| Prelude | [Part 1](#12504) | [Part
2](#12505) | [Part
3](#12506) | [Part
4](#12507) | [Part
5](#12509) |

This is a set of support utilities and helpers added as part of the
`TagHelperCollection` changes:

- Added `InterlockedOperations.Initialize(...)` overloads for lock free
initialization with a factory method.
(f3686aa)
- Added two `LazyValue` structs that use the new
`InterlockedOperations.Initialize(...)` overloads. These are useful for
lazily initializing a value without extra allocations or locks.
(81795f5)
- Added `OverloadResolutionPriorityAttribute` polyfill type.
(27ab174)
- Refactored `TagHelperCache` to extract `CleanableWeakCache<TKey,
TValue>`. This caches items as weak references. When the number of items
added reaches a configurable threshold, the cache is cleaned up, and any
dead weak references are removed.
(673a9b5)

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| [Prelude](#12503) | [Part
1](#12504) | Part 2 | [Part
3](#12506) | [Part
4](#12507) | [Part
5](#12509) |

> [!WARNING]
> This pull request contains breaking changes for the RazorSdk. Once
this is merged and flows to the VMR,
dotnet/dotnet@9a7e708
will need to be cherry-picked to resolve build breaks in
`src/sdk/src/RazorSdk`.

These commits represent the (mostly) mechanical changes needed to
integrate `TagHelperCollection` across the Razor code base. Most
references to `ImmutableArrary<TagHelperDescriptor>`,
`IReadOnlyList<TagHelperDescriptor>`,
`IEnumerable<TagHelperDescriptor>`, and `TagHelperDescriptor[]` have
been replaced with `TagHelperCollection`. This is **by far** the largest
of the `TagHelperCollection` pull requests.

While most of the commits contain mechanical changes across the code
base, there are few that include more substantial work that require a
bit more scrutiny:

- **Update `RenameService` to remove
`ImmutableArray<TagHelperDescriptor>`**
(fa3ad2b)
This includes a fair amount of refactoring in `RenameService` to fix
bugs found when moving to `TagHelperCollection`.

- **Update `TagHelperFacts` to use `TagHelperCollection`**
Extra work was done in `DirectiveAttributeComplationItemProvider` to
clean up a bit following #12473.

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…c in source generator (#12506)

| [Prelude](#12503) | [Part
1](#12504) | [Part
2](#12505) | Part 3 | [Part
4](#12507) | [Part
5](#12509) |

This is a relatively small change to remove LINQ from the Razor source
generator and use `TagHelperCollection` when checking for added/removed
tag helpers.

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| [Prelude](#12503) | [Part
1](#12504) | [Part
2](#12505) | [Part
3](#12506) | Part 4 | [Part
5](#12509) |

> [!WARNING]
> This pull request contains breaking changes for the RazorSdk. Once
this is merged and flows to the VMR,
dotnet/dotnet@dc17a09
will need to be cherry-picked to resolve build breaks in
`src/sdk/src/RazorSdk`.

Previously, tag helpers were discovered by
`ITagHelperDescriptorProvider`. Each provider was responsible for
walking a compilation's assemblies and producing `TagHelperDescriptors`
from the types within. This change inverts the tag helper discovery
process by introducing `ITagHelperDiscoveryService` and moving the tag
helper construction logic into a set of `TagHelperProducers`. The
`ITagHelperDiscoveryService` performs a single walk of the compilation
or assembly and calls the producers as needed.

Importantly, the new process allows a more expansive cache to be
maintained. There is now a per-assembly cache that holds onto
`TagHelperCollection` instances. The old cache that was owned by
providers via `TagHelperCollector` has been removed.

To complete this change, `ITagHelperDescriptorProvider` and related
types have been _deleted_.

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…xt (#12509)

| [Prelude](#12503) | [Part
1](#12504) | [Part
2](#12505) | [Part
3](#12506) | [Part
4](#12507) | Part 5 |

This change introduces a weak cache for `TagHelperDocumentContext` keyed
by the tag helper prefix string and `TagHelperCollection` checksum. This
helps avoid creating new `TagHelperBinders` for the same set of tag
helpers, since `TagHelperBinder` is expensive to create.

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