Consolidate OS detection to OsConstants by paulmedynski · Pull Request #4255 · dotnet/SqlClient

paulmedynski · 2026-05-01T15:36:33Z

Summary

This PR consolidates all OS detection logic into a single internal OsConstants class, giving the codebase one consistent, terse way to ask "what OS are we on?" (OsConstants.IsWindows, IsLinux, IsMacOS, IsFreeBSD) and a single seam for any future OS-specific handling.

Just as importantly, the flags are implemented so they remain statically analyzable, which is what lets the JIT and the IL trimmer eliminate OS-specific branches (and their dependencies, including Windows-only native SNI) in downstream apps.

OsConstants design

Each flag is an expression-bodied property that returns an OS check directly — it is not cached in a static field or computed in a static constructor.
On .NET (net8.0/net9.0): uses OperatingSystem.IsWindows()/IsLinux()/IsMacOS()/IsFreeBSD(), which the JIT recognizes as intrinsics and constant-folds, and which the IL trimmer also understands.
On .NET Framework (net462): falls back to RuntimeInformation.IsOSPlatform(...), since the OperatingSystem platform-check helpers don't exist there. IsFreeBSD is #if NET-only.

Why not static readonly fields / a static constructor?

The original approach cached the results in static readonly fields populated by a static constructor. That defeats trimming: the IL trimmer can't analyze a static constructor, so it can't prove a flag is constant-false on a given OS and conservatively keeps the OS-specific code (including the native SNI DLL graph) in apps published for other platforms. Returning the intrinsic check directly preserves both the JIT constant-folding and trimmer dead-code elimination.

Usage requirement (documented in the class)

For trimming to actually drop a branch, each guard must be used inline in the same method as the OS-specific code it gates. The trimmer's constant folding is shallow, so a guard hidden behind a throw-helper traps the constant inside that helper and leaves the protected code reachable. The class XML docs include do/don't examples.

Call-site replacements (10 files)

Consolidated assorted ad-hoc OS checks onto OsConstants:

TdsParserStaticMethods.cs, TdsParser.cs, LocalAppContextSwitches.cs — replaced RuntimeInformation.IsOSPlatform() / OperatingSystem.IsWindows().
UserAgent.cs — replaced RuntimeInformation.IsOSPlatform() and added FreeBSD detection.
AdapterUtil.cs — removed the ADP.IsWindows member; OsConstants is now the single source.
SqlFileStream.cs, SqlColumnEncryptionCngProvider.cs, SqlColumnEncryptionCspProvider.cs — replaced ADP.IsWindows.
SqlColumnEncryptionCertificateStoreProvider.cs, SqlUtil.cs — replaced Environment.OSVersion-based checks.

All existing guards were verified to be inline with the code they protect (no throw-helper indirection), so they remain trimmer-foldable.

Benefits

Single, consistent point of control for OS detection.
Preserves JIT constant-folding on .NET via OperatingSystem.Is*() intrinsics.
Preserves IL trimming so apps published for a specific RID can drop other-OS code paths (incl. Windows-only native dependencies) — supporting the goal of a single managed assembly per TFM.
Correct on .NET-Framework-on-non-Windows (no longer hard-codes IsWindows = true).

Notes

The UseManagedNetworking IL trimming substitution (ILLink.Substitutions.xml) is independent of this change — it body-stubs the getter based on the UseManagedNetworkingOnWindows feature switch and never reads OsConstants.

Copilot

Pull request overview

This PR centralizes runtime OS detection behind a new internal OsConstants type, replacing scattered RuntimeInformation / Environment.OSVersion / OperatingSystem.IsWindows() checks to keep platform branching consistent across the driver.

Changes:

Added OsConstants with cached OS flags (IsWindows, IsLinux, IsMacOS, IsFreeBSD (NET), IsUnix).
Replaced OS checks across SqlClient core, encryption providers, registry helpers, and SqlFileStream.
Simplified some call sites by removing ADP.IsWindows and other ad-hoc platform detection.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/OsConstants.cs	Introduces centralized OS detection flags used by the rest of the PR.
src/Microsoft.Data.SqlClient/src/Microsoft/Data/Common/AdapterUtil.cs	Removes `ADP.IsWindows` and uses `OsConstants` for registry availability checks.
src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/TdsParserStaticMethods.cs	Switches Windows-only registry/NIC logic to `OsConstants.IsWindows`.
src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/TdsParser.cs	Replaces `OperatingSystem.IsWindows()` with `OsConstants.IsWindows` in SSL handshake path.
src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/UserAgent.cs	Uses `OsConstants` for OS name selection, including FreeBSD under `#if NET`.
src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/LocalAppContextSwitches.cs	Uses `OsConstants` in managed/native networking switch logic.
src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/SqlUtil.cs	Replaces `Environment.OSVersion.Platform` checks with `OsConstants.IsWindows` for error shaping.
src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/SqlColumnEncryptionCertificateStoreProvider.cs	Uses `OsConstants.IsWindows` to gate LocalMachine vs CurrentUser behavior.
src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/SqlColumnEncryptionCngProvider.cs	Uses `OsConstants` for platform guards around Windows-only CNG operations.
src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/SqlColumnEncryptionCspProvider.cs	Uses `OsConstants` for platform guards around Windows-only CSP operations.
src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlTypes/SqlFileStream.cs	Replaces `ADP.IsWindows` with `OsConstants.IsUnix` for platform not supported gating.

Comments suppressed due to low confidence (1)

src/Microsoft.Data.SqlClient/src/Microsoft/Data/Common/AdapterUtil.cs:442

This check uses OsConstants.IsUnix, but the comment says "No registry in non-Windows environments". If IsUnix remains limited to Linux/macOS/FreeBSD, this will attempt registry access on other non-Windows platforms. Prefer if (!OsConstants.IsWindows) here (or ensure IsUnix is equivalent to !IsWindows).

            #if NET
            if (OsConstants.IsUnix)
            {
                // No registry in non-Windows environments
                return null;
            }

paulmedynski · 2026-05-01T15:39:44Z

-        /// rather than in a throw helper.
-        /// </remarks>
-        #if NETFRAMEWORK
-        public const bool IsWindows = true;


This isn't true - TFM != OS. We may happen to only support .NET Framework when running on Windows, but we shouldn't be conflating the two. We currently have _WINDOWS and _UNIX to conditionally compile some specific code/blocks for OSes.

codecov · 2026-05-01T18:54:39Z

Codecov Report

❌ Patch coverage is 88.46154% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 63.78%. Comparing base (44e1b72) to head (6d509a8).
⚠️ Report is 14 commits behind head on main.

Files with missing lines	Patch %	Lines
...Client/src/Microsoft/Data/SqlClient/OsConstants.cs	75.00%	1 Missing ⚠️
...qlClient/src/Microsoft/Data/SqlClient/UserAgent.cs	75.00%	1 Missing ⚠️
...lient/src/Microsoft/Data/SqlTypes/SqlFileStream.cs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4255      +/-   ##
==========================================
- Coverage   65.32%   63.78%   -1.55%     
==========================================
  Files         285      282       -3     
  Lines       43373    66642   +23269     
==========================================
+ Hits        28335    42505   +14170     
- Misses      15038    24137    +9099

Flag	Coverage Δ
CI-SqlClient	`?`
PR-SqlClient-Project	`63.78% <88.46%> (?)`

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- Create new OsConstants class with IsWindows, IsLinux, IsMacOS, IsFreeBSD, and IsUnix fields - Add comprehensive XML documentation and explain why static constructor is preferred over [ModuleInitializer] (CA2255 rule) - Replace all RuntimeInformation.IsOSPlatform() calls with OsConstants fields in: - TdsParserStaticMethods.cs - UserAgent.cs - AdapterUtil.cs (now forwards to OsConstants) - Replace Environment.OSVersion.Platform checks with OsConstants in: - SqlColumnEncryptionCertificateStoreProvider.cs (3 instances) - SqlUtil.cs (3 instances) - Replace OperatingSystem static methods with OsConstants in: - LocalAppContextSwitches.cs (uses IsUnix for clearer semantics) - TdsParser.cs - Replace all ADP.IsWindows usage with OsConstants in: - SqlFileStream.cs - SqlColumnEncryptionCngProvider.cs (4 instances) - SqlColumnEncryptionCspProvider.cs (4 instances) - Remove unused AdapterUtil.IsWindows property Benefits: - Single point of control for OS detection - Improved JIT optimization through static readonly cached flags - Clearer semantics with IsUnix flag for Unix-like platforms - Consistent API surface across the codebase

- Remove OsConstants.IsUnix to avoid non-Windows ambiguity - Update Windows-only guards in SqlFileStream, CNG, CSP, and switch logic - Keep explicit OS flags (Windows/Linux/macOS/FreeBSD)

Copilot

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 1 comment.

@edwardneal

Replace the static readonly fields and static constructor in OsConstants with properties that directly return RuntimeInformation.IsOSPlatform(...). The IL trimmer cannot analyze a static constructor, so the cached-field design left OS-specific code (including Windows-only native dependencies) in apps published for other platforms. Returning the intrinsic directly lets the trimmer fold each guard to a constant and drop the dead branch. Also document why the type exists (brevity and encapsulation), the inline-guard requirement for trimming, and reconcile the stale remark about JIT branch elision. Addresses PR #4255 review feedback from @edwardneal.

On modern .NET, OperatingSystem.IsWindows()/IsLinux()/IsMacOS()/IsFreeBSD() are JIT intrinsics that get constant-folded (and are recognized by the IL trimmer), so switch the OsConstants properties to them under #if NET. .NET Framework keeps RuntimeInformation.IsOSPlatform(...) since the OperatingSystem platform-check helpers do not exist there. This addresses the automated reviewer feedback that RuntimeInformation .IsOSPlatform(...) misses the JIT constant-folding optimization on net8/net9, while preserving the trimming correctness from the prior change. Addresses PR #4255 review feedback.

Copilot

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 1 comment.

Copilot AI review requested due to automatic review settings May 1, 2026 15:36

github-project-automation Bot added this to SqlClient Board May 1, 2026

github-project-automation Bot moved this to To triage in SqlClient Board May 1, 2026

Copilot started reviewing on behalf of paulmedynski May 1, 2026 15:37 View session

paulmedynski added this to the 7.1.0-preview2 milestone May 1, 2026

paulmedynski moved this from To triage to In progress in SqlClient Board May 1, 2026

paulmedynski added the Code Health 💊 Issues/PRs that are targeted to source code quality improvements. label May 1, 2026

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Comment thread src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/OsConstants.cs Outdated

paulmedynski modified the milestones: 7.1.0-preview2, 7.1.0-preview3 Jun 26, 2026

paulmedynski added 2 commits June 26, 2026 12:13

Address Copilot OS guard feedback

8f5e2d0

- Remove OsConstants.IsUnix to avoid non-Windows ambiguity - Update Windows-only guards in SqlFileStream, CNG, CSP, and switch logic - Keep explicit OS flags (Windows/Linux/macOS/FreeBSD)

Copilot AI review requested due to automatic review settings June 26, 2026 15:15

paulmedynski force-pushed the dev/paul/os-constants branch from f5035e4 to 8f5e2d0 Compare June 26, 2026 15:15

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Comment thread src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/OsConstants.cs Outdated

paulmedynski added 2 commits June 26, 2026 12:32

Copilot AI review requested due to automatic review settings June 26, 2026 15:54

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Comment thread src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/OsConstants.cs

paulmedynski modified the milestones: 7.1.0-preview3, 7.1.0-preview2 Jun 26, 2026

paulmedynski marked this pull request as ready for review June 26, 2026 17:15

paulmedynski requested a review from a team as a code owner June 26, 2026 17:15

paulmedynski enabled auto-merge (squash) June 26, 2026 17:15

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paulmedynski assigned mdaigle and unassigned cheenamalhotra Jun 29, 2026

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Consolidate OS detection to OsConstants#4255

Consolidate OS detection to OsConstants#4255
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Summary

OsConstants design

Why not static readonly fields / a static constructor?

Usage requirement (documented in the class)

Call-site replacements (10 files)

Benefits

Notes

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Pull request overview

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