write first test and let changeset errors return error json in controller

.vscode/tasks.json

@@ -0,0 +1,67 @@
+{
+    "version": "2.0.0",
+    "tasks": [{
+        "label": "mix test",
+        "type": "shell",
+        "command": "mix",
+        "args": [
+          "test",
+          "--exclude",
+          "integration",
+          "--exclude",
+          "feature",
+          "--color"
+        ],
+        "options": {
+          "cwd": "${workspaceRoot}",
+          "requireFiles": [
+            "test/**/test_helper.exs",
+            "test/**/*_test.exs"
+          ]
+        },
+        "problemMatcher": "$mixTestFailure"
+      },
+      {
+        "label": "mix test file",
+        "type": "shell",
+        "command": "mix",
+        "args": [
+          "test",
+          "${relativeFile}",
+          "--color",
+          "--trace"
+        ],
+        "options": {
+          "cwd": "${workspaceRoot}",
+          "requireFiles": [
+            "test/**/test_helper.exs",
+            "test/**/*_test.exs"
+          ]
+        },
+        "problemMatcher": "$mixTestFailure"
+      },
+      {
+        "label": "mix test focused",
+        "type": "shell",
+        "command": "mix",
+        "args": [
+          "test",
+          "${relativeFile}:${lineNumber}",
+          "--color",
+          "--trace"
+        ],
+        "options": {
+          "cwd": "${workspaceRoot}",
+          "requireFiles": [
+            "test/**/test_helper.exs",
+            "test/**/*_test.exs"
+          ]
+        },
+        "problemMatcher": "$mixTestFailure",
+        "group": {
+          "kind": "test",
+          "isDefault": true
+        }
+      }
+    ]
+  }

config/config.exs

@@ -10,6 +10,8 @@ use Mix.Config
 config :entendu,
   ecto_repos: [Entendu.Repo]
 
+config :entendu, Entendu.Repo, migration_primary_key: [type: :uuid]
+
 # Configures the endpoint
 config :entendu, EntenduWeb.Endpoint,
   url: [host: "dev.intended.link"],

lib/entendu/links/link.ex

@@ -2,6 +2,8 @@ defmodule Entendu.Links.Link do
   use Ecto.Schema
   import Ecto.Changeset
 
+  @primary_key {:id, Ecto.UUID, autogenerate: true}
+
   schema "links" do
     field :burn_after_reading, :boolean, default: false
     field :expires, :utc_datetime
@@ -16,7 +18,13 @@ defmodule Entendu.Links.Link do
   @doc false
   def changeset(link, attrs) do
     link
-    |> cast(attrs, [:expires, :burn_after_reading, :filename, :filetype, :text_content, :file_content])
+    |> cast(attrs, [
-    |> validate_required([:expires, :burn_after_reading, :filename, :filetype])
+      :expires,
+      :burn_after_reading,
+      :filename,
+      :filetype,
+      :text_content,
+      :file_content
+    ])
   end
 end

lib/entendu_web/controllers/fallback_controller.ex

@@ -0,0 +1,10 @@
+defmodule EntenduWeb.FallbackController do
+  use EntenduWeb, :controller
+
+  def call(conn, {:error, %Ecto.Changeset{} = changeset}) do
+    conn
+    |> put_status(:unprocessable_entity)
+    |> put_view(EntenduWeb.ChangesetView)
+    |> render("error.json", changeset: changeset)
+  end
+end

lib/entendu_web/controllers/link_controller.ex

@@ -9,27 +9,33 @@ defmodule EntenduWeb.LinkController do
   alias Entendu.Links
   alias Links.Link
   alias Ecto.Changeset
+  alias EntenduWeb.FallbackController
+
+  action_fallback(FallbackController)
 
   def just_page(conn, _params) do
     render(conn, "just.html")
   end
 
-  defparams first_step %{
+  defparams(
+    first_step(%{
       burn_after_reading: [field: :boolean, default: false],
       expires: :utc_datetime,
       filename: :string,
       filetype: :string,
       text_content: :string,
       file_content: :string
-  }
+    })
+  )
 
   def just(conn, params) do
     with %Changeset{valid?: true} = changeset <- first_step(params),
          link_params <- Params.to_map(changeset),
          {:ok, %Link{} = link} <- Links.create_link(link_params) do
       conn
+      |> put_status(:created)
       |> assign(:link, link)
-      |> render("show_authorized", link: link)
+      |> render("show_authorized.json", %{link: link})
     end
   end
 

lib/entendu_web/views/changeset_view.ex

@@ -0,0 +1,15 @@
+defmodule EntenduWeb.ChangesetView do
+  use EntenduWeb, :view
+
+  def translate_errors(%Ecto.Changeset{} = changeset) do
+    Ecto.Changeset.traverse_errors(changeset, &translate_error/1)
+  end
+
+  def translate_errors(errors = %{}), do: errors
+
+  def render("error.json", %{changeset: changeset}) do
+    # When encoded, the changeset returns its errors
+    # as a JSON object. So we just pass it forward.
+    %{errors: translate_errors(changeset)}
+  end
+end

test/entendu_web/controllers/links_controller_test.exs

@@ -0,0 +1,27 @@
+defmodule EntenduWeb.ErrorViewTest do
+  use EntenduWeb.ConnCase, async: true
+
+  # Bring render/3 and render_to_string/3 for testing custom views
+  import Phoenix.View
+
+  test "renders 404.html" do
+    assert render_to_string(EntenduWeb.ErrorView, "404.html", []) == "Not Found"
+  end
+
+  test "just endpoint creates a link with valid attrs", %{conn: conn} do
+    params = %{
+      "text_content" => "some gibberish",
+      "filename" => "more gibberish"
+    }
+
+    conn = post(conn, Routes.link_path(conn, :just), params)
+
+    response = json_response(conn, 201)
+
+    assert %{
+             "id" => _link_id,
+             "text_content" => "some gibberish",
+             "filename" => "more gibberish"
+           } = response
+  end
+end