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author | Alyssa Ross <hi@alyssa.is> | 2021-07-23 09:26:00 +0000 |
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committer | Alyssa Ross <hi@alyssa.is> | 2021-07-23 09:26:00 +0000 |
commit | ab63e0bb8dcf2b1bf8d4a26ed360af777b8f241d (patch) | |
tree | 504b28a058661f6c1cbb7d3f580020e50367ca7f /nixpkgs/lib/types.nix | |
parent | 55cc63c079f49e81d695a25bc2f5b3902f2bd290 (diff) | |
parent | b09661d41fb93562fd53f31574dbf781b130ac44 (diff) | |
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Merge commit 'b09661d41fb93562fd53f31574dbf781b130ac44'
Diffstat (limited to 'nixpkgs/lib/types.nix')
-rw-r--r-- | nixpkgs/lib/types.nix | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/nixpkgs/lib/types.nix b/nixpkgs/lib/types.nix index f47a1f92de72..c35f055e17f5 100644 --- a/nixpkgs/lib/types.nix +++ b/nixpkgs/lib/types.nix @@ -581,7 +581,17 @@ rec { in mkOptionType rec { name = "enum"; - description = "one of ${concatMapStringsSep ", " show values}"; + description = + # Length 0 or 1 enums may occur in a design pattern with type merging + # where an "interface" module declares an empty enum and other modules + # provide implementations, each extending the enum with their own + # identifier. + if values == [] then + "impossible (empty enum)" + else if builtins.length values == 1 then + "value ${show (builtins.head values)} (singular enum)" + else + "one of ${concatMapStringsSep ", " show values}"; check = flip elem values; merge = mergeEqualOption; functor = (defaultFunctor name) // { payload = values; binOp = a: b: unique (a ++ b); }; |