qapi: More rigourous checking of types

Now that we know every expression is valid with regards to
its keys, we can add further tests that those keys refer to
valid types. With this patch, all uses of a type (the 'data':
of command, type, union, alternate, and event; the 'returns':
of command; the 'base': of type and union) must resolve to an
appropriate subset of metatypes declared by the current qapi
parse; this includes recursing into each member of a data
dictionary. Dealing with '**' and nested anonymous structs
will be done in later patches.

Backports commit dd883c6f0547f02ae805d02852ff3691f6d08f85 from qemu

qemu/scripts/qapi.py

@@ -276,6 +276,64 @@ def discriminator_find_enum_define(expr):
 
     return find_enum(discriminator_type)
 
+def check_type(expr_info, source, value, allow_array = False,
+               allow_dict = False, allow_metas = []):
+    global all_names
+    orig_value = value
+
+    if value is None:
+        return
+
+    if value == '**':
+        return
+
+    # Check if array type for value is okay
+    if isinstance(value, list):
+        if not allow_array:
+            raise QAPIExprError(expr_info,
+                                "%s cannot be an array" % source)
+        if len(value) != 1 or not isinstance(value[0], str):
+            raise QAPIExprError(expr_info,
+                                "%s: array type must contain single type name"
+                                % source)
+        value = value[0]
+        orig_value = "array of %s" %value
+
+    # Check if type name for value is okay
+    if isinstance(value, str):
+        if not value in all_names:
+            raise QAPIExprError(expr_info,
+                                "%s uses unknown type '%s'"
+                                % (source, orig_value))
+        if not all_names[value] in allow_metas:
+            raise QAPIExprError(expr_info,
+                                "%s cannot use %s type '%s'"
+                                % (source, all_names[value], orig_value))
+        return
+
+    # value is a dictionary, check that each member is okay
+    if not isinstance(value, OrderedDict):
+        raise QAPIExprError(expr_info,
+                            "%s should be a dictionary" % source)
+    if not allow_dict:
+        raise QAPIExprError(expr_info,
+                            "%s should be a type name" % source)
+    for (key, arg) in value.items():
+        check_type(expr_info, "Member '%s' of %s" % (key, source), arg,
+                   allow_array=True, allow_dict=True,
+                   allow_metas=['built-in', 'union', 'alternate', 'struct',
+                                'enum'])
+
+def check_command(expr, expr_info):
+    name = expr['command']
+    check_type(expr_info, "'data' for command '%s'" % name,
+               expr.get('data'), allow_dict=True,
+               allow_metas=['union', 'struct'])
+    check_type(expr_info, "'returns' for command '%s'" % name,
+               expr.get('returns'), allow_array=True, allow_dict=True,
+               allow_metas=['built-in', 'union', 'alternate', 'struct',
+                            'enum'])
+
 def check_event(expr, expr_info):
     global events
     name = expr['event']
@@ -284,6 +342,9 @@ def check_event(expr, expr_info):
     if name.upper() == 'MAX':
         raise QAPIExprError(expr_info, "Event name 'MAX' cannot be created")
     events.append(name)
+    check_type(expr_info, "'data' for event '%s'" % name,
+               expr.get('data'), allow_dict=True,
+               allow_metas=['union', 'struct'])
 
     if params:
         for argname, argentry, optional, structured in parse_args(params):
@@ -313,6 +374,7 @@ def check_union(expr, expr_info):
     # With no discriminator it is a simple union.
     if discriminator is None:
         enum_define = None
+        allow_metas=['built-in', 'union', 'alternate', 'struct', 'enum']
         if base is not None:
             raise QAPIExprError(expr_info,
                                 "Simple union '%s' must not have a base"
@@ -343,6 +405,7 @@ def check_union(expr, expr_info):
                                 "type '%s'"
                                 % (discriminator, base))
         enum_define = find_enum(discriminator_type)
+        allow_metas=['struct']
         # Do not allow string discriminator
         if not enum_define:
             raise QAPIExprError(expr_info,
@@ -351,6 +414,11 @@ def check_union(expr, expr_info):
 
     # Check every branch
     for (key, value) in members.items():
+        # Each value must name a known type; furthermore, in flat unions,
+        # branches must be a struct
+        check_type(expr_info, "Member '%s' of union '%s'" % (key, name),
+                   value, allow_array=True, allow_metas=allow_metas)
+
         # If the discriminator names an enum type, then all members
         # of 'data' must also be members of the enum type.
         if enum_define:
@@ -386,15 +454,11 @@ def check_alternate(expr, expr_info):
         values[c_key] = key
 
         # Ensure alternates have no type conflicts.
-        if isinstance(value, list):
-            raise QAPIExprError(expr_info,
-                                "Alternate '%s' member '%s' must "
-                                "not be array type" % (name, key))
+        check_type(expr_info, "Member '%s' of alternate '%s'" % (key, name),
+                   value,
+                   allow_metas=['built-in', 'union', 'struct', 'enum'])
         qtype = find_alternate_member_qtype(value)
-        if not qtype:
-            raise QAPIExprError(expr_info,
-                                "Alternate '%s' member '%s' has "
-                                "invalid type '%s'" % (name, key, value))
+        assert qtype
         if qtype in types_seen:
             raise QAPIExprError(expr_info,
                                 "Alternate '%s' member '%s' can't "
@@ -422,6 +486,15 @@ def check_enum(expr, expr_info):
                                 % (name, member, values[key]))
         values[key] = member
 
+def check_struct(expr, expr_info):
+    name = expr['type']
+    members = expr['data']
+
+    check_type(expr_info, "'data' for type '%s'" % name, members,
+               allow_dict=True)
+    check_type(expr_info, "'base' for type '%s'" % name, expr.get('base'),
+               allow_metas=['struct'])
+
 def check_exprs(schema):
     for expr_elem in schema.exprs:
         expr = expr_elem['expr']
@@ -433,8 +506,14 @@ def check_exprs(schema):
             check_union(expr, info)
         elif expr.has_key('alternate'):
             check_alternate(expr, info)
+        elif expr.has_key('type'):
+            check_struct(expr, info)
+        elif expr.has_key('command'):
+            check_command(expr, info)
         elif expr.has_key('event'):
             check_event(expr, info)
+        else:
+            assert False, 'unexpected meta type'
 
 def check_keys(expr_elem, meta, required, optional=[]):
     expr = expr_elem['expr']