corn 7

INSTALLATION

pip install corn

INSTALLATION FOR DEVELOPMENT

Clone the corn repo and install with pip:

git clone https://gitlab.com/saltstack/pop/corn.git
pip install -e corn

EXECUTION

After installation the corn command should now be available.

The command will have no output until it is vertically extended (details below).

TESTING

install requirements-test.txt with pip and run pytest:

pip install -r corn/requirements-test.txt
pytest corn/tests

VERTICAL APP-MERGING

Instructions for extending corn

Install pop:

pip install --upgrade pop

Create a new directory for the project:

mkdir corn_{project_name}
cd corn_{project_name}

Use pop-seed to generate the structure of a project that extends corn:

pop-seed -t v corn_{project_name} -d corn

• “-t v” specifies that this is a vertically app-merged project

• “-d corn” says that we want to implement the dynamic name of “corn”

Notice that some structure has been created for you. We especially care about the new directory in corn_{project_name}/corn

Add “corn” to the requirements.txt:

echo "corn" >> requirements.txt

CREATING CORNS

• Create a new file in “corn_{project_name}/corn”

  • The directory should already have been created by pop-seed.

  • The file name is arbitrary.

  • Every file in this directory, then it’s subdirectories, will be parsed “simultaneously” (as far as that makes sense for asyncio).

  • Corns that are dependant on each other should be assigned in the same function.

  • Do NOT rely on the collector’s recursion strategy for corns to depend on each other.

• Add your new project to the python path

  • alternatively, run “pip install -e .” from your project’s root directory

    • you only need to do this once

• Create an async function in this file with a descriptive yet arbitrary name

  • By convention it should start with “load”

  • Make it async unless you have a really really really good reason.

  • Grains that depend on each other already belong in the same function, don’t depend on synchronous programming for determinism

  • Corns can be accessed and assigned like a dictionary, but our convention is to use the namespace

Example:

async def load_my_corn(hub):
    hub.corn.CORN.new_corn = "Hello World!"

And that’s it! Now verify that your corn is collected from the command line:

corn new_corn

Output:

new_corn:
    Hello World!