Clarify that schema files may not be empty

Thanks for the report! This is an intentional change due to the adoption of Source instances with source location information for better debugging. Unfortunately it does not support empty strings, so this is a behaviour change.

I've pushed a fix to clarify the exception being thrown and show this is intentional, I've also added a change record to the original issue (and linked it to this one) to better clarify this change and provide the proposed solution.

Tested MR !90 on Drupal Forge and confirmed it works as expected. Empty schema files now trigger a clear InvalidPluginDefinitionException with the specific message, instead of a generic failure.

Unfortunately this breaks our use case, so we will have to revert parts of this.

A graphql extension module can have an extension definition, but not a base definition.

Example:
jobiqo_analytics.base.graphqls: empty or should not exist
jobiqo_analytics.extension.graphqls: contains extensions like

extend type Job {
  """
  Analytics performance data job visits.
  """
  analyticsJobVisits: Int
  """
  Analytics performance data job apply start.
  """
  analyticsJobApplyStart: Int
  """
  Analytics performance data job apply complete.
  """
  analyticsJobApplyComplete: Int
}

Proposed solution: allow empty and missing *.graphqls files.

MR created, if you are ok with the approach I can add a test case.

Sorry, I should have a read the change notice ...

So that should also work for us, hopefully not too many schema extension classes to update.

Setting this back to fixed for now.