Re: [Qemu-devel] [PATCH v8 12/18] qapi: Track location that created an implicit type

[Markus Armbruster <armbru@redhat.com>]

Eric Blake <eblake@redhat.com> writes:

> A future patch will move some error checking from the parser
> to the various QAPISchema*.check() methods, which run only
> after parsing completes.  It will thus be possible to create
> a python instance representing an implicit QAPI type that
> parses fine but will fail validation during check().  Since
> all errors have to have an associated 'info' location, we
> need a location to be associated with those implicit types.
> The intuitive info to use is the location of the enclosing
> entity that caused the creation of the implicit type; similar
> to what was done for array types in an earlier patch.
>
> Note that we do not anticipate builtin types being used in
> an error message (as they are not part of the user's QAPI
> input, the user can't cause a semantic error in their
> behavior), so we exempt those types from requiring info, by
> setting a flag to track the completion of _def_predefineds(),
> and tracking that flag in _def_entity().
>
> No change to the generated code.
>
> Signed-off-by: Eric Blake <eblake@redhat.com>
>
> ---
> v8: rebase to earlier changes, improve comment, rework predefined
> flag name
> v7: better commit message and comments, fix info assertion to
> use instance flag rather than ugly leaky abstraction static flag
> v6: improve commit message, track implicit enum info, rebase
> on new lazy array handling
> ---
>  scripts/qapi.py | 32 ++++++++++++++++++--------------
>  1 file changed, 18 insertions(+), 14 deletions(-)
>
> diff --git a/scripts/qapi.py b/scripts/qapi.py
> index 80c026b..c9ce9ee 100644
> --- a/scripts/qapi.py
> +++ b/scripts/qapi.py
> @@ -793,9 +793,9 @@ class QAPISchemaEntity(object):
>          # For explicitly defined entities, info points to the (explicit)
>          # definition.  For builtins (and their arrays), info is None.
>          # For other arrays, info points to an explicit place that uses
> -        # the array (there may be more than one such place).
> -        # TODO For other implicitly defined entities, it should point to
> -        # a place that triggers implicit definition.
> +        # the array (there may be more than one such place).  For other
> +        # implicitly defined entities, it points to the place that
> +        # triggered the implicit definition.

How does info for implicitly defined arrays differ from info for other
implicitly defined entities?  I suspect it doesn't, and this comment
should become simpler:

        # For explicitly defined entities, info points to the (explicit)
        # definition.  For builtins (and their arrays), info is None.
        # For implicitly defined entities, info points to a place that
        # triggered the implicit definition (there may be more than one
        # such place).

>          self.info = info
>
>      def c_name(self):
[...]