···

       
72
       
72
       
 
       
  # into one where changes made in the first are available in the

     

       
73
       
73
       
 
       
  # 'super' of the second

     

       
74
       
74
       
 
       
  composeExtensions =

     

       
75
       
75
       
-
       
    f: g: self: super:

     

       
76
       
76
       
-
       
      let fApplied = f self super;

     

       
77
       
77
       
-
       
          super' = super // fApplied;

     

       
78
       
78
       
-
       
      in fApplied // g self super';

     

       
75
       
75
       
+
       
    f: g: final: prev:

     

       
76
       
76
       
+
       
      let fApplied = f final prev;

     

       
77
       
77
       
+
       
          prev' = prev // fApplied;

     

       
78
       
78
       
+
       
      in fApplied // g final prev';

     

       
79
       
79
       
 
       


     

       
80
       
80
       
 
       
  # Compose several extending functions of the type expected by 'extends' into

     

       
81
       
81
       
 
       
  # one where changes made in preceding functions are made available to

     
···

       
84
       
84
       
 
       
  # composeManyExtensions : [packageSet -> packageSet -> packageSet] -> packageSet -> packageSet -> packageSet

     

       
85
       
85
       
 
       
  #                          ^final        ^prev         ^overrides     ^final        ^prev         ^overrides

     

       
86
       
86
       
 
       
  composeManyExtensions =

     

       
87
       
87
       
-
       
    lib.foldr (x: y: composeExtensions x y) (self: super: {});

     

       
87
       
87
       
+
       
    lib.foldr (x: y: composeExtensions x y) (final: prev: {});

     

       
88
       
88
       
 
       


     

       
89
       
89
       
 
       
  # Create an overridable, recursive attribute set. For example:

     

       
90
       
90
       
 
       
  #