D 2018-07-04T15:44:44.414
L depends
N text/x-markdown
P 4e6fd14579f5ee2859be2dcf92f9c933d3bdf3cd1055bfc7b47214b1db15cc54
U mario
W 1767
## # 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](wiki/id), 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. Most other version expression gimmicks are likely overkill for simple applicatiion-level features.


## System/language dependencies

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](wiki/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.


## Related fields

Depending on complexity other fields might be used alongside:

  * `# provides:`
  * `# conflicts:`
  * `# suggests:`

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