From 0d83dc4a45ebecedc7d8e9645da7744c8d655f30 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jonatan=20K=C5=82osko?= <jonatanklosko@gmail.com>
Date: Tue, 29 Aug 2023 12:24:42 +0200
Subject: [PATCH 1/2] Add Kino.start_child!/1

---
 lib/kino.ex | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/lib/kino.ex b/lib/kino.ex
index 0b2ae7ef..4fd4eea9 100644
--- a/lib/kino.ex
+++ b/lib/kino.ex
@@ -445,6 +445,18 @@ defmodule Kino do
     DynamicSupervisor.start_child(Kino.DynamicSupervisor, child_spec)
   end
 
+  @doc """
+  Similar to `start_child/2` but returns the new pid or raises an error.
+  """
+  @spec start_child!(Supervisor.child_spec() | {module(), term()} | module()) :: pid()
+  def start_child!(child_spec) do
+    case start_child(child_spec) do
+      {:ok, pid} -> pid
+      {:ok, pid, _info} -> pid
+      other -> raise "failed to start child, reason: #{Kernel.inspect(other)}"
+    end
+  end
+
   @doc """
   Terminates a child started with `start_child/1`.
 

From 7f05819d850080b3cc02882ff76832fbc490952e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jonatan=20K=C5=82osko?= <jonatanklosko@gmail.com>
Date: Tue, 29 Aug 2023 13:53:36 +0200
Subject: [PATCH 2/2] Up

---
 lib/kino.ex | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/lib/kino.ex b/lib/kino.ex
index 4fd4eea9..c45120b7 100644
--- a/lib/kino.ex
+++ b/lib/kino.ex
@@ -451,12 +451,26 @@ defmodule Kino do
   @spec start_child!(Supervisor.child_spec() | {module(), term()} | module()) :: pid()
   def start_child!(child_spec) do
     case start_child(child_spec) do
-      {:ok, pid} -> pid
-      {:ok, pid, _info} -> pid
-      other -> raise "failed to start child, reason: #{Kernel.inspect(other)}"
+      {:ok, pid} ->
+        pid
+
+      {:ok, pid, _info} ->
+        pid
+
+      {:error, reason} ->
+        raise "failed to start child with the spec #{Kernel.inspect(child_spec)}.\n" <>
+                "Reason: #{start_supervised_error(reason)}"
     end
   end
 
+  defp start_supervised_error({{:EXIT, reason}, info}) when is_tuple(info),
+    do: Exception.format_exit(reason)
+
+  defp start_supervised_error({reason, info}) when is_tuple(info),
+    do: Exception.format_exit(reason)
+
+  defp start_supervised_error(reason), do: Exception.format_exit(reason)
+
   @doc """
   Terminates a child started with `start_child/1`.