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author | Shea Levy <shea@shealevy.com> | 2017-04-07 14:03:40 -0400 |
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committer | Shea Levy <shea@shealevy.com> | 2017-04-07 14:30:05 -0400 |
commit | 0a15af2ed170b30636a264b6b535a9327effddc5 (patch) | |
tree | 831f89fc2ff64af9402542d3c54ad8347ea95782 /lib | |
parent | a5ee494046b4259a4a2dfea95776faa898d1bd26 (diff) |
lib: Add composeExtensions for composing extension functions
Diffstat (limited to 'lib')
-rw-r--r-- | lib/trivial.nix | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/lib/trivial.nix b/lib/trivial.nix index 40499b2b5092..acbd687dd98f 100644 --- a/lib/trivial.nix +++ b/lib/trivial.nix @@ -80,6 +80,15 @@ rec { # argument, but it's nice this way if several uses of `extends` are cascaded. extends = f: rattrs: self: let super = rattrs self; in super // f self super; + # Compose two extending functions of the type expected by 'extends' + # into one where changes made in the first are available in the + # 'super' of the second + composeExtensions = + f: g: self: super: + let fApplied = f self super; + super' = super // fApplied; + in fApplied // g self super'; + # Create an overridable, recursive attribute set. For example: # # nix-repl> obj = makeExtensible (self: { }) |