[Qemu-devel] [PATCH RFC v5 32/32] qapi-introspect: Hide type names

[Markus Armbruster <armbru@redhat.com>]

To eliminate the temptation for clients to look up types by name
(which are not ABI), replace all type names by meaningless strings.

Reduces output of query-schema by 13 out of 85KiB.

As a debugging aid, provide option -u to suppress the hiding.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
---
 docs/qapi-code-gen.txt     | 36 +++++++++++++++++-------------------
 qapi/introspect.json       | 11 +++--------
 scripts/qapi-introspect.py | 41 +++++++++++++++++++++++++++++++++++------
 3 files changed, 55 insertions(+), 33 deletions(-)

diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt
index 458b217..01e292b 100644
--- a/docs/qapi-code-gen.txt
+++ b/docs/qapi-code-gen.txt
@@ -522,13 +522,16 @@ additional variant members depending on the value of meta-type.
 Each SchemaInfo object describes a wire ABI entity of a certain
 meta-type: a command, event or one of several kinds of type.
 
-SchemaInfo for entities defined in the QAPI schema have the same name
-as in the schema.  This is the case for all commands and events, and
-most types.
+SchemaInfo for commands and events have the same name as in the QAPI
+schema.
 
 Command and event names are part of the wire ABI, but type names are
-not.  Therefore, looking up a type by its name in the QAPI schema is
-wrong.  Look up the command or event, then follow references by name.
+not.  Therefore, the SchemaInfo for types have auto-generated
+meaningless names.  For readability, the examples in this section use
+meaningful type names instead.
+
+To examine a type, start with a command or event using it, then follow
+references by name.
 
 QAPI schema definitions not reachable that way are omitted.
 
@@ -559,8 +562,7 @@ object type without members.  The event may not have a data member on
 the wire then.
 
 Each command or event defined with dictionary-valued 'data' in the
-QAPI schema implicitly defines an object type called ":obj-NAME-arg",
-where NAME is the command or event's name.
+QAPI schema implicitly defines an object type.
 
 Example: the SchemaInfo for EVENT_C from section Events
 
@@ -615,12 +617,9 @@ Note that base types are "flattened": its members are included in the
 
 A simple union implicitly defines an enumeration type for its implicit
 discriminator (called "type" on the wire, see section Union types).
-Such a type's name is made by appending "Kind" to the simple union's
-name.
 
 A simple union implicitly defines an object type for each of its
-variants.  The type's name is ":obj-NAME-wrapper", where NAME is the
-name of the name of the variant's type.
+variants.
 
 Example: the SchemaInfo for simple union BlockdevOptions from section
 Union types
@@ -651,8 +650,7 @@ Example: the SchemaInfo for BlockRef from section Alternate types
 
 The SchemaInfo for an array type has meta-type "array", and variant
 member "element-type", which names the array's element type.  Array
-types are implicitly defined.  An array type's name is made by
-appending "List" to its element type's name.
+types are implicitly defined.
 
 Example: the SchemaInfo for ['str']
 
@@ -1059,13 +1057,13 @@ Example:
 [Uninteresting stuff omitted...]
 
     const char example_qmp_schema_json[] = "["
-        "{\"arg-type\": \":empty\", \"meta-type\": \"event\", \"name\": \"MY_EVENT\"}, "
+        "{\"arg-type\": \"0\", \"meta-type\": \"event\", \"name\": \"MY_EVENT\"}, "
+        "{\"arg-type\": \"1\", \"meta-type\": \"command\", \"name\": \"my-command\", \"ret-type\": \"2\"}, "
+        "{\"members\": [], \"meta-type\": \"object\", \"name\": \"0\"}, "
+        "{\"members\": [{\"name\": \"arg1\", \"type\": \"2\"}], \"meta-type\": \"object\", \"name\": \"1\"}, "
+        "{\"members\": [{\"name\": \"integer\", \"type\": \"int\"}, {\"name\": \"string\", \"type\": \"str\"}], \"meta-type\": \"object\", \"name\": \"2\"}, "
         "{\"json-type\": \"int\", \"meta-type\": \"builtin\", \"name\": \"int\"}, "
-        "{\"json-type\": \"string\", \"meta-type\": \"builtin\", \"name\": \"str\"}, "
-        "{\"members\": [], \"meta-type\": \"object\", \"name\": \":empty\"}, "
-        "{\"members\": [{\"name\": \"arg1\", \"type\": \"UserDefOne\"}], \"meta-type\": \"object\", \"name\": \":obj-my-command-arg\"}, "
-        "{\"members\": [{\"name\": \"integer\", \"type\": \"int\"}, {\"name\": \"string\", \"type\": \"str\"}], \"meta-type\": \"object\", \"name\": \"UserDefOne\"}, "
-        "{\"arg-type\": \":obj-my-command-arg\", \"meta-type\": \"command\", \"name\": \"my-command\", \"ret-type\": \"UserDefOne\"}]";
+        "{\"json-type\": \"string\", \"meta-type\": \"builtin\", \"name\": \"str\"}]";
     $ cat qapi-generated/example-qmp-introspect.h
 [Uninteresting stuff omitted...]
 
diff --git a/qapi/introspect.json b/qapi/introspect.json
index 5b4713b..d6faa11 100644
--- a/qapi/introspect.json
+++ b/qapi/introspect.json
@@ -75,17 +75,12 @@
 # @SchemaInfo
 #
 # @name: the entity's name, inherited from @base.
-# Entities defined in the QAPI schema have the name defined in the schema.
-# Implicitly defined entities have generated names.  See
-# docs/qapi-code-gen.txt section "Client JSON Protocol introspection"
-# for details.
+# Commands and events have the name defined in the QAPI schema.
+# Unlike command and event names, type names are not part of the wire
+# ABI.  Consequently, type names are meaningless strings here.
 #
 # All references to other SchemaInfo are by name.
 #
-# Command and event names are part of the wire ABI, but type names are
-# not.  Therefore, looking up a type by "well-known" name is wrong.
-# Look up the command or event, then follow the references.
-#
 # @meta-type: the entity's meta type, inherited from @base.
 #
 # Additional members depend on the value of @meta-type.
diff --git a/scripts/qapi-introspect.py b/scripts/qapi-introspect.py
index 1bc26f0..ce98321 100644
--- a/scripts/qapi-introspect.py
+++ b/scripts/qapi-introspect.py
@@ -40,32 +40,37 @@ def to_c_string(string):
 
 
 class QAPISchemaGenIntrospectVisitor(QAPISchemaVisitor):
-    def __init__(self):
+    def __init__(self, unmask):
+        self._unmask = unmask
         self.defn = None
         self.decl = None
         self._schema = None
         self._jsons = None
         self._used_types = None
+        self._name_map = None
 
     def visit_begin(self, schema):
         self._schema = schema
         self._jsons = []
         self._used_types = []
+        self._name_map = {}
         return QAPISchemaType   # don't visit types for now
 
     def visit_end(self):
         # visit the types that are actually used
+        jsons = self._jsons
+        self._jsons = []
         for typ in self._used_types:
             typ.visit(self)
-        self._jsons.sort()
         # generate C
         # TODO can generate awfully long lines
+        jsons.extend(self._jsons)
         name = prefix + 'qmp_schema_json'
         self.decl = mcgen('''
 extern const char %(c_name)s[];
 ''',
                           c_name=c_name(name))
-        lines = to_json(self._jsons).split('\n')
+        lines = to_json(jsons).split('\n')
         c_string = '\n    '.join([to_c_string(line) for line in lines])
         self.defn = mcgen('''
 const char %(c_name)s[] = %(c_string)s;
@@ -75,6 +80,14 @@ const char %(c_name)s[] = %(c_string)s;
         self._schema = None
         self._jsons = None
         self._used_types = None
+        self._name_map = None
+
+    def _name(self, name):
+        if self._unmask:
+            return name
+        if name not in self._name_map:
+            self._name_map[name] = '%d' % len(self._name_map)
+        return self._name_map[name]
 
     def _use_type(self, typ):
         # Map the various integer types to plain int
@@ -86,9 +99,16 @@ const char %(c_name)s[] = %(c_string)s;
         # Add type to work queue if new
         if typ not in self._used_types:
             self._used_types.append(typ)
-        return typ.name
+        # Clients should examine commands and events, not types.  Hide
+        # type names to reduce the temptation.  Also saves a few
+        # characters.
+        if isinstance(typ, QAPISchemaBuiltinType):
+            return typ.name
+        return self._name(typ.name)
 
     def _gen_json(self, name, mtype, obj):
+        if mtype != 'command' and mtype != 'event' and mtype != 'builtin':
+            name = self._name(name)
         obj['name'] = name
         obj['meta-type'] = mtype
         self._jsons.append(obj)
@@ -140,7 +160,16 @@ const char %(c_name)s[] = %(c_string)s;
         arg_type = arg_type or self._schema.the_empty_object_type
         self._gen_json(name, 'event', {'arg-type': self._use_type(arg_type)})
 
-(input_file, output_dir, do_c, do_h, prefix, dummy) = parse_command_line()
+# Debugging aid: unmask QAPI schema's type names
+# We normally mask them, because they're not QMP wire ABI
+opt_unmask = False
+
+(input_file, output_dir, do_c, do_h, prefix, opts) = \
+    parse_command_line("u", ["unmask-non-abi-names"])
+
+for o, a in opts:
+    if o in ("-u", "--unmask-non-abi-names"):
+        opt_unmask = True
 
 c_comment = '''
 /*
@@ -176,7 +205,7 @@ fdef.write(mcgen('''
                  prefix=prefix))
 
 schema = QAPISchema(input_file)
-gen = QAPISchemaGenIntrospectVisitor()
+gen = QAPISchemaGenIntrospectVisitor(opt_unmask)
 schema.visit(gen)
 fdef.write(gen.defn)
 fdecl.write(gen.decl)
-- 
2.4.3