Re: [PATCH 04/14] qapi: Split up check_type()

[Eric Blake <eblake@redhat.com>]

On Thu, Mar 16, 2023 at 08:13:15AM +0100, Markus Armbruster wrote:
> check_type() can check type names, arrays, and implicit struct types.
> Callers pass flags to select from this menu.  This makes the function
> somewhat hard to read.  Moreover, a few minor bugs are hiding in
> there, as we'll see shortly.
> 
> Split it into check_type_name(), check_type_name_or_implicit().  Each

You omitted check_type_name_or_array() in this summary

> of them is a copy of the original specialized to a certain set of
> flags.
> 
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> ---
>  scripts/qapi/expr.py | 116 +++++++++++++++++++++++++------------------
>  1 file changed, 67 insertions(+), 49 deletions(-)

> 
> diff --git a/scripts/qapi/expr.py b/scripts/qapi/expr.py
> index 59bdd86024..bc04bf34c2 100644
> --- a/scripts/qapi/expr.py
> +++ b/scripts/qapi/expr.py
> @@ -333,62 +333,74 @@ def normalize_members(members: object) -> None:
>              members[key] = {'type': arg}
>  
>  
> -def check_type(value: Optional[object],
> -               info: QAPISourceInfo,
> -               source: str,
> -               allow_array: bool = False,
> -               allow_dict: Union[bool, str] = False) -> None:

There are few enough callers to see that they do indeed have exactly
one of (nearly) three call patterns.

> -    """
> -    Normalize and validate the QAPI type of ``value``.
> -
> -    Python types of ``str`` or ``None`` are always allowed.
> -
> -    :param value: The value to check.
> -    :param info: QAPI schema source file information.
> -    :param source: Error string describing this ``value``.
> -    :param allow_array:
> -        Allow a ``List[str]`` of length 1, which indicates an array of
> -        the type named by the list element.
> -    :param allow_dict:
> -        Allow a dict.  Its members can be struct type members or union
> -        branches.  When the value of ``allow_dict`` is in pragma
> -        ``member-name-exceptions``, the dict's keys may violate the
> -        member naming rules.  The dict members are normalized in place.
> -
> -    :raise QAPISemError: When ``value`` fails validation.
> -    :return: None, ``value`` is normalized in-place as needed.
> -    """
> +def check_type_name(value: Optional[object],
> +                    info: QAPISourceInfo, source: str) -> None:

check_type_name() replaces callers that relied on the default for
allow_array and allow_dict

> +    if value is None:

Loses out on the documentation.  Not sure how much that matters to
you?

> +        return
> +
> +    if isinstance(value, str):
> +        return
> +
> +    if isinstance(value, list):
> +        raise QAPISemError(info, "%s cannot be an array" % source)
> +
> +    raise QAPISemError(info, "%s should be a type name" % source)
> +
> +
> +def check_type_name_or_array(value: Optional[object],
> +                             info: QAPISourceInfo, source: str) -> None:

check_type_name_or_array() replaces all callers that passed
allow_array=True.

>      if value is None:

Another copy without documentation.

>          return
>  
> -    # Type name
>      if isinstance(value, str):
>          return
>  
> -    # Array type
>      if isinstance(value, list):
> -        if not allow_array:
> -            raise QAPISemError(info, "%s cannot be an array" % source)
>          if len(value) != 1 or not isinstance(value[0], str):
>              raise QAPISemError(info,
>                                 "%s: array type must contain single type name" %
>                                 source)
>          return
>  
> -    # Anonymous type
> +    raise QAPISemError(info,
> +                       "%s should be a type name" % source)
>  
> -    if not allow_dict:
> -        raise QAPISemError(info, "%s should be a type name" % source)
> +
> +def check_type_name_or_implicit(value: Optional[object],
> +                                info: QAPISourceInfo, source: str,
> +                                parent_name: Optional[str]) -> None:

And check_type_name_or_implicit replaces all callers that passed
allow_dict=str, where str is now the parent_name.  (Wow, that was an
odd overload of the parameter name - I like the split version better).

...
> @@ -560,10 +572,13 @@ def check_command(expr: QAPIExpression) -> None:
>      rets = expr.get('returns')
>      boxed = expr.get('boxed', False)
>  
> -    if boxed and args is None:
> -        raise QAPISemError(expr.info, "'boxed': true requires 'data'")
> -    check_type(args, expr.info, "'data'", allow_dict=not boxed)
> -    check_type(rets, expr.info, "'returns'", allow_array=True)
> +    if boxed:
> +        if args is None:
> +            raise QAPISemError(expr.info, "'boxed': true requires 'data'")
> +        check_type_name(args, expr.info, "'data'")
> +    else:
> +        check_type_name_or_implicit(args, expr.info, "'data'", None)

And this use of allow_dict was the weirdest, where it really does fit
better as calls into two separate functions.

With the fixed commit message, and with or without more function docs,

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
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