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Merge pull request #311 from dtolnay/deserialize_with

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Field with deserialize_with should not implement Deserialize
This commit is contained in:
Oliver Schneider
2016-05-11 11:48:19 +02:00
parent 6596f77e91 76b70455ec
commit 7374ac499d
3 changed files with 41 additions and 38 deletions
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serde_codegen/src/de.rs
+23 -19
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@@ -113,22 +113,7 @@ fn deserialized_by_us(field: &ast::StructField) -> bool {
return false
}
ast::MetaItemKind::NameValue(ref name, _) if name == &"deserialize_with" => {
// TODO: For now we require `T: Deserialize` even if the
// field has `deserialize_with`. The reason is the signature
// of serde::de::MapVisitor::missing_field which looks like:
//
// fn missing_field<T>(...) -> Result<T, Self::Error> where T: Deserialize
//
// So in order to use missing_field, the type must have the
// `T: Deserialize` bound. Some formats rely on this bound
// because they treat missing fields as unit.
//
// Long-term the fix would be to change the signature of
// missing_field so it can, for example, use the
// `deserialize_with` function to visit a unit in place of
// the missing field.
//
// See https://github.com/serde-rs/serde/issues/259
return false
}
_ => {}
}
@@ -519,7 +504,7 @@ fn deserialize_struct_as_seq(
.map(|(i, &(field, ref attrs))| {
let name = builder.id(format!("__field{}", i));
if attrs.skip_deserializing_field() {
let default = attrs.expr_is_missing();
let default = expr_is_missing(cx, attrs);
quote_stmt!(cx,
let $name = $default;
).unwrap()
@@ -1204,7 +1189,7 @@ fn deserialize_map(
let extract_values = fields_attrs_names.iter()
.filter(|&&(_, ref attrs, _)| !attrs.skip_deserializing_field())
.map(|&(_, ref attrs, name)| {
let missing_expr = attrs.expr_is_missing();
let missing_expr = expr_is_missing(cx, attrs);
Ok(quote_stmt!(cx,
let $name = match $name {
@@ -1229,7 +1214,7 @@ fn deserialize_map(
}
},
if attrs.skip_deserializing_field() {
attrs.expr_is_missing()
expr_is_missing(cx, attrs)
} else {
builder.expr().id(name)
}
@@ -1323,3 +1308,22 @@ fn wrap_deserialize_with(
wrapper_ty,
)
}
fn expr_is_missing(
cx: &ExtCtxt,
attrs: &attr::FieldAttrs,
) -> P<ast::Expr> {
if let Some(expr) = attrs.default_expr_if_missing() {
return expr.clone();
}
let name = attrs.name().deserialize_name_expr();
match attrs.deserialize_with() {
None => {
quote_expr!(cx, try!(visitor.missing_field($name)))
}
Some(_) => {
quote_expr!(cx, return Err(
<__V::Error as _serde::de::Error>::missing_field($name)))
}
}
}