Ensure template is not sent for Structured logs with no parameters

[jamescrosswell]

Resolves #4480:

• Make sure the .NET SDK only sets sentry.message.template on logs if sentry.message.parameter values are also defined #4480

---

Note

Skip emitting sentry.message.template in structured logs without parameters; adds coverage and updates changelog.

• Structured Logs:
  • Update src/Sentry/SentryLog.cs to only write attributes.sentry.message.template when Template is set and Parameters has length > 0.
• Tests:
  • Add WriteTo_NoParameters_NoTemplate theory in test/Sentry.Tests/SentryLogTests.cs to assert presence/absence of sentry.message.template based on parameters.
• Docs/Changelog:
  • Update CHANGELOG.md under Fixes to note templates aren’t sent for logs without parameters.

^{Written by Cursor Bugbot for commit faad68a. This will update automatically on new commits. Configure here.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.48%. Comparing base (2dc1551) to head (faad68a).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4544      +/-   ##
==========================================
+ Coverage   73.33%   73.48%   +0.14%     
==========================================
  Files         479      482       +3     
  Lines       17509    17679     +170     
  Branches     3445     3495      +50     
==========================================
+ Hits        12840    12991     +151     
- Misses       3789     3798       +9     
- Partials      880      890      +10     

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[Flash0ver]

potential issue: Accessing Length could throw NullReferenceException when default

Suggested change

	if (Template is not null && Parameters is { Length: > 0 })
	if (Template is not null && !Parameters.IsDefaultOrEmpty)

---

Admittedly, this is a bit pedantic. We currently have no flow setting the Parameters to default, but we technically could make a (semi-)related change in the future and then run into an NRE along the line.

ImmutableArray<KeyValuePair<string, object>> parameters = default;
_ = parameters.Length; // System.NullReferenceException: Object reference not set to an instance of an object.

The ImmutableArray<T>.Length property is accessing the underlying array directly, which is null when the struct ImmutableArray<T> is (explicitly/implicitly) default.
ImmutableArray<T>.IsEmpty has a similar behavior.

To be on the safe side, I suggest using ImmutableArray<T>.IsDefaultOrEmpty which ensures that this struct instance isn't default by checking whether the underlying array is null before accessing its Length.

Context:
I decided to use ImmutableArray<T> here, because we expose the SentryLog.Parameters publicly and to render this collection immutable through e.g. the user-defined SetBeforeSendLog(Func<SentryLog, SentryLog?>) delegate. It does have its usage quirks for the benefit of similar performance characteristics to using a mutable Array directly.

[jamescrosswell]

I think this us guarded against. If the condition was Parameters is { } then it would ensure Parameters isn't null... and so Parameters is { Length: > 0 } ensures that it's not null and has more than one element right?

EDIT: Oh, I see... default != null

[Flash0ver]

Yeah ... ImmutableArray`1 is a value type. But the underlying array is a reference type. And the Length property does not perform a null check on the underlying array, which actually is null should the ImmutableArray`1 be initialized to default.

[cursor]

Bug: Default ImmutableArray Length Access Throws Exception

The condition Parameters is { Length: > 0 } can throw an InvalidOperationException if Parameters is a default ImmutableArray<T>. Accessing the Length property on a default ImmutableArray causes this exception, which is inconsistent with how ImmutableArray is handled elsewhere.

 

[Flash0ver]

Partially correct.
The get_Length property does indeed throw when Parameters is a default ImmutableArray<T>.
But it does not throw an InvalidOperationException, but a NullReferenceException!