Create DiagnosticSuppressor for CS8602 in Linq expressions and Includes

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
csharp
Domain
database

Research direction

Start by examining EF Core's IQueryable LINQ methods and Include/ThenInclude entry points, using the issue's nullable-property examples as the expected scenarios. Determine how a DiagnosticSuppressor can target CS8602 only for database-translated expressions, then verify that the warning is suppressed in those cases without being suppressed elsewhere.

Written by the indexing model from the issue text.

Description

area-analyzer customer-reported

Currently CS8602 (Dereference of possibly null reference) is triggered for nullable properties in linq expressions, even though no NRE possible when query is executed on DB side.

Example 1 (Linq):

class User
{
    public string FirstName {get;set;}
    public string? MiddleName {get;set;}
    public string LastName {get;set;} 
}
...
string searchTerm = "...";

await dbContext.Users
    .Where(u => u => u.FirstName.Contains(searchTerm)
          || u.MiddleName.Contains(searchTerm)       <---------- CS8602 is reported, as 'MiddleName' is nullable
          || u.LastName.Contains(searchTerm))
    .ToListAsync();

Example 2 (Includes):

class SomeModel
{
    public class NavigationModel Navigation? {get;set;}
}

class NavigationModel 
{
    public class AnotherNavigationModel DeeperNavigation {get;set;}
}

dbContext.Models
   .Include(m => m.Navigation)
        .ThenInclude(n => n.DeeperNavigation)   <----- CS8602 is reported, as 'n' is nullable

Suggestion:
Create DiagnosticSuppressor for CS8602 for IQueryable expressions in Linq methods and for Include/ThenInclude methods.

Dominant language
C#
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