From a1cba8fe49dc867d465f0ccad7a3a8789978bcba Mon Sep 17 00:00:00 2001
From: Arlo Siemsen <arsiem@microsoft.com>
Date: Mon, 3 Apr 2023 11:27:11 -0500
Subject: [PATCH] Fix Cargo warning about unused sparse configuration key

When doing a credential lookup, Cargo deserializes the registry configuration and detects the
registries.crates-io.protocol key as unused and issues a warning.

This fixes the issue by adding the field to the struct
---
 src/cargo/util/auth.rs          |  2 ++
 tests/testsuite/alt_registry.rs | 27 +++++++++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/src/cargo/util/auth.rs b/src/cargo/util/auth.rs
index f7d0fc8c4a2..f45adc6b745 100644
--- a/src/cargo/util/auth.rs
+++ b/src/cargo/util/auth.rs
@@ -133,6 +133,8 @@ pub fn registry_credential_config(
         secret_key_subject: Option<String>,
         #[serde(rename = "default")]
         _default: Option<String>,
+        #[serde(rename = "protocol")]
+        _protocol: Option<String>,
     }
 
     log::trace!("loading credential config for {}", sid);
diff --git a/tests/testsuite/alt_registry.rs b/tests/testsuite/alt_registry.rs
index 26bd864b008..97da909b83c 100644
--- a/tests/testsuite/alt_registry.rs
+++ b/tests/testsuite/alt_registry.rs
@@ -437,6 +437,33 @@ or use environment variable CARGO_REGISTRIES_ALTERNATIVE_TOKEN",
         .run();
 }
 
+#[cargo_test]
+fn cargo_registries_crates_io_protocol() {
+    let _ = RegistryBuilder::new()
+        .no_configure_token()
+        .alternative()
+        .build();
+    // Should not produce a warning due to the registries.crates-io.protocol = 'sparse' configuration
+    let p = project()
+        .file("src/lib.rs", "")
+        .file(
+            ".cargo/config.toml",
+            "[registries.crates-io]
+            protocol = 'sparse'",
+        )
+        .build();
+
+    p.cargo("publish --registry alternative")
+        .with_status(101)
+        .with_stderr(
+            "\
+[UPDATING] `alternative` index
+error: no token found for `alternative`, please run `cargo login --registry alternative`
+or use environment variable CARGO_REGISTRIES_ALTERNATIVE_TOKEN",
+        )
+        .run();
+}
+
 #[cargo_test]
 fn publish_to_alt_registry() {
     let _reg = RegistryBuilder::new()