[code-simplifier] Deduplicate accepted-child-await guard in middleware pipeline

> [!TIP]
> **Your pull request is ready to create! 🎉 ✅**
>
> Everything is OK—the changes have been pushed to branch `code-simplifier/dedupe-middleware-pipeline-guard-2026-09-30-d522983bfb920594`. Please review the changes, including any protected files, before creating the pull request.
>
> **[Create the pull request](https://github.com/microsoft/testfx/compare/main...code-simplifier/dedupe-middleware-pipeline-guard-2026-09-30-d522983bfb920594?expand=1&title=%5Bcode-simplifier%5D%20Deduplicate%20accepted-child-await%20guard%20in%20middleware%20pipeline)**
>
> The original pull request description is below.

---

## Code Simplification - 2026-09-30

This PR simplifies code from #11607 (merged in the last 24 hours) to remove duplication while preserving all functionality.

### Files Simplified

- `src/Platform/Microsoft.Testing.Platform/TestHostOrchestrator/TestHostExecutionOrchestratorMiddlewarePipeline.cs` - Extracted a repeated conditional-await block into a single helper method.

### Improvements Made

1. **Reduced Duplication**
   - `InvokeFrameAsync` had the exact same `if (guard.WasInvoked) { await guard.DownstreamTask... }` block (with the same explanatory comment) appearing twice: once in the `catch` after a synchronous middleware-invocation throw, and once in the `catch` after the middleware's returned `Task` faulted.
   - Extracted both occurrences into a new private helper, `AwaitAcceptedChildOnFaultAsync(SingleInvocationNext guard)`, which awaits the accepted downstream child only if the guard recorded an invocation, preserving the original explanatory comment on the new helper.

2. **Enhanced Clarity**
   - Both call sites are now a single line (`await AwaitAcceptedChildOnFaultAsync(guard).ConfigureAwait(false);`), making the "on fault, drain the accepted child before rethrowing" intent explicit and centralized in one place instead of duplicated inline logic.

### Changes Based On

- #11607 - Add composable test-host orchestrator middleware

### Testing

- ✅ `dotnet build test/UnitTests/Microsoft.Testing.Platform.UnitTests` succeeds (Debug, net8.0)
- ✅ All 26 `TestHostExecutionOrchestratorMiddlewarePipelineTests` pass
- ✅ All 41 related orchestrator/host/builder unit tests pass (`TestHostOrchestrator*` + `TestHostBuilderTests`)
- ✅ No functional changes - behavior is identical; only a mechanical extract-method refactor

### Review Focus

Please verify:
- The extracted helper preserves the exact same control flow (await only when `guard.WasInvoked` is true) at both call sites
- No unintended change to exception propagation (the `throw;` after the helper call at each site is unchanged)




---

> [!NOTE]
> GitHub Actions is not permitted to create or approve pull requests in this repository.

> The changes have been pushed to branch `code-simplifier/dedupe-middleware-pipeline-guard-2026-09-30-d522983bfb920594` and are ready to review.

To fix the permissions issue, go to **Settings** → **Actions** → **General** and enable **Allow GitHub Actions to create and approve pull requests**. See also: [gh-aw FAQ](https://github.github.com/gh-aw/reference/faq/#why-is-my-create-pull-request-workflow-failing-with-github-actions-is-not-permitted-to-create-or-approve-pull-requests)

<details><summary>Show patch preview (37 of 74 lines)</summary>

```diff
From 759134bbe6313d6dd412e7f6115f964639fce7d8 Mon Sep 17 00:00:00 2001
X-GH-AW-Base-Commit: 7c99d9073d45aeb0901faf327fcf49d287e41c2e
From: "github-actions[bot]" <github-actions[bot]@users.noreply.github.com>
Date: Wed, 30 Sep 2026 13:35:23 +0000
Subject: [PATCH] Deduplicate accepted-child-await guard in middleware pipeline

Extract the repeated 'await accepted child on middleware fault'
block in TestHostExecutionOrchestratorMiddlewarePipeline.InvokeFrameAsync
into a single AwaitAcceptedChildOnFaultAsync helper, preserving the
same explanatory comment and exact behavior. No functional changes.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 ...ExecutionOrchestratorMiddlewarePipeline.cs | 29 +++++++++----------
 1 file changed, 13 insertions(+), 16 deletions(-)

diff --git a/src/Platform/Microsoft.Testing.Platform/TestHostOrchestrator/TestHostExecutionOrchestratorMiddlewarePipeline.cs b/src/Platform/Microsoft.Testing.Platform/TestHostOrchestrator/TestHostExecutionOrchestratorMiddlewarePipeline.cs
index 715d283..8fb3976 100644
--- a/src/Platform/Microsoft.Testing.Platform/TestHostOrchestrator/TestHostExecutionOrchestratorMiddlewarePipeline.cs
+++ b/src/Platform/Microsoft.Testing.Platform/TestHostOrchestrator/TestHostExecutionOrchestratorMiddlewarePipeline.cs
@@ -88,14 +88,7 @@ private static async Task<int> InvokeFrameAsync(
         catch
         {
             guard.Close();
-            if (guard.WasInvoked)
-            {
-                // A middleware failure cannot replace a downstream failure or cancellation. Await the
-                // accepted child even when this frame faulted, then preserve the middleware failure only
-                // when the child completed successfully.
-                await guard.DownstreamTask.ConfigureAwait(false);
-            }
-
+            await AwaitAcceptedChildOnFaultAsync(guard).ConfigureAwait(false);
             throw;
         }
 
@@ -111,14 +104,7 @@ private static async Task<int> Invoke
... (truncated)
```

</details>

> [!WARNING]
> <details>
> <summary>Firewall blocked 76 domains</summary>
>
> The following domains were blocked by the firewall during workflow execution:
>
> - `0t3vsblobprodcus362.vsblob.vsassets.io`
> - `11vvsblobprodcus336.vsblob.vsassets.io`
> - `169.254.169.254`
> - `1k9vsblobprodcus379.vsblob.vsassets.io`
> - `1s1vsblobprodcus386.vsblob.vsassets.io`
> - `2kmvsblobprodcus39.vsblob.vsassets.io`
> - `37bvsblobprodcus311.vsblob.vsassets.io`
> - `37cvsblobprodcus359.vsblob.vsassets.io`
> - `4m6vsblobprodcus384.vsblob.vsassets.io`
> - `4vyvsblobprodcus361.vsblob.vsassets.io`
> - `4zjvsblobprodcus390.vsblob.vsassets.io`
> - `51yvsblobprodcus36.vsblob.vsassets.io`
> - `5dkvsblobprodcus355.vsblob.vsassets.io`
> - `5rqvsblobprodcus385.vsblob.vsassets.io`
> - `7k6vsblobprodcus337.vsblob.vsassets.io`
> - `7tjvsblobprodcus341.vsblob.vsassets.io`
> - `80zvsblobprodcus35.vsblob.vsassets.io`
> - `8xbvsblobprodcus382.vsblob.vsassets.io`
> - `96bvsblobprodcus338.vsblob.vsassets.io`
> - `ajhvsblobprodcus363.vsblob.vsassets.io`
> - `bcnvsblobprodcus378.vsblob.vsassets.io`
> - `builds.dotnet.microsoft.com`
> - `c78vsblobprodcus322.vsblob.vsassets.io`
> - `cflvsblobprodcus383.vsblob.vsassets.io`
> - `ci.dot.net`
> - `ckzvsblobprodcus347.vsblob.vsassets.io`
> - `d0svsblobprodcus381.vsblob.vsassets.io`
> - `data.nuget.org`
> - `dlbvsblobprodcus316.vsblob.vsassets.io`
> - `e7bvsblobprodcus348.vsblob.vsassets.io`
> - `fdpvsblobprodcus345.vsblob.vsassets.io`
> - `frdvsblobprodcus327.vsblob.vsassets.io`
> - `gbsvsblobprodcus365.vsblob.vsassets.io`
> - `h6tvsblobprodcus346.vsblob.vsassets.io`
> - `i1qvsblobprodcus353.vsblob.vsassets.io`
> - `jd4vsblobprodcus366.vsblob.vsassets.io`
> - `josvsblobprodcus372.vsblob.vsassets.io`
> - `jrqvsblobprodcus343.vsblob.vsassets.io`
> - `k0ivsblobprodcus356.vsblob.vsassets.io`
> - `k4kvsblobprodcus344.vsblob.vsassets.io`
> - `kgfvsblobprodcus314.vsblob.vsassets.io`
> - `kh4vsblobprodcus325.vsblob.vsassets.io`
> - `kijvsblobprodcus387.vsblob.vsassets.io`
> - `kxqvsblobprodcus376.vsblob.vsassets.io`
> - `l49vsblobprodcus358.vsblob.vsassets.io`
> - `ljcvsblobprodcus317.vsblob.vsassets.io`
> - `lylvsblobprodcus31.vsblob.vsassets.io`
> - `m16vsblobprodcus374.vsblob.vsassets.io`
> - `m6xvsblobprodcus342.vsblob.vsassets.io`
> - `mfjvsblobprodcus373.vsblob.vsassets.io`
> - `n3kvsblobprodcus335.vsblob.vsassets.io`
> - `o3svsblobprodcus318.vsblob.vsassets.io`
> - `ofvvsblobprodcus315.vsblob.vsassets.io`
> - `p2ovsblobprodcus312.vsblob.vsassets.io`
> - `pc2vsblobprodcus360.vsblob.vsassets.io`
> - `pdfvsblobprodcus380.vsblob.vsassets.io`
> - `pe3vsblobprodcus354.vsblob.vsassets.io`
> - `pkgs.dev.azure.com`
> - `rcxvsblobprodcus328.vsblob.vsassets.io`
> - `s8mvsblobprodcus38.vsblob.vsassets.io`
> - `se1vsblobprodcus349.vsblob.vsassets.io`
> - `southcentralus0.in.applicationinsights.azure.com`
> - `sqdvsblobprodcus333.vsblob.vsassets.io`
> - `st8vsblobprodcus339.vsblob.vsassets.io`
> - `tphvsblobprodcus375.vsblob.vsassets.io`
> - `u3hvsblobprodcus371.vsblob.vsassets.io`
> - `u6ovsblobprodcus377.vsblob.vsassets.io`
> - `ukkvsblobprodcus352.vsblob.vsassets.io`
> - `uy6vsblobprodcus34.vsblob.vsassets.io`
> - `v53vsblobprodcus320.vsblob.vsassets.io`
> - `vb4vsblobprodcus33.vsblob.vsassets.io`
> - `vwvvsblobprodcus334.vsblob.vsassets.io`
> - `x3yvsblobprodcus370.vsblob.vsassets.io`
> - `xupvsblobprodcus332.vsblob.vsassets.io`
> - `yluvsblobprodcus367.vsblob.vsassets.io`
> - `yttvsblobprodcus357.vsblob.vsassets.io`
>
> To allow these domains, add them to the `network.allowed` list in your workflow frontmatter:
>
> ```yaml
> network:
>   allowed:
>     - defaults
>     - "0t3vsblobprodcus362.vsblob.vsassets.io"
>     - "11vvsblobprodcus336.vsblob.vsassets.io"
>     - "169.254.169.254"
>     - "1k9vsblobprodcus379.vsblob.vsassets.io"
>     - "1s1vsblobprodcus386.vsblob.vsassets.io"
>     - "2kmvsblobprodcus39.vsblob.vsassets.io"
>     - "37bvsblobprodcus311.vsblob.vsassets.io"
>     - "37cvsblobprodcus359.vsblob.vsassets.io"
>     - "4m6vsblobprodcus384.vsblob.vsassets.io"
>     - "4vyvsblobprodcus361.vsblob.vsassets.io"
>     - "4zjvsblobprodcus390.vsblob.vsassets.io"
>     - "51yvsblobprodcus36.vsblob.vsassets.io"
>     - "5dkvsblobprodcus355.vsblob.vsassets.io"
>     - "5rqvsblobprodcus385.vsblob.vsassets.io"
>     - "7k6vsblobprodcus337.vsblob.vsassets.io"
>     - "7tjvsblobprodcus341.vsblob.vsassets.io"
>     - "80zvsblobprodcus35.vsblob.vsassets.io"
>     - "8xbvsblobprodcus382.vsblob.vsassets.io"
>     - "96bvsblobprodcus338.vsblob.vsassets.io"
>     - "ajhvsblobprodcus363.vsblob.vsassets.io"
>     - "bcnvsblobprodcus378.vsblob.vsassets.io"
>     - "builds.dotnet.microsoft.com"
>     - "c78vsblobprodcus322.vsblob.vsassets.io"
>     - "cflvsblobprodcus383.vsblob.vsassets.io"
>     - "ci.dot.net"
>     - "ckzvsblobprodcus347.vsblob.vsassets.io"
>     - "d0svsblobprodcus381.vsblob.vsassets.io"
>     - "data.nuget.org"
>     - "dlbvsblobprodcus316.vsblob.vsassets.io"
>     - "e7bvsblobprodcus348.vsblob.vsassets.io"
>     - "fdpvsblobprodcus345.vsblob.vsassets.io"
>     - "frdvsblobprodcus327.vsblob.vsassets.io"
>     - "gbsvsblobprodcus365.vsblob.vsassets.io"
>     - "h6tvsblobprodcus346.vsblob.vsassets.io"
>     - "i1qvsblobprodcus353.vsblob.vsassets.io"
>     - "jd4vsblobprodcus366.vsblob.vsassets.io"
>     - "josvsblobprodcus372.vsblob.vsassets.io"
>     - "jrqvsblobprodcus343.vsblob.vsassets.io"
>     - "k0ivsblobprodcus356.vsblob.vsassets.io"
>     - "k4kvsblobprodcus344.vsblob.vsassets.io"
>     - "kgfvsblobprodcus314.vsblob.vsassets.io"
>     - "kh4vsblobprodcus325.vsblob.vsassets.io"
>     - "kijvsblobprodcus387.vsblob.vsassets.io"
>     - "kxqvsblobprodcus376.vsblob.vsassets.io"
>     - "l49vsblobprodcus358.vsblob.vsassets.io"
>     - "ljcvsblobprodcus317.vsblob.vsassets.io"
>     - "lylvsblobprodcus31.vsblob.vsassets.io"
>     - "m16vsblobprodcus374.vsblob.vsassets.io"
>     - "m6xvsblobprodcus342.vsblob.vsassets.io"
>     - "mfjvsblobprodcus373.vsblob.vsassets.io"
>     - "n3kvsblobprodcus335.vsblob.vsassets.io"
>     - "o3svsblobprodcus318.vsblob.vsassets.io"
>     - "ofvvsblobprodcus315.vsblob.vsassets.io"
>     - "p2ovsblobprodcus312.vsblob.vsassets.io"
>     - "pc2vsblobprodcus360.vsblob.vsassets.io"
>     - "pdfvsblobprodcus380.vsblob.vsassets.io"
>     - "pe3vsblobprodcus354.vsblob.vsassets.io"
>     - "pkgs.dev.azure.com"
>     - "rcxvsblobprodcus328.vsblob.vsassets.io"
>     - "s8mvsblobprodcus38.vsblob.vsassets.io"
>     - "se1vsblobprodcus349.vsblob.vsassets.io"
>     - "southcentralus0.in.applicationinsights.azure.com"
>     - "sqdvsblobprodcus333.vsblob.vsassets.io"
>     - "st8vsblobprodcus339.vsblob.vsassets.io"
>     - "tphvsblobprodcus375.vsblob.vsassets.io"
>     - "u3hvsblobprodcus371.vsblob.vsassets.io"
>     - "u6ovsblobprodcus377.vsblob.vsassets.io"
>     - "ukkvsblobprodcus352.vsblob.vsassets.io"
>     - "uy6vsblobprodcus34.vsblob.vsassets.io"
>     - "v53vsblobprodcus320.vsblob.vsassets.io"
>     - "vb4vsblobprodcus33.vsblob.vsassets.io"
>     - "vwvvsblobprodcus334.vsblob.vsassets.io"
>     - "x3yvsblobprodcus370.vsblob.vsassets.io"
>     - "xupvsblobprodcus332.vsblob.vsassets.io"
>     - "yluvsblobprodcus367.vsblob.vsassets.io"
>     - "yttvsblobprodcus357.vsblob.vsassets.io"
> ```
>
> See [Network Configuration](https://github.github.com/gh-aw/reference/network/) for more information.
>
> </details>

> 🤖 **Automated content by GitHub Copilot.** Generated by the [Code Simplifier](https://github.com/microsoft/testfx/actions/runs/36721422800/agentic_workflow) workflow. · copilot · auto · 198.7 AIC · ⌖ 12.2 AIC · ⊞ 14.5K · [◷]( · [◷](https://github.com/search?q=repo%3Amicrosoft%2Ftestfx+%22gh-aw-workflow-id%3A+code-simplifier%22&type=pullrequests))
>
<details>
<summary><sub>Add this agentic workflow to your repo</sub></summary>

To install this agentic workflow, run

```
gh aw add githubnext/agentics/workflows/code-simplifier.md@main
```
</details>

> - [x] expires  on Oct 1, 2026, 1:38 PM UTC

Navigation Menu

[code-simplifier] Deduplicate accepted-child-await guard in middleware pipeline #11660

Code Simplification - 2026-09-30

Files Simplified

Improvements Made

Changes Based On

Testing

Review Focus

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

[code-simplifier] Deduplicate accepted-child-await guard in middleware pipeline #11660

Description

Code Simplification - 2026-09-30

Files Simplified

Improvements Made

Changes Based On

Testing

Review Focus

Activity

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions