InterfaceGenerator/Speckle.InterfaceGenerator/SymbolExtensions.cs

using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.CodeAnalysis;

namespace Speckle.InterfaceGenerator;

internal static class SymbolExtensions
{
    private static readonly HashSet<string> _defaults = new() { "System", "Microsoft" };
    public static string GetNamespaceAndType(this ITypeSymbol typeSymbol)
    {
        if (typeSymbol is ITypeParameterSymbol t)
        {
            return t.Name;
        }
        if (typeSymbol.SpecialType != SpecialType.None)
        {
            return typeSymbol.ToString();
        }

        if (typeSymbol.NullableAnnotation == NullableAnnotation.Annotated)
        {
            return typeSymbol.ToString();
        }
        var namespacez = new List<string>();
        var ns = typeSymbol.ContainingNamespace;
        while (ns is not null && !ns.IsGlobalNamespace)
        {
            namespacez.Insert(0, ns.Name);
            ns = ns.ContainingNamespace;
        }

        if (namespacez.Any())
        {
            if (!_defaults.Contains(namespacez.First()))
            {
                var candidate = string.Join(".", namespacez);
                var name = typeSymbol.ToString();
                if (!name.StartsWith(candidate))
                {
                    name += candidate + "." + name;
                }
                return "global::" + name;
            }
        }

        return typeSymbol.ToString();
    }
    public static bool TryGetAttribute(
        this ISymbol symbol,
        INamedTypeSymbol attributeType,
        out IEnumerable<AttributeData> attributes
    )
    {
        attributes = symbol
            .GetAttributes()
            .Where(a => SymbolEqualityComparer.Default.Equals(a.AttributeClass, attributeType));
        return attributes.Any();
    }

    public static bool HasAttribute(this ISymbol symbol, INamedTypeSymbol attributeType)
    {
        return symbol
            .GetAttributes()
            .Any(a => SymbolEqualityComparer.Default.Equals(a.AttributeClass, attributeType));
    }

    //Ref: https://stackoverflow.com/questions/27105909/get-fully-qualified-metadata-name-in-roslyn
    public static string GetFullMetadataName(this ISymbol symbol, bool useNameWhenNotFound = false)
    {
        if (IsRootNamespace(symbol))
        {
            return useNameWhenNotFound ? symbol.Name : string.Empty;
        }

        var stringBuilder = new StringBuilder(symbol.MetadataName);
        var last = symbol;

        symbol = symbol.ContainingSymbol;

        while (!IsRootNamespace(symbol))
        {
            if (symbol is ITypeSymbol && last is ITypeSymbol)
            {
                stringBuilder.Insert(0, '+');
            }
            else
            {
                stringBuilder.Insert(0, '.');
            }

            stringBuilder.Insert(
                0,
                symbol.OriginalDefinition.ToDisplayString(
                    SymbolDisplayFormat.MinimallyQualifiedFormat
                )
            );
            symbol = symbol.ContainingSymbol;
        }

        var retVal = stringBuilder.ToString();
        if (string.IsNullOrWhiteSpace(retVal) && useNameWhenNotFound)
        {
            return symbol.Name;
        }

        return retVal;
    }

    private static bool IsRootNamespace(ISymbol symbol)
    {
        return symbol is INamespaceSymbol { IsGlobalNamespace: true };
    }
}