Shorten binary serialization for true and false (#256)

Fixes #225

Author: leregdos

scrapscript.py

@@ -984,6 +984,8 @@ class Variant(Object):
     TYPE_ACCESS := b"@",
     TYPE_SPREAD := b"S",
     TYPE_NAMED_SPREAD := b"R",
+    TYPE_TRUE := b"T",
+    TYPE_FALSE := b"F",
 ]
 FLAG_REF = 0x80
 
@@ -1091,6 +1093,10 @@ def serialize(self, obj: Object) -> None:
                 self.serialize(item)
             return
         if isinstance(obj, Variant):
+            if obj.tag == "true" and isinstance(obj.value, Hole):
+                return self.emit(TYPE_TRUE)
+            if obj.tag == "false" and isinstance(obj.value, Hole):
+                return self.emit(TYPE_FALSE)
             # TODO(max): Determine if this should be a ref
             self.emit(TYPE_VARIANT)
             # TODO(max): String pool (via refs) for strings longer than some length?
@@ -1329,6 +1335,12 @@ def parse(self) -> Object:
             return Spread()
         if ty == TYPE_NAMED_SPREAD:
             return Spread(self._string())
+        if ty == TYPE_TRUE:
+            assert not is_ref
+            return Variant("true", Hole())
+        if ty == TYPE_FALSE:
+            assert not is_ref
+            return Variant("false", Hole())
         raise NotImplementedError(bytes(ty))
 
 
@@ -2531,7 +2543,7 @@ def do_GET(self) -> None:
             if scrap is not None:
                 self.send_response(200)
                 self.send_header("Content-Type", "application/scrap; charset=binary")
-                self.send_header("Content-Disposition", f'attachment; filename={json.dumps(f"{path}.scrap")}')
+                self.send_header("Content-Disposition", f"attachment; filename={json.dumps(f'{path}.scrap')}")
                 self.send_header("Content-Length", str(len(scrap)))
                 self.end_headers()
                 self.wfile.write(scrap)

scrapscript_tests.py

@@ -3778,6 +3778,22 @@ def test_access(self) -> None:
     def test_spread(self) -> None:
         self.assertEqual(self._serialize(Spread()), TYPE_SPREAD)
         self.assertEqual(self._serialize(Spread("rest")), TYPE_NAMED_SPREAD + b"\x08rest")
+    
+    def test_true_variant(self) -> None:
+        obj = Variant("true", Hole())
+        self.assertEqual(self._serialize(obj), TYPE_TRUE)
+
+    def test_false_variant(self) -> None:
+        obj = Variant("false", Hole())
+        self.assertEqual(self._serialize(obj), TYPE_FALSE)
+
+    def test_true_variant_with_non_hole_uses_regular_variant(self) -> None:
+        obj = Variant("true", Int(123))
+        self.assertEqual(self._serialize(obj), TYPE_VARIANT + b"\x08truei\xf6\x01")
+
+    def test_false_variant_with_non_hole_uses_regular_variant(self) -> None:
+        obj = Variant("false", Int(123))
+        self.assertEqual(self._serialize(obj), TYPE_VARIANT + b"\x0afalsei\xf6\x01")
 
 
 class RoundTripSerializationTests(unittest.TestCase):