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{ lib
}:
/*
This is a set of tools to manipulate update scripts as recognized by update.nix.
It is still very experimental with **instability** almost guaranteed so any use
outside Nixpkgs is discouraged.
update.nix currently accepts the following type:
type UpdateScript
// Simple path to script to execute script
= FilePath
// Path to execute plus arguments to pass it
| [ (FilePath | String) ]
// Advanced attribue set (experimental)
| {
// Script to execute (same as basic update script above)
command : (FilePath | [ (FilePath | String) ])
// Features that the script supports
// - commit: (experimental) returns commit message in stdout
// - silent: (experimental) returns no stdout
supportedFeatures : ?[ ("commit" | "silent") ]
// Override attribute path detected by update.nix
attrPath : ?String
}
*/
let
/*
type ShellArg = String | { __rawShell : String }
*/
/*
Quotes all arguments to be safely passed to the Bourne shell.
escapeShellArgs' : [ShellArg] -> String
*/
escapeShellArgs' = lib.concatMapStringsSep " " (arg: if arg ? __rawShell then arg.__rawShell else lib.escapeShellArg arg);
/*
processArg : { maxArgIndex : Int, args : [ShellArg], paths : [FilePath] } → (String|FilePath) → { maxArgIndex : Int, args : [ShellArg], paths : [FilePath] }
Helper reducer function for building a command arguments where file paths are replaced with argv[x] reference.
*/
processArg =
{ maxArgIndex, args, paths }:
arg:
if builtins.isPath arg then {
args = args ++ [ { __rawShell = "\"\$${builtins.toString maxArgIndex}\""; } ];
maxArgIndex = maxArgIndex + 1;
paths = paths ++ [ arg ];
} else {
args = args ++ [ arg ];
inherit maxArgIndex paths;
};
/*
extractPaths : Int → [ (String|FilePath) ] → { maxArgIndex : Int, args : [ShellArg], paths : [FilePath] }
Helper function that extracts file paths from command arguments and replaces them with argv[x] references.
*/
extractPaths = maxArgIndex: command: builtins.foldl' processArg { inherit maxArgIndex; args = [ ]; paths = [ ]; } command;
/*
processCommand : { maxArgIndex : Int, commands : [[ShellArg]], paths : [FilePath] } → [ (String|FilePath) ] → { maxArgIndex : Int, commands : [[ShellArg]], paths : [FilePath] }
Helper reducer function for extracting file paths from individual commands.
*/
processCommand =
{ maxArgIndex, commands, paths }:
command:
let
new = extractPaths maxArgIndex command;
in
{
commands = commands ++ [ new.args ];
paths = paths ++ new.paths;
maxArgIndex = new.maxArgIndex;
};
/*
extractCommands : Int → [[ (String|FilePath) ]] → { maxArgIndex : Int, commands : [[ShellArg]], paths : [FilePath] }
Helper function for extracting file paths from a list of commands and replacing them with argv[x] references.
*/
extractCommands = maxArgIndex: commands: builtins.foldl' processCommand { inherit maxArgIndex; commands = [ ]; paths = [ ]; } commands;
/*
commandsToShellInvocation : [[ (String|FilePath) ]] → [ (String|FilePath) ]
Converts a list of commands into a single command by turning them into a shell script and passing them to `sh -c`.
*/
commandsToShellInvocation = commands:
let
extracted = extractCommands 0 commands;
in
[
"sh"
"-c"
(lib.concatMapStringsSep ";" escapeShellArgs' extracted.commands)
# We need paths as separate arguments so that update.nix can ensure they refer to the local directory
# rather than a store path.
] ++ extracted.paths;
in
rec {
/*
normalize : UpdateScript → UpdateScript
EXPERIMENTAL! Converts a basic update script to the experimental attribute set form.
*/
normalize = updateScript: {
command = lib.toList (updateScript.command or updateScript);
supportedFeatures = updateScript.supportedFeatures or [ ];
} // lib.optionalAttrs (updateScript ? attrPath) {
inherit (updateScript) attrPath;
};
/*
sequence : [UpdateScript] → UpdateScript
EXPERIMENTAL! Combines multiple update scripts to run in sequence.
*/
sequence =
scripts:
let
scriptsNormalized = builtins.map normalize scripts;
in
let
scripts = scriptsNormalized;
hasCommitSupport = lib.findSingle ({ supportedFeatures, ... }: supportedFeatures == [ "commit" ]) null null scripts != null;
validateFeatures =
if hasCommitSupport then
({ supportedFeatures, ... }: supportedFeatures == [ "commit" ] || supportedFeatures == [ "silent" ])
else
({ supportedFeatures, ... }: supportedFeatures == [ ]);
in
assert lib.assertMsg (lib.all validateFeatures scripts) "Combining update scripts with features enabled (other than a single script with “commit” and all other with “silent”) is currently unsupported.";
assert lib.assertMsg (builtins.length (lib.unique (builtins.map ({ attrPath ? null, ... }: attrPath) scripts)) == 1) "Combining update scripts with different attr paths is currently unsupported.";
{
command = commandsToShellInvocation (builtins.map ({ command, ... }: command) scripts);
supportedFeatures = lib.optionals hasCommitSupport [
"commit"
];
};
/*
copyAttrOutputToFile : String → FilePath → UpdateScript
EXPERIMENTAL! Simple update script that copies the output of Nix derivation built by `attr` to `path`.
*/
copyAttrOutputToFile =
attr:
path:
{
command = [
"sh"
"-c"
"cp --no-preserve=all \"$(nix-build -A ${attr})\" \"$0\" > /dev/null"
path
];
supportedFeatures = [ "silent" ];
};
}
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