feat(ryuk): honor ryuk.container.privileged property and env var

Mirror testcontainers-dotnet behavior and resolve SELinux denials on
Fedora (issue #183) by letting users run Ryuk in privileged mode via
either the `ryuk.container.privileged` property in
`~/.testcontainers.properties` or the
`TESTCONTAINERS_RYUK_CONTAINER_PRIVILEGED` environment variable. Both
`"true"` and `"1"` are treated as truthy. The environment variable
takes precedence over the property when both are set, matching the
dotnet implementation.

The resolver is extracted as `Testcontainers.ryuk_privileged?/1`
(@doc false) so it can be unit-tested without launching Ryuk.

Fixes #183

Author: jarlah

lib/testcontainers.ex

@@ -450,6 +450,32 @@ defmodule Testcontainers do
     end
   end
 
+  @doc false
+  # Resolves whether Ryuk should run in privileged mode.
+  #
+  # Mirrors testcontainers-dotnet: honors the `ryuk.container.privileged`
+  # property and the `TESTCONTAINERS_RYUK_CONTAINER_PRIVILEGED` environment
+  # variable. The environment variable takes precedence when both are set.
+  # Values `"true"` and `"1"` are treated as truthy.
+  def ryuk_privileged?(properties) when is_map(properties) do
+    env_value = System.get_env("TESTCONTAINERS_RYUK_CONTAINER_PRIVILEGED")
+    prop_value = Map.get(properties, "ryuk.container.privileged")
+
+    value = env_value || prop_value
+
+    truthy?(value)
+  end
+
+  defp truthy?(value) when is_binary(value) do
+    case String.downcase(String.trim(value)) do
+      "true" -> true
+      "1" -> true
+      _ -> false
+    end
+  end
+
+  defp truthy?(_), do: false
+
   @doc false
   def running_in_container?(
         dockerenv_path \\ "/.dockerenv",
@@ -668,7 +694,7 @@ defmodule Testcontainers do
   end
 
   defp start_ryuk(conn, session_id, properties, docker_host, docker_hostname) do
-    ryuk_privileged = Map.get(properties, "ryuk.container.privileged", "false") == "true"
+    ryuk_privileged = ryuk_privileged?(properties)
 
     ryuk_config =
       Container.new("testcontainers/ryuk:#{Constants.ryuk_version()}")

test/testcontainers_test.exs

@@ -2,7 +2,88 @@ defmodule TestcontainersTest do
   alias Testcontainers.Connection
   alias Testcontainers.Container
   alias Testcontainers.Docker
-  use ExUnit.Case, async: true
+  # async: false because ryuk_privileged? tests mutate process environment
+  use ExUnit.Case, async: false
+
+  @ryuk_privileged_env "TESTCONTAINERS_RYUK_CONTAINER_PRIVILEGED"
+  @ryuk_privileged_prop "ryuk.container.privileged"
+
+  describe "ryuk_privileged?/1" do
+    setup do
+      original = System.get_env(@ryuk_privileged_env)
+
+      on_exit(fn ->
+        case original do
+          nil -> System.delete_env(@ryuk_privileged_env)
+          value -> System.put_env(@ryuk_privileged_env, value)
+        end
+      end)
+
+      :ok
+    end
+
+    test "returns false when neither property nor env var is set" do
+      System.delete_env(@ryuk_privileged_env)
+      refute Testcontainers.ryuk_privileged?(%{})
+    end
+
+    test "returns true when property is 'true'" do
+      System.delete_env(@ryuk_privileged_env)
+      assert Testcontainers.ryuk_privileged?(%{@ryuk_privileged_prop => "true"})
+    end
+
+    test "returns true when property is '1'" do
+      System.delete_env(@ryuk_privileged_env)
+      assert Testcontainers.ryuk_privileged?(%{@ryuk_privileged_prop => "1"})
+    end
+
+    test "returns false when property is 'false'" do
+      System.delete_env(@ryuk_privileged_env)
+      refute Testcontainers.ryuk_privileged?(%{@ryuk_privileged_prop => "false"})
+    end
+
+    test "returns false when property is '0'" do
+      System.delete_env(@ryuk_privileged_env)
+      refute Testcontainers.ryuk_privileged?(%{@ryuk_privileged_prop => "0"})
+    end
+
+    test "returns true when env var is 'true'" do
+      System.put_env(@ryuk_privileged_env, "true")
+      assert Testcontainers.ryuk_privileged?(%{})
+    end
+
+    test "returns true when env var is '1'" do
+      System.put_env(@ryuk_privileged_env, "1")
+      assert Testcontainers.ryuk_privileged?(%{})
+    end
+
+    test "returns false when env var is 'false'" do
+      System.put_env(@ryuk_privileged_env, "false")
+      refute Testcontainers.ryuk_privileged?(%{@ryuk_privileged_prop => "true"})
+    end
+
+    test "env var takes precedence over property (env false, prop true)" do
+      System.put_env(@ryuk_privileged_env, "false")
+      refute Testcontainers.ryuk_privileged?(%{@ryuk_privileged_prop => "true"})
+    end
+
+    test "env var takes precedence over property (env true, prop false)" do
+      System.put_env(@ryuk_privileged_env, "true")
+      assert Testcontainers.ryuk_privileged?(%{@ryuk_privileged_prop => "false"})
+    end
+
+    test "treats arbitrary strings as falsy" do
+      System.delete_env(@ryuk_privileged_env)
+      refute Testcontainers.ryuk_privileged?(%{@ryuk_privileged_prop => "yes"})
+      refute Testcontainers.ryuk_privileged?(%{@ryuk_privileged_prop => ""})
+    end
+
+    test "is case-insensitive and trims whitespace" do
+      System.delete_env(@ryuk_privileged_env)
+      assert Testcontainers.ryuk_privileged?(%{@ryuk_privileged_prop => "TRUE"})
+      assert Testcontainers.ryuk_privileged?(%{@ryuk_privileged_prop => "  true  "})
+    end
+  end
 
   test "cleans up containers on terminate" do
     {:ok, pid} = Testcontainers.start_link(name: :cleanup_test1)