give structured context when unpacking fails

Author: Skgland

src/crates/registry.rs

@@ -1,5 +1,5 @@
 use super::CrateTrait;
-use crate::Workspace;
+use crate::{PrepareError, Workspace};
 use anyhow::Context as _;
 use flate2::read::GzDecoder;
 use log::info;
@@ -194,10 +194,10 @@ impl CrateTrait for RegistryCrate {
         );
         if let Err(err) = unpack_without_first_dir(&mut tar, dest) {
             let _ = crate::utils::remove_dir_all(dest);
-            Err(err.context(format!(
-                "unable to download {} version {}",
-                self.name, self.version
-            )))
+            Err(err.context(PrepareError::UnpackFailed {
+                krate: self.name.clone(),
+                version: self.version.clone(),
+            }))
         } else {
             Ok(())
         }

src/prepare.rs

@@ -424,6 +424,14 @@ pub enum PrepareError {
         /// repo url
         url: String,
     },
+    /// failed to unpack crate
+    #[error("failed to unpack {krate} version {version}")]
+    UnpackFailed {
+        /// the crates name
+        krate: String,
+        /// the crates version
+        version: String,
+    },
 }
 
 #[cfg(test)]