Refactor: AggregateManager static mutable state and ArrayList return types

[jordanpadams]

Summary

AggregateManager has two related problems: a static ArrayList field mutated from unsynchronized public methods, and multiple methods that return ArrayList<Target> rather than the List<Target> interface.

Unsynchronized static mutable field

private static ArrayList<Target> m_ignoreList = new ArrayList<>();
private static String m_location = null;
private static Target m_latestBundle = null;

buildBundleIgnoreList, buildCollectionIgnoreList, and makeException all mutate or read m_ignoreList without synchronization. Concurrent bundle validations calling makeException can interleave addAll operations, causing ConcurrentModificationException or lost updates. m_location and m_latestBundle have unsynchronized read/write.

Live-reference getter

public static ArrayList<Target> getIgnoreList() {
    return (AggregateManager.m_ignoreList);
}

Returns the actual backing list — callers can clear or mutate it.

Concrete return types

getIgnoreList(), buildBundleIgnoreList(...), buildCollectionIgnoreList(...), findOtherBundleFiles(...), findOtherCollectionFiles(...), and getCollectionFilesWithSameLogicalIdentifier(...) all return ArrayList<Target> instead of List<Target>.

Recommended fix

• Replace m_ignoreList with CopyOnWriteArrayList or wrap all accesses with synchronized (AggregateManager.class).
• Use volatile for m_location and m_latestBundle.
• Change getIgnoreList() return type to List<Target> and return Collections.unmodifiableList(m_ignoreList).
• Change all other method return types from ArrayList<Target> to List<Target>.

Related

Identified during immutability/synchronization audit triggered by PR #1607 review feedback.

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