Support nullable types in mojom.

mojo/public/tools/bindings/pylib/mojom/generate/module.py

 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # This module's classes provide an interface to mojo modules. Modules are
 # collections of interfaces and structs to be used by mojo ipc clients and
 # servers.
 #
 # A simple interface would be created this way:
 # module = mojom.generate.module.Module('Foo')
 # interface = module.AddInterface('Bar')
 # method = interface.AddMethod('Tat', 0)
 # method.AddParameter('baz', 0, mojom.INT32)
 #
 
+
 class Kind(object):
   def __init__(self, spec=None):
     self.spec = spec
     self.parent_kind = None
 
+
+class ReferenceKind(Kind):
+  """ReferenceKind represents pointer types and handle types.
+     A type is nullable means that NULL (for pointer types) or invalid handle
+     (for handle types) is a legal value for the type.
+  """
+
+  def __init__(self, spec=None, is_nullable=False):
+    assert spec is None or is_nullable == spec.startswith('?')
+    Kind.__init__(self, spec)
+    self.is_nullable = is_nullable
+
+
 # Initialize the set of primitive types. These can be accessed by clients.
-BOOL         = Kind('b')
-INT8         = Kind('i8')
-INT16        = Kind('i16')
-INT32        = Kind('i32')
-INT64        = Kind('i64')
-UINT8        = Kind('u8')
-UINT16       = Kind('u16')
-UINT32       = Kind('u32')
-UINT64       = Kind('u64')
-FLOAT        = Kind('f')
-DOUBLE       = Kind('d')
-STRING       = Kind('s')
-HANDLE       = Kind('h')
-DCPIPE       = Kind('h:d:c')
-DPPIPE       = Kind('h:d:p')
-MSGPIPE      = Kind('h:m')
-SHAREDBUFFER = Kind('h:s')
+BOOL              = Kind('b')
+INT8              = Kind('i8')
+INT16             = Kind('i16')
+INT32             = Kind('i32')
+INT64             = Kind('i64')
+UINT8             = Kind('u8')
+UINT16            = Kind('u16')
+UINT32            = Kind('u32')
+UINT64            = Kind('u64')
+FLOAT             = Kind('f')
+DOUBLE            = Kind('d')
+STRING            = ReferenceKind('s')
+HANDLE            = ReferenceKind('h')
+DCPIPE            = ReferenceKind('h:d:c')
+DPPIPE            = ReferenceKind('h:d:p')
+MSGPIPE           = ReferenceKind('h:m')
+SHAREDBUFFER      = ReferenceKind('h:s')
+NLBL_STRING       = ReferenceKind('?s', True)
+NLBL_HANDLE       = ReferenceKind('?h', True)
+NLBL_DCPIPE       = ReferenceKind('?h:d:c', True)
+NLBL_DPPIPE       = ReferenceKind('?h:d:p', True)
+NLBL_MSGPIPE      = ReferenceKind('?h:m', True)
+NLBL_SHAREDBUFFER = ReferenceKind('?h:s', True)
 
 
 # Collection of all Primitive types
 PRIMITIVES = (
   BOOL,
   INT8,
   INT16,
   INT32,
   INT64,
   UINT8,
   UINT16,
   UINT32,
   UINT64,
   FLOAT,
   DOUBLE,
   STRING,
   HANDLE,
   DCPIPE,
   DPPIPE,
   MSGPIPE,
-  SHAREDBUFFER
+  SHAREDBUFFER,
+  NLBL_STRING,
+  NLBL_HANDLE,
+  NLBL_DCPIPE,
+  NLBL_DPPIPE,
+  NLBL_MSGPIPE,
+  NLBL_SHAREDBUFFER
 )
 
 
 class NamedValue(object):
   def __init__(self, module, parent_kind, name):
     self.module = module
     self.namespace = module.namespace
     self.parent_kind = parent_kind
     self.name = name
     self.imported_from = None
@@ skipping 23 matching lines @@
 
 
 class Field(object):
   def __init__(self, name=None, kind=None, ordinal=None, default=None):
     self.name = name
     self.kind = kind
     self.ordinal = ordinal
     self.default = default
 
 
-class Struct(Kind):
+class Struct(ReferenceKind):
   def __init__(self, name=None, module=None):
     self.name = name
     self.module = module
     self.imported_from = None
     if name is not None:
       spec = 'x:' + name
     else:
       spec = None
-    Kind.__init__(self, spec)
+    ReferenceKind.__init__(self, spec)
     self.fields = []
 
   def AddField(self, name, kind, ordinal=None, default=None):
     field = Field(name, kind, ordinal, default)
     self.fields.append(field)
     return field
 
 
-class Array(Kind):
+class Array(ReferenceKind):
   def __init__(self, kind=None):
     self.kind = kind
     if kind is not None:
-      Kind.__init__(self, 'a:' + kind.spec)
+      ReferenceKind.__init__(self, 'a:' + kind.spec)
     else:
-      Kind.__init__(self)
+      ReferenceKind.__init__(self)
 
-class FixedArray(Kind):
-  def __init__(self, length, kind=None):
+
+class FixedArray(ReferenceKind):
+  def __init__(self, length=-1, kind=None):
     self.kind = kind
     self.length = length
     if kind is not None:
-      Kind.__init__(self, 'a' + length + ':' + kind.spec)
+      ReferenceKind.__init__(self, 'a%d:%s' % (length, kind.spec))
     else:
-      Kind.__init__(self)
+      ReferenceKind.__init__(self)
 
-class InterfaceRequest(Kind):
+
+class InterfaceRequest(ReferenceKind):
   def __init__(self, kind=None):
     self.kind = kind
     if kind is not None:
-      Kind.__init__(self, 'r:' + kind.spec)
+      ReferenceKind.__init__(self, 'r:' + kind.spec)
     else:
-      Kind.__init__(self)
+      ReferenceKind.__init__(self)
 
 
 class Parameter(object):
   def __init__(self, name=None, kind=None, ordinal=None, default=None):
     self.name = name
     self.ordinal = ordinal
     self.kind = kind
     self.default = default
 
 
@@ skipping 11 matching lines @@
     return parameter
 
   def AddResponseParameter(self, name, kind, ordinal=None, default=None):
     if self.response_parameters == None:
       self.response_parameters = []
     parameter = Parameter(name, kind, ordinal, default)
     self.response_parameters.append(parameter)
     return parameter
 
 
-class Interface(Kind):
+class Interface(ReferenceKind):
   def __init__(self, name=None, client=None, module=None):
     self.module = module
     self.name = name
     self.imported_from = None
     if name is not None:
       spec = 'x:' + name
     else:
       spec = None
-    Kind.__init__(self, spec)
+    ReferenceKind.__init__(self, spec)
     self.client = client
     self.methods = []
 
   def AddMethod(self, name, ordinal=None):
     method = Method(self, name, ordinal=ordinal)
     self.methods.append(method)
     return method
 
 
 class EnumField(object):
@@ skipping 25 matching lines @@
 
   def AddInterface(self, name):
     interface=Interface(name, module=self);
     self.interfaces.append(interface)
     return interface
 
   def AddStruct(self, name):
     struct=Struct(name, module=self)
     self.structs.append(struct)
     return struct
+
+
+def MakeNullableKind(ref_kind):
+  assert isinstance(ref_kind, ReferenceKind)
+  assert not ref_kind.is_nullable
+
+  if ref_kind == STRING:
+    return NLBL_STRING
+  if ref_kind == HANDLE:
+    return NLBL_HANDLE
+  if ref_kind == DCPIPE:
+    return NLBL_DCPIPE
+  if ref_kind == DPPIPE:
+    return NLBL_DPPIPE
+  if ref_kind == MSGPIPE:
+    return NLBL_MSGPIPE
+  if ref_kind == SHAREDBUFFER:
+    return NLBL_SHAREDBUFFER
+
+  nullable_kind = type(ref_kind)()
+  # Make a shallow copy of the instance's attributes.
+  nullable_kind.__dict__  = ref_kind.__dict__.copy()

[yzshen1, 2014/08/05 05:11:43]

Hmm... Thinking more about this solution and it seems pretty hacky. :/

|ref_kind| is subject to change after calling MakeNullableKind(), e.g., the
|fields| attribute is filled. A shallow copy happens to work for this case
because |nullable_kind| and |ref_kind| points to the same list . However, if we
change the code to assign a new list to |fields|, |nullable_kind| and |ref_kind|
will be out of sync.

Maybe the previous solution makes more sense (having Nullable as a wrapper class
which points to a Struct/Array/etc. kind). Hmm...

[yzshen1, 2014/08/06 21:39:27]

I think I have addressed this issue in the latest patch. Please take a look.

+  if ref_kind.spec is not None:
+    nullable_kind.spec = '?' + ref_kind.spec
+  nullable_kind.is_nullable = True
+
+  return nullable_kind