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Skip_serializing_if function is invoked too many times #1050

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dtolnay opened this issue Sep 9, 2017 · 0 comments

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derive

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dtolnay commented Sep 9, 2017

#[derive(Serialize)]
struct S {
    #[serde(skip_serializing_if = "skip")]
    a: usize,
}

This turns into (effectively):

let len = if skip(&self.a) { 0 } else { 1 };
let mut state = serializer.serialize_struct("S", len)?;
if !skip(&self.a) {
    state.serialize_field("a", &self.a)?;
}
state.end()

It would be more reasonable like this:

let skip_a = skip(&self.a);
let len = if skip_a { 0 } else { 1 };
let mut state = serializer.serialize_struct("S", len)?;
if !skip_a {
    state.serialize_field("a", &self.a)?;
}
state.end()

dtolnay added the derive label

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