feature-flags.rst

Feature flags

Feature flags provide a convenient way to define package selections without making it necessary to list each package explicitly.

The main feature flag definition file is package/features, but each package feed can provide additional defintions in a file called features at the root of the feed repository.

Each flag $flag without any explicit definition will simply include the package with the name gluon-$flag by default. The feature definition file can modify the package selection in two ways:

• The nodefault function suppresses default of including the gluon-$flag package
• The packages function adds a list of packages (or removes, when package names are prepended with minus signs) when a given logical expression is satisfied

Example:

nodefault 'web-wizard'

packages 'web-wizard' \
  'gluon-config-mode-hostname' \
  'gluon-config-mode-geo-location' \
  'gluon-config-mode-contact-info'

packages 'web-wizard & (mesh-vpn-fastd | mesh-vpn-tunneldigger)' \
  'gluon-config-mode-mesh-vpn'

This will

• Disable the inclusion of a (non-existent) package called gluon-web-wizard
• Enable three config mode packages when the web-wizard feature is enabled
• Enable gluon-config-mode-mesh-vpn when both web-wizard and one of mesh-vpn-fastd and mesh-vpn-tunneldigger are enabled

Supported syntax elements of logical expressions are:

• & (and)
• | (or)
• ! (not)
• parentheses