Charmcraft analyzers and linters

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The following are the different checks that Charmcraft will run explicitly (when the user executes its analyze method) or implicitly (when packing charms).

Any linter or analysis can be set in the config to be excluded from the normal execution. Also note that if any linter ends in error it will block the charm packing (you can pack it anyway using the --force option).

You can read more about these checks in the Charmcraft Analyze Specification.

Contents:

Language attribute

If through analysis, the charm can be detected as being a Python based charm, then language shall be set to python. If not, it shall be set to unknown.

When working with Python, it is possible to only publish byte-code. By doing so, troubleshooting is a harder task. Charms with Python sources delivered are preferred.

This attribute meets the requirements to be set to python when:

  • the charm has a text dispatch which executes a .py
  • the charm has a .py entry point
  • the entry point file is executable

Framework attribute

When using the Operator Framework, it is best to import it from a common path and not make customisation or package forks from it. If the Operator Framework is detected in the charm sources, this attribute’s value shall be set to operator. If not, the charm may be using the Reactive Framework, and in this case the attribute value will be reactive. Else, it shall be set to unknown.

This check hint meets the requirements for Operative Framework when:

  • language attribute is set to python
  • the charm contains venv/ops
  • the charm imports ops in the entry point

The requirements for Reactive Framework are:

…or the Reactive Framework is used, if the charm…

  • has a metadata.yaml with name in it
  • has a reactive/<name>.py file that imports charms.reactive
  • has a file name that starts with charms.reactive- inside the wheelhouse directory

Juju metadata linter

This linter verifies that the metadata.yaml file exists and is sane.

The charm is considered to have a valid metadata if the following checks are true:

  • the metadata.yaml is present
  • it is a valid YAML file
  • it has at least the following fields: name, summary, and description

Juju actions linter

(new in 1.4)

This linter verifies that the actions.yaml file, if exists, is a valid YAML file. The file is optional. The file contents are not verified.

Juju config linter

(new in 1.4)

This linter verifies that the config.yaml file, if exists, is valid. This file is optional.

If the file exists, it is considered valid if the following checks are true:

  • it has the options key
  • it is a dictionary
  • each item inside has the mandatory type key

Check how to create config.yaml and configure charms for more information.

Charm entrypoint linter

(new in 2.1)

Check the entry point is correct. Note that even if most modern charms has a typical src/charm.py entry point, not all charms have one, as Juju has different ways to deliver its events.

This linter validates that, if an entry point is called from the dispatch file, that entry point…

  • exists
  • is a file
  • is executable

The entry point content is not validated.

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