Improve error message for HTTP validation in auth services (#15768)

Follows https://github.com/astral-sh/uv/pull/15755

crates/uv-auth/src/service.rs

@@ -8,8 +8,10 @@ use uv_redacted::DisplaySafeUrl;
 pub enum ServiceParseError {
     #[error(transparent)]
     InvalidUrl(#[from] url::ParseError),
-    #[error("only HTTPS (or HTTP on localhost) is supported")]
-    UnsupportedScheme,
+    #[error("Unsupported scheme: {0}")]
+    UnsupportedScheme(String),
+    #[error("HTTPS is required for non-local hosts")]
+    HttpsRequired,
 }
 
 /// A service URL that wraps [`DisplaySafeUrl`] for CLI usage.
@@ -36,9 +38,8 @@ impl Service {
         match url.scheme() {
             "https" => Ok(()),
             "http" if matches!(url.host_str(), Some("localhost" | "127.0.0.1")) => Ok(()),
-            #[cfg(test)]
-            "http" => Ok(()),
-            _ => Err(ServiceParseError::UnsupportedScheme),
+            "http" => Err(ServiceParseError::HttpsRequired),
+            value => Err(ServiceParseError::UnsupportedScheme(value.to_string())),
         }
     }
 }

crates/uv/tests/it/auth.rs

@@ -616,7 +616,7 @@ fn login_native_auth_url() {
     ----- stdout -----
 
     ----- stderr -----
-    error: invalid value 'http://example.com' for '<SERVICE>': only HTTPS (or HTTP on localhost) is supported
+    error: invalid value 'http://example.com' for '<SERVICE>': HTTPS is required for non-local hosts
 
     For more information, try '--help'.
     ");
@@ -761,7 +761,7 @@ fn login_native_auth_url() {
 fn login_text_store() {
     let context = TestContext::new_with_versions(&[]);
 
-    // Successful login without keyring provider (uses text store)
+    // Login with a username and password
     uv_snapshot!(context.auth_login()
         .arg("https://pypi-proxy.fly.dev/basic-auth/simple")
         .arg("--username")
@@ -777,7 +777,7 @@ fn login_text_store() {
     "
     );
 
-    // Token-based login
+    // Login with a token
     uv_snapshot!(context.auth_login()
         .arg("https://example.com/simple")
         .arg("--token")
@@ -822,6 +822,70 @@ fn login_text_store() {
     error: Password cannot be empty
     "
     );
+
+    // HTTP should fail
+    uv_snapshot!(context.auth_login()
+        .arg("http://example.com/simple")
+        .arg("--username")
+        .arg("testuser")
+        .arg("--password")
+        .arg("testpass"), @r"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: invalid value 'http://example.com/simple' for '<SERVICE>': HTTPS is required for non-local hosts
+
+    For more information, try '--help'.
+    ");
+
+    // Other protocol should fail
+    uv_snapshot!(context.auth_login()
+        .arg("ftp://example.com/simple")
+        .arg("--username")
+        .arg("testuser")
+        .arg("--password")
+        .arg("testpass"), @r"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: invalid value 'ftp://example.com/simple' for '<SERVICE>': Unsupported scheme: ftp
+
+    For more information, try '--help'.
+    ");
+
+    // HTTP should be allowed on localhost
+    uv_snapshot!(context.auth_login()
+        .arg("http://127.0.0.1/simple")
+        .arg("--username")
+        .arg("testuser")
+        .arg("--password")
+        .arg("testpass"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Stored credentials for testuser@http://127.0.0.1/
+    ");
+
+    // HTTP should be allowed on localhost
+    uv_snapshot!(context.auth_login()
+        .arg("http://localhost/simple")
+        .arg("--username")
+        .arg("testuser")
+        .arg("--password")
+        .arg("testpass"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Stored credentials for testuser@http://localhost/
+    ");
 }
 
 #[test]