gha-cache: Strip UTF-8 BOM in error responses

Cargo.lock

@@ -445,6 +445,7 @@ dependencies = [
  "thiserror",
  "tokio",
  "tracing",
+ "unicode-bom",
 ]
 
 [[package]]
@@ -1419,6 +1420,12 @@ version = "0.3.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "92888ba5573ff080736b3648696b70cafad7d250551175acbaa4e0385b3e1460"
 
+[[package]]
+name = "unicode-bom"
+version = "2.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "98e90c70c9f0d4d1ee6d0a7d04aa06cb9bbd53d8cfbdd62a0269a7c2eb640552"
+
 [[package]]
 name = "unicode-ident"
 version = "1.0.8"

gha-cache/Cargo.toml

@@ -16,6 +16,7 @@ serde_json = "1.0.96"
 sha2 = "0.10.6"
 thiserror = "1.0.40"
 tracing = "0.1.37"
+unicode-bom = "2.0.2"
 
 [dependencies.tokio]
 version = "1.28.0"

gha-cache/src/api.rs

@@ -19,6 +19,7 @@ use serde::{de::DeserializeOwned, Deserialize, Serialize};
 use sha2::{Digest, Sha256};
 use thiserror::Error;
 use tokio::{io::AsyncRead, sync::Semaphore};
+use unicode_bom::Bom;
 
 use crate::credentials::Credentials;
 use crate::util::read_chunk_async;
@@ -525,16 +526,21 @@ impl ResponseExt for reqwest::Response {
 async fn handle_error(res: reqwest::Response) -> Error {
     let status = res.status();
     let bytes = match res.bytes().await {
-        Ok(bytes) => bytes,
+        Ok(bytes) => {
+            let bom = Bom::from(bytes.as_ref());
+            bytes.slice(bom.len()..)
+        }
         Err(e) => {
             return e.into();
         }
     };
 
-    let info = if let Ok(structured) = serde_json::from_slice(&bytes) {
-        ApiErrorInfo::Structured(structured)
-    } else {
-        ApiErrorInfo::Unstructured(bytes)
+    let info = match serde_json::from_slice(&bytes) {
+        Ok(structured) => ApiErrorInfo::Structured(structured),
+        Err(e) => {
+            tracing::info!("failed to decode error: {}", e);
+            ApiErrorInfo::Unstructured(bytes)
+        }
     };
 
     Error::ApiError { status, info }