serde: Wrap base64::DecodeError to make base64 a private dependency

crates/ruma-serde/src/base64.rs

@@ -83,8 +83,8 @@ impl<C: Base64Config> Base64<C> {
     }
 
     /// Parse some base64-encoded data to create a `Base64` instance.
-    pub fn parse(encoded: impl AsRef<[u8]>) -> Result<Self, base64::DecodeError> {
-        base64::decode_config(encoded, C::CONF.0).map(Self::new)
+    pub fn parse(encoded: impl AsRef<[u8]>) -> Result<Self, Base64DecodeError> {
+        base64::decode_config(encoded, C::CONF.0).map(Self::new).map_err(Base64DecodeError)
     }
 }
 
@@ -118,3 +118,21 @@ impl<C: Base64Config, B: AsRef<[u8]>> Serialize for Base64<C, B> {
         serializer.serialize_str(&self.encode())
     }
 }
+
+/// An error that occurred while decoding a base64 string.
+#[derive(Clone)]
+pub struct Base64DecodeError(base64::DecodeError);
+
+impl fmt::Debug for Base64DecodeError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl fmt::Display for Base64DecodeError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl std::error::Error for Base64DecodeError {}

crates/ruma-serde/src/lib.rs

@@ -22,7 +22,7 @@ pub mod test;
 pub mod urlencoded;
 
 pub use self::{
-    base64::Base64,
+    base64::{Base64, Base64DecodeError},
     buf::{json_to_buf, slice_to_buf},
     can_be_empty::{is_empty, CanBeEmpty},
     canonical_json::{

crates/ruma-signatures/src/error.rs

@@ -1,4 +1,5 @@
 use ruma_identifiers::{EventId, RoomVersionId, ServerName};
+use ruma_serde::Base64DecodeError;
 use thiserror::Error;
 
 /// `ruma-signature`'s error type, wraps a number of other error types.
@@ -228,7 +229,7 @@ pub enum ParseError {
         string: String,
         /// The originating error.
         #[source]
-        source: base64::DecodeError,
+        source: Base64DecodeError,
     },
 }
 
@@ -254,7 +255,7 @@ impl ParseError {
     pub(crate) fn base64<T1: Into<String>, T2: Into<String>>(
         of_type: T1,
         string: T2,
-        source: base64::DecodeError,
+        source: Base64DecodeError,
     ) -> Error {
         Self::Base64 { of_type: of_type.into(), string: string.into(), source }.into()
     }