[dotnet-code] Extract portable message unwrap helper

[Michelle Clayton (michelle-clayton-work)]

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The original pull request description is below.

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Summary

Extracts the workflow message router's PortableValue unwrapping into a small unexported helper. This keeps Go routing behavior the same while making the route flow more structurally similar to the .NET MessageRouter.RouteMessageAsync conversion step, which should make future .NET-to-Go comparisons easier.

.NET Reference

• dotnet/src/Microsoft.Agents.AI.Workflows/Execution/MessageRouter.cs - unwraps PortableValue messages to the registered runtime type before handler lookup.

Public API and Behavior

No public Go API changed. No intentional behavior change was made.

Tests

• gofmt -w workflow/route.go
• go test ./workflow

Notes

Rejected candidates:

• dotnet/src/Microsoft.Agents.AI.Workflows.Declarative/Interpreter/WorkflowModel.cs - no current Go declarative workflow counterpart was found, so a structural cleanup would be speculative.
• dotnet/tests/Microsoft.Agents.AI.Workflows.Declarative.Mcp.UnitTests/DefaultMcpToolHandlerTests.cs - nearest Go MCP areas are provider/tool-facing and broader than the requested tiny portability cleanup.
• Open approved [dotnet-code] PR found: [dotnet-port-api] Add compaction-backed history provider #1092, covering compaction rather than this workflow router area. Two lower-integrity PR search results were filtered by the environment and were not inspected.

The upstream .NET git fetch was blocked by the environment network boundary, so the .NET reference was sampled/read via the read-only GitHub MCP CLI instead.

Closes #1106

[Copilot]

Copilot review overview

🟡 Changes recommended

Pass PortableValue by pointer or otherwise propagate cache mutations to preserve existing behavior.

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Review effort: Lite
Findings: 1

Open (1)

• Pass PortableValue by reference to preserve cache mutation · New

What changed in this PR

Extracts portable message unwrapping into an unexported workflow router helper.

Changes:

• Replaces inline unwrapping with unwrapPortableMessage.
• Preserves registered and polymorphic routing paths.
• No public API changes.

File	Summary
workflow/​route.go	Extracts portable message unwrapping. Moderate issue: passing PortableValue by value prevents cache updates from propagating.

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[Michelle Clayton (michelle-clayton-work)]

Copilot address PR feedback

[Copilot]

Copilot address PR feedback

Addressed in 46af8bb (with the pointer-cache requirement documented in 34cd37d). Added a regression assertion for the delayed catch-all path; go test ./workflow passes.

[github-actions]

Scope: internal-only

Changed Go contract: None. messageRouter.unwrapPortableMessage is an unexported helper on an unexported type; no exported functions, methods, types, fields, constants, or options were added, removed, or changed. PortableValue.Delayed() already existed prior to this PR and is unchanged in signature.

Upstream evidence reviewed: dotnet/src/Microsoft.Agents.AI.Workflows/Execution/MessageRouter.cs — the PR description cites this as the structural model for the extracted conversion step (unwrap PortableValue/registered runtime type before handler dispatch). No equivalent Go-specific "delayed deserialization cache" concept exists in .NET (which does not defer JSON decoding the same way), so no direct upstream symbol maps to the cache-preservation bugfix itself; this is a Go-implementation-specific correctness detail.

Result: aligned (out of scope for parity concerns)

Summary: This PR (1) extracts the existing portable-value unwrap logic in routeMessage into a small helper unwrapPortableMessage, mirroring the .NET MessageRouter conversion step structurally, and (2) fixes a bug where the unwrap path previously returned a stale copy of pvalue instead of the copy with its lazily-populated cache field, so catch-all handlers now receive a PortableValue that reports Delayed() == false once decoded. Both changes are confined to internal/unexported code paths (workflow/route.go) plus a test assertion addition (workflow/route_test.go) verifying the cache fix. No exported Go API surface changed, so public-api-change is not applicable, and no examples were touched. No cross-language parity issue is introduced since the affected mechanism (delayed JSON deserialization caching) is Go-internal plumbing without a corresponding .NET/Python public contract.

Generated by Go API Consistency Review Agent for #1108 · copilot · auto · 34.8 AIC · ⌖ 6.95 AIC · ⊞ 9.2K · ◷