Improve test fixture output for errors in throwOnFieldError transforms

Reviewed By: evanyeung

Differential Revision: D65447769

fbshipit-source-id: b0f5a8014c4d1ae7d7635b4fcab9f78eb463132e

Author: captbaritone

compiler/crates/relay-codegen/tests/throw_on_field_error_directive_codegen.rs

@@ -14,6 +14,7 @@ use fixture_tests::Fixture;
 use graphql_ir::build;
 use graphql_ir::ExecutableDefinition;
 use graphql_syntax::parse_executable;
+use graphql_test_helpers::diagnostics_to_sorted_string;
 use relay_codegen::print_fragment;
 use relay_codegen::print_operation;
 use relay_config::ProjectConfig;
@@ -69,11 +70,5 @@ pub async fn transform_fixture(fixture: &Fixture<'_>) -> Result<String, String>
                 .collect::<Vec<_>>()
                 .join("\n\n")
         })
-        .map_err(|errors| {
-            errors
-                .into_iter()
-                .map(|error| format!("{:?}", error))
-                .collect::<Vec<_>>()
-                .join("\n\n")
-        })
+        .map_err(|diagnostics| diagnostics_to_sorted_string(fixture.content, &diagnostics))
 }

compiler/crates/relay-codegen/tests/throw_on_field_error_directive_codegen/fixtures/throw_on_field_error_mutation_directive.expected

@@ -7,4 +7,10 @@ mutation MyMutation @throwOnFieldError {
   }
 }
 ==================================== ERROR ====================================
-Diagnostic(DiagnosticData { message: InvalidDirectiveUsageUnsupportedLocation { directive_name: DirectiveName("throwOnFieldError"), valid_locations: "QUERY, FRAGMENT_DEFINITION" }, location: throw_on_field_error_mutation_directive.graphql:42:59, related_information: [], tags: [], severity: Error, data: [], machine_readable: {} })
+✖︎ Directive 'throwOnFieldError' not supported in this location. Supported location(s): QUERY, FRAGMENT_DEFINITION
+
+  throw_on_field_error_mutation_directive.graphql:3:22
+    2 │ 
+    3 │ mutation MyMutation @throwOnFieldError {
+      │                      ^^^^^^^^^^^^^^^^^
+    4 │   setName(name: "Alice") {