Support aliasing of built-in property names (for Serilog.Filters.Expressions migration)

[nblumhardt]

Phew! Sorry that took a while, @warrenbuckley :-) Hope you had a great weekend!

I think you're right about keeping the scope limited. Here's how the LegacyFilterSyntaxNameResolver would look, with this change (untested :-)):

public class LegacyLevelPropertyNameResolver: NameResolver
{
    public static LogEventPropertyValue? Has(LogEventPropertyValue? value)
    {
        return new ScalarValue(value != null);
    }
    
    public override bool TryResolveFunctionName(string name, [NotNullWhen(true)] out MethodInfo? implementation)
    {
        if ("Has".Equals(name, StringComparison.OrdinalIgnoreCase))
        {
            implementation = GetType().GetMethod("Has", BindingFlags.Static | BindingFlags.Public)!;
            return true;
        }

        implementation = null;
        return false;
    }

    public override bool TryResolveBuiltInPropertyName(string alias, [NotNullWhen(true)] out string? target)
    {
        target = alias switch
        {
            "Exception" => "x",
            "Level" => "l",
            "Message" => "m",
            "MessageTemplate" => "mt",
            "Properties" => "p",
            "Timestamp" => "t",
            _ => null
        };
        
        return target != null;
    }
}

Fixes #63
Fixes #64

[nblumhardt]

(Requiring that the target Has function is public is a bit of a flaw in NameResolver, might think about offering an alternative (e.g. lambda) option, one of these days 🤔)

[nblumhardt]

A little more naming consistency :-)

[warrenbuckley]

Looks good to me @nblumhardt 👍
The new TryResolveBuiltInPropertyName method to override will solve this problem and again once this PR is done then the readme can be updated to show this example

Keeping my eyes peeled 👀 for when I can use an updated release

[nblumhardt]

👍 - 3.2.2-dev-00083 is now on NuGet, if this does the trick for you I'll queue up a release build (which should probably be 3.3.0, since the added feature warrants a minor version bump.)

[warrenbuckley]

Hiya @nblumhardt
I have updated a draft Umbraco PR and a draft PR to the electron desktop app and both are working fine with the updated 3.2.2-dev-00083 build.

Are you able to notify me please when 3.3.0 is released so I can finalize these PRs 😄