A standalone implementation of Leiningen's meta-merge function
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README.md

Meta-Merge

Build Status

This is a standalone implementation of the Leiningen meta-merge function. It's particularly useful for merging configuration maps.

Installation

To install, add the following to your project :dependencies:

[meta-merge "1.0.0"]

Usage

The meta-merge function recursively merges two data structures.

(require '[meta-merge.core :refer [meta-merge]])

(meta-merge {:a [:b :c]} {:a [:d]})
=> {:a [:b :c :d]}

Metadata

Metadata hints can be provided to override the default behavior:

Prepend

When meta-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.

(meta-merge {:a [:b :c]} {:a ^:prepend [:d]})
=> {:a [:d :b :c]}

Replace

When meta-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:

(meta-merge {:a [:b :c]} {:a ^:replace [:d]})
=> {:a [:d]}

With replace the map to the right takes precedence.

Displace

When meta-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:

(meta-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.

License

Copyright © 2016 Phil Hagelberg, James Reeves and all the Leiningen contributors.

Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.