Replace all unreachable! with proper error handling in gix-url

Co-authored-by: Byron <63622+Byron@users.noreply.github.com>

Author: Copilot

gix-url/src/lib.rs

@@ -353,7 +353,12 @@ impl Url {
                 out.write_all(host.as_bytes())?;
             }
             (None, None) => {}
-            (Some(_user), None) => unreachable!("BUG: should not be possible to have a user but no host"),
+            (Some(_user), None) => {
+                return Err(std::io::Error::new(
+                    std::io::ErrorKind::InvalidData,
+                    "Invalid URL structure: user specified without host"
+                ));
+            }
         }
         if let Some(port) = &self.port {
             write!(out, ":{port}")?;
@@ -377,7 +382,12 @@ impl Url {
                 out.write_all(host.as_bytes())?;
             }
             (None, None) => {}
-            (Some(_user), None) => unreachable!("BUG: should not be possible to have a user but no host"),
+            (Some(_user), None) => {
+                return Err(std::io::Error::new(
+                    std::io::ErrorKind::InvalidData,
+                    "Invalid URL structure: user specified without host"
+                ));
+            }
         }
         assert!(self.port.is_none(), "BUG: cannot serialize port in alternative form");
         if self.scheme == Scheme::Ssh {

gix-url/src/parse.rs

@@ -28,11 +28,15 @@ pub enum Error {
     MissingRepositoryPath { url: BString, kind: UrlKind },
     #[error("URL {url:?} is relative which is not allowed in this context")]
     RelativeUrl { url: String },
+    #[error("URL has invalid structure: user specified without host")]
+    InvalidUrlStructure,
 }
 
 impl From<Infallible> for Error {
     fn from(_: Infallible) -> Self {
-        unreachable!("Cannot actually happen, but it seems there can't be a blanket impl for this")
+        // This should theoretically never happen since Infallible can never be constructed,
+        // but with public URL fields, we need to handle it gracefully
+        Error::InvalidUrlStructure
     }
 }
 

gix-url/tests/url/expand_path.rs

@@ -39,7 +39,10 @@ fn without_username() -> crate::Result {
 fn with_username() -> crate::Result {
     let (user, resolved_path) = expand_path::parse(b"/~byron/hello/git".as_bstr())?;
     let resolved_path = expand_path::with(user.as_ref(), resolved_path.as_ref(), |user: &ForUser| match user {
-        ForUser::Current => unreachable!("we have a name"),
+        ForUser::Current => {
+            // This test expects a specific user name, not the current user
+            None // Return None to trigger the MissingHome error
+        },
         ForUser::Name(name) => Some(user_home(name.to_str_lossy().as_ref())),
     })?;
     assert_eq!(resolved_path, expected_path());