nixpkgs/lib/generators.nix
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/**
Functions that generate widespread file
formats from nix data structures.
They all follow a similar interface:
```nix
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/misc.nix
Further Documentation can be found [here](#sec-generators).
*/
{ lib }:
let
inherit (lib)
addErrorContext
assertMsg
attrNames
concatLists
concatMapStringsSep
concatStrings
concatStringsSep
const
elem
escape
filter
flatten
foldl
functionArgs # Note: not the builtin; considers `__functor` in attrsets.
gvariant
hasInfix
head
id
init
isAttrs
isBool
isDerivation
isFloat
isFunction # Note: not the builtin; considers `__functor` in attrsets.
isInt
isList
isPath
isString
last
length
mapAttrs
mapAttrsToList
optionals
recursiveUpdate
replaceStrings
reverseList
splitString
tail
toList
;
inherit (lib.strings)
escapeNixIdentifier
floatToString
match
split
toJSON
typeOf
;
## -- HELPER FUNCTIONS & DEFAULTS --
in rec {
/**
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
*/
mkValueStringDefault = {}: v:
let err = t: v: abort
("generators.mkValueStringDefault: " +
"${t} not supported: ${toPretty {} v}");
in if isInt v then toString v
# convert derivations to store paths
else if isDerivation v then toString v
# we default to not quoting strings
else if isString v then v
# isString returns "1", which is not a good default
else if true == v then "true"
# here it returns to "", which is even less of a good default
else if false == v then "false"
else if null == v then "null"
# if you have lists you probably want to replace this
else if isList v then err "lists" v
# same as for lists, might want to replace
else if isAttrs v then err "attrsets" v
# functions cant be printed of course
else if isFunction v then err "functions" v
# Floats currently can't be converted to precise strings,
# condition warning on nix version once this isn't a problem anymore
# See https://github.com/NixOS/nix/pull/3480
else if isFloat v then floatToString v
else err "this value is" (toString v);
/**
Generate a line of key k and value v, separated by
character sep. If sep appears in k, it is escaped.
Helper for synaxes with different separators.
mkValueString specifies how values should be formatted.
```nix
mkKeyValueDefault {} ":" "f:oo" "bar"
> "f\:oo:bar"
```
# Inputs
Structured function argument
: mkValueString (optional, default: `mkValueStringDefault {}`)
: Function to convert values to strings
`sep`
: 2\. Function argument
`k`
: 3\. Function argument
`v`
: 4\. Function argument
*/
mkKeyValueDefault = {
mkValueString ? mkValueStringDefault {}
}: sep: k: v:
"${escape [sep] k}${sep}${mkValueString v}";
## -- FILE FORMAT GENERATORS --
/**
Generate a key-value-style config file from an attrset.
# Inputs
Structured function argument
: mkKeyValue (optional, default: `mkKeyValueDefault {} "="`)
: format a setting line from key and value
: listsAsDuplicateKeys (optional, default: `false`)
: allow lists as values for duplicate keys
: indent (optional, default: `""`)
: Initial indentation level
*/
toKeyValue = {
mkKeyValue ? mkKeyValueDefault {} "=",
listsAsDuplicateKeys ? false,
indent ? ""
}:
let mkLine = k: v: indent + mkKeyValue k v + "\n";
mkLines = if listsAsDuplicateKeys
then k: v: map (mkLine k) (if isList v then v else [v])
else k: v: [ (mkLine k v) ];
in attrs: concatStrings (concatLists (mapAttrsToList mkLines attrs));
/**
Generate an INI-style config file from an
attrset of sections to an attrset of key-value pairs.
# Inputs
Structured function argument
: mkSectionName (optional, default: `(name: escape [ "[" "]" ] name)`)
: apply transformations (e.g. escapes) to section names
: mkKeyValue (optional, default: `{} "="`)
: format a setting line from key and value
: listsAsDuplicateKeys (optional, default: `false`)
: allow lists as values for duplicate keys
# Examples
:::{.example}
## `lib.generators.toINI` usage example
```nix
generators.toINI {} {
foo = { hi = "${pkgs.hello}"; ciao = "bar"; };
baz = { "also, integers" = 42; };
}
> [baz]
> also, integers=42
>
> [foo]
> ciao=bar
> hi=/nix/store/y93qql1p5ggfnaqjjqhxcw0vqw95rlz0-hello-2.10
```
The mk* configuration attributes can generically change
the way sections and key-value strings are generated.
For more examples see the test cases in ./tests/misc.nix.
:::
*/
toINI = {
mkSectionName ? (name: escape [ "[" "]" ] name),
mkKeyValue ? mkKeyValueDefault {} "=",
listsAsDuplicateKeys ? false
}: attrsOfAttrs:
let
# map function to string for each key val
mapAttrsToStringsSep = sep: mapFn: attrs:
concatStringsSep sep
(mapAttrsToList mapFn attrs);
mkSection = sectName: sectValues: ''
[${mkSectionName sectName}]
'' + toKeyValue { inherit mkKeyValue listsAsDuplicateKeys; } sectValues;
in
# map input to ini sections
mapAttrsToStringsSep "\n" mkSection attrsOfAttrs;
/**
Generate an INI-style config file from an attrset
specifying the global section (no header), and an
attrset of sections to an attrset of key-value pairs.
# Inputs
1\. Structured function argument
: mkSectionName (optional, default: `(name: escape [ "[" "]" ] name)`)
: apply transformations (e.g. escapes) to section names
: mkKeyValue (optional, default: `{} "="`)
: format a setting line from key and value
: listsAsDuplicateKeys (optional, default: `false`)
: allow lists as values for duplicate keys
2\. Structured function argument
: globalSection (required)
: global section key-value pairs
: sections (optional, default: `{}`)
: attrset of sections to key-value pairs
# Examples
:::{.example}
## `lib.generators.toINIWithGlobalSection` usage example
```nix
generators.toINIWithGlobalSection {} {
globalSection = {
someGlobalKey = "hi";
};
sections = {
foo = { hi = "${pkgs.hello}"; ciao = "bar"; };
baz = { "also, integers" = 42; };
}
> someGlobalKey=hi
>
> [baz]
> also, integers=42
>
> [foo]
> ciao=bar
> hi=/nix/store/y93qql1p5ggfnaqjjqhxcw0vqw95rlz0-hello-2.10
```
The mk* configuration attributes can generically change
the way sections and key-value strings are generated.
For more examples see the test cases in ./tests/misc.nix.
:::
If you dont need a global section, you can also use
`generators.toINI` directly, which only takes
the part in `sections`.
*/
toINIWithGlobalSection = {
mkSectionName ? (name: escape [ "[" "]" ] name),
mkKeyValue ? mkKeyValueDefault {} "=",
listsAsDuplicateKeys ? false
}: { globalSection, sections ? {} }:
( if globalSection == {}
then ""
else (toKeyValue { inherit mkKeyValue listsAsDuplicateKeys; } globalSection)
+ "\n")
+ (toINI { inherit mkSectionName mkKeyValue listsAsDuplicateKeys; } sections);
/**
Generate a git-config file from an attrset.
It has two major differences from the regular INI format:
1. values are indented with tabs
2. sections can have sub-sections
Further: https://git-scm.com/docs/git-config#EXAMPLES
# Examples
:::{.example}
## `lib.generators.toGitINI` usage example
```nix
generators.toGitINI {
url."ssh://git@github.com/".insteadOf = "https://github.com";
user.name = "edolstra";
}
> [url "ssh://git@github.com/"]
> insteadOf = "https://github.com"
>
> [user]
> name = "edolstra"
```
:::
# Inputs
`attrs`
: Key-value pairs to be converted to a git-config file.
See: https://git-scm.com/docs/git-config#_variables for possible values.
*/
toGitINI = attrs:
let
mkSectionName = name:
let
containsQuote = hasInfix ''"'' name;
sections = splitString "." name;
section = head sections;
subsections = tail sections;
subsection = concatStringsSep "." subsections;
in if containsQuote || subsections == [ ] then
name
else
''${section} "${subsection}"'';
mkValueString = v:
let
escapedV = ''
"${
replaceStrings [ "\n" " " ''"'' "\\" ] [ "\\n" "\\t" ''\"'' "\\\\" ] v
}"'';
in mkValueStringDefault { } (if isString v then escapedV else v);
# generation for multiple ini values
mkKeyValue = k: v:
let mkKeyValue = mkKeyValueDefault { inherit mkValueString; } " = " k;
in concatStringsSep "\n" (map (kv: "\t" + mkKeyValue kv) (toList v));
# converts { a.b.c = 5; } to { "a.b".c = 5; } for toINI
gitFlattenAttrs = let
recurse = path: value:
if isAttrs value && !isDerivation value then
mapAttrsToList (name: value: recurse ([ name ] ++ path) value) value
else if length path > 1 then {
${concatStringsSep "." (reverseList (tail path))}.${head path} = value;
} else {
${head path} = value;
};
in attrs: foldl recursiveUpdate { } (flatten (recurse [ ] attrs));
toINI_ = toINI { inherit mkKeyValue mkSectionName; };
in
toINI_ (gitFlattenAttrs attrs);
/**
mkKeyValueDefault wrapper that handles dconf INI quirks.
The main differences of the format is that it requires strings to be quoted.
*/
mkDconfKeyValue = mkKeyValueDefault { mkValueString = v: toString (gvariant.mkValue v); } "=";
/**
Generates INI in dconf keyfile style. See https://help.gnome.org/admin/system-admin-guide/stable/dconf-keyfiles.html.en
for details.
*/
toDconfINI = toINI { mkKeyValue = mkDconfKeyValue; };
/**
Recurses through a `Value` limited to a certain depth. (`depthLimit`)
If the depth is exceeded, an error is thrown, unless `throwOnDepthLimit` is set to `false`.
# Inputs
Structured function argument
: depthLimit (required)
: If this option is not null, the given value will stop evaluating at a certain depth
: throwOnDepthLimit (optional, default: `true`)
: If this option is true, an error will be thrown, if a certain given depth is exceeded
Value
: The value to be evaluated recursively
*/
withRecursion =
{
depthLimit,
throwOnDepthLimit ? true
}:
assert isInt depthLimit;
let
specialAttrs = [
"__functor"
"__functionArgs"
"__toString"
"__pretty"
];
stepIntoAttr = evalNext: name:
if elem name specialAttrs
then id
else evalNext;
transform = depth:
if depthLimit != null && depth > depthLimit then
if throwOnDepthLimit
then throw "Exceeded maximum eval-depth limit of ${toString depthLimit} while trying to evaluate with `generators.withRecursion'!"
else const "<unevaluated>"
else id;
mapAny = depth: v:
let
evalNext = x: mapAny (depth + 1) (transform (depth + 1) x);
in
if isAttrs v then mapAttrs (stepIntoAttr evalNext) v
else if isList v then map evalNext v
else transform (depth + 1) v;
in
mapAny 0;
/**
Pretty print a value, akin to `builtins.trace`.
Should probably be a builtin as well.
The pretty-printed string should be suitable for rendering default values
in the NixOS manual. In particular, it should be as close to a valid Nix expression
as possible.
# Inputs
Structured function argument
: allowPrettyValues
: If this option is true, attrsets like { __pretty = fn; val = ; }
will use fn to convert val to a pretty printed representation.
(This means fn is type Val -> String.)
: multiline
: If this option is true, the output is indented with newlines for attribute sets and lists
: indent
: Initial indentation level
Value
: The value to be pretty printed
*/
toPretty = {
allowPrettyValues ? false,
multiline ? true,
indent ? ""
}:
let
go = indent: v:
let introSpace = if multiline then "\n${indent} " else " ";
outroSpace = if multiline then "\n${indent}" else " ";
in if isInt v then toString v
# toString loses precision on floats, so we use toJSON instead. This isn't perfect
# as the resulting string may not parse back as a float (e.g. 42, 1e-06), but for
# pretty-printing purposes this is acceptable.
else if isFloat v then builtins.toJSON v
else if isString v then
let
lines = filter (v: ! isList v) (split "\n" v);
escapeSingleline = escape [ "\\" "\"" "\${" ];
escapeMultiline = replaceStrings [ "\${" "''" ] [ "''\${" "'''" ];
singlelineResult = "\"" + concatStringsSep "\\n" (map escapeSingleline lines) + "\"";
multilineResult = let
escapedLines = map escapeMultiline lines;
# The last line gets a special treatment: if it's empty, '' is on its own line at the "outer"
# indentation level. Otherwise, '' is appended to the last line.
lastLine = last escapedLines;
in "''" + introSpace + concatStringsSep introSpace (init escapedLines)
+ (if lastLine == "" then outroSpace else introSpace + lastLine) + "''";
in
if multiline && length lines > 1 then multilineResult else singlelineResult
else if true == v then "true"
else if false == v then "false"
else if null == v then "null"
else if isPath v then toString v
else if isList v then
if v == [] then "[ ]"
else "[" + introSpace
+ concatMapStringsSep introSpace (go (indent + " ")) v
+ outroSpace + "]"
else if isFunction v then
let fna = functionArgs v;
showFnas = concatStringsSep ", " (mapAttrsToList
(name: hasDefVal: if hasDefVal then name + "?" else name)
fna);
in if fna == {} then "<function>"
else "<function, args: {${showFnas}}>"
else if isAttrs v then
# apply pretty values if allowed
if allowPrettyValues && v ? __pretty && v ? val
then v.__pretty v.val
else if v == {} then "{ }"
else if v ? type && v.type == "derivation" then
"<derivation ${v.name or "???"}>"
else "{" + introSpace
+ concatStringsSep introSpace (mapAttrsToList
(name: value:
"${escapeNixIdentifier name} = ${
addErrorContext "while evaluating an attribute `${name}`"
(go (indent + " ") value)
};") v)
+ outroSpace + "}"
else abort "generators.toPretty: should never happen (v = ${v})";
in go indent;
/**
Translate a simple Nix expression to [Plist notation](https://en.wikipedia.org/wiki/Property_list).
# Inputs
Options
: Empty set, there may be configuration options in the future
Value
: The value to be converted to Plist
*/
toPlist = {}: v: let
expr = ind: x:
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 isPath x then str ind (toString 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: concatMapStringsSep "\n" (indent ind);
list = ind: x: concatStringsSep "\n" [
(literal ind "<array>")
(item ind x)
(literal ind "</array>")
];
attrs = ind: x: concatStringsSep "\n" [
(literal ind "<dict>")
(attr ind x)
(literal ind "</dict>")
];
attr = let attrFilter = name: value: name != "_module" && value != null;
in ind: x: concatStringsSep "\n" (flatten (mapAttrsToList
(name: value: optionals (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.
# Inputs
Options
: Empty set, there may be configuration options in the future
Value
: The value to be converted to Dhall
*/
toDhall = { }@args: v:
let concatItems = concatStringsSep ", ";
in if isAttrs v then
"{ ${
concatItems (mapAttrsToList
(key: value: "${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 "+"}${toString v}"
else if isBool v then
(if v then "True" else "False")
else if isFunction v then
abort "generators.toDhall: cannot convert a function to Dhall"
else if v == null then
abort "generators.toDhall: cannot convert a null to Dhall"
else
toJSON v;
/**
Translate a simple Nix expression to Lua representation with occasional
Lua-inlines that can be constructed by mkLuaInline function.
Configuration:
* multiline - by default is true which results in indented block-like view.
* indent - initial indent.
* asBindings - by default generate single value, but with this use attrset to set global vars.
Attention:
Regardless of multiline parameter there is no trailing newline.
# Inputs
Structured function argument
: multiline (optional, default: `true`)
: If this option is true, the output is indented with newlines for attribute sets and lists
: indent (optional, default: `""`)
: Initial indentation level
: asBindings (optional, default: `false`)
: Interpret as variable bindings
Value
: The value to be converted to Lua
# Type
```
toLua :: AttrSet -> Any -> String
```
# Examples
:::{.example}
## `lib.generators.toLua` usage example
```nix
generators.toLua {}
{
cmd = [ "typescript-language-server" "--stdio" ];
settings.workspace.library = mkLuaInline ''vim.api.nvim_get_runtime_file("", true)'';
}
->
{
["cmd"] = {
"typescript-language-server",
"--stdio"
},
["settings"] = {
["workspace"] = {
["library"] = (vim.api.nvim_get_runtime_file("", true))
}
}
}
```
:::
*/
toLua = {
multiline ? true,
indent ? "",
asBindings ? false,
}@args: v:
let
innerIndent = "${indent} ";
introSpace = if multiline then "\n${innerIndent}" else " ";
outroSpace = if multiline then "\n${indent}" else " ";
innerArgs = args // {
indent = if asBindings then indent else innerIndent;
asBindings = false;
};
concatItems = concatStringsSep ",${introSpace}";
isLuaInline = { _type ? null, ... }: _type == "lua-inline";
generatedBindings =
assert assertMsg (badVarNames == []) "Bad Lua var names: ${toPretty {} badVarNames}";
concatStrings (
mapAttrsToList (key: value: "${indent}${key} = ${toLua innerArgs value}\n") v
);
# https://en.wikibooks.org/wiki/Lua_Programming/variable#Variable_names
matchVarName = match "[[:alpha:]_][[:alnum:]_]*(\\.[[:alpha:]_][[:alnum:]_]*)*";
badVarNames = filter (name: matchVarName name == null) (attrNames v);
in
if asBindings then
generatedBindings
else if v == null then
"nil"
else if isInt v || isFloat v || isString v || isBool v then
toJSON v
else if isList v then
(if v == [ ] then "{}" else
"{${introSpace}${concatItems (map (value: "${toLua innerArgs value}") v)}${outroSpace}}")
else if isAttrs v then
(
if isLuaInline v then
"(${v.expr})"
else if v == { } then
"{}"
else if isDerivation v then
''"${toString v}"''
else
"{${introSpace}${concatItems (
mapAttrsToList (key: value: "[${toJSON key}] = ${toLua innerArgs value}") v
)}${outroSpace}}"
)
else
abort "generators.toLua: type ${typeOf v} is unsupported";
/**
Mark string as Lua expression to be inlined when processed by toLua.
# Inputs
`expr`
: 1\. Function argument
# Type
```
mkLuaInline :: String -> AttrSet
```
*/
mkLuaInline = expr: { _type = "lua-inline"; inherit expr; };
} // {
/**
Generates JSON from an arbitrary (non-function) value.
For more information see the documentation of the builtin.
# Inputs
Options
: Empty set, there may be configuration options in the future
Value
: The value to be converted to JSON
*/
toJSON = {}: lib.strings.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.
# Inputs
Options
: Empty set, there may be configuration options in the future
Value
: The value to be converted to YAML
*/
toYAML = {}: lib.strings.toJSON;
}