# depends:

Lists other plugins or language/system libraries which the current plugin expects:

# depends: corefuncs, json_io, bin:bash

Each entry is a plugin basename, and indicates it must be available/active alongside.

  • The recommended field name is "depends" and not "require" - for parity with the Debian packaging spec, and because it sounds less stringent.

  • Not every application would want to enforce this strictly. Because dynamic languages can soft-detect dependencies usually.

  • Within a plugin management UI, the depends: list could be used for installation warnings.

It's optional, and might be treated as documentation in some implementations.

Versioned dependencies

Additionally the plugin names can be suffixed with a version comparison:

# depends: core (>= 2.0.0)

Which obviously does require the plugin manager to be somewhat more involved. You'll often get away just implementing a >= check. Other version expressions are usually overkill for simple application-level features.

System/language references

While a TYPE:name entry can reference other scopes (instead of application-local plugins)

bin:imagemagick verify a binary exists
python:lxml for language modules
sys:amd64 e.g. the architecture.
deb:anacron as hint for the system package manager.
api:archnemesis see api

This is quite informal still. There's seldomly practical value to implement such complex dependency lookups, or these exact ones. This is just the advised syntax.

Magic basenames

Optionally one could handle a few plain basenames specically For instance checking the current language runtime with:

 # depends: python (>= 3.4)

Or, if feasible, even module versions

 # depends: php:sqlite (>= 3.24)

Related fields

Depending on complexity other fields might be used alongside:

# conflicts:

Does occasionally make sense for variants or mutally exclusive features. Though could be implemented as # depends: !feature or feature (< 0.0) with version expression support.

# provides:

Defines a virtual feature identifier to be present. Less commonly needed for application plugins.

# suggests:

A weak recommendation of other plugins to go along with. Should foremost be handled in the admin UI or a plugin download interface.