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fix(nix): Support retrieving differently cased top-level attributes

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As described in issue #14, the registry API does not allow image names
with uppercase-characters in them.

However, the Nix package set has several top-level keys with uppercase
characters in them which could previously not be retrieved using
Nixery.

This change implements a method for retrieving those keys, but it is
explicitly only working for the top-level package set as nested
sets (such as `haskellPackages`) often contain packages that differ in
case only.
This commit is contained in:
Vincent Ambo 2019-08-03 18:27:26 +01:00 committed by Vincent Ambo
parent aa260af1ff
commit 20103640fa
1 changed files with 29 additions and 4 deletions
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33
tools/nixery/build-registry-image.nix
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@ -113,11 +113,36 @@ let
# For top-level items, the name of the key yields the result directly. Nested
# items are fetched by using dot-syntax, as in Nix itself.
#
# For example, `deepFetch pkgs "xorg.xev"` retrieves `pkgs.xorg.xev`.
deepFetch = s: n:
let path = lib.strings.splitString "." n;
# Due to a restriction of the registry API specification it is not possible to
# pass uppercase characters in an image name, however the Nix package set
# makes use of camelCasing repeatedly (for example for `haskellPackages`).
#
# To work around this, if no value is found on the top-level a second lookup
# is done on the package set using lowercase-names. This is not done for
# nested sets, as they often have keys that only differ in case.
#
# For example, `deepFetch pkgs "xorg.xev"` retrieves `pkgs.xorg.xev` and
# `deepFetch haskellpackages.stylish-haskell` retrieves
# `haskellPackages.stylish-haskell`.
deepFetch = with lib; s: n:
let path = splitString "." n;
err = { error = "not_found"; pkg = n; };
in lib.attrsets.attrByPath path err s;
# The most efficient way I've found to do a lookup against
# case-differing versions of an attribute is to first construct a
# mapping of all lowercased attribute names to their differently cased
# equivalents.
#
# This map is then used for a second lookup if the top-level
# (case-sensitive) one does not yield a result.
hasUpper = str: (match ".*[A-Z].*" str) != null;
allUpperKeys = filter hasUpper (attrNames s);
lowercased = listToAttrs (map (k: {
name = toLower k;
value = k;
}) allUpperKeys);
caseAmendedPath = map (v: if hasAttr v lowercased then lowercased."${v}" else v) path;
fetchLower = attrByPath caseAmendedPath err s;
in attrByPath path fetchLower s;
# allContents is the combination of all derivations and store paths passed in
# directly, as well as packages referred to by name.