Start migrating upb_msglayout to be suitable for generated code.

This involves:

- remove upb_msglayout -> upb_msgfactory dependency.
- remove upb_msglayout -> upb_msgdef dependency (in progress).
- make upb_msglayout use a representation that can be
  statically initialized by generated code.

The goal here is that upb_msglayout becomes a kind of "descriptor
lite": it contains enough data to parser and serialize protobufs
and manipulate a upb_msg in memory, while being far smaller and
simpler than a full descriptor.  It also does not include field
names, which can be a benefit for applications that do not want
to leak field names.

Generated code can then create a upb_msglayout, and do most things
without ever needing to construct full descriptors/defs if they
don't want to.

1 files changed, 21 insertions, 14 deletions

diff --git a/tests/bindings/lua/test_upb.lua b/tests/bindings/lua/test_upb.lua
index 1dc0717..07d794c 100644
--- a/tests/bindings/lua/test_upb.lua
+++ b/tests/bindings/lua/test_upb.lua
@@ -565,13 +565,20 @@ function test_msg_primitives()
 
   local symtab = upb.SymbolTable{
     upb.MessageDef{full_name = "TestMessage", fields = {
-      upb.FieldDef{name = "i32", number = 1, type = upb.TYPE_INT32},
-      upb.FieldDef{name = "u32", number = 2, type = upb.TYPE_UINT32},
-      upb.FieldDef{name = "i64", number = 3, type = upb.TYPE_INT64},
-      upb.FieldDef{name = "u64", number = 4, type = upb.TYPE_UINT64},
-      upb.FieldDef{name = "dbl", number = 5, type = upb.TYPE_DOUBLE},
-      upb.FieldDef{name = "flt", number = 6, type = upb.TYPE_FLOAT},
-      upb.FieldDef{name = "bool", number = 7, type = upb.TYPE_BOOL},
+      upb.FieldDef{
+          name = "i32", number = 1, type = upb.TYPE_INT32, default = 1},
+      upb.FieldDef{
+          name = "u32", number = 2, type = upb.TYPE_UINT32, default = 2},
+      upb.FieldDef{
+          name = "i64", number = 3, type = upb.TYPE_INT64, default = 3},
+      upb.FieldDef{
+          name = "u64", number = 4, type = upb.TYPE_UINT64, default = 4},
+      upb.FieldDef{
+          name = "dbl", number = 5, type = upb.TYPE_DOUBLE, default = 5},
+      upb.FieldDef{
+          name = "flt", number = 6, type = upb.TYPE_FLOAT, default = 6},
+      upb.FieldDef{
+          name = "bool", number = 7, type = upb.TYPE_BOOL, default = true},
       }
     }
   }
@@ -581,13 +588,13 @@ function test_msg_primitives()
   msg = TestMessage()
 
   -- Unset member returns default value.
-  assert_equal(0, msg.i32)
-  assert_equal(0, msg.u32)
-  assert_equal(0, msg.i64)
-  assert_equal(0, msg.u64)
-  assert_equal(0, msg.dbl)
-  assert_equal(0, msg.flt)
-  assert_equal(false, msg.bool)
+  assert_equal(1, msg.i32)
+  assert_equal(2, msg.u32)
+  assert_equal(3, msg.i64)
+  assert_equal(4, msg.u64)
+  assert_equal(5, msg.dbl)
+  assert_equal(6, msg.flt)
+  assert_equal(true, msg.bool)
 
   -- Attempts to access non-existent fields fail.
   assert_error_match("no such field", function() msg.no_such = 1 end)