[release/8.0] Optimize Options Source Gen when no need to run

[github-actions]

Backport of #93427 to release/8.0

/cc @tarekgh

Customer Impact

The Options source generator was introduced in .NET 8.0 and is activated by default, requiring no user intervention for its use. During design time, the generator is invoked with every keystroke. The modification here aims to prevent the generator from executing when no code generation is required. This enhancement accelerates this scenario and minimizes unnecessary memory allocation, addressing a minor performance regression that we have already observed.

Testing

Successfully passed all regression tests without any failures. We don't currently have a way to test privates for VS test runs and we'll look into improving that once we have the VMR

Risk

There is virtually no risk associated with this change. It is a minor, non-impactful modification that should not disrupt the logic of the source generator.

IMPORTANT: If this backport is for a servicing release, please verify that:

• The PR target branch is release/X.0-staging, not release/X.0.

• If the change touches code that ships in a NuGet package, you have added the necessary package authoring and gotten it explicitly reviewed.

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Tagging subscribers to this area: @dotnet/area-infrastructure-libraries
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Issue Details

---

Backport of #93427 to release/8.0

/cc @tarekgh

Customer Impact

Testing

Risk

IMPORTANT: If this backport is for a servicing release, please verify that:

• The PR target branch is release/X.0-staging, not release/X.0.

• If the change touches code that ships in a NuGet package, you have added the necessary package authoring and gotten it explicitly reviewed.

Author:	github-actions[bot]
Assignees:	-
Labels:	area-Infrastructure-libraries
Milestone:	-

[ghost]

Tagging subscribers to this area: @dotnet/area-extensions-options
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Backport of #93427 to release/8.0

/cc @tarekgh

Customer Impact

Testing

Risk

IMPORTANT: If this backport is for a servicing release, please verify that:

• The PR target branch is release/X.0-staging, not release/X.0.

• If the change touches code that ships in a NuGet package, you have added the necessary package authoring and gotten it explicitly reviewed.

Author:	github-actions[bot]
Assignees:	-
Labels:	Servicing-consider, area-Extensions-Options, source-generator
Milestone:	-

[tarekgh]

@artl93 this one is ready for your review.

[artl93]

M2 approved.

@tarekgh - Just a thought - is it possible to assert the optimization worked for this case in a unit test? E.g. context did not end up adding sources, perhaps? (Curious)

[tarekgh]

@artl93 part of my manual testing I did is I confirmed the behavior under the debugger and ensured the generator didn't do anything and exited early when there is no need to generate any code. We have a work planned for 9.0 to address the whole incremental change with this generator and other generators. When we do that, I expect we'll add more granular test cases that should cover the concerned scenarios. Checking added sources is not going to confirm our scenario here because the generator can run fully and still does not generate any code.

[carlossanlop]

Approved by Tactics via email.