GenAPI: Optionally wrap types in conditional compilation

src/Microsoft.Cci.Extensions/Filters/DocIdExcludeListFilter.cs

@@ -28,10 +28,12 @@ public DocIdExcludeListFilter(string excludeListFilePath, bool excludeMembers)
             _excludeMembers = excludeMembers;
         }
 
+        public bool IncludeForwardedTypes { get; set; }
+
         public bool Include(INamespaceDefinition ns)
         {
             // Only include non-empty namespaces
-            if (!ns.GetTypes().Any(Include))
+            if (!ns.GetTypes(IncludeForwardedTypes).Any(Include))
                 return false;
 
             string namespaceId = ns.DocId();

src/Microsoft.Cci.Extensions/Filters/DocIdIncludeListFilter.cs

@@ -26,10 +26,12 @@ public DocIdIncludeListFilter(string includeListFilePath)
 
         public bool AlwaysIncludeNonEmptyTypes { get; set; }
 
+        public bool IncludeForwardedTypes { get; set; }
+
         public bool Include(INamespaceDefinition ns)
         {
             // Only include non-empty namespaces
-            if (!ns.GetTypes().Any(Include))
+            if (!ns.GetTypes(IncludeForwardedTypes).Any(Include))
                 return false;
 
             string namespaceId = ns.DocId();

src/Microsoft.Cci.Extensions/Writers/CSharp/CSharpWriter.cs

@@ -22,6 +22,7 @@ public class CSharpWriter : SimpleTypeMemberTraverser, ICciWriter, IDisposable
         private readonly bool _apiOnly;
         private readonly ICciFilter _cciFilter;
         private bool _firstMemberGroup;
+        private ICciFilter _currentTypeListFilter;
 
         public CSharpWriter(ISyntaxWriter writer, ICciFilter filter, bool apiOnly, bool writeAssemblyAttributes = false)
             : base(filter)
@@ -34,6 +35,12 @@ public CSharpWriter(ISyntaxWriter writer, ICciFilter filter, bool apiOnly, bool
             _writeAssemblyAttributes = writeAssemblyAttributes;
         }
 
+        public class ConditionalTypeList
+        {
+            public ICciFilter Filter { get; set; }
+            public string Symbol { get; set; }
+        }
+
         public ISyntaxWriter SyntaxWriter { get { return _syntaxWriter; } }
 
         public ICciDeclarationWriter DeclarationWriter { get { return _declarationWriter; } }
@@ -48,6 +55,10 @@ public CSharpWriter(ISyntaxWriter writer, ICciFilter filter, bool apiOnly, bool
 
         public bool PutBraceOnNewLine { get; set; }
 
+        public IEnumerable<ConditionalTypeList> ConditionalTypeLists { get; set; }
+
+        public string DefaultCondition { get; set; }
+
         public bool IncludeGlobalPrefixForCompilation
         {
             get { return _declarationWriter.ForCompilationIncludeGlobalPrefix; }
@@ -87,7 +98,23 @@ public override void Visit(IAssembly assembly)
                 _declarationWriter.WriteDeclaration(assembly);
             }
 
-            base.Visit(assembly);
+            var namespaces = assembly.GetAllNamespaces();
+            _currentTypeListFilter = null;
+
+            // first pass, visit types *not* mentioned in ConditionalTypeLists
+            WriteConditionStart(DefaultCondition);
+            Visit(namespaces);
+            WriteConditionEnd(DefaultCondition);
+
+            // second pass, visit types mentioned in ConditionalTypeLists
+            foreach (var typeList in ConditionalTypeLists ?? Enumerable.Empty<ConditionalTypeList>())
+            {
+                _currentTypeListFilter = typeList.Filter;
+
+                WriteConditionStart(typeList.Symbol);
+                Visit(namespaces.Where(_currentTypeListFilter.Include));
+                WriteConditionEnd(typeList.Symbol);
+            }
         }
 
         public override void Visit(INamespaceDefinition ns)
@@ -102,7 +129,16 @@ public override void Visit(INamespaceDefinition ns)
 
                 using (_syntaxWriter.StartBraceBlock(PutBraceOnNewLine))
                 {
-                    base.Visit(ns);
+                    var types = ns.GetTypes(this.IncludeForwardedTypes);
+                    if (ConditionalTypeLists != null)
+                    {
+                        // in the first pass we want all types *except* the ones in ConditionalTypeLists filters
+                        // in the second pass we want *only* the types in ConditionalTypeLists filters
+                        var firstPass = _currentTypeListFilter == null;
+                        types = types.Where(t => ConditionalTypeLists.Any(c => c.Filter.Include(t) == !firstPass));
+                    }
+
+                    Visit(types);
                 }
             }
 
@@ -296,6 +332,24 @@ private void WriteMemberGroupHeader(ITypeDefinitionMember member)
             }
         }
 
+        private void WriteConditionStart(string condition)
+        {
+            if (!string.IsNullOrEmpty(condition))
+            {
+                _syntaxWriter.Write($"#if {condition}");
+                _syntaxWriter.WriteLine();
+            }
+        }
+
+        private void WriteConditionEnd(string condition)
+        {
+            if (!string.IsNullOrEmpty(condition))
+            {
+                _syntaxWriter.Write($"#endif // {condition}");
+                _syntaxWriter.WriteLine();
+            }
+        }
+
         public static string MemberGroupHeading(ITypeDefinitionMember member)
         {
             if (member == null)

src/Microsoft.DotNet.GenAPI/GenAPITask.cs

@@ -155,13 +155,24 @@ public string DocIdKinds
         /// </summary>
         public bool AlwaysIncludeBase { get; set; }
 
+        /// <summary>
+        /// [CSDecl] Specify one or more namespace+type list(s) in the DocId format of types that should be wrapped inside an #if with the symbol specified in the <c>Symbol</c> metadata item.
+        /// If the <c>Symbol</c> metadata item is empty the types won't be wrapped but will still be output after all other types, this can be used in combination with <see cref="DefaultCondition" /> to wrap all other types.
+        /// </summary>
+        public ITaskItem[] ConditionalTypeLists { get; set; }
+
+        /// <summary>
+        /// [CSDecl] #if condition to apply to all types not included in <see cref="ConditionalTypeLists" />.
+        /// </summary>
+        public string DefaultCondition { get; set; }
+
         /// <summary>
         /// Exclude members when return value or parameter types are excluded.
         /// </summary>
         public bool ExcludeMembers { get; set; }
 
         /// <summary>
-        /// Language Version to target.
+        /// [CSDecl] Language Version to target.
         /// </summary>
         public string LangVersion { get; set; }
 
@@ -333,7 +344,7 @@ private static ICciFilter GetFilter(
 
             if (!string.IsNullOrWhiteSpace(excludeApiList))
             {
-                includeFilter = new IntersectionFilter(includeFilter, new DocIdExcludeListFilter(excludeApiList, excludeMembers));
+                includeFilter = new IntersectionFilter(includeFilter, new DocIdExcludeListFilter(excludeApiList, excludeMembers) { IncludeForwardedTypes = includeForwardedTypes });
             }
 
             if (!string.IsNullOrWhiteSpace(excludeAttributesList))
@@ -394,6 +405,16 @@ private ICciWriter GetWriter(TextWriter output, ISyntaxWriter syntaxWriter, bool
                         writer.AlwaysIncludeBase = AlwaysIncludeBase;
                         writer.LangVersion = GetLangVersion(LangVersion);
                         writer.IncludeForwardedTypes = FollowTypeForwards;
+                        writer.DefaultCondition = DefaultCondition;
+                        if (ConditionalTypeLists != null)
+                        {
+                            writer.ConditionalTypeLists = ConditionalTypeLists.Select(c =>
+                                new CSharpWriter.ConditionalTypeList
+                                {
+                                    Symbol = c.GetMetadata("Symbol"),
+                                    Filter = new DocIdIncludeListFilter(c.ItemSpec) { IncludeForwardedTypes = FollowTypeForwards }
+                                });
+                        }
                         return writer;
                     }
             }

src/Microsoft.DotNet.GenAPI/build/Microsoft.DotNet.GenAPI.targets

@@ -49,6 +49,8 @@
       Assembly="$(GenAPIInputAssembly)"
       LibPath="$(GenAPILibPath)"
       ApiList="$(GenAPIApiList)"
+      ConditionalTypeLists="@(GenAPIConditionalTypeLists)"
+      DefaultCondition="$(GenAPIDefaultCondition)"
       OutputPath="$(GenAPITargetPath)"
       HeaderFile="$(GenAPIHeaderFile)"
       WriterType="$(GenAPIWriterType)"