This allows a field to be deserialized with an expression instead
of the default deserializer. This simplifies deserializing a struct
or enum that contains an external type that doesn't implement
`serde::Deserialize`. This expression is passed a variable
`deserializer` that needs to be used to deserialize the expression.
This allows end users to use an arbitrary expression to decide whether
or not to serialize some field. This expression has access to all the
fields in the struct, but none of the internal state of the Serialize
implementation. For structs, serde implements this by creating a
temporary trait and implementing the struct for it. For struct variants,
the fields are copied by reference into a temporary struct first
before implementing the temporary trait.
This also fixes a bug where the serde_codegen wasn't making calls to
Serializer::serialize_{tuple,struct}_variant{,_elt}.
This feature adds support for the default to be specified to be
some expression (which unfortunately needs to be parsed from
a string) without needing this value to have an implementation
of `Default`, or for a new-type wrapper in order to provide an
alternative implementation. This expression is run in a function,
and therefore has no access to any of the internal state of
the deserializer.
According to #61, if one uses serde to serialize requests that pass
url-encoded parameters to a server, it might get responses back
with a different capitalization scheme. This patch restores the
behavior implemented in #62.
# Conflicts:
# serde_codegen/src/attr.rs
# serde_codegen/src/de.rs
# serde_tests/tests/test_annotations.rs
This feature has never been used, and it's complicating the
implementation of #207. We could restore this functionality if there is
ever interest in it.
Closes#211.
Formats that do not provide type hints in the serialized format
(bincode, redis) rely on hinting in the deserializer. Struct key hinting
was not previously supported. This was not an issue in the past because
bincode serializes structs as a keyless sequence of values. However,
redis data is stored (key, value, key, value, ...), and the keys must be
deserialized to properly create a struct.
The default implementation of `visit_struct_key` is simply `visit` since
that was the previous method called in codegen.
