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Simplify implementation of #[serde(default=...)]

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This commit is contained in:
David Tolnay
2016-06-09 23:21:42 -07:00
parent bb059b97c0
commit 3119cc8857
4 changed files with 35 additions and 43 deletions
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serde_codegen/src/attr.rs
+20 -22
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@@ -212,13 +212,24 @@ pub struct FieldAttrs {
skip_serializing_field: bool,
skip_deserializing_field: bool,
skip_serializing_if: Option<ast::Path>,
default_expr_if_missing: Option<P<ast::Expr>>,
default: FieldDefault,
serialize_with: Option<ast::Path>,
deserialize_with: Option<ast::Path>,
ser_bound: Option<Vec<ast::WherePredicate>>,
de_bound: Option<Vec<ast::WherePredicate>>,
}
/// Represents the default to use for a field when deserializing.
#[derive(Debug, PartialEq)]
pub enum FieldDefault {
/// Field must always be specified because it does not have a default.
None,
/// The default is given by `std::default::Default::default()`.
Default,
/// The default is given by this function.
Path(ast::Path),
}
impl FieldAttrs {
/// Extract out the `#[serde(...)]` attributes from a struct field.
pub fn from_field(cx: &ExtCtxt,
@@ -236,7 +247,7 @@ impl FieldAttrs {
skip_serializing_field: false,
skip_deserializing_field: false,
skip_serializing_if: None,
default_expr_if_missing: None,
default: FieldDefault::None,
serialize_with: None,
deserialize_with: None,
ser_bound: None,
@@ -266,17 +277,13 @@ impl FieldAttrs {
// Parse `#[serde(default)]`
ast::MetaItemKind::Word(ref name) if name == &"default" => {
let default_expr = builder.expr().default();
field_attrs.default_expr_if_missing = Some(default_expr);
field_attrs.default = FieldDefault::Default;
}
// Parse `#[serde(default="...")]`
ast::MetaItemKind::NameValue(ref name, ref lit) if name == &"default" => {
let wrapped_expr = wrap_default(
try!(parse_lit_into_path(cx, name, lit)),
);
field_attrs.default_expr_if_missing = Some(wrapped_expr);
let path = try!(parse_lit_into_path(cx, name, lit));
field_attrs.default = FieldDefault::Path(path);
}
// Parse `#[serde(skip_serializing)]`
@@ -290,9 +297,8 @@ impl FieldAttrs {
// Initialize field to Default::default() unless a different
// default is specified by `#[serde(default="...")]`
if field_attrs.default_expr_if_missing.is_none() {
let default_expr = builder.expr().default();
field_attrs.default_expr_if_missing = Some(default_expr);
if field_attrs.default == FieldDefault::None {
field_attrs.default = FieldDefault::Default;
}
}
@@ -363,8 +369,8 @@ impl FieldAttrs {
self.skip_serializing_if.as_ref()
}
pub fn default_expr_if_missing(&self) -> Option<&P<ast::Expr>> {
self.default_expr_if_missing.as_ref()
pub fn default(&self) -> &FieldDefault {
&self.default
}
pub fn serialize_with(&self) -> Option<&ast::Path> {
@@ -584,11 +590,3 @@ fn parse_lit_into_where(cx: &ExtCtxt, name: &str, lit: &ast::Lit) -> Result<Vec<
Ok(where_clause.predicates)
})
}
/// This function wraps the expression in `#[serde(default="...")]` in a function to prevent it
/// from accessing the internal `Deserialize` state.
fn wrap_default(path: ast::Path) -> P<ast::Expr> {
AstBuilder::new().expr().call()
.build_path(path)
.build()
}