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author | Profpatsch <mail@profpatsch.de> | 2017-06-06 22:41:22 +0200 |
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committer | Profpatsch <mail@profpatsch.de> | 2017-06-22 00:58:59 +0200 |
commit | b1ffe5e4c029c9f5675bcc42997413fd1b21fbf1 (patch) | |
tree | f8569d068102606b54724713c1c6a51cc4f539dc /lib/generators.nix | |
parent | dd3f2e648a6ee5dc7ba88bf2e3d13b6b47686350 (diff) | |
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lib/generators: toPretty
`toPretty` implements a pretty printer for nix values.
Diffstat (limited to 'lib/generators.nix')
-rw-r--r-- | lib/generators.nix | 32 |
1 files changed, 32 insertions, 0 deletions
diff --git a/lib/generators.nix b/lib/generators.nix index 4d3c920b0ae..0e5ce864356 100644 --- a/lib/generators.nix +++ b/lib/generators.nix @@ -90,4 +90,36 @@ rec { * parsers as well. */ toYAML = {}@args: toJSON args; + + # TODO we need some kind of pattern matching sometimes + /* Pretty print a value, akin to `builtins.trace`. + * Should probably be a builtin as well. + */ + toPretty = { + /* If this option is true, attrsets like { __pretty = fn; val = …; } + will use fn to convert val to a pretty printed representation. + (This means fn is type Val -> String.) */ + allowPrettyValues ? false + }@args: v: with builtins; + if isInt v then toString v + else if isBool v then (if v == true then "true" else "false") + else if isString v then "\"" + v + "\"" + else if null == v then "null" + else if isFunction v then "<λ>" + else if isList v then "[ " + + libStr.concatMapStringsSep " " (toPretty args) v + + " ]" + else if isAttrs v then + # apply pretty values if allowed + if attrNames v == [ "__pretty" "val" ] && allowPrettyValues + then v.__pretty v.val + # TODO: there is probably a better representation? + else if v ? type && v.type == "derivation" then "<δ>" + else "{ " + + libStr.concatStringsSep " " (libAttr.mapAttrsToList + (name: value: + "${toPretty args name} = ${toPretty args value};") v) + + " }" + else "toPretty: should never happen (v = ${v})"; + } |