943592f698
Among other things, this will allow *2nix tools to output plain data while still being composable with the traditional callPackage/.override interfaces.
127 lines
3.6 KiB
Nix
127 lines
3.6 KiB
Nix
{ lib }:
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rec {
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/* The identity function
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For when you need a function that does “nothing”.
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Type: id :: a -> a
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*/
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id = x: x;
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/* The constant function
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Ignores the second argument.
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Or: Construct a function that always returns a static value.
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Type: const :: a -> b -> a
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Example:
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let f = const 5; in f 10
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=> 5
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*/
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const = x: y: x;
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## Named versions corresponding to some builtin operators.
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/* Concat two strings */
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concat = x: y: x ++ y;
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/* boolean “or” */
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or = x: y: x || y;
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/* boolean “and” */
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and = x: y: x && y;
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/* Convert a boolean to a string.
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Note that toString on a bool returns "1" and "".
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*/
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boolToString = b: if b then "true" else "false";
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/* Merge two attribute sets shallowly, right side trumps left
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Example:
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mergeAttrs { a = 1; b = 2; } { b = 3; c = 4; }
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=> { a = 1; b = 3; c = 4; }
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*/
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mergeAttrs = x: y: x // y;
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# Flip the order of the arguments of a binary function.
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flip = f: a: b: f b a;
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# Apply function if argument is non-null
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mapNullable = f: a: if isNull a then a else f a;
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# Pull in some builtins not included elsewhere.
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inherit (builtins)
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pathExists readFile isBool
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isInt add sub lessThan
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seq deepSeq genericClosure;
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inherit (lib.strings) fileContents;
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# Return the Nixpkgs version number.
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nixpkgsVersion =
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let suffixFile = ../.version-suffix; in
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fileContents ../.version
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+ (if pathExists suffixFile then fileContents suffixFile else "pre-git");
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# Whether we're being called by nix-shell.
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inNixShell = builtins.getEnv "IN_NIX_SHELL" != "";
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# Return minimum/maximum of two numbers.
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min = x: y: if x < y then x else y;
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max = x: y: if x > y then x else y;
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/* Integer modulus
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Example:
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mod 11 10
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=> 1
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mod 1 10
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=> 1
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*/
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mod = base: int: base - (int * (builtins.div base int));
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/* Reads a JSON file. */
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importJSON = path:
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builtins.fromJSON (builtins.readFile path);
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/* See https://github.com/NixOS/nix/issues/749. Eventually we'd like these
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to expand to Nix builtins that carry metadata so that Nix can filter out
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the INFO messages without parsing the message string.
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Usage:
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{
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foo = lib.warn "foo is deprecated" oldFoo;
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}
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TODO: figure out a clever way to integrate location information from
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something like __unsafeGetAttrPos.
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*/
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warn = msg: builtins.trace "WARNING: ${msg}";
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info = msg: builtins.trace "INFO: ${msg}";
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# | Add metadata about expected function arguments to a function.
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# The metadata should match the format given by
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# builtins.functionArgs, i.e. a set from expected argument to a bool
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# representing whether that argument has a default or not.
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# setFunctionArgs : (a → b) → Map String Bool → (a → b)
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#
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# This function is necessary because you can't dynamically create a
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# function of the { a, b ? foo, ... }: format, but some facilities
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# like callPackage expect to be able to query expected arguments.
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setFunctionArgs = f: args:
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{ # TODO: Should we add call-time "type" checking like built in?
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__functor = self: f;
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__functionArgs = args;
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};
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# | Extract the expected function arguments from a function.
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# This works both with nix-native { a, b ? foo, ... }: style
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# functions and functions with args set with 'setFunctionArgs'. It
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# has the same return type and semantics as builtins.functionArgs.
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# setFunctionArgs : (a → b) → Map String Bool.
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functionArgs = f: f.__functionArgs or (builtins.functionArgs f);
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isFunction = f: builtins.isFunction f ||
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(f ? __functor && isFunction (f.__functor f));
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}
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