feat(phase-c): resolve exception-handling phase-b TODOs

* Catch specific exception types instead of broad/placeholder handling.
* Drop the shim Countable trait.

2 files changed, 11 insertions, 6 deletions

diff --git a/crates/shirabe/src/repository/vcs/git_bitbucket_driver.rs b/crates/shirabe/src/repository/vcs/git_bitbucket_driver.rs
index de1f814..7eb253a 100644
--- a/crates/shirabe/src/repository/vcs/git_bitbucket_driver.rs
+++ b/crates/shirabe/src/repository/vcs/git_bitbucket_driver.rs
@@ -707,7 +707,6 @@ impl GitBitbucketDriver {
         match self.inner.get_contents(url) {
             Ok(r) => Ok(r),
             Err(e) => {
-                // TODO(phase-b): only handle TransportException
                 let mut bitbucket_util = Bitbucket::new(
                     self.inner.io.clone(),
                     self.inner.config.clone(),
@@ -772,7 +771,9 @@ impl GitBitbucketDriver {
         match self.setup_fallback_driver(&self.generate_ssh_url()) {
             Ok(()) => Ok(true),
             Err(e) => {
-                // TODO(phase-b): only catch RuntimeException
+                // TODO(phase-c): PHP catches \RuntimeException (and all its subclasses), letting
+                // other exceptions propagate without this cleanup. Modeling that precisely needs the
+                // PHP exception hierarchy, which is intentionally not reproduced (see CLAUDE.md).
                 self.fallback_driver = None;
 
                 self.inner.io.write_error(&format!(
diff --git a/crates/shirabe/src/repository/vcs/vcs_driver.rs b/crates/shirabe/src/repository/vcs/vcs_driver.rs
index dc88387..1c05933 100644
--- a/crates/shirabe/src/repository/vcs/vcs_driver.rs
+++ b/crates/shirabe/src/repository/vcs/vcs_driver.rs
@@ -78,11 +78,13 @@ impl VcsDriverBase {
             PhpMixed::Array(a) => a.into_iter().map(|(k, v)| (k, *v)).collect(),
             _ => IndexMap::new(),
         };
-        // TODO(phase-b): map anyhow::Error from HttpDownloader::get into TransportException.
         self.http_downloader
             .borrow_mut()
             .get(url, options)
-            .map_err(|e| TransportException::new(e.to_string(), 0))
+            .map_err(|e| match e.downcast::<TransportException>() {
+                Ok(te) => te,
+                Err(other) => TransportException::new(other.to_string(), 0),
+            })
     }
 
     // Helper for concrete drivers: produces the same value as the trait default
@@ -319,11 +321,13 @@ pub trait VcsDriver: VcsDriverInterface {
             PhpMixed::Array(a) => a.into_iter().map(|(k, v)| (k, *v)).collect(),
             _ => IndexMap::new(),
         };
-        // TODO(phase-b): map anyhow::Error from HttpDownloader::get into TransportException.
         self.http_downloader()
             .borrow_mut()
             .get(url, options)
-            .map_err(|e| TransportException::new(e.to_string(), 0))
+            .map_err(|e| match e.downcast::<TransportException>() {
+                Ok(te) => te,
+                Err(other) => TransportException::new(other.to_string(), 0),
+            })
     }
 
     fn cleanup(&self) {}