Add docco warning against resolving ScenarioContext here

[craigfowler]

🤔 What's changed?

Add a C# documentation comment for the CustomizeScenarioDependencies event hook (for plugin authors). This warns them off attempting to resolve a ScenarioContext, as doing so will result in a crash error which is difficult to diagnose.

⚡️ What's your motivation?

A cautionary tale - if you attempt to resolve the ScenarioContext from this event, then it won't have been created/initialised by the ContextManager yet. That means that the DI container attempts to create it during resolution.

If that happens, you'll encounter an object container exception, because the container in-turn tries to resolve a RuleInfo instance, which also has yet to be added to the container. Because RuleInfo has ctor params which include primitives (strings), this throws because the container doesn't permit the resolution of primitives (for good reason).

FYI, resolving scenario context from this location had worked in old SpecFlow and worked in Reqnroll 2.x. I suspect that this came about because of the changes made here:

• This PR: Add RuleInfo to ScenarioContext #454
• Particularly this comment: Add RuleInfo to ScenarioContext #454 (review)
  • At the point where CustomizeScenarioDependencies is invoked, it seems that the context manager initialization hasn't happened yet
  • Which in-turn becomes another way to trigger the troublesome container behaviour documented in that discussion

I think it's most likely that it was never intended for a plugin to attempt to resolve ScenarioContext from this position; the fact that it had worked before the addition of RuleInfo is likely a coincidence. That's why I wouldn't describe this as a bug or regression, even though "something that used to work doesn't anymore". In essence the already-documented breaking change in 3.0.0 has a slightly wider impact than previously documented. That's why I think that this docco is a useful addition, to warn future plugin-authors away from doing something bad, which could take a while to diagnose.

In my specific case, I found out that I was being stupid and resolving ScenarioContext from this event, when all I ever wanted was ScenarioInfo. So, I've fixed my own plugin code by resolving the info type and not the context type.

🏷️ What kind of change is this?

• 📖 Documentation (improvements without changing code)

♻️ Anything particular you want feedback on?

Are my presumptions in the Motivations section correct? If not then maybe this needs more than just a docco tweak?

[Copilot]

Pull request overview

This PR adds XML documentation to the CustomizeScenarioDependencies event in the RuntimePluginEvents class. The documentation warns plugin authors not to resolve ScenarioContext from this event, as it will cause an ObjectContainerException because the scenario context hasn't been initialized at that point. The documentation suggests using ScenarioInfo instead.

Changes:

• Added XML documentation comment with summary and remarks to the CustomizeScenarioDependencies event

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[gasparnagy]

thx!