qapi: More rigorous checking for type safety bypass

Now that we have a way to validate every type, we can also be
stricter about enforcing that callers that want to bypass
type safety in generated code.  Prior to this patch, it didn't
matter what value was associated with the key 'gen', but it
looked odd that 'gen':'yes' could result in bypassing the
generated code.  These changes also enforce the changes made
earlier in the series for documentation and consolidation of
using '**' as the wildcard type, as well as 'gen':false as the
canonical spelling for requesting type bypass.

Note that 'gen':false is a one-way switch away from the default;
we do not support 'gen':true (similar for 'success-response').
In practice, this doesn't matter.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

scripts/qapi.py

@@ -324,14 +324,15 @@ def check_name(expr_info, source, name, allow_optional = False,
                             "%s uses invalid name '%s'" % (source, name))
 
 def check_type(expr_info, source, value, allow_array = False,
-               allow_dict = False, allow_optional = False, allow_metas = []):
+               allow_dict = False, allow_optional = False,
+               allow_star = False, allow_metas = []):
     global all_names
     orig_value = value
 
     if value is None:
         return
 
-    if value == '**':
+    if allow_star and value == '**':
         return
 
     # Check if array type for value is okay
@@ -348,6 +349,10 @@ def check_type(expr_info, source, value, allow_array = False,
 
     # Check if type name for value is okay
     if isinstance(value, str):
+        if value == '**':
+            raise QAPIExprError(expr_info,
+                                "%s uses '**' but did not request 'gen':false"
+                                % source)
         if not value in all_names:
             raise QAPIExprError(expr_info,
                                 "%s uses unknown type '%s'"
@@ -371,19 +376,22 @@ def check_type(expr_info, source, value, allow_array = False,
         check_type(expr_info, "Member '%s' of %s" % (key, source), arg,
                    allow_array=True, allow_dict=True, allow_optional=True,
                    allow_metas=['built-in', 'union', 'alternate', 'struct',
-                                'enum'])
+                                'enum'], allow_star=allow_star)
 
 def check_command(expr, expr_info):
     name = expr['command']
+    allow_star = expr.has_key('gen')
+
     check_type(expr_info, "'data' for command '%s'" % name,
                expr.get('data'), allow_dict=True, allow_optional=True,
-               allow_metas=['union', 'struct'])
+               allow_metas=['union', 'struct'], allow_star=allow_star)
     returns_meta = ['union', 'struct']
     if name in returns_whitelist:
         returns_meta += ['built-in', 'alternate', 'enum']
     check_type(expr_info, "'returns' for command '%s'" % name,
                expr.get('returns'), allow_array=True, allow_dict=True,
-               allow_optional=True, allow_metas=returns_meta)
+               allow_optional=True, allow_metas=returns_meta,
+               allow_star=allow_star)
 
 def check_event(expr, expr_info):
     global events
@@ -579,6 +587,10 @@ def check_keys(expr_elem, meta, required, optional=[]):
             raise QAPIExprError(info,
                                 "Unknown key '%s' in %s '%s'"
                                 % (key, meta, name))
+        if (key == 'gen' or key == 'success-response') and value != False:
+            raise QAPIExprError(info,
+                                "'%s' of %s '%s' should only use false value"
+                                % (key, meta, name))
     for key in required:
         if not expr.has_key(key):
             raise QAPIExprError(info,

tests/qapi-schema/type-bypass-bad-gen.err

@@ -0,0 +1 @@
+tests/qapi-schema/type-bypass-bad-gen.json:2: 'gen' of command 'foo' should only use false value

tests/qapi-schema/type-bypass-bad-gen.exit

@@ -1 +1 @@
-0
+1

tests/qapi-schema/type-bypass-bad-gen.json

@@ -1,2 +1,2 @@
-# FIXME: 'gen' should only appear with value false
+# 'gen' should only appear with value false
 { 'command': 'foo', 'gen': 'whatever' }

tests/qapi-schema/type-bypass-bad-gen.out

@@ -1,3 +0,0 @@
-[OrderedDict([('command', 'foo'), ('gen', 'whatever')])]
-[]
-[]

tests/qapi-schema/type-bypass-no-gen.err

@@ -0,0 +1 @@
+tests/qapi-schema/type-bypass-no-gen.json:2: Member 'arg' of 'data' for command 'unsafe' uses '**' but did not request 'gen':false

tests/qapi-schema/type-bypass-no-gen.exit

@@ -1 +1 @@
-0
+1

tests/qapi-schema/type-bypass-no-gen.json

@@ -1,2 +1,2 @@
-# FIXME: type bypass should only work with 'gen':false
+# type bypass only works with 'gen':false
 { 'command': 'unsafe', 'data': { 'arg': '**' }, 'returns': '**' }

tests/qapi-schema/type-bypass-no-gen.out

@@ -1,3 +0,0 @@
-[OrderedDict([('command', 'unsafe'), ('data', OrderedDict([('arg', '**')])), ('returns', '**')])]
-[]
-[]