Include error details into Identity exceptions

sdk/identity/azure-identity/CHANGELOG.md

@@ -10,6 +10,8 @@
 
 ### Other Changes
 
+- [[#5141]](https://github.com/Azure/azure-sdk-for-cpp/issues/5141) Added error response details to the Identity exceptions thrown when the authority host returns error response.
+
 ## 1.6.0 (2023-11-10)
 
 ### Features Added

sdk/identity/azure-identity/src/token_credential_impl.cpp

@@ -72,16 +72,13 @@ std::string TokenCredentialImpl::FormatScopes(
 
     if (scopesIter != scopesEnd)
     {
-      auto const scope = *scopesIter;
-      scopesStr += OptionalUrlEncode(scope, urlEncode);
-    }
-
-    for (++scopesIter; scopesIter != scopesEnd; ++scopesIter)
-    {
-      auto const Separator = std::string(" "); // Element separator never gets URL-encoded
+      scopesStr += OptionalUrlEncode(*scopesIter, urlEncode);
 
-      auto const scope = *scopesIter;
-      scopesStr += Separator + OptionalUrlEncode(scope, urlEncode);
+      constexpr auto Separator = " "; // Element separator never gets URL-encoded
+      for (++scopesIter; scopesIter != scopesEnd; ++scopesIter)
+      {
+        scopesStr += Separator + OptionalUrlEncode(*scopesIter, urlEncode);
+      }
     }
   }
 
@@ -117,11 +114,16 @@ AccessToken TokenCredentialImpl::GetToken(
         request = shouldRetry(statusCode, *response);
         if (request == nullptr)
         {
+          auto const bodyStream = response->ExtractBodyStream();
+          auto const bodyVec = bodyStream ? bodyStream->ReadToEnd(context) : response->GetBody();
+          auto const responseBody
+              = std::string(reinterpret_cast<char const*>(bodyVec.data()), bodyVec.size());
+
           throw std::runtime_error(
               std::string("error response: ")
               + std::to_string(
                   static_cast<std::underlying_type<decltype(statusCode)>::type>(statusCode))
-              + " " + response->GetReasonPhrase());
+              + " " + response->GetReasonPhrase() + "\n\n" + responseBody);
         }
 
         response.reset();

sdk/identity/azure-identity/test/ut/token_credential_impl_test.cpp

@@ -710,6 +710,49 @@ TEST(TokenCredentialImpl, MaxValues)
       std::exception);
 }
 
+TEST(TokenCredentialImpl, AuthErrorResponse)
+{
+  std::string const errorJson
+      = "{\"error\":\"invalid_request\","
+        "\"error_description\":\"AADSTS90014: "
+        "The required field 'scope' is missing from the credential. "
+        "Ensure that you have all the necessary parameters for the login request. "
+        "Trace ID: 01234567-89ab-cdef-0123-456789abcdef "
+        "Correlation ID: fedcba98-7654-3210-0123-456789abcdef "
+        "Timestamp: 2023-11-30 00:51:37Z\","
+        "\"error_codes\":[90014],"
+        "\"timestamp\":\"2023-11-30 00:51:37Z\","
+        "\"trace_id\":\"01234567-89ab-cdef-0123-456789abcdef\","
+        "\"correlation_id\":\"fedcba98-7654-3210-0123-456789abcdef\","
+        "\"error_uri\":\"https://login.microsoftonline.com/error?code=90014\"}";
+
+  try
+  {
+    using Azure::Core::Http::HttpStatusCode;
+    std::vector<std::string> const testScopes;
+    CredentialTestHelper::TokenRequestSimulationServerResponse testResponse;
+    testResponse.StatusCode = HttpStatusCode::BadRequest;
+    testResponse.Body = errorJson;
+
+    static_cast<void>(CredentialTestHelper::SimulateTokenRequest(
+        [](auto transport) {
+          TokenCredentialOptions options;
+          options.Transport.Transport = transport;
+
+          return std::make_unique<TokenCredentialImplTester>(
+              HttpMethod::Delete, Url("https://outlook.com/"), options);
+        },
+        {testScopes},
+        {testResponse}));
+
+    EXPECT_TRUE(!"TokenCredentialImpl should throw given the response above.");
+  }
+  catch (AuthenticationException const& ex)
+  {
+    EXPECT_EQ(ex.what(), "GetToken(): error response: 400 Test\n\n" + errorJson);
+  }
+}
+
 TEST(TokenCredentialImpl, Diagnosability)
 {
   using Azure::Core::Diagnostics::Logger;