Rework Generator interface and add GenerationOutputMode option.

src/Generator/Generator.cs

@@ -22,7 +22,7 @@ namespace CppSharp.Generators
     /// <summary>
     /// Output generated by each backend generator.
     /// </summary>
-    public struct GeneratorOutput
+    public class GeneratorOutput
     {
         /// <summary>
         /// Translation unit associated with output.
@@ -66,81 +66,103 @@ namespace CppSharp.Generators
 
         }
 
+        /// <summary>
+        /// Generates the outputs for the given translation units.
+        /// </summary>
+        /// <param name="units">The units to generate outputs for.</param>
+        public abstract List<CodeGenerator> Generate(IEnumerable<TranslationUnit> units);
+
         /// <summary>
         /// Generates the outputs.
         /// </summary>
         public virtual List<GeneratorOutput> Generate()
         {
-            var outputs = new List<GeneratorOutput>();
+            var outputMode = Context.Options.GenerationOutputMode;
 
-            var units = Context.ASTContext.TranslationUnits.GetGenerated().ToList();
+            // TODO: Remove this once file per module works for C++ backend
+            if (!Context.Options.IsCSharpGenerator)
+                outputMode = GenerationOutputMode.FilePerUnit;
+            
+            var outputs = new List<GeneratorOutput>();
 
-            if (Context.Options.IsCSharpGenerator &&
-                Context.Options.GenerateSingleCSharpFile)
+            if (outputMode == GenerationOutputMode.FilePerModule)
             {
                 foreach (var module in Context.Options.Modules)
-                    outputs.Add(GenerateModuleTemplate(module));
+                {
+                    var output = GenerateModule(module);
+                    if (output != null)
+                    {
+                        OnUnitGenerated(output);
+                        outputs.Add(output);
+                    }
+                }
             }
             else
             {
-                GenerateTemplates(outputs, units.Where(u => !u.IsSystemHeader));
+                var units = Context.ASTContext.TranslationUnits.GetGenerated()
+                    .Where(u => !u.IsSystemHeader).ToList();
 
-                if (Context.Options.IsCSharpGenerator && Context.Options.SystemModule != null)
-                    outputs.Add(GenerateModuleTemplate(Context.Options.SystemModule));
+                foreach (var unit in units)
+                {
+                    var output = GenerateUnit(unit);
+                    if (output != null)
+                    {
+                        outputs.Add(output);
+                        OnUnitGenerated(output);
+                    }
+                }
+
+                if (Context.Options.SystemModule != null)
+                {
+                    var output = GenerateModule(Context.Options.SystemModule);
+                    if (output != null)
+                    {
+                        OnUnitGenerated(output);
+                        outputs.Add(output);
+                    }
+                }
             }
 
             return outputs;
         }
 
-        private void GenerateTemplates(List<GeneratorOutput> outputs, IEnumerable<TranslationUnit> units)
+        public virtual GeneratorOutput GenerateUnit(TranslationUnit unit)
         {
-            foreach (var unit in units)
-            {
-                var templates = Generate(new[] { unit });
-                if (templates.Count == 0)
-                    return;
+            var codeGenerators = Generate(new[] { unit });
+            if (codeGenerators.Count == 0)
+                return null;
 
-                foreach (var template in templates)
-                {
-                    template.Process();
-                }
-
-                var output = new GeneratorOutput
-                {
-                    TranslationUnit = unit,
-                    Outputs = templates
-                };
+            foreach (var codeGen in codeGenerators)
+            {
+                codeGen.Process();
+            }
 
-                outputs.Add(output);
+            var output = new GeneratorOutput
+            {
+                TranslationUnit = unit,
+                Outputs = codeGenerators
+            };
 
-                OnUnitGenerated(output);
-            }
+            return output;
         }
 
-        private GeneratorOutput GenerateModuleTemplate(Module module)
+        public virtual GeneratorOutput GenerateModule(Module module)
         {
             var output = new GeneratorOutput
             {
                 TranslationUnit = new TranslationUnit
                 {
-                    FilePath = $"{module.LibraryName}.cs",
+                    FilePath = $"{module.LibraryName}",
                     Module = module
                 },
                 Outputs = Generate(module.Units.GetGenerated())
             };
-            output.Outputs[0].Process();
 
-            OnUnitGenerated(output);
+            output.Outputs[0].Process();
 
             return output;
         }
 
-        /// <summary>
-        /// Generates the outputs for the given translation units.
-        /// </summary>
-        /// <param name="units">The units to generate outputs for.</param>
-        public abstract List<CodeGenerator> Generate(IEnumerable<TranslationUnit> units);
-
         protected abstract string TypePrinterDelegate(CppSharp.AST.Type type);
 
         public static string GeneratedIdentifier(string id) =>

src/Generator/Generators/C/CCodeGenerator.cs

@@ -35,9 +35,12 @@ namespace CppSharp.Generators.C
             typePrinter = new CppTypePrinter(context);
         }
 
-        public abstract override string FileExtension { get; }
+        public override string FileExtension { get; } = "h";
 
-        public abstract override void Process();
+        public override void Process()
+        {
+
+        }
 
         public ISet<CInclude> Includes = new HashSet<CInclude>();
 

src/Generator/Generators/CodeGenerator.cs

@@ -61,7 +61,8 @@ namespace CppSharp.Generators
         protected CodeGenerator(BindingContext context, IEnumerable<TranslationUnit> units)
         {
             Context = context;
-            TranslationUnits = new List<TranslationUnit>(units);
+            if (units != null)
+                TranslationUnits = new List<TranslationUnit>(units);
         }
 
         public abstract void Process();

src/Generator/Options.cs

@@ -8,6 +8,12 @@ using CppSharp.Generators;
 
 namespace CppSharp
 {
+    public enum GenerationOutputMode
+    {
+        FilePerModule,
+        FilePerUnit
+    }
+
     public class DriverOptions
     {
         public DriverOptions()
@@ -137,7 +143,20 @@ namespace CppSharp
         /// <summary>
         /// Generates a single C# file.
         /// </summary>
-        public bool GenerateSingleCSharpFile { get; set; } = true;
+        [Obsolete("Use the more general GenerationOutputMode property instead.")]
+        public bool GenerateSingleCSharpFile
+        {
+            get { return GenerationOutputMode == GenerationOutputMode.FilePerModule; }
+
+            set
+            {
+                GenerationOutputMode = value ? GenerationOutputMode.FilePerModule
+                    : GenerationOutputMode.FilePerUnit;
+            }
+        }
+
+        public GenerationOutputMode GenerationOutputMode { get; set; } =
+            GenerationOutputMode.FilePerModule;
 
         /// <summary>
         /// Generates default values of arguments in the C# code.