Update auth error message to specify args for cargo login.

src/cargo/sources/registry/http_remote.rs

@@ -551,6 +551,7 @@ impl<'cfg> RegistryData for HttpRegistry<'cfg> {
                     if self.auth_required {
                         return Poll::Ready(err.context(auth::AuthorizationError {
                             sid: self.source_id.clone(),
+                            default_registry: self.config.default_registry()?,
                             login_url: self.login_url.clone(),
                             reason: auth::AuthorizationErrorReason::TokenRejected,
                         }));

src/cargo/util/auth.rs

@@ -347,6 +347,8 @@ impl fmt::Display for AuthorizationErrorReason {
 pub struct AuthorizationError {
     /// Url that was attempted
     pub sid: SourceId,
+    /// The `registry.default` config value.
+    pub default_registry: Option<String>,
     /// Url where the user could log in.
     pub login_url: Option<Url>,
     /// Specific reason indicating what failed
@@ -356,9 +358,14 @@ impl Error for AuthorizationError {}
 impl fmt::Display for AuthorizationError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         if self.sid.is_crates_io() {
+            let args = if self.default_registry.is_some() {
+                " --registry crates-io"
+            } else {
+                ""
+            };
             write!(
                 f,
-                "{}, please run `cargo login`\nor use environment variable CARGO_REGISTRY_TOKEN",
+                "{}, please run `cargo login{args}`\nor use environment variable CARGO_REGISTRY_TOKEN",
                 self.reason
             )
         } else if let Some(name) = self.sid.alt_registry_key() {
@@ -421,6 +428,7 @@ pub fn auth_token(
         Some(token) => Ok(token.expose()),
         None => Err(AuthorizationError {
             sid: sid.clone(),
+            default_registry: config.default_registry()?,
             login_url: login_url.cloned(),
             reason: AuthorizationErrorReason::TokenMissing,
         }

tests/testsuite/registry.rs

@@ -3192,3 +3192,85 @@ required by package `foo v0.0.1 ([ROOT]/foo)`
         ]
     );
 }
+
+#[cargo_test]
+fn default_auth_error() {
+    // Check for the error message for an authentication error when default is set.
+    let crates_io = RegistryBuilder::new().http_api().build();
+    let _alternative = RegistryBuilder::new().http_api().alternative().build();
+
+    paths::home().join(".cargo/credentials.toml").rm_rf();
+
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                [package]
+                name = "foo"
+                version = "0.1.0"
+                license = "MIT"
+                description = "foo"
+            "#,
+        )
+        .file("src/lib.rs", "")
+        .build();
+
+    // Test output before setting the default.
+    p.cargo("publish --no-verify")
+        .replace_crates_io(crates_io.index_url())
+        .with_stderr(
+            "\
+[UPDATING] crates.io index
+error: no token found, please run `cargo login`
+or use environment variable CARGO_REGISTRY_TOKEN
+",
+        )
+        .with_status(101)
+        .run();
+
+    p.cargo("publish --no-verify --registry alternative")
+        .replace_crates_io(crates_io.index_url())
+        .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
+",
+        )
+        .with_status(101)
+        .run();
+
+    // Test the output with the default.
+    cargo_util::paths::append(
+        &cargo_home().join("config"),
+        br#"
+            [registry]
+            default = "alternative"
+        "#,
+    )
+    .unwrap();
+
+    p.cargo("publish --no-verify")
+        .replace_crates_io(crates_io.index_url())
+        .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
+",
+        )
+        .with_status(101)
+        .run();
+
+    p.cargo("publish --no-verify --registry crates-io")
+        .replace_crates_io(crates_io.index_url())
+        .with_stderr(
+            "\
+[UPDATING] crates.io index
+error: no token found, please run `cargo login --registry crates-io`
+or use environment variable CARGO_REGISTRY_TOKEN
+",
+        )
+        .with_status(101)
+        .run();
+}

tests/testsuite/registry_auth.rs

@@ -1,4 +1,4 @@
-//! Tests for normal registry dependencies.
+//! Tests for registry authentication.
 
 use cargo_test_support::registry::{Package, RegistryBuilder};
 use cargo_test_support::{project, Execs, Project};