Fix KeyNotFoundException when DoNotUnpack flag is set on containers

[Copilot]

Description

The SignTool throws KeyNotFoundException when attempting to access dictionary entries for containers with DoNotUnpack=true. When this flag is set, containers skip unpacking and aren't added to _zipDataMap, but subsequent code directly accesses the dictionary without checking for existence.

Changes

Modified Configuration.cs to use conditional dictionary access:

• Line 282-296: Changed _zipDataMap[key] to TryGetValue pattern. Handles both DoNotUnpack skips and failed unpacking attempts. Logs error if container was expected but not unpacked.

• Line 364-369: Added TryGetValue for parent container collision ID lookups. Falls back to empty string and logs detailed error with parent hash when lookup fails.

To double check:

• The right tests are in and the right validation has happened. Guidance: https://github.com/dotnet/arcade/blob/main/Documentation/Validation.md

Original prompt

Since the merge of PR #16371, the sign tool throws a KeyNotFoundException when the DoNotUnpack flag is set on a container (e.g., .zip or .nupkg). The error occurs when the signing logic attempts to access dictionary entries for files inside containers that are no longer unpacked for signing. This update modifies Configuration.cs so that when DoNotUnpack is set, inner files are not tracked or looked up in the relevant dictionary, preventing KeyNotFoundException. It uses conditional TryGetValue access to the dictionary and skips tracking or lookup for children of DoNotUnpack containers. The error message is also improved for other missing keys.

This pull request was created from Copilot chat.

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[ericstj]

I thought you were saying that key not found was expected in some cases, yet this will error in that case.