Re: [PATCH 12/16] qapi/expr.py: Add docstrings

[John Snow <jsnow@redhat.com>]

On 9/24/20 8:59 PM, Cleber Rosa wrote:
> On Tue, Sep 22, 2020 at 05:13:09PM -0400, John Snow wrote:
>> Signed-off-by: John Snow <jsnow@redhat.com>
>> ---
>>   scripts/qapi/expr.py | 157 ++++++++++++++++++++++++++++++++++++++++++-
>>   1 file changed, 155 insertions(+), 2 deletions(-)
>>
>> diff --git a/scripts/qapi/expr.py b/scripts/qapi/expr.py
>> index f244e9648c..4bba09f6e5 100644
>> --- a/scripts/qapi/expr.py
>> +++ b/scripts/qapi/expr.py
>> @@ -1,7 +1,5 @@
>>   # -*- coding: utf-8 -*-
>>   #
>> -# Check (context-free) QAPI schema expression structure
>> -#
>>   # Copyright IBM, Corp. 2011
>>   # Copyright (c) 2013-2019 Red Hat Inc.
>>   #
>> @@ -14,6 +12,25 @@
>>   # This work is licensed under the terms of the GNU GPL, version 2.
>>   # See the COPYING file in the top-level directory.
>>   
>> +"""
>> +Normalize and validate (context-free) QAPI schema expression structures.
>> +
>> +After QAPI expressions are parsed from disk, they are stored in
>> +recursively nested Python data structures using Dict, List, str, bool,
>> +and int. This module ensures that those nested structures have the
>> +correct type(s) and key(s) where appropriate for the QAPI context-free
>> +grammar.
>> +
>> +The QAPI schema expression language also allows for syntactic sugar;
>> +this module also handles the normalization process of these nested
>> +structures.
>> +
>> +See `check_exprs` for the main entry point.
>> +
>> +See `schema.QAPISchema` for processing into native Python data
>> +structures and contextual semantic validation.
>> +"""
>> +
>>   import re
>>   from typing import (
>>       Iterable,
>> @@ -46,6 +63,7 @@
>>   def check_name_is_str(name: object,
>>                         info: QAPISourceInfo,
>>                         source: str) -> None:
>> +    """Ensures that `name` is a string. [Const]"""
>>       if not isinstance(name, str):
>>           raise QAPISemError(info, "%s requires a string name" % source)
>>   
>> @@ -56,6 +74,24 @@ def check_name_str(name: str,
>>                      allow_optional: bool = False,
>>                      enum_member: bool = False,
>>                      permit_upper: bool = False) -> None:
>> +    """
>> +    Ensures a string is a legal name. [Const]
>> +
>> +    A name is legal in the default case when:
>> +    - It matches ``(__[a-z0-9.-]+_)?[a-z][a-z0-9_-]*``
>> +    - It does not start with ``q_`` or ``q-``
>> +
>> +    :param name:           Name to check.
>> +    :param info:           QAPI source file information.
>> +    :param source:         Human-readable str describing "what" this name is.
>> +    :param allow_optional: Allow the very first character to be ``*``.
>> +                           (Cannot be used with `enum_member`)
>> +    :param enum_member:    Allow the very first character to be a digit.
>> +                           (Cannot be used with `allow_optional`)
>> +    :param permit_upper:   Allows upper-case characters wherever
>> +                           lower-case characters are allowed.
>> +    """
>> +    assert not (allow_optional and enum_member)
>>       membername = name
>>   
>>       if allow_optional and name.startswith('*'):
>> @@ -76,6 +112,17 @@ def check_name_str(name: str,
>>   
>>   
>>   def check_defn_name_str(name: str, info: QAPISourceInfo, meta: str) -> None:
>> +    """
>> +    Ensures a name is a legal definition name. [Const]
>> +
>> +    A legal definition name:
>> +     - Adheres to the criteria in `check_name_str`, with uppercase permitted
>> +     - Does not end with ``Kind`` or ``List``.
>> +
>> +    :param name: Name to check.
>> +    :param info: QAPI source file information.
>> +    :param meta: Type name of the QAPI expression.
>> +    """
>>       check_name_str(name, info, meta, permit_upper=True)
>>       if name.endswith('Kind') or name.endswith('List'):
>>           raise QAPISemError(
>> @@ -87,6 +134,15 @@ def check_keys(value: _JSObject,
>>                  source: str,
>>                  required: List[str],
>>                  optional: List[str]) -> None:
>> +    """
>> +    Ensures an object has a specific set of keys. [Const]
>> +
>> +    :param value:    The object to check.
>> +    :param info:     QAPI source file information.
>> +    :param source:   Human-readable str describing "what" this object is.
>> +    :param required: Keys that *must* be present.
>> +    :param optional: Keys that *may* be present.
>> +    """
>>   
>>       def pprint(elems: Iterable[str]) -> str:
>>           return ', '.join("'" + e + "'" for e in sorted(elems))
>> @@ -109,6 +165,12 @@ def pprint(elems: Iterable[str]) -> str:
>>   
>>   
>>   def check_flags(expr: Expression, info: QAPISourceInfo) -> None:
>> +    """
>> +    Ensures common fields in an Expression are correct. [Const]
>> +
>> +    :param expr: Expression to validate.
>> +    :param info: QAPI source file information.
>> +    """
>>       for key in ['gen', 'success-response']:
>>           if key in expr and expr[key] is not False:
>>               raise QAPISemError(
>> @@ -120,6 +182,18 @@ def check_flags(expr: Expression, info: QAPISourceInfo) -> None:
>>   
>>   
>>   def check_if(expr: _JSObject, info: QAPISourceInfo, source: str) -> None:
>> +    """
>> +    Syntactically validate and normalize the ``if`` field of an object. [RW]
>> +
>> +    The ``if`` field may be either a `str` or a `List[str]`.
>> +    A `str` element will be normalized to `List[str]`.
>> +
>> +    Sugared: `Union[str, List[str]]`
>> +    Ifcond: `List[str]`
>> +
>> +    :param expr: A `dict`; the ``if`` field, if present, will be validated.
>> +    :param info: QAPI source file information.
>> +    """
>>   
>>       def check_if_str(ifcond: object) -> None:
>>           if not isinstance(ifcond, str):
>> @@ -148,6 +222,16 @@ def check_if_str(ifcond: object) -> None:
>>   
>>   
>>   def normalize_members(members: object) -> None:
>> +    """
>> +    Normalize a "members" value. [RW]
>> +
>> +    If `members` is an object, for every value in that object, if that
>> +    value is not itself already an object, normalize it to
>> +    ``{'type': value}``.
>> +
>> +    Sugared: `Dict[str, Union[str, TypeRef]]`
>> +    Members: `Dict[str, TypeRef]`
>> +    """
>>       if isinstance(members, dict):
>>           for key, arg in members.items():
>>               if isinstance(arg, dict):
>> @@ -160,6 +244,18 @@ def check_type(value: Optional[object],
>>                  source: str,
>>                  allow_array: bool = False,
>>                  allow_dict: Union[bool, str] = False) -> None:
>> +    """
>> +    Check the QAPI type of `value`. [RW]
>> +
>> +    Python types of `str` or `None` are always allowed.
>> +
>> +    :param value:       The value to check.
>> +    :param info:        QAPI Source file information.
>> +    :param source:      Human readable string describing "what" the value is.
>> +    :param allow_array: Allow a `List[str]` of length 1,
>> +                        which indicates an Array<T> type.
>> +    :param allow_dict:  Allow a dict, treated as an anonymous type.
>> +    """
>>       if value is None:
>>           return
>>   
>> @@ -205,6 +301,15 @@ def check_type(value: Optional[object],
>>   
>>   def check_features(features: Optional[object],
>>                      info: QAPISourceInfo) -> None:
>> +    """
>> +    Syntactically validate and normalize the "features" field. [RW]
>> +
>> +    `features` may be a List of either `str` or `dict`.
>> +    Any `str` element will be normalized to `{'name': element}`.
>> +
>> +    Sugared: `List[Union[str, Feature]]`
>> +    Features: `List[Feature]`
>> +    """
>>       if features is None:
>>           return
>>       if not isinstance(features, list):
>> @@ -222,6 +327,12 @@ def check_features(features: Optional[object],
>>   
>>   
>>   def check_enum(expr: Expression, info: QAPISourceInfo) -> None:
>> +    """
>> +    Validate this `Expression` as an ``enum`` expression. [RW]
>> +
>> +    :param expr: `Expression` to validate.
>> +    :param info: QAPI source file information.
>> +    """
>>       name = expr['enum']
>>       members = expr['data']
>>       prefix = expr.get('prefix')
>> @@ -246,6 +357,12 @@ def check_enum(expr: Expression, info: QAPISourceInfo) -> None:
>>   
>>   
>>   def check_struct(expr: Expression, info: QAPISourceInfo) -> None:
>> +    """
>> +    Validate this `Expression` as a ``struct`` expression. [RW]
>> +
>> +    :param expr: `Expression` to validate.
>> +    :param info: QAPI source file information.
>> +    """
>>       name = cast(str, expr['struct'])  # Asserted in check_exprs
>>       members = expr['data']
>>   
>> @@ -254,6 +371,12 @@ def check_struct(expr: Expression, info: QAPISourceInfo) -> None:
>>   
>>   
>>   def check_union(expr: Expression, info: QAPISourceInfo) -> None:
>> +    """
>> +    Validate this `Expression` as a ``union`` expression. [RW]
>> +
>> +    :param expr: `Expression` to validate.
>> +    :param info: QAPI source file information.
>> +    """
>>       name = cast(str, expr['union'])  # Asserted in check_exprs
>>       base = expr.get('base')
>>       discriminator = expr.get('discriminator')
>> @@ -280,6 +403,12 @@ def check_union(expr: Expression, info: QAPISourceInfo) -> None:
>>   
>>   
>>   def check_alternate(expr: Expression, info: QAPISourceInfo) -> None:
>> +    """
>> +    Validate this `Expression` as an ``alternate`` expression. [RW]
>> +
>> +    :param expr: Expression to validate.
>> +    :param info: QAPI source file information.
>> +    """
>>       members = expr['data']
>>   
>>       if not members:
>> @@ -297,6 +426,12 @@ def check_alternate(expr: Expression, info: QAPISourceInfo) -> None:
>>   
>>   
>>   def check_command(expr: Expression, info: QAPISourceInfo) -> None:
>> +    """
>> +    Validate this `Expression` as a ``command`` expression. [RW]
>> +
>> +    :param expr: `Expression` to validate.
>> +    :param info: QAPI source file information.
>> +    """
>>       args = expr.get('data')
>>       rets = expr.get('returns')
>>       boxed = expr.get('boxed', False)
>> @@ -308,6 +443,16 @@ def check_command(expr: Expression, info: QAPISourceInfo) -> None:
>>   
>>   
>>   def check_event(expr: Expression, info: QAPISourceInfo) -> None:
>> +    """
>> +    Normalize and syntactically validate the ``event`` expression. [RW]
>> +
>> +    Event:
>> +        event:    `str`
>> +        data:     `Optional[Dict[str, Member]]`
>> +        boxed:    `Optional[bool]`
>> +        if:       `Optional[Ifcond]`
>> +        features: `Optional[Features]`
>> +    """
>>       args = expr.get('data')
>>       boxed = expr.get('boxed', False)
>>   
>> @@ -317,6 +462,14 @@ def check_event(expr: Expression, info: QAPISourceInfo) -> None:
>>   
>>   
>>   def check_exprs(exprs: List[_JSObject]) -> List[_JSObject]:
>> +    """
>> +    Validate and normalize a list of parsed QAPI schema expressions. [RW]
>> +
>> +    This function accepts a list of expressions + metadta as returned by
>> +    the parser. It destructively normalizes the expressions in-place.
>> +
>> +    :param exprs: The list of expressions to normalize/validate.
>> +    """
> 
> This is a huge improvement already, but maybe also take the
> opportunity to add ":return:" too?  Anyway,
> 
> Reviewed-by: Cleber Rosa <crosa@redhat.com>
> 

Yeah, I can do that. The only reason I added docstrings here -- and 
basically nowhere else -- was I found this code hardest to understand, 
because of the highly dynamic type structures it's dealing with.

So I wrote a bunch of notes for myself, and ... may as well share those.

Thanks!