mock: correct contextual/explicit parent assertions #2812
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When recording the parent of an event or span, the `MockCollector` treats an explicit parent of `None` (i.e. an event or span that is an explicit root) in the same way as if there is no explicit root. This leads to it picking up the contextual parent or treating the event or span as a contextual root. This change refactors the recording of the parent to use `is_contextual` to distinguish whether or not an explicit parent has been specified. The actual parent is also written into a `Parent` enum so that the expected and actual values can be compared in a more explicit way. Additionally, the `Parent` struct has been moved into its own module and the check behavior has been fixed. The error message has also been unified across all cases. Given the number of different cases involved in checking parents, separate integration tests have been added to `tracing-mock` specifically for testing all the positive and negative cases when asserting on the parents of events and spans. There were two tests in `tracing-attributes` which specified both an explicit and a contextual parent. This behavior was never intended to work as all events and spans are either contextual or not. The tests have been corrected to only expect one of the two. Fixes: #2440
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The clippy failure is unrelated to this change, so don't worry about that. |
| .with_contextual_parent(None) | ||
| .with_explicit_parent(None), |
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it seems like the fact that both of these methods can be called on an ExpectedSpan creates some ambiguity in the tracing-mock API surface. what do you think about getting rid of with_contextual_parent() and with_explicit_parent(), and replacing them with a single with_parent() method taking a Parent enum? something like this:
expect::span()
.with_parent(Parent::Contextual(Some("whatever"))this way, the user can no longer construct a span that expects both a contextual parent and an explicit parent at the same time.
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I started doing this, but the change is huge. It also has some unfortunate side-efffects (at lesat the way that I implemented it). Because then we'll need:
expect::span()
.with_parent(Parent::Contextual(Some("whatever".to_owned())))Which starts to get a bit long. Also, exposing the Parent enum makes everything longer too.
I think that there is room for improvement here, but I would like to look at it in a separate PR so as not to make this one too large. What do you think?
| let get_parent = || { | ||
| if span.is_contextual() { | ||
| if let Some(parent) = cx.lookup_current() { | ||
| let contextual_parent = cx.span(&parent.id()).expect( | ||
| "tracing-mock: contextual parent cannot \ | ||
| be looked up by ID. Was it recorded correctly?", | ||
| ); | ||
| Parent::Contextual(contextual_parent.name().to_string()) | ||
| } else { | ||
| Parent::ContextualRoot | ||
| } | ||
| } else if span.is_root() { | ||
| Parent::ExplicitRoot | ||
| } else { | ||
| let parent_id = span.parent().expect( | ||
| "tracing-mock: is_contextual=false is_root=false \ | ||
| but no explicit parent found. This is a bug!", | ||
| ); | ||
| let explicit_parent = cx.span(parent_id).expect( | ||
| "tracing-mock: explicit parent cannot be looked \ | ||
| up by ID. Is the provided Span ID valid: {parent_id}?", | ||
| ); | ||
| Parent::Explicit(explicit_parent.name().to_string()) | ||
| } |
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this code is kinda duplicated here and in collector.rs, although not quite...i wonder if some of it can be factored out? idk. not a blocker.
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I tried to refactor this a couple of times and didn't come up with anything that wasn't more verbose than this. On top of that, the indirection required to handle different span lookups and context fetching tends to make it all longer as well.
I'd leave tis as is for now if that's OK.
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Marked this PR as a draft as it has been superceded by #3004. |
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Closing this one in favor of #3004 which has now been merged. |
Motivation
When recording the parent of an event or span, the
MockCollectortreats an explicit parent of
None(i.e. an event or span that is anexplicit root) in the same way as if there is no explicit root. This
leads to it picking up the contextual parent or treating the event or
span as a contextual root.
Solution
This change refactors the recording of the parent to use
is_contextualto distinguish whether or not an explicit parent has been specified. The
actual parent is also written into a
Parentenum so that the expectedand actual values can be compared in a more explicit way.
Additionally, the
Parentstruct has been moved into its own module andthe check behavior has been fixed. The error message has also been
unified across all cases.
Given the number of different cases involved in checking parents,
separate integration tests have been added to
tracing-mockspecifically for testing all the positive and negative cases when
asserting on the parents of events and spans.
There were two tests in
tracing-attributeswhich specified both anexplicit and a contextual parent. This behavior was never intended to
work as all events and spans are either contextual or not. The tests
have been corrected to only expect one of the two.
Fixes: #2440