Re: [Qemu-devel] [PATCH V9 07/10] qapi script: support enum type as discriminator in union

[Wenchao Xia <wenchaoqemu@gmail.com>]

于 2014/3/6 16:25, Markus Armbruster 写道:
> Wenchao Xia <wenchaoqemu@gmail.com> writes:
>
>> By default, any union will automatically generate a enum type as
>> "[UnionName]Kind" in C code, and it is duplicated when the discriminator
>> is specified as a pre-defined enum type in schema. After this patch,
>> the pre-defined enum type will be really used as the switch case
>> condition in generated C code, if discriminator is an enum field.
>>
>> Signed-off-by: Wenchao Xia <wenchaoqemu@gmail.com>
>> Reviewed-by: Eric Blake <eblake@redhat.com>
>> ---
>>  docs/qapi-code-gen.txt                           |    8 ++++-
>>  scripts/qapi-types.py                            |   18 +++++++++---
>>  scripts/qapi-visit.py                            |   29 +++++++++++++------
>>  scripts/qapi.py                                  |   32 +++++++++++++++++++++-
>>  tests/Makefile                                   |    2 +-
>>  tests/qapi-schema/flat-union-reverse-define.exit |    1 +
>>  tests/qapi-schema/flat-union-reverse-define.json |   17 +++++++++++
>>  tests/qapi-schema/flat-union-reverse-define.out  |    9 ++++++
>>  8 files changed, 99 insertions(+), 17 deletions(-)
>>  create mode 100644 tests/qapi-schema/flat-union-reverse-define.err
>>  create mode 100644 tests/qapi-schema/flat-union-reverse-define.exit
>>  create mode 100644 tests/qapi-schema/flat-union-reverse-define.json
>>  create mode 100644 tests/qapi-schema/flat-union-reverse-define.out
>>
>> diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt
>> index 0728f36..a2e7921 100644
>> --- a/docs/qapi-code-gen.txt
>> +++ b/docs/qapi-code-gen.txt
>> @@ -123,11 +123,15 @@ And it looks like this on the wire:
>>  
>>  Flat union types avoid the nesting on the wire. They are used whenever a
>>  specific field of the base type is declared as the discriminator ('type' is
>> -then no longer generated). The discriminator must always be a string field.
>> +then no longer generated). The discriminator can be a string field or a
>> +predefined enum field. If it is a string field, a hidden enum type will be
>> +generated as "[UNION_NAME]Kind". If it is an enum field, a compile time check
>> +will be done to verify the correctness. It is recommended to use an enum field.
>>  The above example can then be modified as follows:
>>  
>> + { 'enum': 'BlockdevDriver', 'data': [ 'raw', 'qcow2' ] }
>>   { 'type': 'BlockdevCommonOptions',
>> -   'data': { 'driver': 'str', 'readonly': 'bool' } }
>> +   'data': { 'driver': 'BlockdevDriver', 'readonly': 'bool' } }
>>   { 'union': 'BlockdevOptions',
>>     'base': 'BlockdevCommonOptions',
>>     'discriminator': 'driver',
>> diff --git a/scripts/qapi-types.py b/scripts/qapi-types.py
>> index 5885bac..10864ef 100644
>> --- a/scripts/qapi-types.py
>> +++ b/scripts/qapi-types.py
>> @@ -201,14 +201,21 @@ def generate_union(expr):
>>      base = expr.get('base')
>>      discriminator = expr.get('discriminator')
>>  
>> +    enum_define = discriminator_find_enum_define(expr)
>> +    if enum_define:
>> +        discriminator_type_name = enum_define['enum_name']
>> +    else:
>> +        discriminator_type_name = '%sKind' % (name)
>> +
>>      ret = mcgen('''
>>  struct %(name)s
>>  {
>> -    %(name)sKind kind;
>> +    %(discriminator_type_name)s kind;
>>      union {
>>          void *data;
>>  ''',
>> -                name=name)
>> +                name=name,
>> +                discriminator_type_name=discriminator_type_name)
>>  
>>      for key in typeinfo:
>>          ret += mcgen('''
>> @@ -389,8 +396,11 @@ for expr in exprs:
>>          fdef.write(generate_enum_lookup(expr['enum'], expr['data']))
>>      elif expr.has_key('union'):
>>          ret += generate_fwd_struct(expr['union'], expr['data']) + "\n"
>> -        ret += generate_enum('%sKind' % expr['union'], expr['data'].keys())
>> -        fdef.write(generate_enum_lookup('%sKind' % expr['union'], expr['data'].keys()))
>> +        enum_define = discriminator_find_enum_define(expr)
>> +        if not enum_define:
>> +            ret += generate_enum('%sKind' % expr['union'], expr['data'].keys())
>> +            fdef.write(generate_enum_lookup('%sKind' % expr['union'],
>> +                                            expr['data'].keys()))
>>          if expr.get('discriminator') == {}:
>>              fdef.write(generate_anon_union_qtypes(expr))
>>      else:
>> diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py
>> index 0baaf60..45ce3a9 100644
>> --- a/scripts/qapi-visit.py
>> +++ b/scripts/qapi-visit.py
>> @@ -259,10 +259,16 @@ def generate_visit_union(expr):
>>          assert not base
>>          return generate_visit_anon_union(name, members)
>>  
>> -    # There will always be a discriminator in the C switch code, by default it
>> -    # is an enum type generated silently as "'%sKind' % (name)"
>> -    ret = generate_visit_enum('%sKind' % name, members.keys())
>> -    disc_type = '%sKind' % (name)
>> +    enum_define = discriminator_find_enum_define(expr)
>> +    if enum_define:
>> +        # Use the enum type as discriminator
>> +        ret = ""
>> +        disc_type = enum_define['enum_name']
>> +    else:
>> +        # There will always be a discriminator in the C switch code, by default it
>> +        # is an enum type generated silently as "'%sKind' % (name)"
>> +        ret = generate_visit_enum('%sKind' % name, members.keys())
>> +        disc_type = '%sKind' % (name)
>>  
>>      if base:
>>          base_fields = find_struct(base)['data']
>> @@ -298,15 +304,16 @@ void visit_type_%(name)s(Visitor *m, %(name)s ** obj, const char *name, Error **
>>      pop_indent()
>>  
>>      if not discriminator:
>> -        desc_type = "type"
>> +        disc_key = "type"
>>      else:
>> -        desc_type = discriminator
>> +        disc_key = discriminator
>>      ret += mcgen('''
>> -        visit_type_%(name)sKind(m, &(*obj)->kind, "%(type)s", &err);
>> +        visit_type_%(disc_type)s(m, &(*obj)->kind, "%(disc_key)s", &err);
>>          if (!err) {
>>              switch ((*obj)->kind) {
>>  ''',
>> -                 name=name, type=desc_type)
>> +                 disc_type = disc_type,
>> +                 disc_key = disc_key)
>>  
>>      for key in members:
>>          if not discriminator:
>> @@ -517,7 +524,11 @@ for expr in exprs:
>>          ret += generate_visit_list(expr['union'], expr['data'])
>>          fdef.write(ret)
>>  
>> -        ret = generate_decl_enum('%sKind' % expr['union'], expr['data'].keys())
>> +        enum_define = discriminator_find_enum_define(expr)
>> +        ret = ""
>> +        if not enum_define:
>> +            ret = generate_decl_enum('%sKind' % expr['union'],
>> +                                     expr['data'].keys())
>>          ret += generate_declaration(expr['union'], expr['data'])
>>          fdecl.write(ret)
>>      elif expr.has_key('enum'):
>> diff --git a/scripts/qapi.py b/scripts/qapi.py
>> index eebc8a7..0a504c4 100644
>> --- a/scripts/qapi.py
>> +++ b/scripts/qapi.py
>> @@ -180,6 +180,25 @@ def find_base_fields(base):
>>          return None
>>      return base_struct_define['data']
>>  
>> +# Return the discriminator enum define if discriminator is specified as an
>> +# enum type, otherwise return None.
>> +def discriminator_find_enum_define(expr):
>> +    base = expr.get('base')
>> +    discriminator = expr.get('discriminator')
>> +
>> +    if not (discriminator and base):
>> +        return None
>> +
>> +    base_fields = find_base_fields(base)
>> +    if not base_fields:
>> +        return None
>> +
>> +    discriminator_type = base_fields.get(discriminator)
>> +    if not discriminator_type:
>> +        return None
>> +
>> +    return find_enum(discriminator_type)
>> +
>>  def check_union(expr, expr_info):
>>      name = expr['union']
>>      base = expr.get('base')
>> @@ -254,11 +273,22 @@ def parse_schema(fp):
>>              add_enum(expr['enum'], expr['data'])
>>          elif expr.has_key('union'):
>>              add_union(expr)
>> -            add_enum('%sKind' % expr['union'])
>>          elif expr.has_key('type'):
>>              add_struct(expr)
>>          exprs.append(expr)
>>  
>> +    # Try again for hidden UnionKind enum
>> +    for expr_elem in schema.exprs:
>> +        expr = expr_elem['expr']
>> +        if expr.has_key('union'):
>> +            try:
>> +                enum_define = discriminator_find_enum_define(expr)
>> +            except QAPIExprError, e:
>> +                print >>sys.stderr, e
>> +                exit(1)
> How can we get QAPIExprError here?
>
Ops, for this version Exception wouldn't happen, I forgot
to remove the "try except". It should be simply:

+    # Try again for hidden UnionKind enum
+    for expr_elem in schema.exprs:
+        expr = expr_elem['expr']
+        if expr.has_key('union'):
+            enum_define = discriminator_find_enum_define(expr)

Luiz, do you mind apply this series and correct above directly?
>> +            if not enum_define:
>> +                add_enum('%sKind' % expr['union'])
>> +
>>      try:
>>          check_exprs(schema)
>>      except QAPIExprError, e:
> [...]