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| author | sternenseemann <0rpkxez4ksa01gb3typccl0i@systemli.org> | 2021-01-31 14:25:07 +0100 |
|---|---|---|
| committer | sternenseemann <0rpkxez4ksa01gb3typccl0i@systemli.org> | 2021-01-31 15:35:17 +0100 |
| commit | d9a7d03da8c58aa863911506ae3153729f8931da (patch) | |
| tree | c9d70c6696c1cea8fc04793f9e58f88814996262 /lib | |
| parent | 552d7182874ef1b8fcf25c55d3777719a5ec7bfb (diff) | |
lib/generators: fix toPretty throwing on (partially applied) builtins
An high level example case of this problem occuring can be found below:
nix-repl> lib.generators.toPretty {} (lib.concatStringsSep "\n")
error: 'functionArgs' requires a function, at /home/lukas/src/nix/nixpkgs/lib/trivial.nix:334:42
However this does not happen on other partially applied functions:
nix-repl> lib.generators.toPretty {} (lib.concatMapStringsSep "\n")
"<function>"
The issue, as it turns out is that while builtins are functions,
builtins.functionArgs throws if is passed a builtin or a partially
applied builtin:
nix-repl> lib.generators.toPretty {} builtins.toString
error: 'functionArgs' requires a function, at /home/lukas/src/nix/nixpkgs/lib/trivial.nix:334:42
nix-repl> lib.generators.toPretty {} (builtins.foldl' (a: b: a + b))
error: 'functionArgs' requires a function, at /home/lukas/src/nix/nixpkgs/lib/trivial.nix:334:42
I'm pretty sure this qualifies as a nix bug and should be filed
accordingly, but we can work around it in lib.generators.toPretty by
using tryEval and falling back to {} which functionArgs _should_ return
for builtins.
The nix behavior is inconsistent to say the least:
nix-repl> builtins.functionArgs builtins.functionArgs
error: 'functionArgs' requires a function, at (string):1:1
nix-repl> builtins.typeOf builtins.functionArgs
"lambda"
builtins.functionArgs (a: 1 + a)
{ }
nix-repl> builtins.typeOf (a: 1 + a)
"lambda"
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/generators.nix | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/lib/generators.nix b/lib/generators.nix index 501a23599f45..9546f5b5b0ab 100644 --- a/lib/generators.nix +++ b/lib/generators.nix @@ -236,12 +236,17 @@ rec { + libStr.concatMapStringsSep introSpace (go (indent + " ")) v + outroSpace + "]" else if isFunction v then - let fna = lib.functionArgs v; + # functionArgs throws in case of (partially applied) builtins + # on nix before commit b2748c6e99239ff6803ba0da76c362790c8be192 + # which includes current nix stable + # TODO remove tryEval workaround when the issue is resolved on nix stable + let fna = builtins.tryEval (lib.functionArgs v); showFnas = concatStringsSep ", " (libAttr.mapAttrsToList (name: hasDefVal: if hasDefVal then name + "?" else name) - fna); - in if fna == {} then "<function>" - else "<function, args: {${showFnas}}>" + fna.value); + in if !fna.success || fna.value == {} + then "<function>" + else "<function, args: {${showFnas}}>" else if isAttrs v then # apply pretty values if allowed if attrNames v == [ "__pretty" "val" ] && allowPrettyValues |