Handle empty array default values

Author: rafiss

build/teamcity-test.sh

@@ -3,7 +3,7 @@
 set -euox pipefail
 
 # Download CockroachDB
-VERSION=v20.2.0-beta.3
+VERSION=v20.2.1
 wget -qO- https://binaries.cockroachdb.com/cockroach-$VERSION.linux-amd64.tgz | tar  xvz
 readonly COCKROACH=./cockroach-$VERSION.linux-amd64/cockroach
 

lib/active_record/connection_adapters/cockroachdb_adapter.rb

@@ -114,6 +114,10 @@ def supports_virtual_columns?
         false
       end
 
+      def supports_string_to_array_coercion?
+        @crdb_version >= 202
+      end
+
       # This is hardcoded to 63 (as previously was in ActiveRecord 5.0) to aid in
       # migration from PostgreSQL to CockroachDB. In practice, this limitation
       # is arbitrary since CockroachDB supports index name lengths and table alias
@@ -220,7 +224,8 @@ def configure_connection
         def extract_value_from_default(default)
           super ||
             extract_escaped_string_from_default(default) ||
-            extract_time_from_default(default)
+            extract_time_from_default(default) ||
+            extract_empty_array_from_default(default)
         end
 
         # Both PostgreSQL and CockroachDB use C-style string escapes under the
@@ -262,6 +267,15 @@ def extract_time_from_default(default)
           nil
         end
 
+        # CockroachDB stores default values for arrays in the `ARRAY[...]` format.
+        # In general, it is hard to parse that, but it is easy to handle the common
+        # case of an empty array.
+        def extract_empty_array_from_default(default)
+          return unless supports_string_to_array_coercion? 
+          return unless default =~ /\AARRAY\[\]\z/
+          return "{}"
+        end
+
       # end private
     end
   end

test/excludes/PostgresqlUUIDTest.rb

@@ -1,4 +1,3 @@
 exclude :test_uniqueness_validation_ignores_uuid, "Skipping until we can triage further. See https://github.com/cockroachdb/activerecord-cockroachdb-adapter/issues/48"
-exclude :test_add_column_with_default_array, "Skipping until we can triage further. See https://github.com/cockroachdb/activerecord-cockroachdb-adapter/issues/48"
 exclude :test_change_column_default, "Skipping until we can triage further. See https://github.com/cockroachdb/activerecord-cockroachdb-adapter/issues/48"
 exclude :test_uuid_formats, "Skipping until we can triage further. See https://github.com/cockroachdb/activerecord-cockroachdb-adapter/issues/48"