nixpkgs/lib/generators.nix

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/* Functions that generate widespread file
* formats from nix data structures.
*
* They all follow a similar interface:
* generator { config-attrs } data
*
* `config-attrs` are holes in the generators
* with sensible default implementations that
* can be overwritten. The default implementations
* are mostly generators themselves, called with
* their respective default values; they can be reused.
*
* Tests can be found in ./tests.nix
* Documentation in the manual, #sec-generators
*/
{ lib }:
with (lib).trivial;
let
libStr = lib.strings;
libAttr = lib.attrsets;
inherit (lib) isFunction;
in
rec {
## -- HELPER FUNCTIONS & DEFAULTS --
/* 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.
*/
mkValueStringDefault = {}: v: with builtins;
let err = t: v: abort
("generators.mkValueStringDefault: " +
"${t} not supported: ${toPretty {} v}");
in if isInt v then toString v
# we default to not quoting strings
else if isString v then v
# isString returns "1", which is not a good default
else if true == v then "true"
# here it returns to "", which is even less of a good default
else if false == v then "false"
else if null == v then "null"
# if you have lists you probably want to replace this
else if isList v then err "lists" v
# same as for lists, might want to replace
else if isAttrs v then err "attrsets" v
# functions cant be printed of course
else if isFunction v then err "functions" v
# Floats currently can't be converted to precise strings,
# condition warning on nix version once this isn't a problem anymore
# See https://github.com/NixOS/nix/pull/3480
else if isFloat v then libStr.floatToString v
else err "this value is" (toString v);
/* Generate a line of key k and value v, separated by
* character sep. If sep appears in k, it is escaped.
* Helper for synaxes with different separators.
*
* mkValueString specifies how values should be formatted.
*
* mkKeyValueDefault {} ":" "f:oo" "bar"
* > "f\:oo:bar"
*/
mkKeyValueDefault = {
mkValueString ? mkValueStringDefault {}
}: sep: k: v:
"${libStr.escape [sep] k}${sep}${mkValueString v}";
## -- FILE FORMAT GENERATORS --
/* Generate a key-value-style config file from an attrset.
*
* mkKeyValue is the same as in toINI.
*/
toKeyValue = {
mkKeyValue ? mkKeyValueDefault {} "=",
listsAsDuplicateKeys ? false
}:
let mkLine = k: v: mkKeyValue k v + "\n";
mkLines = if listsAsDuplicateKeys
then k: v: map (mkLine k) (if lib.isList v then v else [v])
else k: v: [ (mkLine k v) ];
in attrs: libStr.concatStrings (lib.concatLists (libAttr.mapAttrsToList mkLines attrs));
/* Generate an INI-style config file from an
* attrset of sections to an attrset of key-value pairs.
*
* generators.toINI {} {
* foo = { hi = "${pkgs.hello}"; ciao = "bar"; };
* baz = { "also, integers" = 42; };
* }
*
*> [baz]
*> also, integers=42
*>
*> [foo]
*> ciao=bar
*> hi=/nix/store/y93qql1p5ggfnaqjjqhxcw0vqw95rlz0-hello-2.10
*
* The mk* configuration attributes can generically change
* the way sections and key-value strings are generated.
*
* For more examples see the test cases in ./tests.nix.
*/
toINI = {
# apply transformations (e.g. escapes) to section names
mkSectionName ? (name: libStr.escape [ "[" "]" ] name),
# format a setting line from key and value
mkKeyValue ? mkKeyValueDefault {} "=",
# allow lists as values for duplicate keys
listsAsDuplicateKeys ? false
}: attrsOfAttrs:
let
# map function to string for each key val
mapAttrsToStringsSep = sep: mapFn: attrs:
libStr.concatStringsSep sep
(libAttr.mapAttrsToList mapFn attrs);
mkSection = sectName: sectValues: ''
[${mkSectionName sectName}]
'' + toKeyValue { inherit mkKeyValue listsAsDuplicateKeys; } sectValues;
in
# map input to ini sections
mapAttrsToStringsSep "\n" mkSection attrsOfAttrs;
/* Generate a git-config file from an attrset.
*
* It has two major differences from the regular INI format:
*
* 1. values are indented with tabs
* 2. sections can have sub-sections
*
* generators.toGitINI {
* url."ssh://git@github.com/".insteadOf = "https://github.com";
* user.name = "edolstra";
* }
*
*> [url "ssh://git@github.com/"]
*> insteadOf = https://github.com/
*>
*> [user]
*> name = edolstra
*/
toGitINI = attrs:
with builtins;
let
mkSectionName = name:
let
containsQuote = libStr.hasInfix ''"'' name;
sections = libStr.splitString "." name;
section = head sections;
subsections = tail sections;
subsection = concatStringsSep "." subsections;
in if containsQuote || subsections == [ ] then
name
else
''${section} "${subsection}"'';
# generation for multiple ini values
mkKeyValue = k: v:
let mkKeyValue = mkKeyValueDefault { } " = " k;
in concatStringsSep "\n" (map (kv: "\t" + mkKeyValue kv) (lib.toList v));
# converts { a.b.c = 5; } to { "a.b".c = 5; } for toINI
gitFlattenAttrs = let
recurse = path: value:
if isAttrs value then
lib.mapAttrsToList (name: value: recurse ([ name ] ++ path) value) value
else if length path > 1 then {
${concatStringsSep "." (lib.reverseList (tail path))}.${head path} = value;
} else {
${head path} = value;
};
in attrs: lib.foldl lib.recursiveUpdate { } (lib.flatten (recurse [ ] attrs));
toINI_ = toINI { inherit mkKeyValue mkSectionName; };
in
toINI_ (gitFlattenAttrs attrs);
/* Generates JSON from an arbitrary (non-function) value.
* For more information see the documentation of the builtin.
*/
toJSON = {}: builtins.toJSON;
/* YAML has been a strict superset of JSON since 1.2, so we
* use toJSON. Before it only had a few differences referring
* to implicit typing rules, so it should work with older
* parsers as well.
*/
toYAML = {}@args: toJSON args;
/* Pretty print a value, akin to `builtins.trace`.
* Should probably be a builtin as well.
*/
toPretty = {
/* If this option is true, attrsets like { __pretty = fn; val = ; }
will use fn to convert val to a pretty printed representation.
(This means fn is type Val -> String.) */
allowPrettyValues ? false,
/* If this option is true, the output is indented with newlines for attribute sets and lists */
multiline ? true
}@args: let
go = indent: v: with builtins;
let isPath = v: typeOf v == "path";
introSpace = if multiline then "\n${indent} " else " ";
outroSpace = if multiline then "\n${indent}" else " ";
in if isInt v then toString v
else if isFloat v then "~${toString v}"
else if isString v then
let
# Separate a string into its lines
newlineSplits = filter (v: ! isList v) (builtins.split "\n" v);
# For a '' string terminated by a \n, which happens when the closing '' is on a new line
multilineResult = "''" + introSpace + concatStringsSep introSpace (lib.init newlineSplits) + outroSpace + "''";
# For a '' string not terminated by a \n, which happens when the closing '' is not on a new line
multilineResult' = "''" + introSpace + concatStringsSep introSpace newlineSplits + "''";
# For single lines, replace all newlines with their escaped representation
singlelineResult = "\"" + libStr.escape [ "\"" ] (concatStringsSep "\\n" newlineSplits) + "\"";
in if multiline && length newlineSplits > 1 then
if lib.last newlineSplits == "" then multilineResult else multilineResult'
else singlelineResult
else if true == v then "true"
else if false == v then "false"
else if null == v then "null"
else if isPath v then toString v
else if isList v then
if v == [] then "[ ]"
else "[" + introSpace
+ libStr.concatMapStringsSep introSpace (go (indent + " ")) v
+ outroSpace + "]"
else if isFunction v then
let fna = 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}}>"
else if isAttrs v then
# apply pretty values if allowed
if attrNames v == [ "__pretty" "val" ] && allowPrettyValues
then v.__pretty v.val
else if v == {} then "{ }"
else if v ? type && v.type == "derivation" then
"<derivation ${v.drvPath}>"
else "{" + introSpace
+ libStr.concatStringsSep introSpace (libAttr.mapAttrsToList
(name: value:
"${libStr.escapeNixIdentifier name} = ${go (indent + " ") value};") v)
+ outroSpace + "}"
else abort "generators.toPretty: should never happen (v = ${v})";
in go "";
# PLIST handling
toPlist = {}: v: let
isFloat = builtins.isFloat or (x: false);
expr = ind: x: with builtins;
if x == null then "" else
if isBool x then bool ind x else
if isInt x then int ind x else
if isString x then str ind x else
if isList x then list ind x else
if isAttrs x then attrs ind x else
if isFloat x then float ind x else
abort "generators.toPlist: should never happen (v = ${v})";
literal = ind: x: ind + x;
bool = ind: x: literal ind (if x then "<true/>" else "<false/>");
int = ind: x: literal ind "<integer>${toString x}</integer>";
str = ind: x: literal ind "<string>${x}</string>";
key = ind: x: literal ind "<key>${x}</key>";
float = ind: x: literal ind "<real>${toString x}</real>";
indent = ind: expr "\t${ind}";
item = ind: libStr.concatMapStringsSep "\n" (indent ind);
list = ind: x: libStr.concatStringsSep "\n" [
(literal ind "<array>")
(item ind x)
(literal ind "</array>")
];
attrs = ind: x: libStr.concatStringsSep "\n" [
(literal ind "<dict>")
(attr ind x)
(literal ind "</dict>")
];
attr = let attrFilter = name: value: name != "_module" && value != null;
in ind: x: libStr.concatStringsSep "\n" (lib.flatten (lib.mapAttrsToList
(name: value: lib.optional (attrFilter name value) [
(key "\t${ind}" name)
(expr "\t${ind}" value)
]) x));
in ''<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
${expr "" v}
</plist>'';
/* Translate a simple Nix expression to Dhall notation.
* Note that integers are translated to Integer and never
* the Natural type.
*/
toDhall = { }@args: v:
with builtins;
let concatItems = lib.strings.concatStringsSep ", ";
in if isAttrs v then
"{ ${
concatItems (lib.attrsets.mapAttrsToList
(key: value: "${key} = ${toDhall args value}") v)
} }"
else if isList v then
"[ ${concatItems (map (toDhall args) v)} ]"
else if isInt v then
"${if v < 0 then "" else "+"}${toString v}"
else if isBool v then
(if v then "True" else "False")
else if isFunction v then
abort "generators.toDhall: cannot convert a function to Dhall"
else if isNull v then
abort "generators.toDhall: cannot convert a null to Dhall"
else
builtins.toJSON v;
}