refactor: add MethodOption location function (#900)

Co-authored-by: Maxim Tschumak <[email protected]>
Co-authored-by: Andrew Paseltiner <[email protected]>

locations/method_locations.go

@@ -34,17 +34,22 @@ func MethodResponseType(m *desc.MethodDescriptor) *dpb.SourceCodeInfo_Location {
 // MethodHTTPRule returns the precise location of the method's `google.api.http`
 // rule, if any.
 func MethodHTTPRule(m *desc.MethodDescriptor) *dpb.SourceCodeInfo_Location {
-	return pathLocation(m, 4, int(apb.E_Http.TypeDescriptor().Number())) // MethodDescriptor.options == 4
+	return MethodOption(m, int(apb.E_Http.TypeDescriptor().Number()))
 }
 
 // MethodOperationInfo returns the precise location of the method's
 // `google.longrunning.operation_info` annotation, if any.
 func MethodOperationInfo(m *desc.MethodDescriptor) *dpb.SourceCodeInfo_Location {
-	return pathLocation(m, 4, int(lrpb.E_OperationInfo.TypeDescriptor().Number())) // MethodDescriptor.options == 4
+	return MethodOption(m, int(lrpb.E_OperationInfo.TypeDescriptor().Number()))
 }
 
 // MethodSignature returns the precise location of the method's
 // `google.api.method_signature` annotation, if any.
 func MethodSignature(m *desc.MethodDescriptor, index int) *dpb.SourceCodeInfo_Location {
 	return pathLocation(m, 4, int(apb.E_MethodSignature.TypeDescriptor().Number()), index) // MethodDescriptor.options == 4
 }
+
+// MethodOption returns the precise location of the method's option with the given field number, if any.
+func MethodOption(m *desc.MethodDescriptor, fieldNumber int) *dpb.SourceCodeInfo_Location {
+	return pathLocation(m, 4, fieldNumber) // MethodDescriptor.options == 4
+}

locations/method_locations_test.go

@@ -117,3 +117,34 @@ func TestMethodSignature(t *testing.T) {
 		}
 	}
 }
+
+func TestMethodOption(t *testing.T) {
+	f := parse(t, `
+		service Library {
+		  rpc GetBook(GetBookRequest) returns (Book) {
+		    option deprecated = true;
+		  }
+		  rpc UpdateBook(UpdateBookRequest) returns (Book) {}
+		}
+		message GetBookRequest{}
+		message Book {}
+		message UpdateBookRequest {}
+	`)
+
+	for _, test := range []struct {
+		name      string
+		methodIdx int
+		want      []int32
+	}{
+		{"OptionSet", 0, []int32{4, 4, 29}},
+		{"OptionNotSet", 1, nil},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			// field number of the deprecated option == 33
+			loc := MethodOption(f.GetServices()[0].GetMethods()[test.methodIdx], 33)
+			if diff := cmp.Diff(loc.GetSpan(), test.want); diff != "" {
+				t.Errorf("Diff: %s", diff)
+			}
+		})
+	}
+}