Merge ~sylvain-pineau/checkbox-ng:no_validation_context_env_var into checkbox-ng:master

[Sylvain Pineau]

If a project snap wants to use the content interface to load the base providers, needless to build it with parts for all those providers.

So far we have to as they are used to pass the project provider validation.

This patch allow such provider to perform only "static" validation (i.e with no context, without trying to load all possible providers).

As an example:

parts:
[...]
  checkbox-provider-foo:
    plugin: plainbox-provider
    source: ./checkbox-provider-foo
    after: [checkbox-ng-dev]
    build-environment:
      - PROVIDER_NO_VALIDATION_CONTEXT: "1"

Note: build-environment requires snapcraft snap from edge

[Jonathan Cave (jocave)]

What is an example of a validation failure that would happen without this change?

[Sylvain Pineau (sylvain-pineau)]

@joc https://pastebin.canonical.com/p/Qbg8xbfg8v/

Unmerged commits

57f5a83... by Sylvain Pineau on 2018-10-11

provider_manager: Validate without context if special env var is set

PROVIDER_NO_VALIDATION_CONTEXT=1

diff --git a/plainbox/provider_manager.py b/plainbox/provider_manager.py
index 96767ea..e50b42b 100644
--- a/plainbox/provider_manager.py
+++ b/plainbox/provider_manager.py
@@ -1075,6 +1075,8 @@ class ValidateCommand(ManageCommand):
         unit_list, exc_list = self.collect_all_units(provider)
         early_issue_gen = self.get_early_issues(exc_list)
         context = UnitValidationContext(provider_list)
+        if os.getenv("PROVIDER_NO_VALIDATION_CONTEXT", default=0):
+            context = None
         issue_gen = self.validate_units_in_context(context, unit_list)
         del context
         failed = False