[file-diet] Refactor HangDumpProcessLifetimeHandler.cs (1045 lines) into focused partial files

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Overview

The file src/Platform/Microsoft.Testing.Extensions.HangDump/HangDumpProcessLifetimeHandler.cs has grown to 1045 lines, making it harder to navigate and maintain. This task involves refactoring it into smaller, more focused files.

Current State

• File: src/Platform/Microsoft.Testing.Extensions.HangDump/HangDumpProcessLifetimeHandler.cs
• Size: 1045 lines
• Language: C#

Structural Analysis

The file contains two top-level types:

1. HangDumpProcessLifetimeHandler (internal sealed class, ~990 lines) implementing ITestHostProcessLifetimeHandler, IOutputDeviceDataProducer, IDataProducer, IAsyncDisposable/IDisposable. It mixes several distinct concerns:
   • Core lifecycle members: constructor, fields, IsEnabledAsync, BeforeTestHostProcessStartAsync, CallbackAsync, OnTestHostProcessStartedAsync, OnTestHostProcessExitedAsync, timer/deadline handling (OnDeadlineTimerElapsed, GetTimerDueTime), and Dispose/DisposeAsync.
   • Process-tree diagnostics helpers: GetProcessTreeWithTimeoutAsync, QueryOnceAndDumpTreeAsync, TryGetProcessById, GetInProgressTestsAsync, QueryInProgressTestsWithTimeoutAsync, RunBestEffortDiagnosticAsync, GetDiskInfo.
   • Dump-taking logic: TriggerDumpOnce, TakeDumpOfTreeAsync, TakeDumpAsync, GetDumpFileNames/DumpFileNames, EnsureProcessIdPlaceholder, GetDumpFileNamePattern.
2. OutputDeviceWriter (internal sealed class, ~20 lines) — an unrelated helper for writing output device data, tacked onto the end of the same file.

Refactoring Strategy

Proposed File Splits

1. HangDumpProcessLifetimeHandler.cs (keep, trimmed to ~350–400 lines)

   • Contents: fields, constructor, properties (Uid, Version, DisplayName, Description, DataTypesProduced), IsEnabledAsync, BeforeTestHostProcessStartAsync, CallbackAsync, OnTestHostProcessStartedAsync, OnTestHostProcessExitedAsync, OnDeadlineTimerElapsed, GetTimerDueTime, Dispose, DisposeAsync
   • Responsibility: Core ITestHostProcessLifetimeHandler lifecycle orchestration and disposal.

2. HangDumpProcessLifetimeHandler.ProcessTree.cs (partial class)

   • Contents: GetProcessTreeWithTimeoutAsync, QueryOnceAndDumpTreeAsync, TryGetProcessById, GetInProgressTestsAsync, QueryInProgressTestsWithTimeoutAsync, RunBestEffortDiagnosticAsync, GetDiskInfo
   • Responsibility: Process-tree discovery and best-effort diagnostic querying.

3. HangDumpProcessLifetimeHandler.DumpTaking.cs (partial class)

   • Contents: TriggerDumpOnce, TakeDumpOfTreeAsync, TakeDumpAsync, GetDumpFileNames, DumpFileNames, EnsureProcessIdPlaceholder, GetDumpFileNamePattern, NotifyCrashDumpServiceIfEnabled
   • Responsibility: Triggering and producing the actual hang dump artifacts.

4. OutputDeviceWriter.cs

   • Contents: OutputDeviceWriter class
   • Responsibility: Thin wrapper for writing IOutputDeviceData — unrelated to hang-dump logic and should live in its own file.

Implementation Guidelines

1. Preserve Behavior: All existing functionality must work identically after the split
2. Maintain Public API: Keep exported/public symbols accessible with the same names (mark the class partial where split across files)
3. Update Imports: Fix all import paths/usings throughout the split files
4. Test After Each Split: Run the test suite after each incremental change
5. One File at a Time: Split one module at a time to make review easier

Acceptance Criteria

• Original file is split into focused modules (using partial class for HangDumpProcessLifetimeHandler)
• Each new file is under 300 lines where practical
• All tests pass after refactoring
• No breaking changes to public API
• All import paths updated correctly

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Priority: Medium
Effort: Medium — mechanical extraction using partial classes with test verification at each step
Expected Impact: Improved code navigability, easier testing, reduced merge conflicts

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• expires on Aug 28, 2026, 7:28 PM UTC