pyo3_macros_backend/
module.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
//! Code generation for the function that initializes a python module and adds classes and function.

use crate::{
    attributes::{
        self, kw, take_attributes, take_pyo3_options, CrateAttribute, ModuleAttribute,
        NameAttribute, SubmoduleAttribute,
    },
    get_doc,
    pyclass::PyClassPyO3Option,
    pyfunction::{impl_wrap_pyfunction, PyFunctionOptions},
    utils::{has_attribute, has_attribute_with_namespace, Ctx, IdentOrStr, LitCStr},
};
use proc_macro2::{Span, TokenStream};
use quote::quote;
use std::ffi::CString;
use syn::{
    ext::IdentExt,
    parse::{Parse, ParseStream},
    parse_quote, parse_quote_spanned,
    punctuated::Punctuated,
    spanned::Spanned,
    token::Comma,
    Item, Meta, Path, Result,
};

#[derive(Default)]
pub struct PyModuleOptions {
    krate: Option<CrateAttribute>,
    name: Option<NameAttribute>,
    module: Option<ModuleAttribute>,
    submodule: Option<kw::submodule>,
}

impl Parse for PyModuleOptions {
    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
        let mut options: PyModuleOptions = Default::default();

        options.add_attributes(
            Punctuated::<PyModulePyO3Option, syn::Token![,]>::parse_terminated(input)?,
        )?;

        Ok(options)
    }
}

impl PyModuleOptions {
    fn take_pyo3_options(&mut self, attrs: &mut Vec<syn::Attribute>) -> Result<()> {
        self.add_attributes(take_pyo3_options(attrs)?)
    }

    fn add_attributes(
        &mut self,
        attrs: impl IntoIterator<Item = PyModulePyO3Option>,
    ) -> Result<()> {
        macro_rules! set_option {
            ($key:ident) => {
                {
                    ensure_spanned!(
                        self.$key.is_none(),
                        $key.span() => concat!("`", stringify!($key), "` may only be specified once")
                    );
                    self.$key = Some($key);
                }
            };
        }
        for attr in attrs {
            match attr {
                PyModulePyO3Option::Crate(krate) => set_option!(krate),
                PyModulePyO3Option::Name(name) => set_option!(name),
                PyModulePyO3Option::Module(module) => set_option!(module),
                PyModulePyO3Option::Submodule(submodule) => set_option!(submodule),
            }
        }
        Ok(())
    }
}

pub fn pymodule_module_impl(
    module: &mut syn::ItemMod,
    mut options: PyModuleOptions,
) -> Result<TokenStream> {
    let syn::ItemMod {
        attrs,
        vis,
        unsafety: _,
        ident,
        mod_token,
        content,
        semi: _,
    } = module;
    let items = if let Some((_, items)) = content {
        items
    } else {
        bail_spanned!(mod_token.span() => "`#[pymodule]` can only be used on inline modules")
    };
    options.take_pyo3_options(attrs)?;
    let ctx = &Ctx::new(&options.krate, None);
    let Ctx { pyo3_path, .. } = ctx;
    let doc = get_doc(attrs, None, ctx);
    let name = options
        .name
        .map_or_else(|| ident.unraw(), |name| name.value.0);
    let full_name = if let Some(module) = &options.module {
        format!("{}.{}", module.value.value(), name)
    } else {
        name.to_string()
    };

    let mut module_items = Vec::new();
    let mut module_items_cfg_attrs = Vec::new();

    fn extract_use_items(
        source: &syn::UseTree,
        cfg_attrs: &[syn::Attribute],
        target_items: &mut Vec<syn::Ident>,
        target_cfg_attrs: &mut Vec<Vec<syn::Attribute>>,
    ) -> Result<()> {
        match source {
            syn::UseTree::Name(name) => {
                target_items.push(name.ident.clone());
                target_cfg_attrs.push(cfg_attrs.to_vec());
            }
            syn::UseTree::Path(path) => {
                extract_use_items(&path.tree, cfg_attrs, target_items, target_cfg_attrs)?
            }
            syn::UseTree::Group(group) => {
                for tree in &group.items {
                    extract_use_items(tree, cfg_attrs, target_items, target_cfg_attrs)?
                }
            }
            syn::UseTree::Glob(glob) => {
                bail_spanned!(glob.span() => "#[pymodule] cannot import glob statements")
            }
            syn::UseTree::Rename(rename) => {
                target_items.push(rename.rename.clone());
                target_cfg_attrs.push(cfg_attrs.to_vec());
            }
        }
        Ok(())
    }

    let mut pymodule_init = None;

    for item in &mut *items {
        match item {
            Item::Use(item_use) => {
                let is_pymodule_export =
                    find_and_remove_attribute(&mut item_use.attrs, "pymodule_export");
                if is_pymodule_export {
                    let cfg_attrs = get_cfg_attributes(&item_use.attrs);
                    extract_use_items(
                        &item_use.tree,
                        &cfg_attrs,
                        &mut module_items,
                        &mut module_items_cfg_attrs,
                    )?;
                }
            }
            Item::Fn(item_fn) => {
                ensure_spanned!(
                    !has_attribute(&item_fn.attrs, "pymodule_export"),
                    item.span() => "`#[pymodule_export]` may only be used on `use` statements"
                );
                let is_pymodule_init =
                    find_and_remove_attribute(&mut item_fn.attrs, "pymodule_init");
                let ident = &item_fn.sig.ident;
                if is_pymodule_init {
                    ensure_spanned!(
                        !has_attribute(&item_fn.attrs, "pyfunction"),
                        item_fn.span() => "`#[pyfunction]` cannot be used alongside `#[pymodule_init]`"
                    );
                    ensure_spanned!(pymodule_init.is_none(), item_fn.span() => "only one `#[pymodule_init]` may be specified");
                    pymodule_init = Some(quote! { #ident(module)?; });
                } else if has_attribute(&item_fn.attrs, "pyfunction")
                    || has_attribute_with_namespace(
                        &item_fn.attrs,
                        Some(pyo3_path),
                        &["pyfunction"],
                    )
                    || has_attribute_with_namespace(
                        &item_fn.attrs,
                        Some(pyo3_path),
                        &["prelude", "pyfunction"],
                    )
                {
                    module_items.push(ident.clone());
                    module_items_cfg_attrs.push(get_cfg_attributes(&item_fn.attrs));
                }
            }
            Item::Struct(item_struct) => {
                ensure_spanned!(
                    !has_attribute(&item_struct.attrs, "pymodule_export"),
                    item.span() => "`#[pymodule_export]` may only be used on `use` statements"
                );
                if has_attribute(&item_struct.attrs, "pyclass")
                    || has_attribute_with_namespace(
                        &item_struct.attrs,
                        Some(pyo3_path),
                        &["pyclass"],
                    )
                    || has_attribute_with_namespace(
                        &item_struct.attrs,
                        Some(pyo3_path),
                        &["prelude", "pyclass"],
                    )
                {
                    module_items.push(item_struct.ident.clone());
                    module_items_cfg_attrs.push(get_cfg_attributes(&item_struct.attrs));
                    if !has_pyo3_module_declared::<PyClassPyO3Option>(
                        &item_struct.attrs,
                        "pyclass",
                        |option| matches!(option, PyClassPyO3Option::Module(_)),
                    )? {
                        set_module_attribute(&mut item_struct.attrs, &full_name);
                    }
                }
            }
            Item::Enum(item_enum) => {
                ensure_spanned!(
                    !has_attribute(&item_enum.attrs, "pymodule_export"),
                    item.span() => "`#[pymodule_export]` may only be used on `use` statements"
                );
                if has_attribute(&item_enum.attrs, "pyclass")
                    || has_attribute_with_namespace(&item_enum.attrs, Some(pyo3_path), &["pyclass"])
                    || has_attribute_with_namespace(
                        &item_enum.attrs,
                        Some(pyo3_path),
                        &["prelude", "pyclass"],
                    )
                {
                    module_items.push(item_enum.ident.clone());
                    module_items_cfg_attrs.push(get_cfg_attributes(&item_enum.attrs));
                    if !has_pyo3_module_declared::<PyClassPyO3Option>(
                        &item_enum.attrs,
                        "pyclass",
                        |option| matches!(option, PyClassPyO3Option::Module(_)),
                    )? {
                        set_module_attribute(&mut item_enum.attrs, &full_name);
                    }
                }
            }
            Item::Mod(item_mod) => {
                ensure_spanned!(
                    !has_attribute(&item_mod.attrs, "pymodule_export"),
                    item.span() => "`#[pymodule_export]` may only be used on `use` statements"
                );
                if has_attribute(&item_mod.attrs, "pymodule")
                    || has_attribute_with_namespace(&item_mod.attrs, Some(pyo3_path), &["pymodule"])
                    || has_attribute_with_namespace(
                        &item_mod.attrs,
                        Some(pyo3_path),
                        &["prelude", "pymodule"],
                    )
                {
                    module_items.push(item_mod.ident.clone());
                    module_items_cfg_attrs.push(get_cfg_attributes(&item_mod.attrs));
                    if !has_pyo3_module_declared::<PyModulePyO3Option>(
                        &item_mod.attrs,
                        "pymodule",
                        |option| matches!(option, PyModulePyO3Option::Module(_)),
                    )? {
                        set_module_attribute(&mut item_mod.attrs, &full_name);
                    }
                }
            }
            Item::ForeignMod(item) => {
                ensure_spanned!(
                    !has_attribute(&item.attrs, "pymodule_export"),
                    item.span() => "`#[pymodule_export]` may only be used on `use` statements"
                );
            }
            Item::Trait(item) => {
                ensure_spanned!(
                    !has_attribute(&item.attrs, "pymodule_export"),
                    item.span() => "`#[pymodule_export]` may only be used on `use` statements"
                );
            }
            Item::Const(item) => {
                ensure_spanned!(
                    !has_attribute(&item.attrs, "pymodule_export"),
                    item.span() => "`#[pymodule_export]` may only be used on `use` statements"
                );
            }
            Item::Static(item) => {
                ensure_spanned!(
                    !has_attribute(&item.attrs, "pymodule_export"),
                    item.span() => "`#[pymodule_export]` may only be used on `use` statements"
                );
            }
            Item::Macro(item) => {
                ensure_spanned!(
                    !has_attribute(&item.attrs, "pymodule_export"),
                    item.span() => "`#[pymodule_export]` may only be used on `use` statements"
                );
            }
            Item::ExternCrate(item) => {
                ensure_spanned!(
                    !has_attribute(&item.attrs, "pymodule_export"),
                    item.span() => "`#[pymodule_export]` may only be used on `use` statements"
                );
            }
            Item::Impl(item) => {
                ensure_spanned!(
                    !has_attribute(&item.attrs, "pymodule_export"),
                    item.span() => "`#[pymodule_export]` may only be used on `use` statements"
                );
            }
            Item::TraitAlias(item) => {
                ensure_spanned!(
                    !has_attribute(&item.attrs, "pymodule_export"),
                    item.span() => "`#[pymodule_export]` may only be used on `use` statements"
                );
            }
            Item::Type(item) => {
                ensure_spanned!(
                    !has_attribute(&item.attrs, "pymodule_export"),
                    item.span() => "`#[pymodule_export]` may only be used on `use` statements"
                );
            }
            Item::Union(item) => {
                ensure_spanned!(
                    !has_attribute(&item.attrs, "pymodule_export"),
                    item.span() => "`#[pymodule_export]` may only be used on `use` statements"
                );
            }
            _ => (),
        }
    }

    let module_def = quote! {{
        use #pyo3_path::impl_::pymodule as impl_;
        const INITIALIZER: impl_::ModuleInitializer = impl_::ModuleInitializer(__pyo3_pymodule);
        unsafe {
           impl_::ModuleDef::new(
                __PYO3_NAME,
                #doc,
                INITIALIZER
            )
        }
    }};
    let initialization = module_initialization(&name, ctx, module_def, options.submodule.is_some());

    Ok(quote!(
        #(#attrs)*
        #vis #mod_token #ident {
            #(#items)*

            #initialization

            fn __pyo3_pymodule(module: &#pyo3_path::Bound<'_, #pyo3_path::types::PyModule>) -> #pyo3_path::PyResult<()> {
                use #pyo3_path::impl_::pymodule::PyAddToModule;
                #(
                    #(#module_items_cfg_attrs)*
                    #module_items::_PYO3_DEF.add_to_module(module)?;
                )*
                #pymodule_init
                ::std::result::Result::Ok(())
            }
        }
    ))
}

/// Generates the function that is called by the python interpreter to initialize the native
/// module
pub fn pymodule_function_impl(
    function: &mut syn::ItemFn,
    mut options: PyModuleOptions,
) -> Result<TokenStream> {
    options.take_pyo3_options(&mut function.attrs)?;
    process_functions_in_module(&options, function)?;
    let ctx = &Ctx::new(&options.krate, None);
    let stmts = std::mem::take(&mut function.block.stmts);
    let Ctx { pyo3_path, .. } = ctx;
    let ident = &function.sig.ident;
    let name = options
        .name
        .map_or_else(|| ident.unraw(), |name| name.value.0);
    let vis = &function.vis;
    let doc = get_doc(&function.attrs, None, ctx);

    let initialization = module_initialization(&name, ctx, quote! { MakeDef::make_def() }, false);

    // Module function called with optional Python<'_> marker as first arg, followed by the module.
    let mut module_args = Vec::new();
    if function.sig.inputs.len() == 2 {
        module_args.push(quote!(module.py()));
    }
    module_args
        .push(quote!(::std::convert::Into::into(#pyo3_path::impl_::pymethods::BoundRef(module))));

    let extractors = function
        .sig
        .inputs
        .iter()
        .filter_map(|param| {
            if let syn::FnArg::Typed(pat_type) = param {
                if let syn::Pat::Ident(pat_ident) = &*pat_type.pat {
                    let ident: &syn::Ident = &pat_ident.ident;
                    return Some([
                        parse_quote!{ let check_gil_refs = #pyo3_path::impl_::deprecations::GilRefs::new(); },
                        parse_quote! { let #ident = #pyo3_path::impl_::deprecations::inspect_type(#ident, &check_gil_refs); },
                        parse_quote_spanned! { pat_type.span() => check_gil_refs.function_arg(); },
                    ]);
                }
            }
            None
        })
        .flatten();

    function.block.stmts = extractors.chain(stmts).collect();
    function
        .attrs
        .push(parse_quote!(#[allow(clippy::used_underscore_binding)]));

    Ok(quote! {
        #[doc(hidden)]
        #vis mod #ident {
            #initialization
        }

        // Generate the definition inside an anonymous function in the same scope as the original function -
        // this avoids complications around the fact that the generated module has a different scope
        // (and `super` doesn't always refer to the outer scope, e.g. if the `#[pymodule] is
        // inside a function body)
        #[allow(unknown_lints, non_local_definitions)]
        impl #ident::MakeDef {
            const fn make_def() -> #pyo3_path::impl_::pymodule::ModuleDef {
                fn __pyo3_pymodule(module: &#pyo3_path::Bound<'_, #pyo3_path::types::PyModule>) -> #pyo3_path::PyResult<()> {
                    #ident(#(#module_args),*)
                }

                const INITIALIZER: #pyo3_path::impl_::pymodule::ModuleInitializer = #pyo3_path::impl_::pymodule::ModuleInitializer(__pyo3_pymodule);
                unsafe {
                    #pyo3_path::impl_::pymodule::ModuleDef::new(
                        #ident::__PYO3_NAME,
                        #doc,
                        INITIALIZER
                    )
                }
            }
        }
    })
}

fn module_initialization(
    name: &syn::Ident,
    ctx: &Ctx,
    module_def: TokenStream,
    is_submodule: bool,
) -> TokenStream {
    let Ctx { pyo3_path, .. } = ctx;
    let pyinit_symbol = format!("PyInit_{}", name);
    let name = name.to_string();
    let pyo3_name = LitCStr::new(CString::new(name).unwrap(), Span::call_site(), ctx);

    let mut result = quote! {
        #[doc(hidden)]
        pub const __PYO3_NAME: &'static ::std::ffi::CStr = #pyo3_name;

        pub(super) struct MakeDef;
        #[doc(hidden)]
        pub static _PYO3_DEF: #pyo3_path::impl_::pymodule::ModuleDef = #module_def;
    };
    if !is_submodule {
        result.extend(quote! {
            /// This autogenerated function is called by the python interpreter when importing
            /// the module.
            #[doc(hidden)]
            #[export_name = #pyinit_symbol]
            pub unsafe extern "C" fn __pyo3_init() -> *mut #pyo3_path::ffi::PyObject {
                #pyo3_path::impl_::trampoline::module_init(|py| _PYO3_DEF.make_module(py))
            }
        });
    }
    result
}

/// Finds and takes care of the #[pyfn(...)] in `#[pymodule]`
fn process_functions_in_module(options: &PyModuleOptions, func: &mut syn::ItemFn) -> Result<()> {
    let ctx = &Ctx::new(&options.krate, None);
    let Ctx { pyo3_path, .. } = ctx;
    let mut stmts: Vec<syn::Stmt> = Vec::new();

    #[cfg(feature = "gil-refs")]
    let imports = quote!(use #pyo3_path::{PyNativeType, types::PyModuleMethods};);
    #[cfg(not(feature = "gil-refs"))]
    let imports = quote!(use #pyo3_path::types::PyModuleMethods;);

    for mut stmt in func.block.stmts.drain(..) {
        if let syn::Stmt::Item(Item::Fn(func)) = &mut stmt {
            if let Some(pyfn_args) = get_pyfn_attr(&mut func.attrs)? {
                let module_name = pyfn_args.modname;
                let wrapped_function = impl_wrap_pyfunction(func, pyfn_args.options)?;
                let name = &func.sig.ident;
                let statements: Vec<syn::Stmt> = syn::parse_quote! {
                    #wrapped_function
                    {
                        #[allow(unknown_lints, unused_imports, redundant_imports)]
                        #imports
                        #module_name.as_borrowed().add_function(#pyo3_path::wrap_pyfunction!(#name, #module_name.as_borrowed())?)?;
                    }
                };
                stmts.extend(statements);
            }
        };
        stmts.push(stmt);
    }

    func.block.stmts = stmts;
    Ok(())
}

pub struct PyFnArgs {
    modname: Path,
    options: PyFunctionOptions,
}

impl Parse for PyFnArgs {
    fn parse(input: syn::parse::ParseStream<'_>) -> syn::Result<Self> {
        let modname = input.parse().map_err(
            |e| err_spanned!(e.span() => "expected module as first argument to #[pyfn()]"),
        )?;

        if input.is_empty() {
            return Ok(Self {
                modname,
                options: Default::default(),
            });
        }

        let _: Comma = input.parse()?;

        Ok(Self {
            modname,
            options: input.parse()?,
        })
    }
}

/// Extracts the data from the #[pyfn(...)] attribute of a function
fn get_pyfn_attr(attrs: &mut Vec<syn::Attribute>) -> syn::Result<Option<PyFnArgs>> {
    let mut pyfn_args: Option<PyFnArgs> = None;

    take_attributes(attrs, |attr| {
        if attr.path().is_ident("pyfn") {
            ensure_spanned!(
                pyfn_args.is_none(),
                attr.span() => "`#[pyfn] may only be specified once"
            );
            pyfn_args = Some(attr.parse_args()?);
            Ok(true)
        } else {
            Ok(false)
        }
    })?;

    if let Some(pyfn_args) = &mut pyfn_args {
        pyfn_args
            .options
            .add_attributes(take_pyo3_options(attrs)?)?;
    }

    Ok(pyfn_args)
}

fn get_cfg_attributes(attrs: &[syn::Attribute]) -> Vec<syn::Attribute> {
    attrs
        .iter()
        .filter(|attr| attr.path().is_ident("cfg"))
        .cloned()
        .collect()
}

fn find_and_remove_attribute(attrs: &mut Vec<syn::Attribute>, ident: &str) -> bool {
    let mut found = false;
    attrs.retain(|attr| {
        if attr.path().is_ident(ident) {
            found = true;
            false
        } else {
            true
        }
    });
    found
}

impl<'a> PartialEq<syn::Ident> for IdentOrStr<'a> {
    fn eq(&self, other: &syn::Ident) -> bool {
        match self {
            IdentOrStr::Str(s) => other == s,
            IdentOrStr::Ident(i) => other == i,
        }
    }
}

fn set_module_attribute(attrs: &mut Vec<syn::Attribute>, module_name: &str) {
    attrs.push(parse_quote!(#[pyo3(module = #module_name)]));
}

fn has_pyo3_module_declared<T: Parse>(
    attrs: &[syn::Attribute],
    root_attribute_name: &str,
    is_module_option: impl Fn(&T) -> bool + Copy,
) -> Result<bool> {
    for attr in attrs {
        if (attr.path().is_ident("pyo3") || attr.path().is_ident(root_attribute_name))
            && matches!(attr.meta, Meta::List(_))
        {
            for option in &attr.parse_args_with(Punctuated::<T, Comma>::parse_terminated)? {
                if is_module_option(option) {
                    return Ok(true);
                }
            }
        }
    }
    Ok(false)
}

enum PyModulePyO3Option {
    Submodule(SubmoduleAttribute),
    Crate(CrateAttribute),
    Name(NameAttribute),
    Module(ModuleAttribute),
}

impl Parse for PyModulePyO3Option {
    fn parse(input: ParseStream<'_>) -> Result<Self> {
        let lookahead = input.lookahead1();
        if lookahead.peek(attributes::kw::name) {
            input.parse().map(PyModulePyO3Option::Name)
        } else if lookahead.peek(syn::Token![crate]) {
            input.parse().map(PyModulePyO3Option::Crate)
        } else if lookahead.peek(attributes::kw::module) {
            input.parse().map(PyModulePyO3Option::Module)
        } else if lookahead.peek(attributes::kw::submodule) {
            input.parse().map(PyModulePyO3Option::Submodule)
        } else {
            Err(lookahead.error())
        }
    }
}