Detect configuration syntax errors

[gitlabform]

Detect configuration syntax errors

[gdubicki]

We can start by checking if the the config is a valid YAML and provide friendly error messages with github.com/adrienverge/yamllint using a method mentioned in adrienverge/yamllint#112 .

[gdubicki]

We have moved this forward a bit in v2.9.0 thanks to switching the YAML parser from PyYAML to ruamel.yaml that by default disallows duplicate dict keys. It is also wrapped in yamlpath that promises to provide more helpful error messages.

I think that the next step will be switch to YAML 1.2 for configuration in gitlabform v3.
UPDATE: ...or not, see #340 (comment).

[armingerten]

In order to move this forward, it could be considered to provide a JSON Schema that describes the basic structure of the config.yml file. Providing such schema has multiple advantages:

• The schema can be used when running gitlabform to validate whether the config.yml is malformed. Libraries like yamale provide an implementation to validate YAML using JSON Schema (Current PyPi download count / day is ~10.000).
• The schema can be integrated into popular IDEs (IDEA, VSCode, etc.) and used for validation, documentation and code completion.
• When added properly to schemastore.org, IDEs automatically detect the schema and offer afore mentioned validation, documentation and code completion out of the box.

WDYT?

[gdubicki]

Closing in favor of the newer #499.