Translate List<T>.Exists to Queryable.Any

[m-x-shokhzod]

Rewrites List<T>.Exists(predicate) to AsQueryable().Any(predicate) in QueryableMethodNormalizingExpressionVisitor, mirroring the existing ICollection<T>.Contains conversion. The Predicate<T> lambda is rebuilt as Func<T, bool> so the resulting Queryable.Any call type-checks.

• New TryConvertListExistsToQueryableAny helper alongside TryConvertCollectionContainsToQueryableContains
• Detection branch gated to List<T> (other types like Array.Exists are out of scope)
• Bails out when the receiver is a literal (new List<T> / new {...}) or the predicate is a non-lambda delegate
• Flips four placeholder tests (Where_Join_Exists, _Inequality, _Constant, Where_Join_Not_Exists) tagged with // Issue #17762 from AssertTranslationFailed to AssertQuery
• Populates SqlServer SQL baselines (EXISTS subquery + optimizer-simplified forms for constant-false predicates)
• Cosmos overrides wrapped in AssertTranslationFailed per Cosmos's existing Issue #17246 pattern for navigation-collection Any translations

Fixes #17762

[Copilot]

Pull request overview

This PR extends EF Core’s query normalization to translate List<T>.Exists(predicate) into Queryable.Any(predicate) (via AsQueryable()), enabling server translation for scenarios like Northwind navigation collections. It also updates Northwind tests and SQL Server baselines to validate the new translation behavior, while keeping Cosmos behavior as translation-failing per existing limitations.

Changes:

• Add List<T>.Exists(...) normalization to Queryable.Any(...) in QueryableMethodNormalizingExpressionVisitor, including rebuilding the predicate delegate type to Func<T, bool>.
• Flip several Northwind “Issue #17762” tests from translation-failure placeholders to actual AssertQuery execution (with SQL Server baselines).
• Keep Cosmos overrides asserting translation failure for these tests in line with existing client-evaluation limitations.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/EFCore/Query/Internal/QueryableMethodNormalizingExpressionVisitor.cs	Adds normalization rewriting List<T>.Exists to Queryable.Any with a rewritten predicate delegate type.
test/EFCore.Specification.Tests/Query/NorthwindMiscellaneousQueryTestBase.cs	Converts Exists tests from AssertTranslationFailed to AssertQuery and adjusts expectations for empty-result cases.
test/EFCore.SqlServer.FunctionalTests/Query/NorthwindMiscellaneousQuerySqlServerTest.cs	Adds SQL baselines validating translation output for the updated Exists tests.
test/EFCore.Cosmos.FunctionalTests/Query/NorthwindMiscellaneousQueryCosmosTest.cs	Wraps the updated base tests in AssertTranslationFailed to preserve Cosmos behavior.

[m-x-shokhzod]

Thanks for the review. I dug into this and inline-list Exists already translates correctly — it does not fall back or fail, so I don't think ListInitExpression should be added to the bailout.

The literal-receiver bailout (MemberInitExpression or NewExpression) was deliberately narrowed in c0f9164797 "Support primitive collections" — it used to also cover ConstantExpression and the query-parameter ParameterExpression, and those were removed precisely because primitive-collection support made inline collections server-translatable. A populated new List<T> { ... } is a ListInitExpression — exactly the inline-collection shape that feature translates — so it's intentionally not in the bailout (the sibling Contains method omits it for the same reason).

Verified against SQL Server (ToQueryString, no DB needed):

// new List<int> { 1, 2, 3 }.Exists(x => x == b.Id)
SELECT [b].[Id], [b].[Name] FROM [Blogs] AS [b]
WHERE [b].[Id] IN (1, 2, 3)

// new List<int> { 1, 2, 3 }.Exists(x => x > b.Id)   (non-IN-able predicate)
SELECT [b].[Id], [b].[Name] FROM [Blogs] AS [b]
WHERE EXISTS (
    SELECT 1
    FROM (VALUES (CAST(1 AS int)), (2), (3)) AS [v]([Value])
    WHERE [v].[Value] > [b].[Id])

Both translate, identically to the explicit .AsQueryable().Any(...) form — equality predicates collapse to IN, general predicates become a VALUES … EXISTS subquery. Adding ListInitExpression to the bailout would only block that translation.

I've added a regression test (Where_inline_collection_Exists_translates) that runs new List<string> { ... }.Exists(id => id == c.CustomerID) end-to-end against Northwind and asserts the IN translation, so this behaviour stays pinned.