types: fix bug where calling String() on a UDT array would panic

It seems like I ran into a proto bug, opened
gogo/protobuf#693.

Release note: None

pkg/sql/logictest/testdata/logic_test/enums

@@ -458,3 +458,14 @@ _collision 100082 0 100083
 __collision 100083 100082 0
 collision 100084 0 100085
 ___collision 100085 100084 0
+
+# Regression for #49756.
+query TT
+SELECT
+ column_name, column_type
+FROM
+ crdb_internal.table_columns
+WHERE
+ descriptor_name = 'enum_array' AND column_name = 'x'
+----
+x family:ArrayFamily width:0 precision:0 locale:"" visible_type:0 oid:100064 array_contents:<InternalType:<family:EnumFamily width:0 precision:0 locale:"" visible_type:0 oid:100063 time_precision_is_set:false udt_metadata:<stable_type_id:63 stable_array_type_id:64 > > TypeMeta:<> > time_precision_is_set:false udt_metadata:<stable_type_id:64 stable_array_type_id:0 >

pkg/sql/types/types.go

@@ -2190,6 +2190,19 @@ func (t *T) String() string {
 // DebugString returns a detailed dump of the type protobuf struct, suitable for
 // debugging scenarios.
 func (t *T) DebugString() string {
+ if t.Family() == ArrayFamily && t.ArrayContents().UserDefined() {
+ // In the case that this type is an array that contains a user defined
+ // type, the introspection that protobuf performs to generate a string
+ // representation will panic if the UserDefinedTypeMetadata field of the
+ // type is populated. It seems to not understand that fields in the element
+ // T could be not generated by proto, and panics trying to operate on the
+ // TypeMeta field of the T. To get around this, we just deep copy the T and
+ // zero out the type metadata to placate proto. See the following issue for
+ // details: https://github.com/gogo/protobuf/issues/693.
+ internalTypeCopy := protoutil.Clone(&t.InternalType).(*InternalType)
+ internalTypeCopy.ArrayContents.TypeMeta = UserDefinedTypeMetadata{}
+ return internalTypeCopy.String()
+ }
  return t.InternalType.String()
 }