[fix-finder] Remove null-forgiving operator (`!`) in BaseTest.AssertApkSigned

[github-actions]

Problem

The repo coding rule states the null-forgiving operator (!) must never be used in C# code — always refactor to an explicit null check that throws. BaseTest.cs uses proc!.StandardOutput after Process.Start, which can return null. If Process.Start returns null, the current code produces a raw NullReferenceException instead of a clear failure message.

Location

• File(s): src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Utilities/BaseTest.cs
• Line(s): 493–494

Current Code

using var proc = Process.Start (psi);
string stdout = proc!.StandardOutput.ReadToEnd ();

Suggested Fix

Replace the null-forgiving operator with a null-coalescing throw so the process handle is validated once and the remaining usages (proc.StandardError, proc.WaitForExit, proc.ExitCode) stay non-null:

using var proc = Process.Start (psi) ?? throw new InvalidOperationException ($"Failed to start '{apksignerExe}'.");
string stdout = proc.StandardOutput.ReadToEnd ();

This removes the only ! in this method; lines 495–497 already dereference proc without ! and need no change.

Guidelines

• Follow dotnet/android formatting: tabs, space before (, Mono style.
• A ?? throw expression is C# 7+ and compiles on the project's TFM ($(DotNetStableTargetFramework)).
• Do not introduce any other ! usages.

Acceptance Criteria

• proc!.StandardOutput no longer uses the null-forgiving operator
• Process.Start result is validated with an explicit throw
• All tests pass
• No new warnings introduced

Fix-finder metadata

• Script: 02-null-forgiving-operator
• Score: 30/30 (actionability: 10, safety: 10, scope: 10)

Generated by Nightly Fix Finder · 67.8 AIC · ⌖ 17.2 AIC · ⊞ 9.3K · ◷

• expires on Jul 18, 2026, 2:25 AM UTC