Commit 5223070c authored by Wenchao Xia's avatar Wenchao Xia Committed by Luiz Capitulino
Browse files

qapi script: do not allow string discriminator 



Since enum based discriminators provide better type-safety and
ensure that future qapi additions do not forget to adjust dependent
unions, forbid using string as discriminator from now on.

Signed-off-by: default avatarWenchao Xia <wenchaoqemu@gmail.com>
Reviewed-by: default avatarEric Blake <eblake@redhat.com>
Reviewed-by: default avatarMarkus Armbruster <armbru@redhat.com>
Signed-off-by: default avatarLuiz Capitulino <lcapitulino@redhat.com>
parent 59ca664e

docs/qapi-code-gen.txt

+1 −4
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@@ -123,10 +123,7 @@ 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 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.

then no longer generated). The discriminator must be of enumeration type.

The above example can then be modified as follows:



 { 'enum': 'BlockdevDriver', 'data': [ 'raw', 'qcow2' ] }

scripts/qapi.py

+5 −0
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@@ -239,6 +239,11 @@ def check_union(expr, expr_info): 
                                "type '%s'"

                                % (discriminator, base))

        enum_define = find_enum(discriminator_type)

        # Do not allow string discriminator

        if not enum_define:

            raise QAPIExprError(expr_info,

                                "Discriminator '%s' must be of enumeration "

                                "type" % discriminator)



    # Check every branch

    for (key, value) in members.items():

tests/Makefile

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@@ -145,7 +145,8 @@ check-qapi-schema-y := $(addprefix tests/qapi-schema/, \ 
        unclosed-list.json unclosed-object.json unclosed-string.json \

        duplicate-key.json union-invalid-base.json flat-union-no-base.json \

        flat-union-invalid-discriminator.json \

        flat-union-invalid-branch-key.json flat-union-reverse-define.json)

        flat-union-invalid-branch-key.json flat-union-reverse-define.json \

        flat-union-string-discriminator.json)



GENERATED_HEADERS += tests/test-qapi-types.h tests/test-qapi-visit.h tests/test-qmp-commands.h

tests/qapi-schema/flat-union-string-discriminator.err

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<stdin>:13: Discriminator 'kind' must be of enumeration type

tests/qapi-schema/flat-union-string-discriminator.exit

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