1 files changed, 68 insertions, 54 deletions
diff --git a/tvix/eval/src/value/attrs.rs b/tvix/eval/src/value/attrs.rs
index 0551fe20d9..6802d195e8 100644
--- a/tvix/eval/src/value/attrs.rs
+++ b/tvix/eval/src/value/attrs.rs
@@ -18,7 +18,7 @@ use super::Value;
 #[cfg(test)]
 mod tests;
 
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, PartialEq)]
 enum AttrsRep {
     Empty,
     Map(BTreeMap<NixString, Value>),
@@ -71,7 +71,7 @@ impl AttrsRep {
 }
 
 #[repr(transparent)]
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, PartialEq)]
 pub struct NixAttrs(AttrsRep);
 
 impl Display for NixAttrs {
@@ -97,58 +97,6 @@ impl Display for NixAttrs {
     }
 }
 
-impl PartialEq for NixAttrs {
-    fn eq(&self, other: &Self) -> bool {
-        match (&self.0, &other.0) {
-            (AttrsRep::Empty, AttrsRep::Empty) => true,
-
-            // It is possible to create an empty attribute set that
-            // has Map representation like so: ` { ${null} = 1; }`.
-            //
-            // Preventing this would incur a cost on all attribute set
-            // construction (we'd have to check the actual number of
-            // elements after key construction). In practice this
-            // probably does not happen, so it's better to just bite
-            // the bullet and implement this branch.
-            (AttrsRep::Empty, AttrsRep::Map(map)) | (AttrsRep::Map(map), AttrsRep::Empty) => {
-                map.is_empty()
-            }
-
-            // Other specialised representations (KV ...) definitely
-            // do not match `Empty`.
-            (AttrsRep::Empty, _) | (_, AttrsRep::Empty) => false,
-
-            (
-                AttrsRep::KV {
-                    name: n1,
-                    value: v1,
-                },
-                AttrsRep::KV {
-                    name: n2,
-                    value: v2,
-                },
-            ) => n1 == n2 && v1 == v2,
-
-            (AttrsRep::Map(map), AttrsRep::KV { name, value })
-            | (AttrsRep::KV { name, value }, AttrsRep::Map(map)) => {
-                if map.len() != 2 {
-                    return false;
-                }
-
-                if let (Some(m_name), Some(m_value)) =
-                    (map.get(&NixString::NAME), map.get(&NixString::VALUE))
-                {
-                    return name == m_name && value == m_value;
-                }
-
-                false
-            }
-
-            (AttrsRep::Map(m1), AttrsRep::Map(m2)) => m1 == m2,
-        }
-    }
-}
-
 #[cfg(feature = "arbitrary")]
 mod arbitrary {
     use super::*;
@@ -337,6 +285,72 @@ impl NixAttrs {
     pub(crate) fn from_map(map: BTreeMap<NixString, Value>) -> Self {
         NixAttrs(AttrsRep::Map(map))
     }
+
+    /// Compare `self` against `other` for equality using Nix equality semantics
+    pub fn nix_eq(&self, other: &Self) -> Result<bool, ErrorKind> {
+        match (&self.0, &other.0) {
+            (AttrsRep::Empty, AttrsRep::Empty) => Ok(true),
+
+            // It is possible to create an empty attribute set that
+            // has Map representation like so: ` { ${null} = 1; }`.
+            //
+            // Preventing this would incur a cost on all attribute set
+            // construction (we'd have to check the actual number of
+            // elements after key construction). In practice this
+            // probably does not happen, so it's better to just bite
+            // the bullet and implement this branch.
+            (AttrsRep::Empty, AttrsRep::Map(map)) | (AttrsRep::Map(map), AttrsRep::Empty) => {
+                Ok(map.is_empty())
+            }
+
+            // Other specialised representations (KV ...) definitely
+            // do not match `Empty`.
+            (AttrsRep::Empty, _) | (_, AttrsRep::Empty) => Ok(false),
+
+            (
+                AttrsRep::KV {
+                    name: n1,
+                    value: v1,
+                },
+                AttrsRep::KV {
+                    name: n2,
+                    value: v2,
+                },
+            ) => Ok(n1.nix_eq(n2)? && v1.nix_eq(v2)?),
+
+            (AttrsRep::Map(map), AttrsRep::KV { name, value })
+            | (AttrsRep::KV { name, value }, AttrsRep::Map(map)) => {
+                if map.len() != 2 {
+                    return Ok(false);
+                }
+
+                if let (Some(m_name), Some(m_value)) =
+                    (map.get(&NixString::NAME), map.get(&NixString::VALUE))
+                {
+                    return Ok(name.nix_eq(m_name)? && value.nix_eq(m_value)?);
+                }
+
+                Ok(false)
+            }
+
+            (AttrsRep::Map(m1), AttrsRep::Map(m2)) => {
+                if m1.len() != m2.len() {
+                    return Ok(false);
+                }
+
+                for (k, v1) in m1 {
+                    if let Some(v2) = m2.get(k) {
+                        if !v1.nix_eq(v2)? {
+                            return Ok(false);
+                        }
+                    } else {
+                        return Ok(false);
+                    }
+                }
+                Ok(true)
+            }
+        }
+    }
 }
 
 /// In Nix, name/value attribute pairs are frequently constructed from