====== Configuration File Inheritance ======

VuFind® allows a configuration file to inherit settings from a parent configuration. Different configuration file types have slightly different inheritance options as described below.

===== Inheritance in .ini Files =====

.ini files do not have any implicit inheritance, but you can define several options in the ''[Parent_Config]'' section of a file to make it inherit settings from a parent file. See the ''[Parent_Config]'' section in [[configuration:files:config.ini|config/vufind/config.ini]] for details. 

===== Inheritance in .yaml Files =====

By default a .yaml file inherits top-level sections from the corresponding base configuration file in config/vufind if they don't exist. 

For example, if the base configuration contains the following settings:

<code yaml>
AllFields:
  DismaxFields:
    - allfields
    - fulltext

Author:
  DismaxFields:
    - author
  DismaxHandler: dismax  

ISN:
  DismaxFields:
    - isbn
</code>

And the local configuration contains the following settings:

<code yaml>
Author:
  DismaxFields:
    - author2
  DismaxHandler: edismax  

Coordinate:
  DismaxFields:
    - long_lat_display
</code>

The result is the equivalent of:

<code yaml>
AllFields:
  DismaxFields:
    - allfields
    - fulltext

Author:
  DismaxFields:
    - author2
  DismaxHandler: edismax  

Coordinate:
  DismaxFields:
    - long_lat_display

ISN:
  DismaxFields:
    - isbn
</code>

You can specify another file to inherit from with a `"@parent_yaml": "parentfile.yaml"` directive at the top of the local yaml file. The file name can be an absolute path or a relative path. 

==== Merging Sections in .yaml Files ====

Starting with VuFind® 9.0 you can also define sections that should be merged together at the top level or a sub-level by using the `"@merge_sections"` directive. This directive should contain an array of paths, where each path is an array starting from the top level down to the desired level. For example assuming the parent config above and the local config below:

<code yaml>
"@merge_sections":
  - [Author, DismaxFields]

Author:
  DismaxFields:
    - author2

Coordinate:
  DismaxFields:
    - long_lat_display
</code>

The result is the equivalent of:

<code yaml>
AllFields:
  DismaxFields:
    - allfields
    - fulltext

Author:
  DismaxFields:
    - author
    - author2
  DismaxHandler: edismax  

Coordinate:
  DismaxFields:
    - long_lat_display

ISN:
  DismaxFields:
    - isbn
</code>

===== Inheritance of Entire Configuration Directories =====

Starting with VuFind® 9.1, you can use [[configuration:local_settings_directory#dirlocationsini|DirLocations.ini]] to chain together a series of [[configuration:local_settings_directory|local settings directories]]. This can be useful in combination with file-based inheritance to solve various configuration organization problems.