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Fix NullReferenceException in tool install when package not found in manifest #52951

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Fix NullReferenceException in tool install when package not found in manifest #52951

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1918794
Initial plan
Copilot Feb 10, 2026
c3841cb
Fix tool install NullReferenceException by reordering manifest lookup
Copilot Feb 10, 2026
9d67e02
Address code review: improve warningMessage scoping
Copilot Feb 10, 2026
0c4ffbf
Refactor to fix issue in shared method instead of duplicating logic
Copilot Feb 11, 2026
14280f6
Add regression test for installing into existing empty manifest
Copilot Feb 12, 2026
4921020
Fix nullability annotations for warningMessage and explicitManifestFile
Copilot Feb 12, 2026
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9 changes: 7 additions & 2 deletions src/Cli/dotnet/Commands/Tool/Common/ToolManifestFinderExtensions.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,8 @@ internal static class ToolManifestFinderExtensions
public static (FilePath? filePath, string warningMessage) ExplicitManifestOrFindManifestContainPackageId(
this IToolManifestFinder toolManifestFinder,
string explicitManifestFile,
PackageId packageId)
PackageId packageId,
bool throwIfNoManifestFound = true)
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Copilot AI Feb 12, 2026

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warningMessage is declared as non-nullable (string) in the tuple return type, but this method returns null for it in several paths (explicit manifest, no match, and now the no-manifest catch). This makes the nullability contract incorrect for nullable-enabled callers and can lead to missed null checks / NRT warnings. Consider enabling nullable for this file (or at least for this method) and changing the signature to return string? warningMessage (and likewise accept string? explicitManifestFile).

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@marcpopMSFT marcpopMSFT Feb 12, 2026

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@copilot apply changes based on this feedback

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Copilot AI Feb 12, 2026

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Fixed the nullability annotations:

  • Removed #nullable disable from ToolManifestFinderExtensions.cs
  • Changed return type to (FilePath? filePath, string? warningMessage)
  • Changed parameter to string? explicitManifestFile
  • Updated calling code in ToolInstallLocalCommand.cs to use string?

All tests pass (21 install + 9 uninstall).

Commit: 4921020

{
if (!string.IsNullOrWhiteSpace(explicitManifestFile))
{
Expand All @@ -29,7 +30,11 @@ public static (FilePath? filePath, string warningMessage) ExplicitManifestOrFind
}
catch (ToolManifestCannotBeFoundException e)
{
throw new GracefulException([e.Message, CliCommandStrings.ToolCommonNoManifestGuide], verboseMessages: [e.VerboseMessage], isUserError: false);
if (throwIfNoManifestFound)
{
throw new GracefulException([e.Message, CliCommandStrings.ToolCommonNoManifestGuide], verboseMessages: [e.VerboseMessage], isUserError: false);
}
return (null, null);
}

if (manifestFilesContainPackageId.Any())
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6 changes: 2 additions & 4 deletions src/Cli/dotnet/Commands/Tool/Install/ToolInstallLocalCommand.cs
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Expand Up @@ -102,17 +102,15 @@ public override int Execute()

private int ExecuteInstallCommand(PackageId packageId, VersionRange? versionRange)
{
FilePath manifestFile = GetManifestFilePath();

(FilePath? manifestFileOptional, string warningMessage) =
_toolManifestFinder.ExplicitManifestOrFindManifestContainPackageId(_explicitManifestFile, packageId);
_toolManifestFinder.ExplicitManifestOrFindManifestContainPackageId(_explicitManifestFile, packageId, throwIfNoManifestFound: false);

if (warningMessage != null)
{
_reporter.WriteLine(warningMessage.Yellow());
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In this nullable-enabled file, warningMessage is deconstructed as non-nullable string, but the called helper can return null for the warning. This forces a redundant warningMessage != null check (and can hide real nullability issues). After adjusting the helper’s signature, consider deconstructing into string? warningMessage here to match the actual behavior.

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@marcpopMSFT marcpopMSFT Feb 12, 2026

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Copilot AI Feb 12, 2026

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This was already addressed in commit 4921020. Line 105 now uses string? warningMessage to properly match the nullable return type from the helper method.

}

manifestFile = manifestFileOptional ?? GetManifestFilePath();
FilePath manifestFile = manifestFileOptional ?? GetManifestFilePath();
var existingPackageWithPackageId = _toolManifestFinder.Find(manifestFile).Where(p => p.PackageId.Equals(packageId));

if (!existingPackageWithPackageId.Any())
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