This is a standalone and enhanced implementation of the Leiningen meta-merge
function, forked from Meta-Merge. It's particularly useful for merging configuration maps.
The merge function recursively merges two data structures.
(require '[ctrl-merge.core :as cm])
(cm/merge {:a [:b :c]} {:a [:d]})
; => {:a [:b :c :d]}Metadata hints can be provided to override the default behavior:
When merge is called with a hash-map that has ^:prepend on it, the
function will take the values on the right and prepend them to the set on the
left (the default would append them as you can see above). You can see this
below.
(cm/merge {:a [:b :c]} {:a ^:prepend [:d]})
; => {:a [:d :b :c]}When merge is called with a hash-map that has ^:replace on it, the
function will take the values on the right and completely replace the ones on
the left. You can see this below:
(cm/merge {:a [:b :c]} {:a ^:replace [:d]})
; => {:a [:d]}With replace the map to the right takes precedence.
When merge is called with a hash-map that has ^:displace on it, the
function will take the values on the right, only if there are no values on the
left. You can see this below:
(cm/merge {:a [:b :c]} {:a ^:displace [:d]})
; => {:a [:b :c]}With displace the map to the left takes precedence. This makes displace a good solution for default values.
merge can be configured using extra options argument. Supported options
| Key | Description |
|---|---|
:replace-nil |
nil value on right position wins |
(cm/merge {:a {:b 1}} {:a nil} {:replace-nil true})
; => {:a nil}Copyright © 2023 Phil Hagelberg, James Reeves, Metosin and all the Leiningen contributors.
Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.