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# Copyright (c) 2019 Vincent Ambo
# Copyright (c) 2020-2021 The TVL Authors
# SPDX-License-Identifier: MIT
#
# Provides a function to automatically read a a filesystem structure
# into a Nix attribute set.
#
# Called with an attribute set taking the following arguments:
#
# path: Path to a directory from which to start reading the tree.
#
# args: Argument set to pass to each imported file.
#
# filter: Function to filter `args` based on the tree location. This should
# be a function of the form `args -> location -> args`, where the
# location is a list of strings representing the path components of
# the current readTree target. Optional.
{ ... }:
let
inherit (builtins)
attrNames
concatMap
concatStringsSep
elem
elemAt
filter
hasAttr
head
isAttrs
listToAttrs
map
match
readDir
substring;
argsWithPath = args: parts:
let meta.locatedAt = parts;
in meta // (if isAttrs args then args else args meta);
readDirVisible = path:
let
children = readDir path;
isVisible = f: f == ".skip-subtree" || (substring 0 1 f) != ".";
names = filter isVisible (attrNames children);
in listToAttrs (map (name: {
inherit name;
value = children.${name};
}) names);
# Create a mark containing the location of this attribute and
# a list of all child attribute names added by readTree.
marker = parts: children: {
__readTree = parts;
__readTreeChildren = builtins.attrNames children;
};
# Import a file and enforce our calling convention
importFile = args: scopedArgs: path: parts: filter:
let
importedFile = if scopedArgs != {}
then builtins.scopedImport scopedArgs path
else import path;
pathType = builtins.typeOf importedFile;
in
if pathType != "lambda"
then builtins.throw "readTree: trying to import ${toString path}, but it’s a ${pathType}, you need to make it a function like { depot, pkgs, ... }"
else importedFile (filter parts (argsWithPath args parts));
nixFileName = file:
let res = match "(.*)\\.nix" file;
in if res == null then null else head res;
readTree = { args, initPath, rootDir, parts, argsFilter, scopedArgs }:
let
dir = readDirVisible initPath;
joinChild = c: initPath + ("/" + c);
self = if rootDir
then { __readTree = []; }
else importFile args scopedArgs initPath parts argsFilter;
# Import subdirectories of the current one, unless the special
# `.skip-subtree` file exists which makes readTree ignore the
# children.
#
# This file can optionally contain information on why the tree
# should be ignored, but its content is not inspected by
# readTree
filterDir = f: dir."${f}" == "directory";
children = if hasAttr ".skip-subtree" dir then [] else map (c: {
name = c;
value = readTree {
inherit argsFilter scopedArgs;
args = args;
initPath = (joinChild c);
rootDir = false;
parts = (parts ++ [ c ]);
};
}) (filter filterDir (attrNames dir));
# Import Nix files
nixFiles = filter (f: f != null) (map nixFileName (attrNames dir));
nixChildren = map (c: let
p = joinChild (c + ".nix");
childParts = parts ++ [ c ];
imported = importFile args scopedArgs p childParts argsFilter;
in {
name = c;
value =
if isAttrs imported
then imported // marker childParts {}
else imported;
}) nixFiles;
nodeValue = if dir ? "default.nix" then self else {};
allChildren = listToAttrs (
if dir ? "default.nix"
then children
else nixChildren ++ children
);
in
if isAttrs nodeValue
then nodeValue // allChildren // (marker parts allChildren)
else nodeValue;
# Function can be used to find all readTree targets within an
# attribute set.
#
# This function will gather physical targets, that is targets which
# correspond directly to a location in the repository, as well as
# subtargets (specified in the meta.targets attribute of a node).
#
# This can be used to discover targets for inclusion in CI
# pipelines.
#
# Called with the arguments:
#
# eligible: Function to determine whether the given derivation
# should be included in the build.
gather = eligible: node:
if node ? __readTree then
# Include the node itself if it is eligible.
(if eligible node then [ node ] else [])
# Include eligible children of the node
++ concatMap (gather eligible) (map (attr: node."${attr}") node.__readTreeChildren)
# Include specified sub-targets of the node
++ filter eligible (map
(k: (node."${k}" or {}) // {
# Keep the same tree location, but explicitly mark this
# node as a subtarget.
__readTree = node.__readTree;
__readTreeChildren = [];
__subtarget = k;
})
(node.meta.targets or []))
else [];
in {
inherit gather;
__functor = _:
{ path
, args
, filter ? (_parts: x: x)
, scopedArgs ? {} }:
readTree {
inherit args scopedArgs;
argsFilter = filter;
initPath = path;
rootDir = true;
parts = [];
};
# In addition to readTree itself, some functionality is exposed that
# is useful for users of readTree.
# Create a readTree filter disallowing access to the specified
# top-level folder in the repository, except for specific exceptions
# specified by their (full) paths.
#
# Called with the arguments:
#
# folder: Name of the restricted top-level folder (e.g. 'experimental')
#
# exceptions: List of readTree parts (e.g. [ [ "services" "some-app" ] ]),
# which should be able to access the restricted folder.
#
# reason: Textual explanation for the restriction (included in errors)
restrictFolder = { folder, exceptions ? [], reason }: parts: args:
if (elemAt parts 0) == folder || elem parts exceptions
then args
else args // {
depot = args.depot // {
"${folder}" = throw ''
Access to targets under //${folder} is not permitted from
other repository paths. Specific exceptions are configured
at the top-level.
${reason}
At location: ${builtins.concatStringsSep "." parts}
'';
};
};
# This definition of fix is identical to <nixpkgs>.lib.fix, but is
# provided here for cases where readTree is used before nixpkgs can
# be imported.
#
# It is often required to create the args attribute set.
fix = f: let x = f x; in x;
}
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