Reduce MEF cache construction allocations

[Andrew Arnott (AArnott)]

Uncreatable sharing-boundary analysis repeatedly scans the entire catalog for every target part and candidate scope. Large catalogs amplify those scans into excessive allocation and can cause cache construction to exceed its cancellation window. Cache viable export-factory edges once per analysis pass while preserving the existing reachability and scope rules.

[Copilot]

🟢 Approval recommended

The change is a contained refactor that preserves the existing reachability/scope logic while reducing repeated scanning and allocations, and no correctness issues were found in the updated control flow.

Pull request overview

This PR optimizes the uncreatable sharing-boundary analysis during MEF cache construction by caching “viable export-factory edges” once per analysis pass, avoiding repeated full-catalog scans that can amplify allocations on large catalogs.

Changes:

• Precomputes a cached list of export-factory relationships (owner, fresh sharing boundaries, exported parts) for reuse during reachability analysis.
• Replaces repeated LINQ-based catalog scanning inside IsPartReachable with iterative loops over the cached export-factory list.
• Removes some LINQ-heavy dominance checks in scope exploration in favor of explicit loops to reduce per-iteration overhead.

File summaries

File	Description
src/Microsoft.VisualStudio.Composition/CompositionConfiguration.cs	Caches export-factory edges and reuses them in sharing-boundary reachability analysis to reduce allocations and repeated scanning.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 0
• Review effort level: Lite

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