DirMgr: Improve display for DocSource

(Also, implement Display for tor_dirclient::SourceInfo).

Cargo.lock

@@ -3446,6 +3446,7 @@ version = "0.3.0"
 dependencies = [
  "async-compression",
  "base64",
+ "derive_more",
  "futures",
  "futures-await-test",
  "hex",

crates/tor-dirclient/Cargo.toml

@@ -29,6 +29,7 @@ tor-rtcompat = { path = "../tor-rtcompat", version = "0.3.0"}
 
 async-compression = { version = "0.3.5", features = ["futures-io", "zlib"] }
 base64 = "0.13.0"
+derive_more = "0.99"
 futures = "0.3.14"
 hex = "0.4"
 http = "0.2"

crates/tor-dirclient/src/response.rs

@@ -23,7 +23,8 @@ pub struct DirResponse {
 ///
 /// We use this to remember when a request has failed, so we can
 /// abandon the circuit.
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, derive_more::Display)]
+#[display(fmt = "{cache_id} via {circuit}")]
 pub struct SourceInfo {
     /// Unique identifier for the circuit we're using
     circuit: UniqId,

crates/tor-dirmgr/src/lib.rs

@@ -255,20 +255,28 @@ impl<'a> BoolResetter<'a> {
 ///
 /// Used (for example) to report where we got a document from if it fails to
 /// parse.
-#[derive(Debug, Clone, derive_more::Display)]
+#[derive(Debug, Clone)]
 #[non_exhaustive]
 pub enum DocSource {
     /// We loaded the document from our cache.
-    #[display(fmt = "local cache")]
     LocalCache,
     /// We fetched the document from a server.
-    #[display(fmt = "directory server")]
     DirServer {
         /// Information about the server we fetched the document from.
         source: Option<SourceInfo>,
     },
 }
 
+impl std::fmt::Display for DocSource {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            DocSource::LocalCache => write!(f, "local cache"),
+            DocSource::DirServer { source: None } => write!(f, "directory server"),
+            DocSource::DirServer { source: Some(info) } => write!(f, "directory server {}", info),
+        }
+    }
+}
+
 impl<R: Runtime> DirMgr<R> {
     /// Try to load the directory from disk, without launching any
     /// kind of update process.