bip32: fix FromStr implementations

Cargo.toml

@@ -13,7 +13,7 @@ edition = "2021"
 license = "Apache-2.0"
 
 [workspace.dependencies]
-amplify = "4.0.0"
+amplify = "4.0.1"
 bitcoin_hashes = "0.12.0"
 bech32 = "0.9.1"
 bp-primitives = "0.10.6"

std/src/index.rs

@@ -363,13 +363,13 @@ impl Idx for HardenedIndex {
     const MAX: Self = Self(u32::MAX);
 
     #[inline]
-    fn from_child_number(index: impl Into<u16>) -> Self { Self(index.into() as u32) }
+    fn from_child_number(child_no: impl Into<u16>) -> Self { Self(child_no.into() as u32) }
 
     #[inline]
-    fn try_from_child_number(index: impl Into<u32>) -> Result<Self, IndexError> {
-        let index = index.into();
+    fn try_from_child_number(child_no: impl Into<u32>) -> Result<Self, IndexError> {
+        let index = child_no.into();
         if index < HARDENED_INDEX_BOUNDARY {
-            Ok(Self(index - HARDENED_INDEX_BOUNDARY))
+            Ok(Self(index))
         } else {
             Err(IndexError {
                 what: "child number",
@@ -386,10 +386,13 @@ impl Idx for HardenedIndex {
     fn child_number(&self) -> u32 { self.0 }
 
     #[inline]
-    fn try_from_index(value: u32) -> Result<Self, IndexError> {
-        Self::try_from_child_number(value - HARDENED_INDEX_BOUNDARY).map_err(|_| IndexError {
+    fn try_from_index(child_no: u32) -> Result<Self, IndexError> {
+        if child_no < HARDENED_INDEX_BOUNDARY {
+            return Ok(Self(child_no));
+        }
+        Self::try_from_child_number(child_no - HARDENED_INDEX_BOUNDARY).map_err(|_| IndexError {
             what: "index",
-            invalid: value,
+            invalid: child_no,
             start: HARDENED_INDEX_BOUNDARY,
             end: u32::MAX,
         })
@@ -448,7 +451,7 @@ impl DerivationIndex {
     pub fn from_index(value: u32) -> Self {
         match value {
             0..=0x0FFFFFFF => NormalIndex(value).into(),
-            _ => HardenedIndex(value).into(),
+            _ => HardenedIndex(value - HARDENED_INDEX_BOUNDARY).into(),
         }
     }
 

std/src/path.rs

@@ -65,11 +65,11 @@ where IndexParseError: From<<I as FromStr>::Err>
 {
     type Err = DerivationParseError;
 
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        if !s.starts_with('/') {
-            return Err(DerivationParseError::InvalidFormat(s.to_owned()));
+    fn from_str(mut s: &str) -> Result<Self, Self::Err> {
+        if s.starts_with('/') {
+            s = &s[1..];
         }
-        let inner = s[1..]
+        let inner = s
             .split('/')
             .map(I::from_str)
             .collect::<Result<Vec<_>, I::Err>>()

std/src/xpub.rs

@@ -350,13 +350,25 @@ impl FromStr for XpubDescriptor {
         }
         if !d.origin.derivation.is_empty() {
             let network = if d.xpub.testnet { HardenedIndex::ONE } else { HardenedIndex::ZERO };
-            if d.origin.derivation.last() != Some(&network.into()) {
-                return Err(XpubParseError::DepthMismatch);
+            if d.origin.derivation.get(1) != Some(&network.into()) {
+                return Err(XpubParseError::NetworkMismatch);
             }
             if d.origin.derivation.last() != Some(&d.xpub.meta.child_number) {
-                return Err(XpubParseError::DepthMismatch);
+                return Err(XpubParseError::ParentMismatch);
             }
         }
         Ok(d)
     }
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn display_from_str() {
+        let s = "[643a7adc/86h/1h/0h]tpubDCNiWHaiSkgnQjuhsg9kjwaUzaxQjUcmhagvYzqQ3TYJTgFGJstVaqnu4yhtFktBhCVFmBNLQ5sN53qKzZbMksm3XEyGJsEhQPfVZdWmTE2";
+        let xpub = XpubDescriptor::from_str(s).unwrap();
+        assert_eq!(s, xpub.to_string());
+    }
+}