From 6874dabb4f0d3503f267bb0ab970d62785d12727 Mon Sep 17 00:00:00 2001
From: Noah Dietz <noahdietz@users.noreply.github.com>
Date: Thu, 8 Aug 2024 19:22:20 -0700
Subject: [PATCH] fix: exit rule if response type cannot be resolved (#1415)

The utility method that resolves the response type descriptor, handling LROs in the process, can return `nil` if either the response type is not resolvable in the protos (very bad) OR the RPC is an LRO that isn't annotated as required by AIP-151 with `google.longrunning.operation_info`. In these cases, anywhere the helper is used should just exit - if the type is unresolvable there are other issues, and if the LRO RPC is unannotated, then AIP-151 rules will warn on that missing annotation.

We definitely shouldn't be going into a `panic`

Updates #1399
---
 rules/aip0133/request_required_fields.go | 3 +++
 rules/aip0134/request_required_fields.go | 3 +++
 rules/aip0136/response_message_name.go   | 6 ++++++
 rules/aip0233/resource_reference_type.go | 3 +++
 rules/internal/utils/common_lints.go     | 6 +++++-
 5 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/rules/aip0133/request_required_fields.go b/rules/aip0133/request_required_fields.go
index 04111a3dd..c547aae5c 100644
--- a/rules/aip0133/request_required_fields.go
+++ b/rules/aip0133/request_required_fields.go
@@ -31,6 +31,9 @@ var requestRequiredFields = &lint.MethodRule{
 	OnlyIf: utils.IsCreateMethodWithResolvedReturnType,
 	LintMethod: func(m *desc.MethodDescriptor) []lint.Problem {
 		ot := utils.GetResponseType(m)
+		if ot == nil {
+			return nil
+		}
 		r := utils.GetResource(ot)
 		resourceMsgName := utils.GetResourceSingular(r)
 
diff --git a/rules/aip0134/request_required_fields.go b/rules/aip0134/request_required_fields.go
index f4cb3c75f..033b51d63 100644
--- a/rules/aip0134/request_required_fields.go
+++ b/rules/aip0134/request_required_fields.go
@@ -29,6 +29,9 @@ var requestRequiredFields = &lint.MethodRule{
 	OnlyIf: utils.IsUpdateMethod,
 	LintMethod: func(m *desc.MethodDescriptor) (problems []lint.Problem) {
 		ot := utils.GetResponseType(m)
+		if ot == nil {
+			return nil
+		}
 		it := m.GetInputType()
 
 		allowedRequiredFields := stringset.New("update_mask")
diff --git a/rules/aip0136/response_message_name.go b/rules/aip0136/response_message_name.go
index 25453b475..ab10dcc30 100644
--- a/rules/aip0136/response_message_name.go
+++ b/rules/aip0136/response_message_name.go
@@ -47,6 +47,12 @@ var responseMessageName = &lint.MethodRule{
 		}
 
 		response := utils.GetResponseType(m)
+		if response == nil {
+			// If the return type is not resolveable (bad) or if an LRO and
+			// missing the operation_info annotation (covered by AIP-151 rules),
+			// just exit.
+			return nil
+		}
 		requestResourceType := utils.GetResourceReference(m.GetInputType().FindFieldByName("name")).GetType()
 		responseResourceType := utils.GetResource(response).GetType()
 
diff --git a/rules/aip0233/resource_reference_type.go b/rules/aip0233/resource_reference_type.go
index 87f1aaafe..7e268692a 100644
--- a/rules/aip0233/resource_reference_type.go
+++ b/rules/aip0233/resource_reference_type.go
@@ -28,6 +28,9 @@ var resourceReferenceType = &lint.MethodRule{
 	OnlyIf: func(m *desc.MethodDescriptor) bool {
 		// Return type of the RPC.
 		ot := utils.GetResponseType(m)
+		if ot == nil {
+			return false
+		}
 
 		// First repeated message field must be annotated with google.api.resource.
 		repeated := utils.GetRepeatedMessageFields(ot)
diff --git a/rules/internal/utils/common_lints.go b/rules/internal/utils/common_lints.go
index 69a8ddac9..14a82ba9b 100644
--- a/rules/internal/utils/common_lints.go
+++ b/rules/internal/utils/common_lints.go
@@ -182,7 +182,11 @@ func LintMethodHasMatchingRequestName(m *desc.MethodDescriptor) []lint.Problem {
 // have a name matching the method's, with a "Response" suffix.
 func LintMethodHasMatchingResponseName(m *desc.MethodDescriptor) []lint.Problem {
 	// GetResponseType handles the LRO case.
-	if got, want := GetResponseType(m).GetName(), m.GetName()+"Response"; got != want {
+	rt := GetResponseType(m)
+	if rt == nil {
+		return nil
+	}
+	if got, want := rt.GetName(), m.GetName()+"Response"; got != want {
 		loc := locations.MethodResponseType(m)
 		suggestion := want