Extending Configs

 

A common pattern is to extend an existing config, overriding and/or adding new config values to it. The extension is done by including the base configuration, and then overriding the chosen values in the current config.

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This page assumes that you are familiar with the contents of The Defaults List.

Extending a config from the same config group:

config.yaml

defaults:
  - db: mysql 

db/mysql.yaml

defaults:
  - base_mysql

user: omry
password: secret
port: 3307
encoding: utf8

db/base_mysql.yaml

host: localhost
port: 3306
user: ???
password: ???

Output:

$ python my_app.py

db:
  host: localhost   # from db/base_mysql
  port: 3307        # overridden by db/mysql.yaml 
  user: omry        # populated by db/mysql.yaml
  password: secret  # populated by db/mysql.yaml
  encoding: utf8    # added by db/mysql.yaml

Extending a config from another config group:

To extend a config from a different config group, include it using an absolute path (/), and override the package to _here_. (_here_ is described in Packages)

db/mysql.yaml

defaults:
  - /db_schema/base_mysql@_here_

It is otherwise identical to extending a config within the same config group.