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{ lib, super }:
from: to:
# Example from / to
# - Lifting `imports` from: _imports, to: imports
#
# Note:
# underscore used as mere convention to signalling to the user the "private"
# nature, they won't be part of the final view presented to the user
let
inherit (builtins)
removeAttrs
;
inherit (lib)
catAttrs
concatLists
;
inherit (super.utils)
concatMapAttrsWith
;
# merge attributes shallowly, but concat values of a specific key into a list in that key
# Type: ((key : String) -> { ... } -> { ... }) -> { ${key} : [ a ], ... }
mergeAttrsButConcatOn = key: x: y:
x // y // {
${key} = concatLists (catAttrs key [ x y ]);
};
in
cursor:
let toplevel = cursor == [ ]; in
concatMapAttrsWith (mergeAttrsButConcatOn (if toplevel then to else from))
(file: value: if ! value ? ${from} then { ${file} = value; } else {
${file} = removeAttrs value [ from ];
# top level ${from} declarations are omitted from merging
${if toplevel then to else from} = value.${from};
})