build: make the IDE code-style analyzers reach the build, and gate IDE0017

[HandyS11]

Why

SonarQube keeps reporting roslyn:IDE0017 ("Simplify object initialization") on code a green dotnet build has just declared clean. This closes that gap for the whole IDE* family.

The part that isn't obvious

EnforceCodeStyleInBuild and TreatWarningsAsErrors were already on, so setting the severity looked like it should be enough. It isn't — I set dotnet_diagnostic.IDE0017.severity = error and a deliberate probe violation still built clean, while a deliberate Sonar S3400 in the same build failed it as expected. Analyzers were running; no IDE* diagnostic was ever reported.

Roslyn's command-line driver skips analyzers whose diagnostics are all info/hidden by default, and that decision happens before your .editorconfig severity is consulted. So the IDE* family was being dropped from the build no matter what severity it was given.

The differentiator is /errorlog. Confirmed by elimination:

Attempt	Result
dotnet_diagnostic.IDE0017.severity = error in .editorconfig	still clean
same, via a .globalconfig (verified it reached csc)	still clean
-p:EnableCodeStyleSeverity=true	still clean
-p:ErrorLog=…	fails with error IDE0017

That also explains the original symptom: SonarScanner sets ErrorLog itself to import roslyn:* issues, so Sonar has been seeing a diagnostic set the build never computed.

Changes

• Directory.Build.targets (new) — sets ErrorLog to obj/…/<Project>.sarif. In .targets rather than .props because IntermediateOutputPath isn't defined that early; from .props it expands to empty and litters a .sarif into every project directory (I hit exactly that). Guarded by Condition="'$(ErrorLog)' == ''" so SonarScanner's own value wins when it runs.
• .editorconfig — dotnet_diagnostic.IDE0017.severity = warning, promoted to an error by TreatWarningsAsErrors.
• CameraControllerSeamTests.cs — the two real violations this surfaced, rewritten to the object-initializer form already used elsewhere in the file.

Verification

• dotnet build RustPlusApi.sln --no-incremental → exit 0. The only IDE0017 hits solution-wide were those two; no flood of newly-unmasked analyzers.
• Probe violation reintroduced → plain dotnet build fails with error IDE0017, exit 1.
• dotnet test RustPlusApi.sln → 1239 passed, 18 projects, both TFM hosts.
• jb cleanupcode on the edited file is idempotent, so the pre-push hook won't reject it.
• .sarif files land in obj/, already covered by .gitignore:31.

The pre-existing MSB3073 warning (git config core.hooksPath exiting 255) is a local sandbox git-lock artifact, present before these changes and unrelated.

Follow-ups (not in this PR)

• This unblocks the entire IDE* family, so any other roslyn:IDE* smell Sonar reports can now be gated by adding a severity line next to IDE0017 — no further plumbing.
• CLAUDE.md's "Commands" section describes the strict build as "TreatWarningsAsErrors + latest-all analyzers"; that's now slightly incomplete. The mechanism is documented in the Directory.Build.targets comment for the moment.

🤖 Generated with Claude Code

[Copilot]

🟢 Approval recommended

The changes are small, consistent with the repo’s strict build configuration, and the updated test code and build-time SARIF logging approach are coherent and self-contained.

Pull request overview

This PR closes the gap between Sonar-reported roslyn:IDE* code-style diagnostics (notably IDE0017) and what a clean dotnet build currently enforces, by ensuring the compiler actually computes and reports IDE analyzer diagnostics during command-line builds.

Changes:

• Add a repo-wide Directory.Build.targets that sets ErrorLog to a per-project SARIF file under obj/ (only when $(ErrorLog) is not already set), which causes Roslyn to include IDE analyzer diagnostics in the build.
• Configure IDE0017 as a warning in .editorconfig, relying on TreatWarningsAsErrors=true to gate it as a build error.
• Update CameraControllerSeamTests to use object initializers, resolving IDE0017 hits surfaced by the new build behavior.

File summaries

File	Description
tests/RustPlusApi.Camera.UnitTests/CameraControllerSeamTests.cs	Refactors two test constructions to object initializers to satisfy IDE0017.
Directory.Build.targets	Enables SARIF error logging in builds (when not already set) so IDE analyzers are not silently skipped.
.editorconfig	Sets IDE0017 severity to warning so it becomes a build-breaking warning under TreatWarningsAsErrors.

Review details

• Files reviewed: 3/3 changed files
• Comments generated: 0
• Review effort level: Lite

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