fix: stringify struct defaults in migration generator

lib/migration_generator/migration_generator.ex

@@ -1630,9 +1630,18 @@ defmodule AshPostgres.MigrationGenerator do
 
   defp default(%{default: value, type: type}, _) do
     case Ash.Type.dump_to_native(type, value) do
-      {:ok, value} -> inspect(value)
-      _ -> "nil"
+      {:ok, value} when is_struct(value) ->
+        to_string(value)
+
+      {:ok, value} ->
+        inspect(value)
+
+      _ ->
+        "nil"
     end
+  rescue
+    _ ->
+      "nil"
   end
 
   defp snapshot_to_binary(snapshot) do

priv/resource_snapshots/test_repo/posts/20210426172049.json

@@ -0,0 +1,106 @@
+{
+  "attributes": [
+    {
+      "allow_nil?": true,
+      "default": "nil",
+      "generated?": false,
+      "name": "category",
+      "primary_key?": false,
+      "references": null,
+      "type": "citext"
+    },
+    {
+      "allow_nil?": true,
+      "default": "0",
+      "generated?": false,
+      "name": "decimal",
+      "primary_key?": false,
+      "references": null,
+      "type": "decimal"
+    },
+    {
+      "allow_nil?": false,
+      "default": "fragment(\"uuid_generate_v4()\")",
+      "generated?": false,
+      "name": "id",
+      "primary_key?": true,
+      "references": null,
+      "type": "uuid"
+    },
+    {
+      "allow_nil?": true,
+      "default": "nil",
+      "generated?": false,
+      "name": "price",
+      "primary_key?": false,
+      "references": null,
+      "type": "bigint"
+    },
+    {
+      "allow_nil?": true,
+      "default": "nil",
+      "generated?": false,
+      "name": "public",
+      "primary_key?": false,
+      "references": null,
+      "type": "boolean"
+    },
+    {
+      "allow_nil?": true,
+      "default": "nil",
+      "generated?": false,
+      "name": "score",
+      "primary_key?": false,
+      "references": null,
+      "type": "bigint"
+    },
+    {
+      "allow_nil?": true,
+      "default": "nil",
+      "generated?": false,
+      "name": "status",
+      "primary_key?": false,
+      "references": null,
+      "type": "status"
+    },
+    {
+      "allow_nil?": true,
+      "default": "nil",
+      "generated?": false,
+      "name": "title",
+      "primary_key?": false,
+      "references": null,
+      "type": "text"
+    },
+    {
+      "allow_nil?": true,
+      "default": "\"sponsored\"",
+      "generated?": false,
+      "name": "type",
+      "primary_key?": false,
+      "references": null,
+      "type": "text"
+    }
+  ],
+  "base_filter": "type = 'sponsored'",
+  "check_constraints": [
+    {
+      "attribute": [
+        "price"
+      ],
+      "base_filter": "type = 'sponsored'",
+      "check": "price > 0",
+      "name": "price_must_be_positive"
+    }
+  ],
+  "has_create_action": true,
+  "hash": "42B75BE079D8BBC3AE0EC4B1517A4D0E150F381E9817F9D8FA53E1E689A80D3B",
+  "identities": [],
+  "multitenancy": {
+    "attribute": null,
+    "global": null,
+    "strategy": null
+  },
+  "repo": "Elixir.AshPostgres.TestRepo",
+  "table": "posts"
+}

priv/test_repo/migrations/20210426172049_migrate_resources9.exs

@@ -0,0 +1,21 @@
+defmodule AshPostgres.TestRepo.Migrations.MigrateResources9 do
+  @moduledoc """
+  Updates resources based on their most recent snapshots.
+
+  This file was autogenerated with `mix ash_postgres.generate_migrations`
+  """
+
+  use Ecto.Migration
+
+  def up do
+    alter table(:posts) do
+      add :decimal, :decimal, default: 0
+    end
+  end
+
+  def down do
+    alter table(:posts) do
+      remove :decimal
+    end
+  end
+end

test/support/resources/post.ex

@@ -4,9 +4,9 @@ defmodule AshPostgres.Test.Post do
     data_layer: AshPostgres.DataLayer
 
   postgres do
-    table "posts"
-    repo AshPostgres.TestRepo
-    base_filter_sql "type = 'sponsored'"
+    table("posts")
+    repo(AshPostgres.TestRepo)
+    base_filter_sql("type = 'sponsored'")
 
     check_constraints do
       check_constraint(:price, "price_must_be_positive",
@@ -44,6 +44,7 @@ defmodule AshPostgres.Test.Post do
     attribute(:category, :ci_string)
     attribute(:type, :atom, default: :sponsored, private?: true, writable?: false)
     attribute(:price, :integer)
+    attribute(:decimal, :decimal, default: Decimal.new(0))
     attribute(:status, AshPostgres.Test.Types.Status)
   end