Upstream Updates

Updating the facade and definitions code generated from the schema to reflect changes in upstream Juju consists of two steps:

• Creating a new schemas-juju-<version>.json file from the Juju code-base
• Generating the libjuju Python code from that schema

Rarely, you may also have to add or update an override.

Creating a Schema File

First, you will need to fetch SchemaGen and a copy of the Juju source. Once your copy of the Juju source is at the version you want to update to (probably the develop branch, or a release tag) and you have updated and reinstalled SchemaGen to reflect those changes, you just need to send the output into a file in the libjuju repository:

schemagen > juju/client/schemas-juju-2.2-rc1.json

The version number you use in the filename should match the upstream version of Juju. You should then also move the latest pointer to the new file:

rm juju/client/schemas-juju-latest.json
ln -s schemas-juju-2.2-rc1.json juju/client/schemas-juju-latest.json

Generating the Python Code

Once you have a new schema file, you can update the Python code using the client make target:

make client

You should expect to see updates to the juju/client/_definitions.py file, as well as one or more of the juju/client/_clientX.py files, depending on which facades were touched.

Overrides

It should be quite rare, but occasionally the generated Python code does not capture all of the logic needed to properly parse the output from the API or may otherwise need some small amount of tweaking. This is what the juju/client/overrides.py file is for. An example of this is the Number type, which isn’t standard JSON and must be parsed slightly differently.

At the top of that file are two lists, __all__ and __patches__. The former replaces entire class implementations, while the latter patches the attributes of the override classes into the matching generated class, leaving the rest of the generated class untouched.