Add e2e.set_github_matrix mix task

Author: gaggle

lib/mix/tasks/e2e/set_github_matrix.ex

@@ -0,0 +1,51 @@
+defmodule Mix.Tasks.E2e.SetGithubMatrix do
+  use Mix.Task
+
+  alias ElixirScript.Core
+  alias ElixirScript.E2e
+  alias ElixirScript.E2e.Entry
+
+  @moduledoc """
+  Mix task to generate matrix information from E2E test data for GitHub Actions workflows.
+  """
+
+  @shortdoc "Generates matrix information from the E2E data file, to feed into a GitHub Actions matrix."
+
+  def run(args) do
+    output_key = List.first(args) || "matrix"
+    E2e.read_test_file()
+    |> log_detected_tests()
+    |> map_entries_for_json()
+    |> encode_for_github_actions()
+    |> Core.set_output(output_key)
+    Core.log_output()
+  end
+
+  # Logs the detected E2E tests to the console.
+  defp log_detected_tests(entries) do
+    IO.puts("E2E tests found:")
+    Enum.each(entries, &log_test_entry/1)
+    entries # Return the unchanged list of entries
+  end
+
+  # Logs a single E2E test entry.
+  defp log_test_entry(entry) do
+    IO.puts("  * \"#{entry.name}\"")
+  end
+
+  # Converts a list of `Entry` structs into a list of maps suitable for JSON encoding.
+  defp map_entries_for_json(entries) do
+    Enum.map(entries, &entry_to_map_for_json/1)
+  end
+
+  # Converts an `Entry` struct to a map for JSON encoding.
+  defp entry_to_map_for_json(%Entry{} = entry) do
+    Map.take(entry, [:name, :script, :expected])
+  end
+
+  # Encodes the provided entries into a JSON structure for GitHub Actions matrix.
+  defp encode_for_github_actions(entries) do
+    %{"include" => entries}
+    |> Jason.encode!()
+  end
+end