nixpkgs/lib/strings.nix
Vincent Ambo 0560caa578 lib/strings: Update documentation comments for doc generation
Updates documentation comments with extra information for nixdoc[1]
compatibility.

Some documentation strings have additionally been reworded for
clarity.

"Faux types" are added where applicable, but some functions do things
that are not trivially representable in the type notation used so they
were ignored for this purpose.

[1]: https://github.com/tazjin/nixdoc
2018-10-29 10:42:43 +01:00

662 lines
19 KiB
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/* String manipulation functions. */
{ lib }:
let
inherit (builtins) length;
in
rec {
inherit (builtins) stringLength substring head tail isString replaceStrings;
/* Concatenate a list of strings.
Type: concatStrings :: [string] -> string
Example:
concatStrings ["foo" "bar"]
=> "foobar"
*/
concatStrings = builtins.concatStringsSep "";
/* Map a function over a list and concatenate the resulting strings.
Type: concatMapStrings :: (a -> string) -> [a] -> string
Example:
concatMapStrings (x: "a" + x) ["foo" "bar"]
=> "afooabar"
*/
concatMapStrings = f: list: concatStrings (map f list);
/* Like `concatMapStrings` except that the f functions also gets the
position as a parameter.
Type: concatImapStrings :: (int -> a -> string) -> [a] -> string
Example:
concatImapStrings (pos: x: "${toString pos}-${x}") ["foo" "bar"]
=> "1-foo2-bar"
*/
concatImapStrings = f: list: concatStrings (lib.imap1 f list);
/* Place an element between each element of a list
Type: intersperse :: a -> [a] -> [a]
Example:
intersperse "/" ["usr" "local" "bin"]
=> ["usr" "/" "local" "/" "bin"].
*/
intersperse =
# Separator to add between elements
separator:
# Input list
list:
if list == [] || length list == 1
then list
else tail (lib.concatMap (x: [separator x]) list);
/* Concatenate a list of strings with a separator between each element
Type: concatStringsSep :: string -> [string] -> string
Example:
concatStringsSep "/" ["usr" "local" "bin"]
=> "usr/local/bin"
*/
concatStringsSep = builtins.concatStringsSep or (separator: list:
concatStrings (intersperse separator list));
/* Maps a function over a list of strings and then concatenates the
result with the specified separator interspersed between
elements.
Type: concatMapStringsSep :: string -> (string -> string) -> [string] -> string
Example:
concatMapStringsSep "-" (x: toUpper x) ["foo" "bar" "baz"]
=> "FOO-BAR-BAZ"
*/
concatMapStringsSep =
# Separator to add between elements
sep:
# Function to map over the list
f:
# List of input strings
list: concatStringsSep sep (map f list);
/* Same as `concatMapStringsSep`, but the mapping function
additionally receives the position of its argument.
Type: concatMapStringsSep :: string -> (int -> string -> string) -> [string] -> string
Example:
concatImapStringsSep "-" (pos: x: toString (x / pos)) [ 6 6 6 ]
=> "6-3-2"
*/
concatImapStringsSep =
# Separator to add between elements
sep:
# Function that receives elements and their positions
f:
# List of input strings
list: concatStringsSep sep (lib.imap1 f list);
/* Construct a Unix-style, colon-separated search path consisting of
the given `subDir` appended to each of the given paths.
Type: makeSearchPath :: string -> [string] -> string
Example:
makeSearchPath "bin" ["/root" "/usr" "/usr/local"]
=> "/root/bin:/usr/bin:/usr/local/bin"
makeSearchPath "bin" [""]
=> "/bin"
*/
makeSearchPath =
# Directory name to append
subDir:
# List of base paths
paths:
concatStringsSep ":" (map (path: path + "/" + subDir) (builtins.filter (x: x != null) paths));
/* Construct a Unix-style search path by appending the given
`subDir` to the specified `output` of each of the packages. If no
output by the given name is found, fallback to `.out` and then to
the default.
Type: string -> string -> [package] -> string
Example:
makeSearchPathOutput "dev" "bin" [ pkgs.openssl pkgs.zlib ]
=> "/nix/store/9rz8gxhzf8sw4kf2j2f1grr49w8zx5vj-openssl-1.0.1r-dev/bin:/nix/store/wwh7mhwh269sfjkm6k5665b5kgp7jrk2-zlib-1.2.8/bin"
*/
makeSearchPathOutput =
# Package output to use
output:
# Directory name to append
subDir:
# List of packages
pkgs: makeSearchPath subDir (map (lib.getOutput output) pkgs);
/* Construct a library search path (such as RPATH) containing the
libraries for a set of packages
Example:
makeLibraryPath [ "/usr" "/usr/local" ]
=> "/usr/lib:/usr/local/lib"
pkgs = import <nixpkgs> { }
makeLibraryPath [ pkgs.openssl pkgs.zlib ]
=> "/nix/store/9rz8gxhzf8sw4kf2j2f1grr49w8zx5vj-openssl-1.0.1r/lib:/nix/store/wwh7mhwh269sfjkm6k5665b5kgp7jrk2-zlib-1.2.8/lib"
*/
makeLibraryPath = makeSearchPathOutput "lib" "lib";
/* Construct a binary search path (such as $PATH) containing the
binaries for a set of packages.
Example:
makeBinPath ["/root" "/usr" "/usr/local"]
=> "/root/bin:/usr/bin:/usr/local/bin"
*/
makeBinPath = makeSearchPathOutput "bin" "bin";
/* Construct a perl search path (such as $PERL5LIB)
Example:
pkgs = import <nixpkgs> { }
makePerlPath [ pkgs.perlPackages.libnet ]
=> "/nix/store/n0m1fk9c960d8wlrs62sncnadygqqc6y-perl-Net-SMTP-1.25/lib/perl5/site_perl"
*/
# FIXME(zimbatm): this should be moved in perl-specific code
makePerlPath = makeSearchPathOutput "lib" "lib/perl5/site_perl";
/* Construct a perl search path recursively including all dependencies (such as $PERL5LIB)
Example:
pkgs = import <nixpkgs> { }
makeFullPerlPath [ pkgs.perlPackages.CGI ]
=> "/nix/store/fddivfrdc1xql02h9q500fpnqy12c74n-perl-CGI-4.38/lib/perl5/site_perl:/nix/store/8hsvdalmsxqkjg0c5ifigpf31vc4vsy2-perl-HTML-Parser-3.72/lib/perl5/site_perl:/nix/store/zhc7wh0xl8hz3y3f71nhlw1559iyvzld-perl-HTML-Tagset-3.20/lib/perl5/site_perl"
*/
makeFullPerlPath = deps: makePerlPath (lib.misc.closePropagation deps);
/* Depending on the boolean `cond', return either the given string
or the empty string. Useful to concatenate against a bigger string.
Type: optionalString :: bool -> string -> string
Example:
optionalString true "some-string"
=> "some-string"
optionalString false "some-string"
=> ""
*/
optionalString =
# Condition
cond:
# String to return if condition is true
string: if cond then string else "";
/* Determine whether a string has given prefix.
Type: hasPrefix :: string -> string -> bool
Example:
hasPrefix "foo" "foobar"
=> true
hasPrefix "foo" "barfoo"
=> false
*/
hasPrefix =
# Prefix to check for
pref:
# Input string
str: substring 0 (stringLength pref) str == pref;
/* Determine whether a string has given suffix.
Type: hasSuffix :: string -> string -> bool
Example:
hasSuffix "foo" "foobar"
=> false
hasSuffix "foo" "barfoo"
=> true
*/
hasSuffix =
# Suffix to check for
suffix:
# Input string
content:
let
lenContent = stringLength content;
lenSuffix = stringLength suffix;
in lenContent >= lenSuffix &&
substring (lenContent - lenSuffix) lenContent content == suffix;
/* Convert a string to a list of characters (i.e. singleton strings).
This allows you to, e.g., map a function over each character. However,
note that this will likely be horribly inefficient; Nix is not a
general purpose programming language. Complex string manipulations
should, if appropriate, be done in a derivation.
Also note that Nix treats strings as a list of bytes and thus doesn't
handle unicode.
Type: stringtoCharacters :: string -> [string]
Example:
stringToCharacters ""
=> [ ]
stringToCharacters "abc"
=> [ "a" "b" "c" ]
stringToCharacters "💩"
=> [ "<EFBFBD>" "<EFBFBD>" "<EFBFBD>" "<EFBFBD>" ]
*/
stringToCharacters = s:
map (p: substring p 1 s) (lib.range 0 (stringLength s - 1));
/* Manipulate a string character by character and replace them by
strings before concatenating the results.
Type: stringAsChars :: (string -> string) -> string -> string
Example:
stringAsChars (x: if x == "a" then "i" else x) "nax"
=> "nix"
*/
stringAsChars =
# Function to map over each individual character
f:
# Input string
s: concatStrings (
map f (stringToCharacters s)
);
/* Escape occurrence of the elements of `list` in `string` by
prefixing it with a backslash.
Type: escape :: [string] -> string -> string
Example:
escape ["(" ")"] "(foo)"
=> "\\(foo\\)"
*/
escape = list: replaceChars list (map (c: "\\${c}") list);
/* Quote string to be used safely within the Bourne shell.
Type: escapeShellArg :: string -> string
Example:
escapeShellArg "esc'ape\nme"
=> "'esc'\\''ape\nme'"
*/
escapeShellArg = arg: "'${replaceStrings ["'"] ["'\\''"] (toString arg)}'";
/* Quote all arguments to be safely passed to the Bourne shell.
Type: escapeShellArgs :: [string] -> string
Example:
escapeShellArgs ["one" "two three" "four'five"]
=> "'one' 'two three' 'four'\\''five'"
*/
escapeShellArgs = concatMapStringsSep " " escapeShellArg;
/* Turn a string into a Nix expression representing that string
Type: string -> string
Example:
escapeNixString "hello\${}\n"
=> "\"hello\\\${}\\n\""
*/
escapeNixString = s: escape ["$"] (builtins.toJSON s);
# Obsolete - use replaceStrings instead.
replaceChars = builtins.replaceStrings or (
del: new: s:
let
substList = lib.zipLists del new;
subst = c:
let found = lib.findFirst (sub: sub.fst == c) null substList; in
if found == null then
c
else
found.snd;
in
stringAsChars subst s);
# Case conversion utilities.
lowerChars = stringToCharacters "abcdefghijklmnopqrstuvwxyz";
upperChars = stringToCharacters "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
/* Converts an ASCII string to lower-case.
Type: toLower :: string -> string
Example:
toLower "HOME"
=> "home"
*/
toLower = replaceChars upperChars lowerChars;
/* Converts an ASCII string to upper-case.
Type: toUpper :: string -> string
Example:
toUpper "home"
=> "HOME"
*/
toUpper = replaceChars lowerChars upperChars;
/* Appends string context from another string. This is an implementation
detail of Nix.
Strings in Nix carry an invisible `context` which is a list of strings
representing store paths. If the string is later used in a derivation
attribute, the derivation will properly populate the inputDrvs and
inputSrcs.
Example:
pkgs = import <nixpkgs> { };
addContextFrom pkgs.coreutils "bar"
=> "bar"
*/
addContextFrom = a: b: substring 0 0 a + b;
/* Cut a string with a separator and produces a list of strings which
were separated by this separator.
NOTE: this function is not performant and should never be used.
Example:
splitString "." "foo.bar.baz"
=> [ "foo" "bar" "baz" ]
splitString "/" "/usr/local/bin"
=> [ "" "usr" "local" "bin" ]
*/
splitString = _sep: _s:
let
sep = addContextFrom _s _sep;
s = addContextFrom _sep _s;
sepLen = stringLength sep;
sLen = stringLength s;
lastSearch = sLen - sepLen;
startWithSep = startAt:
substring startAt sepLen s == sep;
recurse = index: startAt:
let cutUntil = i: [(substring startAt (i - startAt) s)]; in
if index <= lastSearch then
if startWithSep index then
let restartAt = index + sepLen; in
cutUntil index ++ recurse restartAt restartAt
else
recurse (index + 1) startAt
else
cutUntil sLen;
in
recurse 0 0;
/* Return a string without the specified prefix, if the prefix matches.
Type: string -> string -> string
Example:
removePrefix "foo." "foo.bar.baz"
=> "bar.baz"
removePrefix "xxx" "foo.bar.baz"
=> "foo.bar.baz"
*/
removePrefix =
# Prefix to remove if it matches
prefix:
# Input string
str:
let
preLen = stringLength prefix;
sLen = stringLength str;
in
if hasPrefix prefix str then
substring preLen (sLen - preLen) str
else
str;
/* Return a string without the specified suffix, if the suffix matches.
Type: string -> string -> string
Example:
removeSuffix "front" "homefront"
=> "home"
removeSuffix "xxx" "homefront"
=> "homefront"
*/
removeSuffix =
# Suffix to remove if it matches
suffix:
# Input string
str:
let
sufLen = stringLength suffix;
sLen = stringLength str;
in
if sufLen <= sLen && suffix == substring (sLen - sufLen) sufLen str then
substring 0 (sLen - sufLen) str
else
str;
/* Return true if string v1 denotes a version older than v2.
Example:
versionOlder "1.1" "1.2"
=> true
versionOlder "1.1" "1.1"
=> false
*/
versionOlder = v1: v2: builtins.compareVersions v2 v1 == 1;
/* Return true if string v1 denotes a version equal to or newer than v2.
Example:
versionAtLeast "1.1" "1.0"
=> true
versionAtLeast "1.1" "1.1"
=> true
versionAtLeast "1.1" "1.2"
=> false
*/
versionAtLeast = v1: v2: !versionOlder v1 v2;
/* This function takes an argument that's either a derivation or a
derivation's "name" attribute and extracts the version part from that
argument.
Example:
getVersion "youtube-dl-2016.01.01"
=> "2016.01.01"
getVersion pkgs.youtube-dl
=> "2016.01.01"
*/
getVersion = x:
let
parse = drv: (builtins.parseDrvName drv).version;
in if isString x
then parse x
else x.version or (parse x.name);
/* Extract name with version from URL. Ask for separator which is
supposed to start extension.
Example:
nameFromURL "https://nixos.org/releases/nix/nix-1.7/nix-1.7-x86_64-linux.tar.bz2" "-"
=> "nix"
nameFromURL "https://nixos.org/releases/nix/nix-1.7/nix-1.7-x86_64-linux.tar.bz2" "_"
=> "nix-1.7-x86"
*/
nameFromURL = url: sep:
let
components = splitString "/" url;
filename = lib.last components;
name = builtins.head (splitString sep filename);
in assert name != filename; name;
/* Create an --{enable,disable}-<feat> string that can be passed to
standard GNU Autoconf scripts.
Example:
enableFeature true "shared"
=> "--enable-shared"
enableFeature false "shared"
=> "--disable-shared"
*/
enableFeature = enable: feat: "--${if enable then "enable" else "disable"}-${feat}";
/* Create an --{enable-<feat>=<value>,disable-<feat>} string that can be passed to
standard GNU Autoconf scripts.
Example:
enableFeature true "shared" "foo"
=> "--enable-shared=foo"
enableFeature false "shared" (throw "ignored")
=> "--disable-shared"
*/
enableFeatureAs = enable: feat: value: enableFeature enable feat + optionalString enable "=${value}";
/* Create an --{with,without}-<feat> string that can be passed to
standard GNU Autoconf scripts.
Example:
withFeature true "shared"
=> "--with-shared"
withFeature false "shared"
=> "--without-shared"
*/
withFeature = with_: feat: "--${if with_ then "with" else "without"}-${feat}";
/* Create an --{with-<feat>=<value>,without-<feat>} string that can be passed to
standard GNU Autoconf scripts.
Example:
with_Feature true "shared" "foo"
=> "--with-shared=foo"
with_Feature false "shared" (throw "ignored")
=> "--without-shared"
*/
withFeatureAs = with_: feat: value: withFeature with_ feat + optionalString with_ "=${value}";
/* Create a fixed width string with additional prefix to match
required width.
This function will fail if the input string is longer than the
requested length.
Type: fixedWidthString :: int -> string -> string
Example:
fixedWidthString 5 "0" (toString 15)
=> "00015"
*/
fixedWidthString = width: filler: str:
let
strw = lib.stringLength str;
reqWidth = width - (lib.stringLength filler);
in
assert lib.assertMsg (strw <= width)
"fixedWidthString: requested string length (${
toString width}) must not be shorter than actual length (${
toString strw})";
if strw == width then str else filler + fixedWidthString reqWidth filler str;
/* Format a number adding leading zeroes up to fixed width.
Example:
fixedWidthNumber 5 15
=> "00015"
*/
fixedWidthNumber = width: n: fixedWidthString width "0" (toString n);
/* Check whether a value can be coerced to a string */
isCoercibleToString = x:
builtins.elem (builtins.typeOf x) [ "path" "string" "null" "int" "float" "bool" ] ||
(builtins.isList x && lib.all isCoercibleToString x) ||
x ? outPath ||
x ? __toString;
/* Check whether a value is a store path.
Example:
isStorePath "/nix/store/d945ibfx9x185xf04b890y4f9g3cbb63-python-2.7.11/bin/python"
=> false
isStorePath "/nix/store/d945ibfx9x185xf04b890y4f9g3cbb63-python-2.7.11/"
=> true
isStorePath pkgs.python
=> true
isStorePath [] || isStorePath 42 || isStorePath {} ||
=> false
*/
isStorePath = x:
isCoercibleToString x
&& builtins.substring 0 1 (toString x) == "/"
&& dirOf x == builtins.storeDir;
/* Parse a string string as an int.
Type: string -> int
Example:
toInt "1337"
=> 1337
toInt "-4"
=> -4
toInt "3.14"
=> error: floating point JSON numbers are not supported
*/
# Obviously, it is a bit hacky to use fromJSON this way.
toInt = str:
let may_be_int = builtins.fromJSON str; in
if builtins.isInt may_be_int
then may_be_int
else throw "Could not convert ${str} to int.";
/* Read a list of paths from `file`, relative to the `rootPath`.
Lines beginning with `#` are treated as comments and ignored.
Whitespace is significant.
NOTE: This function is not performant and should be avoided.
Example:
readPathsFromFile /prefix
./pkgs/development/libraries/qt-5/5.4/qtbase/series
=> [ "/prefix/dlopen-resolv.patch" "/prefix/tzdir.patch"
"/prefix/dlopen-libXcursor.patch" "/prefix/dlopen-openssl.patch"
"/prefix/dlopen-dbus.patch" "/prefix/xdg-config-dirs.patch"
"/prefix/nix-profiles-library-paths.patch"
"/prefix/compose-search-path.patch" ]
*/
readPathsFromFile = rootPath: file:
let
lines = lib.splitString "\n" (builtins.readFile file);
removeComments = lib.filter (line: line != "" && !(lib.hasPrefix "#" line));
relativePaths = removeComments lines;
absolutePaths = builtins.map (path: rootPath + "/${path}") relativePaths;
in
absolutePaths;
/* Read the contents of a file removing the trailing \n
Type: fileContents :: path -> string
Example:
$ echo "1.0" > ./version
fileContents ./version
=> "1.0"
*/
fileContents = file: removeSuffix "\n" (builtins.readFile file);
}