[DedSec256]

The DependencyGraph cache of the TransparentCompiler never found a cached graph: every request built the graph again, even for the same files at the same versions.

The cache key, built by Extensions.Key in TransparentCompiler.fs, was a tuple of the graph type and the MD5 hash of the file names as a byte[]. LruCache keeps its keys in a Dictionary with the default .NET comparer. For a tuple, that comparer compares an array by reference, and GetKey() creates a new array on every call, so no two keys were ever equal. As a result:

• the graph was built again on every request. Building it means running FileContentMapping.mkFileContent and DependencyResolution.mkGraph over every file in the set. For example, semantic classification or find references on a file that was just checked rebuilt the graph that the check had built;
• every request added a new cache entry. Up to 100 graphs were held strongly and 200 weakly, and none of them could ever be found.

This PR keeps the hash in the key as a string, which the default comparer compares by value. The version of the key was already a string.

The new test Dependency graph of the same files is taken from the cache checks a file, requests its semantic classification and asserts that the graph is only requested, not built again. Without the fix it gets [Requested; Started; Finished].

[github-actions]

✅ Release notes checked

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✅ Found changes and release notes in following paths:

Change path	Release notes path	Description
`src/Compiler`	docs/release-notes/.FSharp.Compiler.Service/11.0.200.md