9.3.1. Bundles configuration and search path

Bundle classes are loaded automatically. The default bundle search path is pylib/gna/bundle/. The bundle search path is a configured option, which is defined in the configuration file config/gna/gnacfg.py:

bundlepaths = [ './pylib/gna/bundles', './pylib/gna/bundles_legacy' ]

The configuration file is included into git repository and should not be modified. Still there is a possibility to override it by providing a local configuration file config_local/gna/gnacfg.py:

mkdir -p config_local/gna
echo "bundlepaths = [ './pylib/gna/bundles', './pylib/gna/bundles_legacy', './macro/tutorial/bundles' ]" > config_local/gna/gnacfg.py

The configuration from the local version is loaded after the global one and overrides its settings. After creating the local configuration file run gna without arguments:

./gna

The output should indicate that local configuration is loaded:

Loading config file: config/gna/gnacfg.py
Loading config file: config_local/gna/gnacfg.py

As one may notice, we have added an extra path to search for bundles. The path contains tutorial bundles.

A bundle is specified by two strings: name and version. The full name is then produced by joining name and version with _ used as a separator. For example for bundle parameters with version ex01 a python file parameters_ex01 will be searched in each of the bundle search paths. The file should define a class with the same name (parameters_ex01) which will be loaded and instantiated.

A typical bundle configuration is a dictionary of the following form:

cfg = NestedDict(
  bundle = 'parameters_ex01',
  option1 = value1,
  option2 = value2,
  ...
)

The bundle is executed calling a method execute_bundle(cfg), which finds relevant bundle class, instantiates it with configuration provided and executes it. In a sense bundle is a function with a lot of arguments.

Are more complex version of the configuration looks like this:

cfg = NestedDict(
  bundle = dict(
                 name='parameters',
                 version='ex01',
                 ...
                 ),
  option1 = value1,
  option2 = value2,
  ...
)

A bundle field is a dictionary which specifies which bundle should be used to parse the configuration. This dictionary may contains some other options. The distinction between configuration options and bundle options are the following: bundle options are parsed by the GNA similarly for all the bundles and may be sometimes overridden. The configuration options are unique to the particular bundle of the particular version and may be parsed only by it.