fix(descriptor): reject bare descriptors in check_wallet_descriptor

Bare descriptors (e.g. pk()) have no standard address form. Passing one
to the wallet would not be caught at creation time and would cause panics
later when address derivation is attempted.

Add an UnsupportedDescriptorType variant to DescriptorError and check for
DescriptorType::Bare in check_wallet_descriptor, returning the new error
before the descriptor reaches wallet internals.

Closes #54

Author: tharu-jwd

src/descriptor/error.rs

@@ -44,6 +44,8 @@ pub enum Error {
     Hex(bitcoin::hex::HexToBytesError),
     /// The provided wallet descriptors are identical
     ExternalAndInternalAreTheSame,
+    /// Descriptor type is not supported by the wallet (e.g. bare scripts have no address form)
+    UnsupportedDescriptorType,
 }
 
 impl From<crate::keys::KeyError> for Error {
@@ -84,6 +86,12 @@ impl fmt::Display for Error {
             Self::ExternalAndInternalAreTheSame => {
                 write!(f, "External and internal descriptors are the same")
             }
+            Self::UnsupportedDescriptorType => {
+                write!(
+                    f,
+                    "Descriptor type is not supported by the wallet; bare scripts have no address form"
+                )
+            }
         }
     }
 }

src/descriptor/mod.rs

@@ -321,6 +321,12 @@ pub(crate) fn check_wallet_descriptor(
         ));
     }
 
+    // Reject bare descriptors: they have no standard address form and would cause panics
+    // inside the wallet when address derivation is attempted.
+    if descriptor.desc_type() == DescriptorType::Bare {
+        return Err(DescriptorError::UnsupportedDescriptorType);
+    }
+
     // Run miniscript's sanity check, which will look for duplicated keys and other potential
     // issues.
     descriptor.sanity_check()?;
@@ -912,6 +918,16 @@ mod test {
         let result = check_wallet_descriptor(&descriptor);
 
         assert!(result.is_err());
+
+        // Bare descriptors (e.g. pk()) have no standard address form and must be rejected.
+        let descriptor = Descriptor::<DescriptorPublicKey>::from_str(
+            "pk(tpubD6NzVbkrYhZ4XHndKkuB8FifXm8r5FQHwrN6oZuWCz13qb93rtgKvD4PQsqC4HP4yhV3tA2fqr2RbY5mNXfM7RxXUoeABoDtsFUq2zJq6YK/0/*)",
+        )
+        .expect("must parse");
+        assert_matches!(
+            check_wallet_descriptor(&descriptor),
+            Err(DescriptorError::UnsupportedDescriptorType)
+        );
     }
 
     #[test]