mkValueStringDefault

lib.generators.mkValueStringDefault

Docs pulled from | This Revision | 10 minutes ago

Convert a value to a sensible default string representation. The builtin toString function has some strange defaults, suitable for bash scripts but not much else.

Inputs

Options: Empty set, there may be configuration options in the future
v: 2. Function argument

Noogle detected

Implementation

The following is the current implementation of this function.

mkValueStringDefault =
    { }:
    v:
    let
      err = t: v: abort ("generators.mkValueStringDefault: " + "${t} not supported: ${toPretty { } v}");
    in
    if isInt v then
      toString v
    # convert derivations to store paths
    else if isDerivation v then
      toString v
    # we default to not quoting strings
    else if isString v then
      v
    # isString returns "1", which is not a good default
    else if true == v then
      "true"
    # here it returns to "", which is even less of a good default
    else if false == v then
      "false"
    else if null == v then
      "null"
    # if you have lists you probably want to replace this
    else if isList v then
      err "lists" v
    # same as for lists, might want to replace
    else if isAttrs v then
      err "attrsets" v
    # functions can’t be printed of course
    else if isFunction v then
      err "functions" v
    # Floats currently can't be converted to precise strings,
    # condition warning on nix version once this isn't a problem anymore
    # See https://github.com/NixOS/nix/pull/3480
    else if isFloat v then
      floatToString v
    else
      err "this value is" (toString v);