Re: [Qemu-devel] [PATCH v8 16/18] qapi: Move duplicate enum value checks to schema check()

[Markus Armbruster]

Eric Blake <address@hidden> writes:

> Similar to the previous commit, move the detection of a collision
> in enum values from parse time to QAPISchemaEnumType.check().
> This happens to also detect collisions in union branch names,
> so for a decent error message, we have to determine if the enum
> is implicit (and if so where the real collision lies).
>
> Testing this showed that the test union-bad-branch and
> union-clash-branches were basically testing the same thing;
> with the minor difference that the former clashes only in the
> enum, while the latter also clashes in the C union member
> names that would be generated. So delete the weaker test.
>
> No change to generated code.
>
> Signed-off-by: Eric Blake <address@hidden>
>
> ---
> v8: rebase to earlier changes; better comments
> v7: retitle and improve commit message; earlier subclass patches
> avoid problem with detecting 'kind' collision
> v6: new patch
> ---
>  scripts/qapi.py                            | 54 
> +++++++++++++-----------------
>  tests/Makefile                             |  1 -
>  tests/qapi-schema/alternate-clash.err      |  2 +-
>  tests/qapi-schema/enum-clash-member.err    |  2 +-
>  tests/qapi-schema/enum-max-member.err      |  2 +-
>  tests/qapi-schema/union-bad-branch.err     |  1 -
>  tests/qapi-schema/union-bad-branch.exit    |  1 -
>  tests/qapi-schema/union-bad-branch.json    |  8 -----
>  tests/qapi-schema/union-bad-branch.out     |  0
>  tests/qapi-schema/union-clash-branches.err |  2 +-
>  tests/qapi-schema/union-clash-type.err     |  2 +-
>  tests/qapi-schema/union-max.err            |  2 +-
>  12 files changed, 29 insertions(+), 48 deletions(-)
>  delete mode 100644 tests/qapi-schema/union-bad-branch.err
>  delete mode 100644 tests/qapi-schema/union-bad-branch.exit
>  delete mode 100644 tests/qapi-schema/union-bad-branch.json
>  delete mode 100644 tests/qapi-schema/union-bad-branch.out
>
> diff --git a/scripts/qapi.py b/scripts/qapi.py
> index 144dd4a..b21e38e 100644
> --- a/scripts/qapi.py
> +++ b/scripts/qapi.py
> @@ -527,7 +527,6 @@ def check_union(expr, expr_info):
>      base = expr.get('base')
>      discriminator = expr.get('discriminator')
>      members = expr['data']
> -    values = {'MAX': '(automatic)', 'KIND': '(automatic)'}

Stupid / tired question: I can see 'MAX' in the new code further down,
but I can't see 'KIND'.  Why?  Was it perhaps covered by the previous
patch?

>
>      # Two types of unions, determined by discriminator.
>
> @@ -587,34 +586,16 @@ def check_union(expr, expr_info):
>                                      "enum '%s'" %
>                                      (key, enum_define["enum_name"]))
>
> -        # Otherwise, check for conflicts in the generated enum
> -        else:
> -            c_key = camel_to_upper(key)
> -            if c_key in values:
> -                raise QAPIExprError(expr_info,
> -                                    "Union '%s' member '%s' clashes with 
> '%s'"
> -                                    % (name, key, values[c_key]))
> -            values[c_key] = key
> -
>
>  def check_alternate(expr, expr_info):
>      name = expr['alternate']
>      members = expr['data']
> -    values = {'MAX': '(automatic)'}
>      types_seen = {}
>
>      # Check every branch
>      for (key, value) in members.items():
>          check_name(expr_info, "Member of alternate '%s'" % name, key)
>
> -        # Check for conflicts in the generated enum
> -        c_key = camel_to_upper(key)
> -        if c_key in values:
> -            raise QAPIExprError(expr_info,
> -                                "Alternate '%s' member '%s' clashes with 
> '%s'"
> -                                % (name, key, values[c_key]))
> -        values[c_key] = key
> -
>          # Ensure alternates have no type conflicts.
>          check_type(expr_info, "Member '%s' of alternate '%s'" % (key, name),
>                     value,
> @@ -633,7 +614,6 @@ def check_enum(expr, expr_info):
>      name = expr['enum']
>      members = expr.get('data')
>      prefix = expr.get('prefix')
> -    values = {'MAX': '(automatic)'}
>
>      if not isinstance(members, list):
>          raise QAPIExprError(expr_info,
> @@ -644,12 +624,6 @@ def check_enum(expr, expr_info):
>      for member in members:
>          check_name(expr_info, "Member of enum '%s'" % name, member,
>                     enum_member=True)
> -        key = camel_to_upper(member)
> -        if key in values:
> -            raise QAPIExprError(expr_info,
> -                                "Enum '%s' member '%s' clashes with '%s'"
> -                                % (name, member, values[key]))
> -        values[key] = member
>
>
>  def check_struct(expr, expr_info):
> @@ -878,7 +852,26 @@ class QAPISchemaEnumType(QAPISchemaType):
>          self.prefix = prefix
>
>      def check(self, schema):
> -        assert len(set(self.values)) == len(self.values)
> +        # Check for collisions on the generated C enum values
> +        seen = {c_enum_const(self.name, 'MAX'): '(automatic MAX)'}
> +        for value in self.values:
> +            c_value = c_enum_const(self.name, value)
> +            if c_value in seen:
> +                # If the enum is implicit, report the error on behalf of
> +                # the union or alternate that triggered the enum
> +                if self.is_implicit():
> +                    owner = schema.lookup_type(self.name[:-4])
> +                    assert owner
> +                    if isinstance(owner, QAPISchemaAlternateType):
> +                        description = "Alternate '%s' branch" % owner.name
> +                    else:
> +                        description = "Union '%s' branch" % owner.name
> +                else:
> +                    description = "Enum '%s' value" % self.name

Computing a reasonable description distracts from the checking job.
Suggest to outline this into a private method.

> +                raise QAPIExprError(self.info,
> +                                    "%s '%s' clashes with '%s'"
> +                                    % (description, value, seen[c_value]))
> +            seen[c_value] = value
>
>      def is_implicit(self):
>          # See QAPISchema._make_implicit_enum_type()
> @@ -1084,10 +1077,9 @@ class 
> QAPISchemaObjectTypeVariant(QAPISchemaObjectTypeMember):
>      # solely by their different tag_type
>      def check(self, schema, info, tag_type, seen, union):
>          # Check that the branch name does not collide with non-variant C
> -        # members, without modifying caller's copy of seen
> -        # TODO Detect collisions between branch names in C - easiest
> -        # will be to check instead for collisions in the corresponding
> -        # enum type
> +        # members, without modifying caller's copy of seen.  Collisions
> +        # between branch names in C is detected elsewhere, when validating
> +        # that the correpsonding enum of tag_type has no collision.
>          QAPISchemaObjectTypeMember.check(self, schema, info, [], dict(seen))
>          assert self.name in tag_type.values
>
> diff --git a/tests/Makefile b/tests/Makefile
> index 35a63f3..2cd5d31 100644
> --- a/tests/Makefile
> +++ b/tests/Makefile
> @@ -331,7 +331,6 @@ qapi-schema += unclosed-list.json
>  qapi-schema += unclosed-object.json
>  qapi-schema += unclosed-string.json
>  qapi-schema += unicode-str.json
> -qapi-schema += union-bad-branch.json
>  qapi-schema += union-base-no-discriminator.json
>  qapi-schema += union-clash-branches.json
>  qapi-schema += union-clash-data.json
> diff --git a/tests/qapi-schema/alternate-clash.err 
> b/tests/qapi-schema/alternate-clash.err
> index a475ab6..7fd3069 100644
> --- a/tests/qapi-schema/alternate-clash.err
> +++ b/tests/qapi-schema/alternate-clash.err
> @@ -1 +1 @@
> -tests/qapi-schema/alternate-clash.json:7: Alternate 'Alt1' member 'a_b' 
> clashes with 'a-b'
> +tests/qapi-schema/alternate-clash.json:7: Alternate 'Alt1' branch 'a_b' 
> clashes with 'a-b'

Our terminology isn't consistent: we use both "branch" and "case".  Not
this patch's problem to fix.

> diff --git a/tests/qapi-schema/enum-clash-member.err 
> b/tests/qapi-schema/enum-clash-member.err
> index 48bd136..84030c5 100644
> --- a/tests/qapi-schema/enum-clash-member.err
> +++ b/tests/qapi-schema/enum-clash-member.err
> @@ -1 +1 @@
> -tests/qapi-schema/enum-clash-member.json:2: Enum 'MyEnum' member 'ONE' 
> clashes with 'one'
> +tests/qapi-schema/enum-clash-member.json:2: Enum 'MyEnum' value 'ONE' 
> clashes with 'one'

I actually prefer calling ONE a member of MyEnum, because that leaves
value for its actual value.

For what it's worth, the C standard also talks about "members of an
enumeration".

> diff --git a/tests/qapi-schema/enum-max-member.err 
> b/tests/qapi-schema/enum-max-member.err
> index f77837f..6b9ef9b 100644
> --- a/tests/qapi-schema/enum-max-member.err
> +++ b/tests/qapi-schema/enum-max-member.err
> @@ -1 +1 @@
> -tests/qapi-schema/enum-max-member.json:3: Enum 'MyEnum' member 'max' clashes 
> with '(automatic)'
> +tests/qapi-schema/enum-max-member.json:3: Enum 'MyEnum' value 'max' clashes 
> with '(automatic MAX)'

(automatic MAX) is a slight improvement over (automatic).

> diff --git a/tests/qapi-schema/union-bad-branch.err 
> b/tests/qapi-schema/union-bad-branch.err
> deleted file mode 100644
> index 8822735..0000000
> --- a/tests/qapi-schema/union-bad-branch.err
> +++ /dev/null
> @@ -1 +0,0 @@
> -tests/qapi-schema/union-bad-branch.json:6: Union 'MyUnion' member 'ONE' 
> clashes with 'one'
> diff --git a/tests/qapi-schema/union-bad-branch.exit 
> b/tests/qapi-schema/union-bad-branch.exit
> deleted file mode 100644
> index d00491f..0000000
> --- a/tests/qapi-schema/union-bad-branch.exit
> +++ /dev/null
> @@ -1 +0,0 @@
> -1
> diff --git a/tests/qapi-schema/union-bad-branch.json 
> b/tests/qapi-schema/union-bad-branch.json
> deleted file mode 100644
> index 913aa38..0000000
> --- a/tests/qapi-schema/union-bad-branch.json
> +++ /dev/null
> @@ -1,8 +0,0 @@
> -# we reject normal unions where branches would collide in C
> -{ 'struct': 'One',
> -  'data': { 'string': 'str' } }
> -{ 'struct': 'Two',
> -  'data': { 'number': 'int' } }
> -{ 'union': 'MyUnion',
> -  'data': { 'one': 'One',
> -            'ONE': 'Two' } }
> diff --git a/tests/qapi-schema/union-bad-branch.out 
> b/tests/qapi-schema/union-bad-branch.out
> deleted file mode 100644
> index e69de29..0000000
> diff --git a/tests/qapi-schema/union-clash-branches.err 
> b/tests/qapi-schema/union-clash-branches.err
> index 005c48d..d8f1265 100644
> --- a/tests/qapi-schema/union-clash-branches.err
> +++ b/tests/qapi-schema/union-clash-branches.err
> @@ -1 +1 @@
> -tests/qapi-schema/union-clash-branches.json:4: Union 'TestUnion' member 
> 'a_b' clashes with 'a-b'
> +tests/qapi-schema/union-clash-branches.json:4: Union 'TestUnion' branch 
> 'a_b' clashes with 'a-b'
> diff --git a/tests/qapi-schema/union-clash-type.err 
> b/tests/qapi-schema/union-clash-type.err
> index a5dead1..ce7f8cd 100644
> --- a/tests/qapi-schema/union-clash-type.err
> +++ b/tests/qapi-schema/union-clash-type.err
> @@ -1 +1 @@
> -tests/qapi-schema/union-clash-type.json:8: Union 'TestUnion' member 'kind' 
> clashes with '(automatic)'
> +tests/qapi-schema/union-clash-type.json:8: 'kind' (branch of TestUnion) 
> collides with 'kind' (implicit tag of TestUnion)
> diff --git a/tests/qapi-schema/union-max.err b/tests/qapi-schema/union-max.err
> index 55ce439..b93beae 100644
> --- a/tests/qapi-schema/union-max.err
> +++ b/tests/qapi-schema/union-max.err
> @@ -1 +1 @@
> -tests/qapi-schema/union-max.json:2: Union 'Union' member 'max' clashes with 
> '(automatic)'
> +tests/qapi-schema/union-max.json:2: Union 'Union' branch 'max' clashes with 
> '(automatic MAX)'