feat: allow custom field mappings

I would like to have some custom fields consistently through whole
application and I didn't find any way how to currently do this.

My reasoning is that writing AshBackpex resources should be as brief as
possible and I really hate the idea of adding `module` to i.e. each
field with date.

Ideal solution would be to have :field_mappings in Application config
which would be found by AshBackpex. But I suppose libraries shouldn't be
based on anything in application so I'm introducing new "attribute" for
resource named field_mappings working like this:

    field_mappings: %{
      Ash.Type.UtcDatetime => MyappWeb.Backpex.Fields.RelativeDateTime,
      Ash.Type.UtcDatetimeUsec => MyappWeb.Backpex.Fields.RelativeDateTime,
      Ash.Type.DateTime => MyappWeb.Backpex.Fields.RelativeDateTime,
      Ash.Type.NaiveDateTime => MyappWeb.Backpex.Fields.RelativeDateTime
    }

That way I can use my custom module with backpex macro which set this as
default for all my admin pages.

Simple test covering the functionality is included.

Author: kepi

lib/ash_backpex/live_resource/dsl.ex

@@ -309,6 +309,12 @@ defmodule AshBackpex.LiveResource.Dsl do
         doc:
           "Panels to be displayed in the admin create/edit forms. Format: [panel_key: \"Panel Title\"]"
       ],
+      field_mappings: [
+        type: {:map, :atom, :atom},
+        default: %{},
+        doc:
+          "Override default Ash type to Backpex field module mappings. Format: %{Ash.Type.DateTime => MyApp.Fields.CustomDateTime}"
+      ],
       pubsub: [
         doc: "PubSub configuration.",
         type: :keyword_list,

lib/ash_backpex/live_resource/transformers/generate_backpex.ex

@@ -146,82 +146,90 @@ defmodule AshBackpex.LiveResource.Transformers.GenerateBackpex do
 
         try_derive_module = fn attribute_name ->
           type = derive_type.(attribute_name)
+          field_mappings = Spark.Dsl.Extension.get_opt(__MODULE__, [:backpex], :field_mappings) || %{}
 
-          case type do
-            Ash.Type.Boolean ->
-              Backpex.Fields.Boolean
+          # Check custom mappings first, then fall back to defaults
+          case Map.get(field_mappings, type) do
+            nil ->
+              case type do
+                Ash.Type.Boolean ->
+                  Backpex.Fields.Boolean
 
-            Ash.Type.String ->
-              attribute_name |> select_or.(Backpex.Fields.Text)
+                Ash.Type.String ->
+                  attribute_name |> select_or.(Backpex.Fields.Text)
 
-            Ash.Type.Atom ->
-              attribute_name |> select_or.(Backpex.Fields.Text)
+                Ash.Type.Atom ->
+                  attribute_name |> select_or.(Backpex.Fields.Text)
 
-            Ash.Type.CiString ->
-              attribute_name |> select_or.(Backpex.Fields.Text)
+                Ash.Type.CiString ->
+                  attribute_name |> select_or.(Backpex.Fields.Text)
 
-            Ash.Type.Time ->
-              Backpex.Fields.Time
+                Ash.Type.Time ->
+                  Backpex.Fields.Time
 
-            Ash.Type.Date ->
-              Backpex.Fields.Date
+                Ash.Type.Date ->
+                  Backpex.Fields.Date
 
-            Ash.Type.UtcDatetime ->
-              Backpex.Fields.DateTime
+                Ash.Type.UtcDatetime ->
+                  Backpex.Fields.DateTime
 
-            Ash.Type.UtcDatetimeUsec ->
-              Backpex.Fields.DateTime
+                Ash.Type.UtcDatetimeUsec ->
+                  Backpex.Fields.DateTime
 
-            Ash.Type.DateTime ->
-              Backpex.Fields.DateTime
+                Ash.Type.DateTime ->
+                  Backpex.Fields.DateTime
 
-            Ash.Type.NaiveDateTime ->
-              Backpex.Fields.DateTime
+                Ash.Type.NaiveDateTime ->
+                  Backpex.Fields.DateTime
 
-            Ash.Type.Integer ->
-              attribute_name |> select_or.(Backpex.Fields.Number)
+                Ash.Type.Integer ->
+                  attribute_name |> select_or.(Backpex.Fields.Number)
 
-            Ash.Type.Float ->
-              attribute_name |> select_or.(Backpex.Fields.Number)
+                Ash.Type.Float ->
+                  attribute_name |> select_or.(Backpex.Fields.Number)
 
-            :belongs_to ->
-              Backpex.Fields.BelongsTo
+                :belongs_to ->
+                  Backpex.Fields.BelongsTo
 
-            :has_many ->
-              Backpex.Fields.HasMany
+                :has_many ->
+                  Backpex.Fields.HasMany
 
-            :count ->
-              Backpex.Fields.Number
+                :count ->
+                  Backpex.Fields.Number
 
-            :exists ->
-              Backpex.Fields.Boolean
+                :exists ->
+                  Backpex.Fields.Boolean
 
-            :sum ->
-              Backpex.Fields.Number
+                :sum ->
+                  Backpex.Fields.Number
 
-            :max ->
-              Backpex.Fields.Number
+                :max ->
+                  Backpex.Fields.Number
 
-            :min ->
-              Backpex.Fields.Number
+                :min ->
+                  Backpex.Fields.Number
 
-            :avg ->
-              Backpex.Fields.Number
+                :avg ->
+                  Backpex.Fields.Number
 
-            {:array, Ash.Type.Atom} ->
-              attribute_name |> multiselect_or.(Backpex.Fields.Text)
+                {:array, Ash.Type.Atom} ->
+                  attribute_name |> multiselect_or.(Backpex.Fields.Text)
 
-            {:array, Ash.Type.String} ->
-              attribute_name |> multiselect_or.(Backpex.Fields.Text)
+                {:array, Ash.Type.String} ->
+                  attribute_name |> multiselect_or.(Backpex.Fields.Text)
 
-            {:array, Ash.Type.CiString} ->
-              attribute_name |> multiselect_or.(Backpex.Fields.Text)
+                {:array, Ash.Type.CiString} ->
+                  attribute_name |> multiselect_or.(Backpex.Fields.Text)
 
-            {:array, Ash.Type.Integer} ->
-              attribute_name |> multiselect_or.(Backpex.Fields.Number)
+                {:array, Ash.Type.Integer} ->
+                  attribute_name |> multiselect_or.(Backpex.Fields.Number)
+
+                {:array, Ash.Type.Float} ->
+                  attribute_name |> multiselect_or.(Backpex.Fields.Number)
+              end
 
-            {:array, Ash.Type.Float} ->
-              attribute_name |> multiselect_or.(Backpex.Fields.Number)
+            custom_module ->
+              custom_module
           end
         end
 

test/ash_backpex/live_resource/transformer_test.exs

@@ -103,6 +103,16 @@ defmodule AshBackpex.LiveResource.TransformerTest do
       assert Keyword.get(fields, :author).module == Backpex.Fields.BelongsTo
     end
 
+    test "derive custom Backpex field types with field overrides" do
+      fields = TestCustomFieldMappingsLive.fields()
+
+      # this one is standard and not overridden
+      assert Keyword.get(fields, :title).module == Backpex.Fields.Text
+
+      # this one would be Ash.Type.DateTime if not overridden
+      assert Keyword.get(fields, :published_at).module == Demo.Backpex.Fields.CustomDateTime
+    end
+
     test "derive default and non-default primary key with init_order" do
       assert TestPostLive.config(:primary_key) == :id
 

test/support/test_live.ex

@@ -170,3 +170,37 @@ defmodule TestNonDefaultPrimaryKeyNameLive do
     end
   end
 end
+
+defmodule Demo.Backpex.Fields.CustomDateTime do
+  @moduledoc "Dummy field module for testing :field_mappings config override"
+  use Backpex.Field
+
+  @impl Backpex.Field
+  def render_value(assigns) do
+    ~H"<span>{@value}</span>"
+  end
+
+  @impl Backpex.Field
+  def render_form(assigns) do
+    ~H"""
+    <input type="datetime-local" />
+    """
+  end
+end
+
+defmodule TestCustomFieldMappingsLive do
+  @moduledoc false
+  use AshBackpex.LiveResource
+
+  backpex do
+    resource(AshBackpex.TestDomain.Post)
+    layout({TestLayout, :admin})
+
+    field_mappings(%{Ash.Type.DateTime => Demo.Backpex.Fields.CustomDateTime})
+
+    fields do
+      field(:title)
+      field(:published_at)
+    end
+  end
+end