improvement: use uuid_generate_v4() to eliminate need for uuid-ossp just for uuid defaults

Thanks to @sevenseacat for pointing this out!

Author: zachdaniel

lib/migration_generator/migration_generator.ex

@@ -1626,7 +1626,47 @@ defmodule AshPostgres.MigrationGenerator do
 
     right = add_source_and_name_and_schema_and_ignore(right, repo)
 
-    left != right
+    {left, right} =
+      case {left.default, right.default} do
+        {"fragment(\"uuid_generate_v4()\")", "fragment(\"gen_random_uuid()\")"} ->
+          {Map.put(left, :default, "fragment(\"gen_random_uuid()\")"), right}
+
+        {"fragment(\"gen_random_uuid()\")", "fragment(\"uuid_generate_v4()\")"} ->
+          {Map.put(left, :default, "fragment(\"uuid_generate_v4()\")"), right}
+
+        _ ->
+          {left, right}
+      end
+
+    {left, right} =
+      case {left[:references][:destination_attribute_default],
+            right[:references][:destination_attribute_default]} do
+        {"fragment(\"uuid_generate_v4()\")", "fragment(\"gen_random_uuid()\")"} ->
+          {put_in(
+             left,
+             [:references, :destination_attribute_default],
+             "fragment(\"gen_random_uuid()\")"
+           ), right}
+
+        {"fragment(\"gen_random_uuid()\")", "fragment(\"uuid_generate_v4()\")"} ->
+          {left,
+           put_in(
+             right,
+             [:references, :destination_attribute_default],
+             "fragment(\"gen_random_uuid()\")"
+           )}
+
+        _ ->
+          {left, right}
+      end
+
+    if left != right do
+      IO.inspect(left)
+      IO.inspect(right)
+      true
+    else
+      false
+    end
   end
 
   defp add_source_and_name_and_schema_and_ignore(attribute, repo) do
@@ -2170,14 +2210,11 @@ defmodule AshPostgres.MigrationGenerator do
 
   @uuid_functions [&Ash.UUID.generate/0, &Ecto.UUID.generate/0]
 
-  defp default(%{default: default}, repo) when is_function(default) do
+  defp default(%{default: default}, _repo) when is_function(default) do
     cond do
-      default in @uuid_functions && pg_version_at_least?(repo, 13) ->
+      default in @uuid_functions ->
         ~S[fragment("gen_random_uuid()")]
 
-      default in @uuid_functions && "uuid-ossp" in (repo.config()[:installed_extensions] || []) ->
-        ~S[fragment("uuid_generate_v4()")]
-
       default == (&DateTime.utc_now/0) ->
         ~S[fragment("now()")]
 
@@ -2190,12 +2227,6 @@ defmodule AshPostgres.MigrationGenerator do
   defp default(%{default: nil}, _), do: "nil"
   defp default(%{default: value}, _), do: EctoMigrationDefault.to_default(value)
 
-  defp pg_version_at_least?(repo, requirement) do
-    pg_version = repo.min_pg_version()
-    if pg_version < 13, do: raise("Minimum acceptable pg version is 13")
-    pg_version >= requirement
-  end
-
   defp snapshot_to_binary(snapshot) do
     snapshot
     |> Map.update!(:attributes, fn attributes ->

lib/migration_generator/operation.ex

@@ -370,8 +370,22 @@ defmodule AshPostgres.MigrationGenerator.Operation do
           ", primary_key: true"
         end
 
+      defaults_different? =
+        cond do
+          attribute.default == "fragment(\"uuid_generate_v4()\")" &&
+              old_attribute.default == "fragment(\"gen_random_uuid()\")" ->
+            false
+
+          old_attribute.default == "fragment(\"uuid_generate_v4()\")" &&
+              attribute.default == "fragment(\"gen_random_uuid()\")" ->
+            false
+
+          true ->
+            attribute.default != old_attribute.default
+        end
+
       default =
-        if attribute.default != old_attribute.default do
+        if defaults_different? do
           if is_nil(attribute.default) do
             ", default: nil"
           else

lib/repo.ex

@@ -12,11 +12,13 @@ defmodule AshPostgres.Repo do
 
   To configure your list of installed extensions, define `installed_extensions/0`
 
+  All extensions present will be automatically added by the migration generator. Some extensions
+  being present in the list can change how AshPostgres behaves.
+
   Extensions that are relevant to ash_postgres:
 
   * "ash-functions" - This isn't really an extension, but it expresses that certain functions
     should be added when generating migrations, to support the `||` and `&&` operators in expressions.
-  * `"uuid-ossp"` - Sets UUID primary keys defaults in the migration generator
   * `"pg_trgm"` - Makes the `AshPostgres.Predicates.Trigram` custom predicate available
   * "citext" - Allows case insensitive fields to be used