From 3399d7ba69b8bb43e92b704bfbf153e6ee678675 Mon Sep 17 00:00:00 2001
From: Luper Rouch <luper.rouch@gmail.com>
Date: Wed, 31 Aug 2022 18:25:49 +0200
Subject: [PATCH 1/2] feat: add parameters option

Allows to add paramameters to the generated struct type.

For example:

  typedstruct parameters: [a, b] do
    field :a, a
    field :b, b | nil
    field :c, integer()
  end

Generates the type:

  @type t(a, b) :: %__MODULE__{
    a: a,
    b: b | nil,
    c: integer()
  }
---
 lib/typed_struct.ex        | 51 +++++++++++++++++++++++++++++++++++---
 test/typed_struct_test.exs | 37 +++++++++++++++++++++++++++
 2 files changed, 84 insertions(+), 4 deletions(-)

diff --git a/lib/typed_struct.ex b/lib/typed_struct.ex
index 371b64a..d893d0a 100644
--- a/lib/typed_struct.ex
+++ b/lib/typed_struct.ex
@@ -35,6 +35,7 @@ defmodule TypedStruct do
       individual fields.
     * `opaque` - if set to true, creates an opaque type for the struct.
     * `module` - if set, creates the struct in a submodule named `module`.
+    * `parameters` - if set, adds these parameters to the generated `t()`.
 
   ## Examples
 
@@ -74,6 +75,42 @@ defmodule TypedStruct do
           field :field_four, atom(), default: :hey
         end
       end
+
+  You can also add type parameters:
+
+      defmodule RepairOrder do
+        use TypedStruct
+
+        @type new :: %{status: :new}
+        @type in_progress :: %{status: :in_progress, progress: integer()}
+        @type completed :: %{status: :completed}
+
+        typedstruct parameters: [state] do
+          field :state, state()
+          customer: String.t()
+        end
+
+        @spec new(String.t()) :: t(new())
+        def new(customer) do
+          %{state: %{status: :new}, customer: customer}
+        end
+
+        @spec start_repair(t(new())) :: t(in_progress())
+        def start_repair(order) do
+          put_in(order.state, %{status: :in_progress, progress: 0})
+        end
+
+        @spec advance_repair(t(in_progress()), integer()) :: t(in_progress())
+        def advance_repair(order, progress) do
+          put_in(order.state.progress, progress)
+        end
+
+        @spec finish_repair(t(in_progress())) :: t(completed())
+        def finish_repair(order) do
+          put_in(order.state, %{status: :completed})
+        end
+      end
+
   """
   defmacro typedstruct(opts \\ [], do: block) do
     ast = TypedStruct.__typedstruct__(block, opts)
@@ -116,13 +153,19 @@ defmodule TypedStruct do
 
   @doc false
   defmacro __type__(types, opts) do
+    type_parameters = Keyword.get(opts, :parameters, [])
+
     if Keyword.get(opts, :opaque, false) do
-      quote bind_quoted: [types: types] do
-        @opaque t() :: %__MODULE__{unquote_splicing(types)}
+      quote bind_quoted: [types: types, type_parameters: type_parameters] do
+        @opaque t(unquote_splicing(type_parameters)) :: %__MODULE__{
+                  unquote_splicing(types)
+                }
       end
     else
-      quote bind_quoted: [types: types] do
-        @type t() :: %__MODULE__{unquote_splicing(types)}
+      quote bind_quoted: [types: types, type_parameters: type_parameters] do
+        @type t(unquote_splicing(type_parameters)) :: %__MODULE__{
+                unquote_splicing(types)
+              }
       end
     end
   end
diff --git a/test/typed_struct_test.exs b/test/typed_struct_test.exs
index d5fc420..61f2cb8 100644
--- a/test/typed_struct_test.exs
+++ b/test/typed_struct_test.exs
@@ -60,9 +60,21 @@ defmodule TypedStructTest do
       end
     end
 
+  {:module, _name, bytecode_parameterized, _exports} =
+    defmodule ParameterizedTestStruct do
+      use TypedStruct
+
+      typedstruct parameters: [a, b] do
+        field :a, a
+        field :b, b | nil
+        field :c, integer()
+      end
+    end
+
   @bytecode bytecode
   @bytecode_opaque bytecode_opaque
   @bytecode_noalias bytecode_noalias
+  @bytecode_parameterized bytecode_parameterized
 
   # Standard struct name used when comparing generated types.
   @standard_struct_name TypedStructTest.TestStruct
@@ -156,6 +168,31 @@ defmodule TypedStructTest do
     assert type1 == type2
   end
 
+  test "generates parameterized types" do
+    # Define a second struct with the type expected for TestStruct.
+    {:module, _name, bytecode2, _exports} =
+      defmodule TestStruct4 do
+        defstruct [:a, :b, :c]
+
+        @type t(a, b) :: %__MODULE__{
+                a: a,
+                b: b | nil,
+                c: integer()
+              }
+      end
+
+    # Get both types and standardise them (remove line numbers and rename
+    # the second struct with the name of the first one).
+    type1 = @bytecode_parameterized |> extract_first_type() |> standardise()
+
+    type2 =
+      bytecode2
+      |> extract_first_type()
+      |> standardise(TypedStructTest.TestStruct4)
+
+    assert type1 == type2
+  end
+
   test "generates the struct in a submodule if `module: ModuleName` is set" do
     assert TestModule.Struct.__struct__() == %TestModule.Struct{field: nil}
   end

From 74bc582515c2aeea63d0d37fa436f65530295926 Mon Sep 17 00:00:00 2001
From: Luper Rouch <luper.rouch@gmail.com>
Date: Thu, 1 Sep 2022 08:54:47 +0200
Subject: [PATCH 2/2] fixup! feat: add parameters option

Change examples because put_in() is not properly analyzed by dialyzer.
---
 lib/typed_struct.ex | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/typed_struct.ex b/lib/typed_struct.ex
index d893d0a..f004f5f 100644
--- a/lib/typed_struct.ex
+++ b/lib/typed_struct.ex
@@ -97,7 +97,7 @@ defmodule TypedStruct do
 
         @spec start_repair(t(new())) :: t(in_progress())
         def start_repair(order) do
-          put_in(order.state, %{status: :in_progress, progress: 0})
+          %{order | state: %{status: :in_progress, progress: 0}}
         end
 
         @spec advance_repair(t(in_progress()), integer()) :: t(in_progress())
@@ -107,7 +107,7 @@ defmodule TypedStruct do
 
         @spec finish_repair(t(in_progress())) :: t(completed())
         def finish_repair(order) do
-          put_in(order.state, %{status: :completed})
+          %{order | state: %{status: :completed}}
         end
       end