Add obsolete compatibility shims for moved Microsoft.Extensions.Logging internal types

[Copilot]

Fixes #126995

Restores source and binary compatibility for types that were previously in *.Internal namespaces. Only [Obsolete(error: true)] + [EditorBrowsable(Never)] shims are added — no new non-obsolete public API surface.

Description

New obsolete shims (all in Microsoft.Extensions.Logging.Abstractions assembly):

Shim	Redirects to
Microsoft.Extensions.Logging.Abstractions.Internal.NullScope	n/a -- trivial copy of Microsoft.Extensions.Logging.NullScope
Microsoft.Extensions.Logging.Abstractions.Internal.TypeNameHelper	Microsoft.Extensions.Internal.TypeNameHelper
Microsoft.Extensions.Logging.Internal.FormattedLogValues	internal FormattedLogValues in same assembly
Microsoft.Extensions.Logging.Internal.LogValuesFormatter	internal LogValuesFormatter in same assembly

File naming: shim files follow the *Obsolete.cs convention (NullScopeObsolete.cs, TypeNameHelperObsolete.cs, etc.).

This work is a continuation of #87480, bringing back some additional types scoped out of that first wave. We follow the same pattern as those.

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[Copilot]

Pull request overview

This PR restores source/binary compatibility for older consumers by reintroducing several previously-available *.Internal-namespace types in Microsoft.Extensions.Logging.Abstractions as [Obsolete(error: true)] + [EditorBrowsable(Never)] shims.

Changes:

• Added obsolete shim types for NullScope and TypeNameHelper under Microsoft.Extensions.Logging.Abstractions.Internal.
• Added obsolete shim wrapper types for FormattedLogValues and LogValuesFormatter under Microsoft.Extensions.Logging.Internal.
• Updated the ref project to include System.Collections and extended the reference surface accordingly.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
src/libraries/Microsoft.Extensions.Logging.Abstractions/src/TypeNameHelperObsolete.cs	Adds obsolete TypeNameHelper shim forwarding to Microsoft.Extensions.Internal.TypeNameHelper.
src/libraries/Microsoft.Extensions.Logging.Abstractions/src/NullScopeObsolete.cs	Adds obsolete NullScope shim type in *.Abstractions.Internal.
src/libraries/Microsoft.Extensions.Logging.Abstractions/src/LogValuesFormatterObsolete.cs	Adds obsolete wrapper for Microsoft.Extensions.Logging.LogValuesFormatter.
src/libraries/Microsoft.Extensions.Logging.Abstractions/src/FormattedLogValuesObsolete.cs	Adds obsolete wrapper for Microsoft.Extensions.Logging.FormattedLogValues.
src/libraries/Microsoft.Extensions.Logging.Abstractions/ref/Microsoft.Extensions.Logging.Abstractions.csproj	Adds System.Collections ref dependency for the updated reference surface.
src/libraries/Microsoft.Extensions.Logging.Abstractions/ref/Microsoft.Extensions.Logging.Abstractions.cs	Updates reference API surface to include the new obsolete types.

[Copilot]

Pull request overview

This PR adds [Obsolete(error: true)] + [EditorBrowsable(Never)] compatibility shims in Microsoft.Extensions.Logging.Abstractions to restore source/binary compatibility for previously-available *.Internal types.

Changes:

• Added obsolete shim types for NullScope, TypeNameHelper, FormattedLogValues, and LogValuesFormatter.
• Updated the reference assembly surface (ref/*.cs) to include the shims.
• Updated the ref-project to reference System.Collections (needed by the new ref surface).

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
src/libraries/Microsoft.Extensions.Logging.Abstractions/src/TypeNameHelperObsolete.cs	Adds obsolete shim forwarding to Microsoft.Extensions.Internal.TypeNameHelper.
src/libraries/Microsoft.Extensions.Logging.Abstractions/src/NullScopeObsolete.cs	Adds obsolete shim for prior Abstractions.Internal.NullScope.
src/libraries/Microsoft.Extensions.Logging.Abstractions/src/FormattedLogValuesObsolete.cs	Adds obsolete shim wrapping internal Microsoft.Extensions.Logging.FormattedLogValues.
src/libraries/Microsoft.Extensions.Logging.Abstractions/src/LogValuesFormatterObsolete.cs	Adds obsolete shim wrapping internal Microsoft.Extensions.Logging.LogValuesFormatter.
src/libraries/Microsoft.Extensions.Logging.Abstractions/ref/Microsoft.Extensions.Logging.Abstractions.csproj	Adds System.Collections ref dependency for the new reference API types.
src/libraries/Microsoft.Extensions.Logging.Abstractions/ref/Microsoft.Extensions.Logging.Abstractions.cs	Adds the shim types to the reference surface.

[tarekgh]

I left a few minor comments, LGTM otherwise.

It will be good if we can add some tests to cover the new exposed APIs if possible, for the sake of the code coverage.

[Copilot]

Pull request overview

Adds [Obsolete(error: true)] + [EditorBrowsable(Never)] compatibility shims in Microsoft.Extensions.Logging.Abstractions to restore binary/source compatibility for several historically-public “*.Internal” logging types that were moved, addressing TypeLoadException scenarios reported in #126995.

Changes:

• Introduces obsolete shim types for NullScope, TypeNameHelper, FormattedLogValues, and LogValuesFormatter in their legacy namespaces.
• Updates the reference assembly (ref/) to include the restored public (obsolete) API surface.
• Adds a missing System.Collections ref dependency needed by the updated reference assembly surface.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/libraries/Microsoft.Extensions.Logging.Abstractions/src/TypeNameHelperObsolete.cs	Adds obsolete Microsoft.Extensions.Logging.Abstractions.Internal.TypeNameHelper shim forwarding to Microsoft.Extensions.Internal.TypeNameHelper.
src/libraries/Microsoft.Extensions.Logging.Abstractions/src/NullScopeObsolete.cs	Adds obsolete Microsoft.Extensions.Logging.Abstractions.Internal.NullScope shim for legacy type availability.
src/libraries/Microsoft.Extensions.Logging.Abstractions/src/LogValuesFormatterObsolete.cs	Adds obsolete Microsoft.Extensions.Logging.Internal.LogValuesFormatter shim that wraps the internal formatter implementation.
src/libraries/Microsoft.Extensions.Logging.Abstractions/src/FormattedLogValuesObsolete.cs	Adds obsolete Microsoft.Extensions.Logging.Internal.FormattedLogValues shim that wraps the internal formatting struct.
src/libraries/Microsoft.Extensions.Logging.Abstractions/ref/Microsoft.Extensions.Logging.Abstractions.csproj	Adds System.Collections ref ProjectReference required by newly exposed List<>/collection types in the ref surface.
src/libraries/Microsoft.Extensions.Logging.Abstractions/ref/Microsoft.Extensions.Logging.Abstractions.cs	Adds the obsolete shim types to the reference assembly surface to restore compile-time/type identity compatibility.

[github-actions]

🤖 Copilot Code Review — PR #127194

Note

This review was generated by Copilot using Claude Opus 4.6 (primary) with GPT-5.3-Codex and Extensions-reviewer cross-validation. This review covers the code at commit 058c150, after the "Apply suggestions from code review" commit that addressed findings from the prior automated review.

Holistic Assessment

Motivation: Justified. Issue #126995 reports a real TypeLoadException regression — old binaries compiled against Microsoft.Extensions.Logging.Abstractions 2.1 crash when run on .NET 11 Preview 4 because four *.Internal namespace types were removed. This is a blocking compat bug.

Approach: Correct. The PR follows the established [Obsolete(error: true)] + [EditorBrowsable(Never)] shim pattern from issue #87480 / PR #85846. The *Obsolete.cs file naming, delegation to internal types, and ref assembly additions are all consistent with prior art.

Summary: ⚠️ Needs Human Review. The code is correct and all ref/src mismatches from the prior review have been resolved. Two items require human judgment: (1) whether the TypeNameHelper shim needs additional method overloads for full binary compat, and (2) whether the existing api-approved label on #87480 covers this second wave of types. Both are questions the PR author (@ericstj) is best positioned to answer, as he indicated he's running APICompat locally.

---

Detailed Findings

⚠️ TypeNameHelper — Verify overload completeness with APICompat

The shim exposes only GetTypeDisplayName(Type type), while the internal TypeNameHelper has a 5-parameter overload (type, fullName, includeGenericParameterNames, includeGenericParameters, nestedTypeDelimiter). GPT-5.3-Codex independently flagged this as a potential binary compat gap — if old assemblies called the overload with additional parameters, they'd get MissingMethodException.

This is likely already covered by @ericstj's local APICompat validation ("I'm doing a pass over these locally with APICompat to make sure we match what was shipped before and it's minimal"). Just confirming: was the 5-parameter overload never public in the old Abstractions assembly? If it was, it should be forwarded.

📍 src/libraries/Microsoft.Extensions.Logging.Abstractions/src/TypeNameHelperObsolete.cs:17-18

---

⚠️ API Approval — Human confirmation needed

This PR adds new public API surface in the ref/ assembly. The linked issue #126995 does not have the api-approved label. Issue #87480 does have api-approved, but that approval was for a first wave of types — NullScope was explicitly scoped out from that wave.

Mitigating factors: All four types are [Obsolete(error: true)] shims restoring previously-shipped surface — not genuinely new API. The runtime team's precedent for such compat shims does not typically require formal API review. @ericstj as a runtime team member is actively reviewing and shaping this PR. A brief confirmation that no separate approval is needed would close this out.

---

💡 FormattedLogValues._inner correctly not readonly — No action needed

The latest commit (058c150) removed readonly from the _inner field. This is correct: the inner FormattedLogValues is a struct whose ToString() mutates _cachedToString via ??=. A readonly field would cause defensive copies, making the cache ineffective. Good catch by whoever suggested this fix.

📍 src/libraries/Microsoft.Extensions.Logging.Abstractions/src/FormattedLogValuesObsolete.cs:19

---

Verified Correct

✅ All prior ref/src mismatches resolved

The prior review identified 3 ref/src metadata mismatches (TypeNameHelper static+signature, FormattedLogValues sealed, LogValuesFormatter sealed). All have been fixed — the ref and src now agree on all type modifiers and method signatures. Verified by reading both files at HEAD.

✅ FormattedLogValues correctly uses class (not struct)

The Extensions-reviewer initially raised a concern about struct→class mismatch, but @ericstj confirmed that FormattedLogValues was a class in 2.1 (changed to struct afterward). Since compat targets 2.1, class is correct.

✅ Delegation patterns are correct and safe

• FormattedLogValuesObsolete.cs: Stores internal struct in non-readonly field, delegates all IReadOnlyList<> members. Correct.
• LogValuesFormatterObsolete.cs: readonly field for internal class, delegates all 5 public members with matching signatures. Correct.
• TypeNameHelperObsolete.cs: Static method delegates to internal static method. Correct.
• NullScopeObsolete.cs: Standalone singleton IDisposable — simplest correct implementation. Correct.

✅ Build dependencies correct

System.Collections ref project reference added because List<string> (used by LogValuesFormatter.ValueNames) lives in System.Collections.dll. The src csproj already had this. No new package dependencies introduced.

✅ Naming convention and obsolete messages consistent

*Obsolete.cs naming matches established convention. Obsolete messages are appropriate — FormattedLogValues/LogValuesFormatter recommend Microsoft.Extensions.Diagnostics.Testing (the modern replacement for test code that inspected log messages), while NullScope/TypeNameHelper use the generic "retained only for compatibility" form.

✅ No type forward conflicts

Verified that the Microsoft.Extensions.Logging assembly does not have type forwards for these types (correctly removed in commit c449159). No conflicts between assemblies.

✅ New files automatically included in build

The src csproj uses <EnableDefaultItems>true</EnableDefaultItems>, so all new *.cs files are automatically picked up. No manual csproj edits needed.

---

Models contributing: Claude Opus 4.6 (primary), GPT-5.3-Codex (cross-validation), Extensions-reviewer (domain-specific).

Generated by Code Review for issue #127194 · ◷

[ericstj]

TypeNameHelper — Verify overload completeness with APICompat

Yes - I specifically removed overloads that weren't present when the type was made internal.

API Approval — Human confirmation needed

Discussed this with @bartonjs and he's good with it.

[ericstj]

/ba-g All test failures are known. The remaining failures are all build timeouts when waiting for helix. These cannot be known issued since they are indistinguishable from build hangs.