Merge #3120

3120: feat: add #[pyo3(from_item_all)] for FromPyObject r=davidhewitt a=BlueGlassBlock

This PR addresses #3112 by implementing ~~`#[pyo3(item_all)]`~~ `#[pyo3(from_item_all)]`.

Co-authored-by: BlueGlassBlock <blueglassblock@outlook.com>

guide/src/conversions/traits.md

@@ -137,6 +137,35 @@ from a mapping with the key `"key"`. The arguments for `attribute` are restricte
 non-empty string literals while `item` can take any valid literal that implements
 `ToBorrowedObject`.
 
+You can use `#[pyo3(from_item_all)]` on a struct to extract every field with `get_item` method.
+In this case, you can't use `#[pyo3(attribute)]` or barely use `#[pyo3(item)]` on any field.
+However, using `#[pyo3(item("key"))]` to specify the key for a field is still allowed.
+
+```rust
+use pyo3::prelude::*;
+
+#[derive(FromPyObject)]
+#[pyo3(from_item_all)]
+struct RustyStruct {
+    foo: String,
+    bar: String,
+    #[pyo3(item("foobar"))]
+    baz: String,
+}
+#
+# fn main() -> PyResult<()> {
+#     Python::with_gil(|py| -> PyResult<()> {
+#         let py_dict = py.eval("{'foo': 'foo', 'bar': 'bar', 'foobar': 'foobar'}", None, None)?;
+#         let rustystruct: RustyStruct = py_dict.extract()?;
+# 		  assert_eq!(rustystruct.foo, "foo");
+#         assert_eq!(rustystruct.bar, "bar");
+#         assert_eq!(rustystruct.baz, "foobar");
+#
+#         Ok(())
+#     })
+# }
+```
+
 #### Deriving [`FromPyObject`] for tuple structs
 
 Tuple structs are also supported but do not allow customizing the extraction. The input is

newsfragments/3120.added.md

@@ -0,0 +1 @@
+Allow using `#[pyo3(from_item_all)]` when deriving `FromPyObject` to specify `get_item` as getter for all fields. 

pyo3-macros-backend/src/attributes.rs

@@ -21,6 +21,7 @@ pub mod kw {
     syn::custom_keyword!(get);
     syn::custom_keyword!(get_all);
     syn::custom_keyword!(item);
+    syn::custom_keyword!(from_item_all);
     syn::custom_keyword!(mapping);
     syn::custom_keyword!(module);
     syn::custom_keyword!(name);

pyo3-macros-backend/src/frompyobject.rs

@@ -171,7 +171,22 @@ impl<'a> Container<'a> {
                             .ident
                             .as_ref()
                             .expect("Named fields should have identifiers");
-                        let attrs = FieldPyO3Attributes::from_attrs(&field.attrs)?;
+                        let mut attrs = FieldPyO3Attributes::from_attrs(&field.attrs)?;
+
+                        if let Some(ref from_item_all) = options.from_item_all {
+                            if let Some(replaced) = attrs.getter.replace(FieldGetter::GetItem(None))
+                            {
+                                match replaced {
+                                    FieldGetter::GetItem(Some(item_name)) => {
+                                        attrs.getter = Some(FieldGetter::GetItem(Some(item_name)));
+                                    }
+                                    FieldGetter::GetItem(None) => bail_spanned!(from_item_all.span() => "Useless `item` - the struct is already annotated with `from_item_all`"),
+                                    FieldGetter::GetAttr(_) => bail_spanned!(
+                                        from_item_all.span() => "The struct is already annotated with `from_item_all`, `attribute` is not allowed"
+                                    ),
+                                }
+                            }
+                        }
 
                         Ok(NamedStructField {
                             ident,
@@ -343,6 +358,8 @@ impl<'a> Container<'a> {
 struct ContainerOptions {
     /// Treat the Container as a Wrapper, directly extract its fields from the input object.
     transparent: bool,
+    /// Force every field to be extracted from item of source Python object.
+    from_item_all: Option<attributes::kw::from_item_all>,
     /// Change the name of an enum variant in the generated error message.
     annotation: Option<syn::LitStr>,
     /// Change the path for the pyo3 crate
@@ -353,6 +370,8 @@ struct ContainerOptions {
 enum ContainerPyO3Attribute {
     /// Treat the Container as a Wrapper, directly extract its fields from the input object.
     Transparent(attributes::kw::transparent),
+    /// Force every field to be extracted from item of source Python object.
+    ItemAll(attributes::kw::from_item_all),
     /// Change the name of an enum variant in the generated error message.
     ErrorAnnotation(LitStr),
     /// Change the path for the pyo3 crate
@@ -365,6 +384,9 @@ impl Parse for ContainerPyO3Attribute {
         if lookahead.peek(attributes::kw::transparent) {
             let kw: attributes::kw::transparent = input.parse()?;
             Ok(ContainerPyO3Attribute::Transparent(kw))
+        } else if lookahead.peek(attributes::kw::from_item_all) {
+            let kw: attributes::kw::from_item_all = input.parse()?;
+            Ok(ContainerPyO3Attribute::ItemAll(kw))
         } else if lookahead.peek(attributes::kw::annotation) {
             let _: attributes::kw::annotation = input.parse()?;
             let _: Token![=] = input.parse()?;
@@ -392,6 +414,13 @@ impl ContainerOptions {
                             );
                             options.transparent = true;
                         }
+                        ContainerPyO3Attribute::ItemAll(kw) => {
+                            ensure_spanned!(
+                                matches!(options.from_item_all, None),
+                                kw.span() => "`from_item_all` may only be provided once"
+                            );
+                            options.from_item_all = Some(kw);
+                        }
                         ContainerPyO3Attribute::ErrorAnnotation(lit_str) => {
                             ensure_spanned!(
                                 options.annotation.is_none(),
@@ -494,7 +523,7 @@ impl FieldPyO3Attributes {
                                 getter.is_none(),
                                 attr.span() => "only one of `attribute` or `item` can be provided"
                             );
-                            getter = Some(field_getter)
+                            getter = Some(field_getter);
                         }
                         FieldPyO3Attribute::FromPyWith(from_py_with_attr) => {
                             ensure_spanned!(

tests/ui/invalid_frompy_derive.rs

@@ -175,4 +175,42 @@ struct InvalidTransparentWithGetter {
     field: String,
 }
 
+#[derive(FromPyObject)]
+#[pyo3(from_item_all)]
+struct FromItemAllOnTuple(String);
+
+#[derive(FromPyObject)]
+#[pyo3(from_item_all)]
+#[pyo3(transparent)]
+struct FromItemAllWithTransparent {
+    field: String,
+}
+
+#[derive(FromPyObject)]
+#[pyo3(from_item_all, from_item_all)]
+struct MultipleFromItemAll {
+    field: String,
+}
+
+#[derive(FromPyObject)]
+#[pyo3(from_item_all)]
+struct UselessItemAttr {
+    #[pyo3(item)]
+    field: String,
+}
+
+#[derive(FromPyObject)]
+#[pyo3(from_item_all)]
+struct FromItemAllConflictAttr {
+    #[pyo3(attribute)]
+    field: String,
+}
+
+#[derive(FromPyObject)]
+#[pyo3(from_item_all)]
+struct FromItemAllConflictAttrWithArgs {
+    #[pyo3(attribute("f"))]
+    field: String,
+}
+
 fn main() {}

tests/ui/invalid_frompy_derive.stderr

@@ -132,7 +132,7 @@ error: only one of `attribute` or `item` can be provided
 118 |     #[pyo3(item, attribute)]
     |     ^
 
-error: expected one of: `transparent`, `annotation`, `crate`
+error: expected one of: `transparent`, `from_item_all`, `annotation`, `crate`
    --> tests/ui/invalid_frompy_derive.rs:123:8
     |
 123 | #[pyo3(unknown = "should not work")]
@@ -193,3 +193,33 @@ error: `transparent` structs may not have a `getter` for the inner field
     |
 175 |     field: String,
     |     ^^^^^
+
+error: `transparent` structs may not have a `getter` for the inner field
+   --> tests/ui/invalid_frompy_derive.rs:186:5
+    |
+186 |     field: String,
+    |     ^^^^^
+
+error: `from_item_all` may only be provided once
+   --> tests/ui/invalid_frompy_derive.rs:190:23
+    |
+190 | #[pyo3(from_item_all, from_item_all)]
+    |                       ^^^^^^^^^^^^^
+
+error: Useless `item` - the struct is already annotated with `from_item_all`
+   --> tests/ui/invalid_frompy_derive.rs:196:8
+    |
+196 | #[pyo3(from_item_all)]
+    |        ^^^^^^^^^^^^^
+
+error: The struct is already annotated with `from_item_all`, `attribute` is not allowed
+   --> tests/ui/invalid_frompy_derive.rs:203:8
+    |
+203 | #[pyo3(from_item_all)]
+    |        ^^^^^^^^^^^^^
+
+error: The struct is already annotated with `from_item_all`, `attribute` is not allowed
+   --> tests/ui/invalid_frompy_derive.rs:210:8
+    |
+210 | #[pyo3(from_item_all)]
+    |        ^^^^^^^^^^^^^