall/src/phase/resolve.rs
@@ -3,6 +3,7 @@ use std::path::{Path, PathBuf};
 
 use crate::error::{Error, ImportError};
 use crate::phase::{Normalized, NormalizedExpr, Parsed, Resolved};
+use dhall_syntax::{FilePath, ImportLocation, URL};
 
 type Import = dhall_syntax::Import<NormalizedExpr>;
 
@@ -105,6 +106,75 @@ pub(crate) fn skip_resolve_expr(
     Ok(Resolved(expr))
 }
 
+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,
+        }
+    }
+}
+
 #[cfg(test)]
 #[rustfmt::skip]
 mod spec_tests {