PEP: Plugin management¶

As written in Envisage documentation, the applications we write need to change over time. We fix bugs, and we add, modify, and remove features. In other words, we spend most of our time either fixing or extending applications.

Sometimes we extend our applications by changing the actual code, sometimes we have other ad hoc extension mechanisms in place – a text file here, a directory of scripts there. As applications grow, they often end up with numerous places where they can be extended, but with a different extension mechanism at each one. This makes it hard for developers who want to extend the application to know :

where they can add extensions

how to add them

Warning

For concrete documentation on how to extend OpenAleaLab, see Extending OpenAleaLab

References¶

Existing implementations¶

Trac component architecture

Yapsy (yet another plugin system) (example of plugin framework. Several links inside)

Envisage

PyUtilib, Architecture Doc (PDF)

Another simple framework

Useful links¶

Fundamental concept of plugin infrastucture

Python plugin framework

PkgResources / entry points¶

pkg_resources official website

ETS Envisage / extension points¶

Envisage official website,

OpenAlea components¶

See How to declare OpenAlea components.

OpenAlea plugins¶

Plugin description¶

Variable or variables describing plugin. work in progress: Potential useful information:

classical meta info (name, icon, desc, authors, license, ...)

python/qt compatibility (does-it work with PyQt4 ? PySide ? Qt 5)

python compatibility (python 2 ? python 3 ?)

interfaces implemented by this widget

dependencies required

These information are used to filter search results. For example:

# Return all widgets
results = search('oalab.applet')

# Example of filter in basic query language

# Return all widget written by John Doe
results = search('oalab.applet', author='John Doe')

Depending of data description structure, we can imagine advanced query languages like SQL, SPARQL, or based on existing libraries

Possible approaches for plugin description:

Flat variables¶

name = 'HelpWidget'
authors = ['John Doe']

JSON¶

data = {
    'name' :
    'oalab': {
        'extensions': ['plantlab', 'tissuelab'],
        },
}

Semantic web¶

data = """
@prefix dc: <http://purl.org/dc/elements/1.1/>.
@prefix oa: <http://openalealab.org>

oa:helpwidget
    dc:title "HelpWidget";
    dc:publisher "OpenAleaLab"
    .
"""