Remove duplicated #if NETCOREAPP / #else primitives in BaseSerializer

[Evangelink]

Summary

Fixes #9765.

BaseSerializer.cs previously implemented every read/write primitive twice — once under #if NETCOREAPP (Span<byte> / ArrayPool<byte> / ReadExactly) and once under #else (heap byte[] + stream.Read). The two branches were structurally identical, so adding or fixing a primitive meant editing both.

This collapses the 12 duplicated primitives into a single byte[]-based implementation. The only remaining conditional is a small private ReadExactly helper:

• On NETCOREAPP it delegates to the framework Stream.ReadExactly.
• Otherwise it loops until the requested byte count is read, throwing EndOfStreamException on premature EOF.

Why byte[] instead of Span everywhere

Microsoft.Testing.Platform intentionally does not reference System.Memory (dropped in #4652), and this file is shared as source into several other projects. Span/ArrayPool are therefore unavailable on the netstandard2.0 target, so the unified path stays byte[]-based.

Bug fix included

The old #else branch used single stream.Read(...) calls that ignored short reads, which could silently return fewer bytes than requested and corrupt data on the .NET Framework / netstandard2.0 path. Routing all reads through ReadExactly fixes this.

Tests

Added BaseSerializerPartialReadTests, which deserialize through a stream that returns one byte per Read (forcing every length prefix / field id / string payload through the ReadExactly loop) and through a truncated stream (asserting EndOfStreamException). These run on net8.0/net9.0 (framework Stream.ReadExactly path) and net462 (the hand-written loop).

InternalAPI baseline changes (to unblock CI — not part of the refactor)

⚠️ These InternalAPI.Unshipped.txt edits are not part of the BaseSerializer refactor. They declare internal symbols that recently landed on main (via #9752 InternalAPI tracking + #9774 DotnetTest serializer dedup) but were left undeclared, so RS0051 currently fails on main and is inherited by every PR. They are included here only to keep this PR's CI green:

• BaseSerializer.ReadFields / WriteListPayload — declared in Platform, Extensions.HangDump, Extensions.MSBuild, Extensions.Retry, Extensions.TrxReport (each compiles BaseSerializer.cs as shared source).
• PlatformServicesConfigurationAdapter — declared in MSTest.TestAdapter. This one is unrelated to this change and was pulled in via the merge with main; happy to split it (and the other baseline updates) into a dedicated PR if preferred.

Validation

• Full solution build passes with 0 code errors across net8.0, net9.0, and netstandard2.0 (all previously-failing RS0051 errors resolved).
• No behavioral public/protected member changes to BaseSerializer (bodies only); the API-baseline files above are updated purely to declare pre-existing-on-main symbols.

[Copilot]

Pull request overview

Refactors BaseSerializer in Microsoft.Testing.Platform’s IPC serializers to remove duplicated #if NETCOREAPP / #else primitive read/write implementations, consolidating onto a single byte[]-based path and centralizing exact-read behavior to avoid short-read corruption on non-NETCOREAPP targets.

Changes:

• Removed duplicated NETCOREAPP vs non-NETCOREAPP implementations for serializer primitives, keeping one byte[] implementation.
• Introduced a private ReadExactly helper that uses Stream.ReadExactly on NETCOREAPP and a looped read on other TFMs.
• Fixed historical short-read behavior by routing primitive reads through ReadExactly.

Show a summary per file

File	Description
src/Platform/Microsoft.Testing.Platform/IPC/Serializers/BaseSerializer.cs	Collapses duplicated primitive serialization logic and centralizes exact-read behavior to avoid short-read corruption.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 1
• Review effort level: Low

[github-actions]

Note

🤖 Automated review by GitHub Copilot. Generated by the Expert Code Review workflow. To request a follow-up action, reply by tagging @copilot directly.

✅ 22/22 dimensions clean — no findings.

Notes on the review:

• Algorithmic Correctness: ReadExactly loop is correct — properly handles count = 0, short reads, and EOF.
• IPC Wire Compatibility: Wire format unchanged — same length-prefix encoding for strings, same byte ordering for primitives.
• Cross-TFM: Stream.ReadExactly(byte[], int, int) correctly guarded behind #if NETCOREAPP (available .NET 7+); fallback loop uses standard Stream.Read.
• Performance: The removal of stackalloc/ArrayPool on NETCOREAPP in favor of byte[] is a deliberate trade-off for maintainability (no System.Memory reference, shared source). For fixed-size primitives (4–8 bytes) the GC cost is negligible; for string buffers this is bounded by IPC message size.
• Bug fix: Short-read correction on non-NETCOREAPP is sound — EndOfStreamException matches the framework's Stream.ReadExactly behavior.
• Public API: No surface changes — internal abstract class with protected static members only.

[Copilot]

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 1
• Review effort level: Medium

[github-actions]

🔍 Build Failure Analysis

Summary — The build fails with 6 RS0051 (undeclared API) errors because PlatformServicesConfigurationAdapter and its members are not listed in the InternalAPI/InternalAPI.Unshipped.txt file. This is a merge conflict with main, not caused by the PR's changes.

Root cause: Missing internal API declaration after main introduced InternalAPI tracking

A recent commit to main (merged between b81ed0d and 1e92d898) added InternalAPI/InternalAPI.Shipped.txt and InternalAPI/InternalAPI.Unshipped.txt as AdditionalFiles in MSTest.TestAdapter.csproj. These files instruct the Public API Analyzer to track all internal symbols visible through InternalsVisibleTo.

The existing internal sealed class PlatformServicesConfigurationAdapter (and its two members) were not added to either InternalAPI file when tracking was introduced. When this PR is merge-queued against the current main, the analyzer fires RS0051 for the 3 undeclared symbols (× 2 TFMs = 6 errors).

Affected file / errors

Code	TFM	File:Line	Symbol
RS0051	net8.0, net9.0	PlatformServicesConfigurationAdapter.cs:12	PlatformServicesConfigurationAdapter (class)
RS0051	net8.0, net9.0	PlatformServicesConfigurationAdapter.cs:16	.ctor(IConfiguration!)
RS0051	net8.0, net9.0	PlatformServicesConfigurationAdapter.cs:19	this[string!].get

Proposed fix

After rebasing on latest main, add the following 3 lines to src/Adapter/MSTest.TestAdapter/InternalAPI/InternalAPI.Unshipped.txt:

 #nullable enable
+Microsoft.VisualStudio.TestTools.UnitTesting.PlatformServicesConfigurationAdapter
+Microsoft.VisualStudio.TestTools.UnitTesting.PlatformServicesConfigurationAdapter.PlatformServicesConfigurationAdapter(Microsoft.Testing.Platform.Configurations.IConfiguration! configuration) -> void
+Microsoft.VisualStudio.TestTools.UnitTesting.PlatformServicesConfigurationAdapter.this[string! key].get -> string?

Note: This fix targets a file that doesn't exist on the PR branch yet — it was introduced on main after this PR was created. Rebasing the branch onto current main will pull in the InternalAPI tracking infrastructure, at which point the 3 lines above can be appended to InternalAPI.Unshipped.txt.

---

Build overview

Field	Value
Result	FAILED
Duration	241.1 s
MSBuild	18.8.0-preview-26302-115
Solution	NonWindowsTests.slnf
Failed project	MSTest.TestAdapter.csproj (net8.0 + net9.0)
Error count	7 (6 unique RS0051 + 1 "Build failed")
Warnings	0

All MSBuild errors (7)

#	Code	Project	File:Line	Message (truncated)
1	RS0051	MSTest.TestAdapter (net8.0)	PlatformServicesConfigurationAdapter.cs:12	Symbol '...PlatformServicesConfigurationAdapter' is not part of the declared API
2	RS0051	MSTest.TestAdapter (net8.0)	PlatformServicesConfigurationAdapter.cs:16	Symbol '...PlatformServicesConfigurationAdapter(...)' is not part of the declared API
3	RS0051	MSTest.TestAdapter (net8.0)	PlatformServicesConfigurationAdapter.cs:19	Symbol '...this[string! key].get' is not part of the declared API
4	RS0051	MSTest.TestAdapter (net9.0)	PlatformServicesConfigurationAdapter.cs:12	Symbol '...PlatformServicesConfigurationAdapter' is not part of the declared API
5	RS0051	MSTest.TestAdapter (net9.0)	PlatformServicesConfigurationAdapter.cs:16	Symbol '...PlatformServicesConfigurationAdapter(...)' is not part of the declared API
6	RS0051	MSTest.TestAdapter (net9.0)	PlatformServicesConfigurationAdapter.cs:19	Symbol '...this[string! key].get' is not part of the declared API
7	—	Build.proj	—	Build failed.

Why this isn't caused by this PR's changes

This PR modifies only:

• src/Platform/Microsoft.Testing.Platform/IPC/Serializers/BaseSerializer.cs (refactor)
• test/UnitTests/Microsoft.Testing.Platform.UnitTests/IPC/BaseSerializerPartialReadTests.cs (new test)

Neither file is in the MSTest.TestAdapter project. The failure is triggered by new InternalAPI tracking infrastructure on main that this PR hasn't picked up yet.

---

_{🤖 Generated by the Build Failure Analysis workflow using (a href="(dev.azure.com/redacted) · commit 4c23558}

🤖 Automated content by GitHub Copilot. Generated by the Build Failure Analysis workflow. · 224.8 AIC · ⌖ 10.5 AIC · ⊞ 7.3K · [◷]( · ◷)

[github-actions]

🧪 Test quality grade — PR #9776

Grade	Test	Notes
A (90–100)	new BaseSerializerPartialReadTests. Deserialize_ WhenStreamIsTruncated_ ThrowsEndOfStreamException	Clear AAA; exact-type exception assertion plus inner-exception type check are solid — consider asserting InnerException is not null first for a cleaner failure message.
A (90–100)	new BaseSerializerPartialReadTests. Deserialize_ WhenStreamReturnsOneBytePerRead_ RoundTripsCorrectly	Three field-equality assertions confirm the partial-read round-trip reconstructs all serialized values correctly. No issues found.

_{This advisory comment was generated automatically. Grades are heuristic
and informational — they do not block merging. Re-run with
/grade-tests.}

🤖 Automated content by GitHub Copilot. Generated by the Grade Tests on PR (on open / sync) workflow. · 64.9 AIC · ⌖ 7.29 AIC · ⊞ 9.5K · [◷]( · ◷)

[Copilot]

Review details

• Files reviewed: 8/8 changed files
• Comments generated: 1
• Review effort level: Medium