Re: [PATCH v2 12/16] scripts/qapi: generate high-level Rust bindings

Paolo Bonzini
2026-03-03T10:01:27Z

On 2/25/26 15:39, Markus Armbruster wrote:
>> +def rs_name(name: str) -> str:
>> + """
>> + Map @name to a valid, possibly raw Rust identifier.
>> + """
>> + name = re.sub(r'[^A-Za-z0-9_]', '_', name)
>> + if name[0].isnumeric():
>
> .isdigit()? It's what c_name() uses...
>
>> + name = '_' + name
>
> In review of v1, I pointed to "The Rust Reference"
>
> Identifiers starting with an underscore are typically used to
> indicate an identifier that is intentionally unused, and will
> silence the unused warning in rustc.
>
> https://doc.rust-lang.org/reference/identifiers.html
>
> You replied "In this case it doesn't really matter: public items (such
> as QAPI enum entries, or struct fields) do not raise the unused warning
> anyway."
>
> What gives us confidence rs_name() will only be used where it doesn't
> really matter?

The fact that all QAPI type definitions are (more or less by design) public.

>> + # avoid some clashes with the standard library
>> + if name in ('String',):
>> + name = 'Qapi' + name
>
> This hides the unwise use of 'String' in qapi/net.json from Rust. I'd
> rather rename that one.

Ok, BoxedString?

>> +
>> + return name
>> +
>> +
>> +def to_camel_case(value: str) -> str:
>> + return ''.join('_' + word if word[0].isdigit()
>> + else word[:1].upper() + word[1:]
>> + for word in filter(None, re.split("[-_]+", value)))
>
> Please use r'...' for regular expressions always.
>
> Why do you need filter()?

To handle - or _ at the beginning or ending of a string, where an empty
string would cause an IndexError in word[0].isdigit().

> This maps 'foo-0123-bar' to 'Foo_0123Bar'. Intentional? I'd kind of
> expect 'Foo0123Bar'.

Will fix (it is meant for 0123-45). New version is:

def to_camel_case(value: str) -> str:
result = ''
for p in re.split(r'[-_]+', value):
if not p:
pass
elif p[0].isalpha() or (result and result[-1].isalpha()):
result += p[0].upper() + p[1:]
else:
result += '_' + p
return result

>> +def mcgen(s: str, **kwds: object) -> str:
>> + s = mcgen_common(s, **kwds)
>> + return re.sub(r'(?: *\n)+', '\n', s)
>
> This eats trailing spaces and blank lines. The latter is a big hammer.
> Without it, I see unwanted blank lines generated. With it, I see wanted
> blank lines eaten. For instance:

Ok, I can look into adding rstrip here and there.

>> + except FileNotFoundError:
>> + pass
>
> This runs rustfmt to clean up the generated file. Silently does nothing
> if we don't have rustfmt.
>
> Should we make rustfmt a hard requirement? Please discuss this briefly
> in the commit message.

It's unnecessary, but it does make the output look nicer. If I add
rstrip, I don't need it.

>> + # Return the Rust type for common use
>
> Are the uncommon uses?
>
> There are for C types, and that's why we have both .c_type(),
> .c_param_type(), nad .c_unboxed_type().

Yes, Box<> and Vec<>. They just don't deserve their own function unlike C.

Paolo