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Add JSON support for DefaultFields #3333

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Add JSON support for DefaultFields #3333

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6c2af38
Correctly state dependency on JsonFields.
skyvine Jul 6, 2025
bb3ea94
Re-introduce genericity
skyvine Jul 13, 2025
df3d0da
Add JSON support for DefaultFields
skyvine Jul 13, 2025
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40 changes: 37 additions & 3 deletions tracing-subscriber/src/fmt/format/json.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@ use crate::{
field::{RecordFields, VisitOutput},
fmt::{
fmt_layer::{FmtContext, FormattedFields},
format::DefaultFields,
writer::WriteAdaptor,
},
registry::LookupSpan,
Expand Down Expand Up @@ -123,6 +124,7 @@ impl<Span, N> serde::ser::Serialize for SerializableContext<'_, '_, Span, N>
where
Span: Subscriber + for<'lookup> crate::registry::LookupSpan<'lookup>,
N: for<'writer> FormatFields<'writer> + 'static,
for<'inner, 'outer> SerializableSpan<'inner, 'outer, Span, N>: serde::Serialize,
{
fn serialize<Ser>(&self, serializer_o: Ser) -> Result<Ser::Ok, Ser::Error>
where
Expand All @@ -149,10 +151,41 @@ where
Span: for<'lookup> crate::registry::LookupSpan<'lookup>,
N: for<'writer> FormatFields<'writer> + 'static;

impl<Span, N> serde::ser::Serialize for SerializableSpan<'_, '_, Span, N>
impl<Span> serde::ser::Serialize for SerializableSpan<'_, '_, Span, DefaultFields>
where
Span: for<'lookup> crate::registry::LookupSpan<'lookup>,
{
fn serialize<Ser>(&self, serializer: Ser) -> Result<Ser::Ok, Ser::Error>
where
Ser: serde::ser::Serializer,
{
let mut serializer = serializer.serialize_map(None)?;

let ext = self.0.extensions();
let data = ext
.get::<FormattedFields<DefaultFields>>()
.expect("Unable to find FormattedFields in extensions; this is a bug");

let fields = data.split(" ");

for key_value_pair in fields {
let mut kvp_iter = key_value_pair.split("=");
if let (Some(key), Some(value)) = (kvp_iter.next(), kvp_iter.next()) {
// The default formatter surrounds the values in literal quotation marks;
// remove these from the serialization so they don't end up in the JSON
// output.
serializer.serialize_entry(&key, &value[1..value.len() - 1]);
}
}

serializer.serialize_entry("name", self.0.metadata().name())?;
serializer.end()
}
}

impl<Span> serde::ser::Serialize for SerializableSpan<'_, '_, Span, JsonFields>
where
Span: for<'lookup> crate::registry::LookupSpan<'lookup>,
N: for<'writer> FormatFields<'writer> + 'static,
{
fn serialize<Ser>(&self, serializer: Ser) -> Result<Ser::Ok, Ser::Error>
where
Expand All @@ -162,7 +195,7 @@ where

let ext = self.0.extensions();
let data = ext
.get::<FormattedFields<N>>()
.get::<FormattedFields<JsonFields>>()
.expect("Unable to find FormattedFields in extensions; this is a bug");

// TODO: let's _not_ do this, but this resolves
Expand Down Expand Up @@ -214,6 +247,7 @@ impl<S, N, T> FormatEvent<S, N> for Format<Json, T>
where
S: Subscriber + for<'lookup> LookupSpan<'lookup>,
N: for<'writer> FormatFields<'writer> + 'static,
for<'inner, 'outer> SerializableSpan<'inner, 'outer, S, N>: serde::Serialize,
T: FormatTime,
{
fn format_event(
Expand Down