[API Proposal]: Add Claim.HasProperties to avoid allocating Properties Dictionary

[eerhardt]

Background and motivation

System.Security.Claims.Claim will lazy load its Properties dictionary:

https://github.com/dotnet/runtime/blob/84b33395057737db3ea342a5151feb6b90c1b6f6/src/libraries/System.Security.Claims/src/System/Security/Claims/Claim.cs#L344

However, if you are writing code to inspect the Claim and checking if there are any Properties, the only way to check is to allocate this Dictionary just to see that its Count == 0. For example, here is some code from the JWT handling code in Microsoft.IdentityModel.JsonWebTokens:

            foreach (Claim jwtClaim in jwtToken.Claims)
            {
                ...

                if (jwtClaim.Properties.Count == 0)
                {
                    identity.AddClaim(new Claim(claimType, jwtClaim.Value, jwtClaim.ValueType, issuer, issuer, identity));
                }
                else
                {
                    Claim claim = new Claim(claimType, jwtClaim.Value, jwtClaim.ValueType, issuer, issuer, identity);

                    foreach (var kv in jwtClaim.Properties)
                        claim.Properties[kv.Key] = kv.Value;

                    identity.AddClaim(claim);
                }

Just doing that first check allocates the Dictionary on the Claim and then basically just throws it away (since the Claim has no Properties).

API Proposal

namespace System.Security.Claims;

public class Claim
{
+    public bool HasProperties { get; }
}

API Usage

foreach (Claim jwtClaim in jwtToken.Claims)
{
    ...

    Claim claim = new Claim(claimType, jwtClaim.Value, jwtClaim.ValueType, issuer, issuer, identity);
    if (jwtClaim.HasProperties)
    {
        foreach (var kv in jwtClaim.Properties)
            claim.Properties[kv.Key] = kv.Value;
    }
    identity.AddClaim(claim);

Alternative Designs

No response

Risks

No response

[dotnet-policy-service[bot]]

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[jmprieur]

@brentschmaltz @keegan-caruso FYI