diff options
Diffstat (limited to 'lib/trivial.nix')
-rw-r--r-- | lib/trivial.nix | 27 |
1 files changed, 26 insertions, 1 deletions
diff --git a/lib/trivial.nix b/lib/trivial.nix index c452c7b65bc..d8d51298143 100644 --- a/lib/trivial.nix +++ b/lib/trivial.nix @@ -52,7 +52,7 @@ rec { # Pull in some builtins not included elsewhere. inherit (builtins) - pathExists readFile isBool isFunction + pathExists readFile isBool isInt add sub lessThan seq deepSeq genericClosure; @@ -99,4 +99,29 @@ rec { */ warn = msg: builtins.trace "WARNING: ${msg}"; info = msg: builtins.trace "INFO: ${msg}"; + + # | Add metadata about expected function arguments to a function. + # The metadata should match the format given by + # builtins.functionArgs, i.e. a set from expected argument to a bool + # representing whether that argument has a default or not. + # setFunctionArgs : (a → b) → Map String Bool → (a → b) + # + # This function is necessary because you can't dynamically create a + # function of the { a, b ? foo, ... }: format, but some facilities + # like callPackage expect to be able to query expected arguments. + setFunctionArgs = f: args: + { # TODO: Should we add call-time "type" checking like built in? + __functor = self: f; + __functionArgs = args; + }; + + # | Extract the expected function arguments from a function. + # This works both with nix-native { a, b ? foo, ... }: style + # functions and functions with args set with 'setFunctionArgs'. It + # has the same return type and semantics as builtins.functionArgs. + # setFunctionArgs : (a → b) → Map String Bool. + functionArgs = f: f.__functionArgs or (builtins.functionArgs f); + + isFunction = f: builtins.isFunction f || + (f ? __functor && isFunction (f.__functor f)); } |