Include Crystal::System::Group instead of extending it (#14930)

src/crystal/system/group.cr

@@ -1,3 +1,13 @@
+module Crystal::System::Group
+  # def system_name : String
+
+  # def system_id : String
+
+  # def self.from_name?(groupname : String) : ::System::Group?
+
+  # def self.from_id?(groupid : String) : ::System::Group?
+end
+
 {% if flag?(:wasi) %}
   require "./wasi/group"
 {% elsif flag?(:unix) %}

src/crystal/system/unix/group.cr

@@ -4,11 +4,22 @@ require "../unix"
 module Crystal::System::Group
   private GETGR_R_SIZE_MAX = 1024 * 16
 
-  private def from_struct(grp)
-    new(String.new(grp.gr_name), grp.gr_gid.to_s)
+  def initialize(@name : String, @id : String)
   end
 
-  private def from_name?(groupname : String)
+  def system_name
+    @name
+  end
+
+  def system_id
+    @id
+  end
+
+  private def self.from_struct(grp)
+    ::System::Group.new(String.new(grp.gr_name), grp.gr_gid.to_s)
+  end
+
+  def self.from_name?(groupname : String)
     groupname.check_no_null_byte
 
     grp = uninitialized LibC::Group
@@ -21,7 +32,7 @@ module Crystal::System::Group
     end
   end
 
-  private def from_id?(groupid : String)
+  def self.from_id?(groupid : String)
     groupid = groupid.to_u32?
     return unless groupid
 

src/crystal/system/wasi/group.cr

@@ -1,9 +1,17 @@
 module Crystal::System::Group
-  private def from_name?(groupname : String)
-    raise NotImplementedError.new("Crystal::System::Group#from_name?")
+  def system_name
+    raise NotImplementedError.new("Crystal::System::Group#system_name")
   end
 
-  private def from_id?(groupid : String)
-    raise NotImplementedError.new("Crystal::System::Group#from_id?")
+  def system_id
+    raise NotImplementedError.new("Crystal::System::Group#system_id")
+  end
+
+  def self.from_name?(groupname : String)
+    raise NotImplementedError.new("Crystal::System::Group.from_name?")
+  end
+
+  def self.from_id?(groupid : String)
+    raise NotImplementedError.new("Crystal::System::Group.from_id?")
   end
 end

src/system/group.cr

@@ -17,19 +17,20 @@ class System::Group
   class NotFoundError < Exception
   end
 
-  extend Crystal::System::Group
+  include Crystal::System::Group
 
   # The group's name.
-  getter name : String
+  def name : String
+    system_name
+  end
 
   # The group's identifier.
-  getter id : String
-
-  def_equals_and_hash @id
-
-  private def initialize(@name, @id)
+  def id : String
+    system_id
   end
 
+  def_equals_and_hash id
+
   # Returns the group associated with the given name.
   #
   # Raises `NotFoundError` if no such group exists.
@@ -41,7 +42,7 @@ class System::Group
   #
   # Returns `nil` if no such group exists.
   def self.find_by?(*, name : String) : System::Group?
-    from_name?(name)
+    Crystal::System::Group.from_name?(name)
   end
 
   # Returns the group associated with the given ID.
@@ -55,7 +56,7 @@ class System::Group
   #
   # Returns `nil` if no such group exists.
   def self.find_by?(*, id : String) : System::Group?
-    from_id?(id)
+    Crystal::System::Group.from_id?(id)
   end
 
   def to_s(io)