improvement: support nils_distinct? in identities

closes #84

Author: zachdaniel

lib/migration_generator/migration_generator.ex

@@ -1633,7 +1633,8 @@ defmodule AshSqlite.MigrationGenerator do
           Enum.find(snapshot.identities, fn identity ->
             identity.name == old_identity.name &&
               Enum.sort(old_identity.keys) == Enum.sort(identity.keys) &&
-              old_identity.base_filter == identity.base_filter
+              old_identity.base_filter == identity.base_filter &&
+              Map.get(old_identity, :nils_distinct?, true) == Map.get(identity, :nils_distinct?, true)
           end)
         end)
       end
@@ -1675,7 +1676,8 @@ defmodule AshSqlite.MigrationGenerator do
           Enum.find(old_snapshot.identities, fn old_identity ->
             old_identity.name == identity.name &&
               Enum.sort(old_identity.keys) == Enum.sort(identity.keys) &&
-              old_identity.base_filter == identity.base_filter
+              old_identity.base_filter == identity.base_filter &&
+              Map.get(old_identity, :nils_distinct?, true) == Map.get(identity, :nils_distinct?, true)
           end)
         end)
       end
@@ -2454,7 +2456,7 @@ defmodule AshSqlite.MigrationGenerator do
       end)
     end)
     |> Enum.sort_by(& &1.name)
-    |> Enum.map(&Map.take(&1, [:name, :keys]))
+    |> Enum.map(&Map.take(&1, [:name, :keys, :nils_distinct?]))
     |> Enum.map(fn %{keys: keys} = identity ->
       %{
         identity
@@ -2473,6 +2475,7 @@ defmodule AshSqlite.MigrationGenerator do
           "#{AshSqlite.DataLayer.Info.table(resource)}_#{identity.name}_index"
       )
     end)
+    |> Enum.map(&Map.put_new(&1, :nils_distinct?, true))
     |> Enum.map(&Map.put(&1, :base_filter, AshSqlite.DataLayer.Info.base_filter_sql(resource)))
   end
 

lib/migration_generator/operation.ex

@@ -31,6 +31,12 @@ defmodule AshSqlite.MigrationGenerator.Operation do
     # sobelow_skip ["DOS.StringToAtom"]
     def as_atom(value), do: Macro.inspect_atom(:remote_call, String.to_atom(value))
 
+    def option(key, value) when key in [:nulls_distinct, "nulls_distinct"] do
+      if !value do
+        "#{as_atom(key)}: #{inspect(value)}"
+      end
+    end
+
     def option(key, value) do
       if value do
         "#{as_atom(key)}: #{inspect(value)}"
@@ -478,10 +484,12 @@ defmodule AshSqlite.MigrationGenerator.Operation do
     import Helper
 
     def up(%{
-          identity: %{name: name, keys: keys, base_filter: base_filter, index_name: index_name},
+          identity: %{name: name, keys: keys, base_filter: base_filter, index_name: index_name} = identity,
           table: table,
           multitenancy: multitenancy
         }) do
+      nils_distinct? = Map.get(identity, :nils_distinct?, true)
+
       keys =
         case multitenancy.strategy do
           :attribute ->
@@ -494,9 +502,9 @@ defmodule AshSqlite.MigrationGenerator.Operation do
       index_name = index_name || "#{table}_#{name}_index"
 
       if base_filter do
-        "create unique_index(:#{as_atom(table)}, [#{Enum.map_join(keys, ", ", &inspect/1)}], where: \"#{base_filter}\", #{join(["name: \"#{index_name}\""])})"
+        "create unique_index(:#{as_atom(table)}, [#{Enum.map_join(keys, ", ", &inspect/1)}], where: \"#{base_filter}\", #{join(["name: \"#{index_name}\"", option("nulls_distinct", nils_distinct?)])})"
       else
-        "create unique_index(:#{as_atom(table)}, [#{Enum.map_join(keys, ", ", &inspect/1)}], #{join(["name: \"#{index_name}\""])})"
+        "create unique_index(:#{as_atom(table)}, [#{Enum.map_join(keys, ", ", &inspect/1)}], #{join(["name: \"#{index_name}\"", option("nulls_distinct", nils_distinct?)])})"
       end
     end