[http-client-csharp] Add ArgumentExpression for ref/out argument support by JonathanCrd · Pull Request #10845 · microsoft/typespec

JonathanCrd · 2026-05-30T00:05:07Z

Summary

Add a new ArgumentExpression class that wraps a ValueExpression with optional ref/out modifiers, cleanly separating argument-passing semantics from variable reference semantics.

Closes #8399

Changes

New ArgumentExpression class — wraps a ValueExpression with IsRef/IsOut, Write() visitor support via Accept(), and Update()
Simplified VariableExpression — removed IsRef/IsOut properties; now a pure variable reference (with backward-compatible shims)
Simplified ParameterProvider — removed dual _asVariable/_asArgument caching pattern; added GetArgumentExpression()
Updated AsArgument() — now returns ValueExpression (an ArgumentExpression) instead of VariableExpression
Added VisitArgumentExpression to LibraryVisitor
Updated call sites: ClientProvider, MrwSerializationTypeDefinition, JsonPatchSnippets, ScmModelProvider
Added tests: ArgumentExpressionTests (8 tests covering ref, out, update, and ParameterProvider integration) and ExpressionVisitorTests

pkg-pr-new · 2026-05-30T00:07:42Z

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commit: 68dfa53

github-actions · 2026-05-30T00:09:56Z

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azure-sdk-automation · 2026-06-02T22:20:08Z

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… support Add a new ArgumentExpression class that wraps a ValueExpression with optional ref/out modifiers, separating argument-passing semantics from variable reference semantics. Changes: - Create ArgumentExpression to handle ref/out keywords in argument context - Remove IsRef/IsOut from VariableExpression (now a pure variable reference) - Simplify ParameterProvider by removing the dual _asVariable/_asArgument pattern - Update AsArgument() to return ArgumentExpression wrapping the variable - Update call sites: ClientProvider, MrwSerializationTypeDefinition, JsonPatchSnippets, ScmModelProvider - Add VisitArgumentExpression to LibraryVisitor - Add comprehensive ArgumentExpressionTests Closes microsoft#8399 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Restore the legacy VariableExpression ref/out constructor and add regression tests for ArgumentExpression visitor handling. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

The pnpm setup:min step in RegenCheck CI fails on Linux runners where NodeTool resolves Node.js 24.x to v24.14.1, which does not satisfy the which@7.0.0 engine requirement (^24.15.0). Temporarily relax engine-strict during workspace setup to unblock CI while the runner images are updated. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Mark VariableExpression.IsRef/IsOut and legacy constructor as [Obsolete] to guide callers toward ArgumentExpression - Replace ByRef() with ArgumentExpression in MrwSerializationTypeDefinition for method argument semantics (ref return in ScmModelProvider is correct) - Fix dead ternary in ExpressionVisitorTests assertion - Keep redundant 2-param VariableExpression(type, name) constructor since it is part of the public API surface and used widely Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

@typespec/http-client-csharp is not in the chronus workspace. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

JoshLove-msft · 2026-06-20T02:31:12Z

+    public record VariableExpression(CSharpType Type, CodeWriterDeclaration Declaration) : ValueExpression
    {
+        [Obsolete("Use ArgumentExpression for ref/out argument semantics.")]
+        public bool IsRef { get; private set; }


Should we swap out all the usages rather than marking obsolete?

Addressed in e2b push (68dfa53) — removed the obsolete IsRef/IsOut properties and the legacy (type, name, isRef, isOut) constructor entirely, plus the isRef/isOut parameters on Update. VariableExpression is now a pure variable reference and all ref/out usages flow through ArgumentExpression.

JoshLove-msft · 2026-06-20T02:32:26Z

                }

-                var cachedClientFieldVar = new VariableExpression(subClient.Type, subClient._clientCachingField.Declaration, IsRef: true);
+                var cachedClientFieldVar = new ArgumentExpression(new VariableExpression(subClient.Type, subClient._clientCachingField.Declaration), IsRef: true);


I think we should have some sort of AsArgument snippet to make the code more readable and intuitive.

Done — added a ValueExpression.AsArgument(isRef, isOut) snippet and updated this call site to new VariableExpression(...).AsArgument(isRef: true). Also applied it in JsonPatchSnippets.

JoshLove-msft · 2026-06-20T02:34:28Z

            if (hookMethod == null)
            {
                // Fall back: no method found, use previous behavior (first known arg, ref variable, no options)
-                return [knownArguments[0].Argument, ByRef(refVariable)];


Should ByRef be updated to return an ArgumentExpression?

Yes — ByRef now returns new ArgumentExpression(expression, IsRef: true) and the call sites here use ByRef(refVariable). (Also added an ArgumentExpression case to UpdateProtocolMethodInvocation so ref/out args are still unwrapped, since they're no longer KeywordExpression.)

- Remove obsolete IsRef/IsOut shims and legacy constructor from VariableExpression - Update ByRef snippet to return an ArgumentExpression - Add ValueExpression.AsArgument snippet for readable ref/out argument wrapping - Use ByRef/AsArgument at call sites (ClientProvider, MrwSerializationTypeDefinition, JsonPatchSnippets) Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

microsoft-github-policy-service Bot added the emitter:client:csharp Issue for the C# client emitter: @typespec/http-client-csharp label May 30, 2026

JonathanCrd force-pushed the joncarde/argument-expression-8399 branch from c34da4a to 30e4276 Compare June 2, 2026 22:09

microsoft-github-policy-service Bot added the eng label Jun 2, 2026

JonathanCrd force-pushed the joncarde/argument-expression-8399 branch from 30e4276 to 56c20d4 Compare June 2, 2026 23:14

JonathanCrd self-assigned this Jun 16, 2026

JonathanCrd and others added 5 commits June 16, 2026 16:08

fix(generator): preserve VariableExpression compatibility

2434bd6

Restore the legacy VariableExpression ref/out constructor and add regression tests for ArgumentExpression visitor handling. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

chore: add changelog entry for ArgumentExpression feature

29c8aa5

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

JonathanCrd force-pushed the joncarde/argument-expression-8399 branch from e7255fb to 29c8aa5 Compare June 16, 2026 23:32

JonathanCrd and others added 2 commits June 16, 2026 16:57

chore: remove invalid changelog entry

a0e2ddf

@typespec/http-client-csharp is not in the chronus workspace. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

chore: remove unrelated engine-strict workaround from Test-Packages.ps1

e92c56c

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

JonathanCrd changed the title ~~[WIP] feat(http-client-csharp): add ArgumentExpression for ref/out argument support~~ [http-client-csharp] Add ArgumentExpression for ref/out argument support Jun 17, 2026

JonathanCrd marked this pull request as ready for review June 17, 2026 07:04

JonathanCrd requested review from JoshLove-msft, ShivangiReja, jorgerangel-msft, joseharriaga, jsquire and m-nash as code owners June 17, 2026 07:04

JoshLove-msft reviewed Jun 20, 2026

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[http-client-csharp] Add ArgumentExpression for ref/out argument support#10845

[http-client-csharp] Add ArgumentExpression for ref/out argument support#10845
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