Cover a few corner cases in reflection API (#1163)

This change adds some new entry points to the reflection API to cover corner cases that a majority of applications won't care about.
These are most likely to come up for users who want to make a complete copy of the Slang reflection information into a data format of their own design.

All of the information is stuff that we already computed as part of layout, and just hadn't exposed:

* Alignment information for type layouts. This is only useful for ordinary/uniform data; in all other cases alignment is always one. Even for uniform/ordinary data, it is unlikely that any application would actually make use of it.

* Layout information for the result of an entry point function. This would be useful for applications that need to enumerate the varying outputs (user- or system-defined) of a shader. Having information available for `out` parameters but not the function result was inconsistent.

* The "element type" of a parameter block type (e.g., going from `ParameterBlock<X>` to `X`). This seems to have been an oversight since `ConstantBuffer<X>` appears to have been implemented, and the case for a type *layout* was handled.

* The "container" variable layout for a parameter block or constant buffer. It took a while for us to arrive at the current representation of layout for parameter groups, and most client code continues to use the original API that requires us to generated kludged "do what I mean" data. However, if we don't expose the more useful new representation fully, there is no way for users to take advantage of it!

The reflection test tool has been updated to print the new information where it makes sense, which provides us some level of coverage for the new code.
Unfortunately, this led to some cascading changes:

* First, a bunch of the tests had their output changed since they include new information. That's the easy bit.

* Next, the "container" and "element" var layouts don't actually have names (because there is no actual variable underlying them), which means that the code to emit variable names in the JSON dump needed to be condition.

* Making the `"name"` output conditional messed up a lot of the delicate logic that had been dealing with when to emit commas for the output JSON (JSON uses commas as separators, and doesn't allow trailing commas). I added a bit of new infrastructure to make it simple(-ish) to track when a comma actually needs to be output.

1 files changed, 199 insertions, 57 deletions

diff --git a/tools/slang-reflection-test/slang-reflection-test-main.cpp b/tools/slang-reflection-test/slang-reflection-test-main.cpp
index 7480b6ae9..6537362d7 100644
--- a/tools/slang-reflection-test/slang-reflection-test-main.cpp
+++ b/tools/slang-reflection-test/slang-reflection-test-main.cpp
@@ -12,8 +12,14 @@
 
 struct PrettyWriter
 {
+    struct CommaState
+    {
+        bool needComma = false;
+    };
+
     bool startOfLine = true;
     int indent = 0;
+    CommaState* commaState = nullptr;
 };
 
 static void writeRaw(PrettyWriter& writer, char const* begin, char const* end)
@@ -154,6 +160,44 @@ static void write(PrettyWriter& writer, float val)
     Slang::StdWriters::getOut().print("%f", val);
 }
 
+    /// Type for tracking whether a comma is needed in a comma-separated JSON list
+struct CommaTrackerRAII
+{
+    CommaTrackerRAII(PrettyWriter& writer)
+        : m_writer(&writer)
+        , m_previousState(writer.commaState)
+    {
+        writer.commaState = &m_state;
+    }
+
+    ~CommaTrackerRAII()
+    {
+        m_writer->commaState = m_previousState;
+    }
+
+private:
+    PrettyWriter::CommaState    m_state;
+
+    PrettyWriter*               m_writer;
+    PrettyWriter::CommaState*   m_previousState;
+};
+
+    /// Call before items in a comma-separated JSON list to emit the comma if/when needed
+static void comma(PrettyWriter& writer)
+{
+    if( auto state = writer.commaState )
+    {
+        if( !state->needComma )
+        {
+            state->needComma = true;
+            return;
+        }
+    }
+
+    write(writer, ",\n");
+}
+
+
 static void emitReflectionVarInfoJSON(PrettyWriter& writer, slang::VariableReflection* var);
 static void emitReflectionTypeLayoutJSON(PrettyWriter& writer, slang::TypeLayoutReflection* type);
 static void emitReflectionTypeJSON(PrettyWriter& writer, slang::TypeReflection* type);
@@ -234,7 +278,7 @@ static void emitReflectionVarBindingInfoJSON(
     auto stage = var->getStage();
     if (stage != SLANG_STAGE_NONE)
     {
-        write(writer, ",\n");
+        comma(writer);
         char const* stageName = "UNKNOWN";
         switch (stage)
         {
@@ -259,7 +303,7 @@ static void emitReflectionVarBindingInfoJSON(
 
     if (categoryCount)
     {
-        write(writer, ",\n");
+        comma(writer);
         if( categoryCount != 1 )
         {
             write(writer,"\"bindings\": [\n");
@@ -298,14 +342,14 @@ static void emitReflectionVarBindingInfoJSON(
 
     if (auto semanticName = var->getSemanticName())
     {
-        write(writer, ",\n");
+        comma(writer);
         write(writer,"\"semanticName\": \"");
         write(writer, semanticName);
         write(writer, "\"");
 
         if (auto semanticIndex = var->getSemanticIndex())
         {
-            write(writer, ",\n");
+            comma(writer);
             write(writer,"\"semanticIndex\": ");
             write(writer, int(semanticIndex));
         }
@@ -328,7 +372,8 @@ static void emitReflectionModifierInfoJSON(
 {
     if( var->findModifier(slang::Modifier::Shared) )
     {
-        write(writer, ",\n\"shared\": true");
+        comma(writer);
+        write(writer, "\"shared\": true");
     }
 }
 
@@ -409,9 +454,15 @@ static void emitReflectionVarLayoutJSON(
     write(writer, "{\n");
     indent(writer);
 
-    emitReflectionNameInfoJSON(writer, var->getName());
-    write(writer, ",\n");
+    CommaTrackerRAII commaTracker(writer);
 
+    if( auto name = var->getName() )
+    {
+        comma(writer);
+        emitReflectionNameInfoJSON(writer, name);
+    }
+
+    comma(writer);
     write(writer, "\"type\": ");
     emitReflectionTypeLayoutJSON(writer, var->getTypeLayout());
 
@@ -456,8 +507,9 @@ static void emitReflectionResourceTypeBaseInfoJSON(
 {
     auto shape  = type->getResourceShape();
     auto access = type->getResourceAccess();
+    comma(writer);
     write(writer, "\"kind\": \"resource\"");
-    write(writer, ",\n");
+    comma(writer);
     write(writer, "\"baseShape\": \"");
     switch (shape & SLANG_RESOURCE_BASE_SHAPE_MASK)
     {
@@ -479,18 +531,19 @@ static void emitReflectionResourceTypeBaseInfoJSON(
     write(writer, "\"");
     if (shape & SLANG_TEXTURE_ARRAY_FLAG)
     {
-        write(writer, ",\n");
+        comma(writer);
         write(writer, "\"array\": true");
     }
     if (shape & SLANG_TEXTURE_MULTISAMPLE_FLAG)
     {
-        write(writer, ",\n");
+        comma(writer);
         write(writer, "\"multisample\": true");
     }
 
     if( access != SLANG_RESOURCE_ACCESS_READ )
     {
-        write(writer, ",\n\"access\": \"");
+        comma(writer);
+        write(writer, "\"access\": \"");
         switch(access)
         {
         default:
@@ -519,6 +572,7 @@ static void emitReflectionTypeInfoJSON(
     switch(kind)
     {
     case slang::TypeReflection::Kind::SamplerState:
+        comma(writer);
         write(writer, "\"kind\": \"samplerState\"");
         break;
 
@@ -539,7 +593,7 @@ static void emitReflectionTypeInfoJSON(
             case SLANG_STRUCTURED_BUFFER:
                 if( auto resultType = type->getResourceResultType() )
                 {
-                    write(writer, ",\n");
+                    comma(writer);
                     write(writer, "\"resultType\": ");
                     emitReflectionTypeJSON(
                         writer,
@@ -551,8 +605,9 @@ static void emitReflectionTypeInfoJSON(
         break;
 
     case slang::TypeReflection::Kind::ConstantBuffer:
+        comma(writer);
         write(writer, "\"kind\": \"constantBuffer\"");
-        write(writer, ",\n");
+        comma(writer);
         write(writer, "\"elementType\": ");
         emitReflectionTypeJSON(
             writer,
@@ -560,8 +615,9 @@ static void emitReflectionTypeInfoJSON(
         break;
 
     case slang::TypeReflection::Kind::ParameterBlock:
+        comma(writer);
         write(writer, "\"kind\": \"parameterBlock\"");
-        write(writer, ",\n");
+        comma(writer);
         write(writer, "\"elementType\": ");
         emitReflectionTypeJSON(
             writer,
@@ -569,8 +625,9 @@ static void emitReflectionTypeInfoJSON(
         break;
 
     case slang::TypeReflection::Kind::TextureBuffer:
+        comma(writer);
         write(writer, "\"kind\": \"textureBuffer\"");
-        write(writer, ",\n");
+        comma(writer);
         write(writer, "\"elementType\": ");
         emitReflectionTypeJSON(
             writer,
@@ -578,8 +635,9 @@ static void emitReflectionTypeInfoJSON(
         break;
 
     case slang::TypeReflection::Kind::ShaderStorageBuffer:
+        comma(writer);
         write(writer, "\"kind\": \"shaderStorageBuffer\"");
-        write(writer, ",\n");
+        comma(writer);
         write(writer, "\"elementType\": ");
         emitReflectionTypeJSON(
             writer,
@@ -587,19 +645,21 @@ static void emitReflectionTypeInfoJSON(
         break;
 
     case slang::TypeReflection::Kind::Scalar:
+        comma(writer);
         write(writer, "\"kind\": \"scalar\"");
-        write(writer, ",\n");
+        comma(writer);
         emitReflectionScalarTypeInfoJSON(
             writer,
             type->getScalarType());
         break;
 
     case slang::TypeReflection::Kind::Vector:
+        comma(writer);
         write(writer, "\"kind\": \"vector\"");
-        write(writer, ",\n");
+        comma(writer);
         write(writer, "\"elementCount\": ");
         write(writer, int(type->getElementCount()));
-        write(writer, ",\n");
+        comma(writer);
         write(writer, "\"elementType\": ");
         emitReflectionTypeJSON(
             writer,
@@ -607,14 +667,15 @@ static void emitReflectionTypeInfoJSON(
         break;
 
     case slang::TypeReflection::Kind::Matrix:
+        comma(writer);
         write(writer, "\"kind\": \"matrix\"");
-        write(writer, ",\n");
+        comma(writer);
         write(writer, "\"rowCount\": ");
         write(writer, type->getRowCount());
-        write(writer, ",\n");
+        comma(writer);
         write(writer, "\"columnCount\": ");
         write(writer, type->getColumnCount());
-        write(writer, ",\n");
+        comma(writer);
         write(writer, "\"elementType\": ");
         emitReflectionTypeJSON(
             writer,
@@ -624,11 +685,12 @@ static void emitReflectionTypeInfoJSON(
     case slang::TypeReflection::Kind::Array:
         {
             auto arrayType = type;
+            comma(writer);
             write(writer, "\"kind\": \"array\"");
-            write(writer, ",\n");
+            comma(writer);
             write(writer, "\"elementCount\": ");
             write(writer, int(arrayType->getElementCount()));
-            write(writer, ",\n");
+            comma(writer);
             write(writer, "\"elementType\": ");
             emitReflectionTypeJSON(writer, arrayType->getElementType());
         }
@@ -636,7 +698,9 @@ static void emitReflectionTypeInfoJSON(
 
     case slang::TypeReflection::Kind::Struct:
         {
-            write(writer, "\"kind\": \"struct\",\n");
+            comma(writer);
+            write(writer, "\"kind\": \"struct\"");
+            comma(writer);
             write(writer, "\"fields\": [\n");
             indent(writer);
 
@@ -655,11 +719,15 @@ static void emitReflectionTypeInfoJSON(
         break;
 
     case slang::TypeReflection::Kind::GenericTypeParameter:
-        write(writer, "\"kind\": \"GenericTypeParameter\",\n");
+        comma(writer);
+        write(writer, "\"kind\": \"GenericTypeParameter\"");
+        comma(writer);
         emitReflectionNameInfoJSON(writer, type->getName());
         break;
     case slang::TypeReflection::Kind::Interface:
-        write(writer, "\"kind\": \"Interface\",\n");
+        comma(writer);
+        write(writer, "\"kind\": \"Interface\"");
+        comma(writer);
         emitReflectionNameInfoJSON(writer, type->getName());
         break;
     default:
@@ -669,6 +737,66 @@ static void emitReflectionTypeInfoJSON(
     emitUserAttributes(writer, type);
 }
 
+static void emitReflectionParameterGroupTypeLayoutInfoJSON(
+    PrettyWriter&                   writer,
+    slang::TypeLayoutReflection*    typeLayout,
+    const char*                     kind)
+{
+    write(writer, "\"kind\": \"");
+    write(writer, kind);
+    write(writer, "\"");
+
+    write(writer, ",\n\"elementType\": ");
+    emitReflectionTypeLayoutJSON(
+        writer,
+        typeLayout->getElementTypeLayout());
+
+    // Note: There is a subtle detail below when it comes to the
+    // container/element variable layouts that get nested inside
+    // a parameter group type layout.
+    //
+    // A top-level parameter group type layout like `ConstantBuffer<Foo>`
+    // needs to store both information about the `ConstantBuffer` part of
+    // things (e.g., it might consume 1 `binding`), as well as the `Foo`
+    // part (e.g., it might consume 4 bytes plus 1 `binding`), and there
+    // is offset information for each.
+    //
+    // The "element" part is easy: it is a variable layout for a variable
+    // of type `Foo`. The actual variable will be null, but everything else
+    // will be filled in as a client would expect.
+    //
+    // The "container" part is thornier: what should the type and type
+    // layout of the "container" variable be? The obvious answer (which
+    // the Slang reflection implementation uses today) is that the type
+    // is the type of the parameter group itself (e.g., `ConstantBuffer<Foo>`),
+    // and the layout is a dummy `TypeLayout` that just reflects the
+    // resource usage of the "container" part of things.
+    //
+    // That means that at runtime the "container var layout" will have
+    // a parameter group type (e.g., `TYPE_KIND_CONSTANT_BUFFER`)
+    // but its type layotu will be a base `TypeLayout` and not a
+    // `ParameterGroupLayout` (since that would introduce infinite regress).
+    //
+    // We thus have to guard here against the recursive path where
+    // we are emitting reflection info for the "container" part of things.
+    //
+    // TODO: We should probably 
+
+    {
+        CommaTrackerRAII commaTracker(writer);
+
+        write(writer, ",\n\"containerVarLayout\": {\n");
+        indent(writer);
+        emitReflectionVarBindingInfoJSON(writer, typeLayout->getContainerVarLayout());
+        dedent(writer);
+        write(writer, "\n}");
+    }
+
+    write(writer, ",\n\"elementVarLayout\": ");
+    emitReflectionVarLayoutJSON(
+        writer,
+        typeLayout->getElementVarLayout());
+}
 
 static void emitReflectionTypeLayoutInfoJSON(
     PrettyWriter&                   writer,
@@ -684,18 +812,22 @@ static void emitReflectionTypeLayoutInfoJSON(
         {
             auto arrayTypeLayout = typeLayout;
             auto elementTypeLayout = arrayTypeLayout->getElementTypeLayout();
+            comma(writer);
             write(writer, "\"kind\": \"array\"");
-            write(writer, ",\n");
+
+            comma(writer);
             write(writer, "\"elementCount\": ");
             write(writer, int(arrayTypeLayout->getElementCount()));
-            write(writer, ",\n");
+
+            comma(writer);
             write(writer, "\"elementType\": ");
             emitReflectionTypeLayoutJSON(
                 writer,
                 elementTypeLayout);
+
             if (arrayTypeLayout->getSize(SLANG_PARAMETER_CATEGORY_UNIFORM) != 0)
             {
-                write(writer, ",\n");
+                comma(writer);
                 write(writer, "\"uniformStride\": ");
                 write(writer, int(arrayTypeLayout->getElementStride(SLANG_PARAMETER_CATEGORY_UNIFORM)));
             }
@@ -706,12 +838,14 @@ static void emitReflectionTypeLayoutInfoJSON(
         {
             auto structTypeLayout = typeLayout;
 
-            write(writer, "\"kind\": \"struct\",\n");
+            comma(writer);
+            write(writer, "\"kind\": \"struct\"");
             if( auto name = structTypeLayout->getName() )
             {
+                comma(writer);
                 emitReflectionNameInfoJSON(writer, structTypeLayout->getName());
-                write(writer, ",\n");
             }
+            comma(writer);
             write(writer, "\"fields\": [\n");
             indent(writer);
 
@@ -731,48 +865,39 @@ static void emitReflectionTypeLayoutInfoJSON(
         break;
 
     case slang::TypeReflection::Kind::ConstantBuffer:
-        write(writer, "\"kind\": \"constantBuffer\"");
-        write(writer, ",\n");
-        write(writer, "\"elementType\": ");
-        emitReflectionTypeLayoutJSON(
-            writer,
-            typeLayout->getElementTypeLayout());
+        emitReflectionParameterGroupTypeLayoutInfoJSON(writer, typeLayout, "constantBuffer");
         break;
 
     case slang::TypeReflection::Kind::ParameterBlock:
-        write(writer, "\"kind\": \"parameterBlock\"");
-        write(writer, ",\n");
-        write(writer, "\"elementType\": ");
-        emitReflectionTypeLayoutJSON(
-            writer,
-            typeLayout->getElementTypeLayout());
+        emitReflectionParameterGroupTypeLayoutInfoJSON(writer, typeLayout, "parameterBlock");
         break;
 
     case slang::TypeReflection::Kind::TextureBuffer:
-        write(writer, "\"kind\": \"textureBuffer\"");
-        write(writer, ",\n");
-        write(writer, "\"elementType\": ");
-        emitReflectionTypeLayoutJSON(
-            writer,
-            typeLayout->getElementTypeLayout());
+        emitReflectionParameterGroupTypeLayoutInfoJSON(writer, typeLayout, "textureBuffer");
         break;
 
     case slang::TypeReflection::Kind::ShaderStorageBuffer:
+        comma(writer);
         write(writer, "\"kind\": \"shaderStorageBuffer\"");
-        write(writer, ",\n");
+
+        comma(writer);
         write(writer, "\"elementType\": ");
         emitReflectionTypeLayoutJSON(
             writer,
             typeLayout->getElementTypeLayout());
         break;
     case slang::TypeReflection::Kind::GenericTypeParameter:
+        comma(writer);
         write(writer, "\"kind\": \"GenericTypeParameter\"");
-        write(writer, ",\n");
+
+        comma(writer);
         emitReflectionNameInfoJSON(writer, typeLayout->getName());
         break;
     case slang::TypeReflection::Kind::Interface:
-        write(writer, "\"kind\": \"Interface\",\n");
-        write(writer, ",\n");
+        comma(writer);
+        write(writer, "\"kind\": \"Interface\"");
+
+        comma(writer);
         emitReflectionNameInfoJSON(writer, typeLayout->getName());
         break;
 
@@ -792,7 +917,7 @@ static void emitReflectionTypeLayoutInfoJSON(
 
                 if( auto resultTypeLayout = typeLayout->getElementTypeLayout() )
                 {
-                    write(writer, ",\n");
+                    comma(writer);
                     write(writer, "\"resultType\": ");
                     emitReflectionTypeLayoutJSON(
                         writer,
@@ -812,6 +937,7 @@ static void emitReflectionTypeLayoutJSON(
     PrettyWriter&                   writer,
     slang::TypeLayoutReflection*    typeLayout)
 {
+    CommaTrackerRAII commaTracker(writer);
     write(writer, "{\n");
     indent(writer);
     emitReflectionTypeLayoutInfoJSON(writer, typeLayout);
@@ -823,6 +949,7 @@ static void emitReflectionTypeJSON(
     PrettyWriter&           writer,
     slang::TypeReflection*  type)
 {
+    CommaTrackerRAII commaTracker(writer);
     write(writer, "{\n");
     indent(writer);
     emitReflectionTypeInfoJSON(writer, type);
@@ -847,16 +974,25 @@ static void emitReflectionParamJSON(
     PrettyWriter&                       writer,
     slang::VariableLayoutReflection*    param)
 {
+    // TODO: This function is likely redundant with `emitReflectionVarLayoutJSON`
+    // and we should try to collapse them into one.
+
     write(writer, "{\n");
     indent(writer);
 
-    emitReflectionNameInfoJSON(writer, param->getName());
+    CommaTrackerRAII commaTracker(writer);
+
+    if( auto name = param->getName() )
+    {
+        comma(writer);
+        emitReflectionNameInfoJSON(writer, name);
+    }
 
     emitReflectionModifierInfoJSON(writer, param->getVariable());
 
     emitReflectionVarBindingInfoJSON(writer, param);
-    write(writer, ",\n");
 
+    comma(writer);
     write(writer, "\"type\": ");
     emitReflectionTypeLayoutJSON(writer, param->getTypeLayout());
 
@@ -931,6 +1067,7 @@ static void emitReflectionTypeParamJSON(
         if (ee != 0) write(writer, ",\n");
         write(writer, "{\n");
         indent(writer);
+        CommaTrackerRAII commaTracker(writer);
         emitReflectionTypeInfoJSON(writer, typeParam->getConstraintByIndex(ee));
         dedent(writer);
         write(writer, "\n}");
@@ -983,6 +1120,11 @@ static void emitReflectionEntryPointJSON(
     {
         write(writer, ",\n\"usesAnySampleRateInput\": true");
     }
+    if( auto resultVarLayout = entryPoint->getResultVarLayout() )
+    {
+        write(writer, ",\n\"result:\": ");
+        emitReflectionParamJSON(writer, resultVarLayout);
+    }
 
     if (entryPoint->getStage() == SLANG_STAGE_COMPUTE)
     {