Structured Tracing Serialization/Deserialization

.github/workflows/check_msrv.yml

@@ -43,7 +43,24 @@ jobs:
       uses: actions-rs/cargo@v1
       with:
         command: check
-        args: --all --exclude=tracing-appender
+        args: --all --exclude=tracing-appender --exclude=tracing-serde
+
+  # TODO: remove this once tracing's MSRV is bumped.
+  check-msrv-serde:
+    # Run `cargo check` on our minimum supported Rust version (1.53.0).
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@main
+    - uses: actions-rs/toolchain@v1
+      with:
+        toolchain: 1.51.0
+        profile: minimal
+        override: true
+    - name: Check
+      uses: actions-rs/cargo@v1
+      with:
+        command: check
+        args: --lib=tracing-serde
 
   # TODO: remove this once tracing's MSRV is bumped.
   check-msrv-appender:
@@ -60,4 +77,4 @@ jobs:
       uses: actions-rs/cargo@v1
       with:
         command: check
-        args: --lib=tracing-appender
+        args: --lib=tracing-appender

tracing-core/src/field.rs

@@ -808,6 +808,19 @@ impl<'a> ValueSet<'a> {
         }
     }
 
+    /// Returns the number of fields in this `ValueSet` that would be visited
+    /// by a given [visitor] to the [`ValueSet::record()`] method.
+    ///
+    /// [visitor]: Visit
+    /// [`ValueSet::record()`]: ValueSet::record()
+    pub fn record_len(&self) -> usize {
+        let my_callsite = self.callsite();
+        self.values
+            .iter()
+            .filter(|(field, _)| field.callsite() == my_callsite)
+            .count()
+    }
+
     /// Returns `true` if this `ValueSet` contains a value for the given `Field`.
     pub(crate) fn contains(&self, field: &Field) -> bool {
         field.callsite() == self.callsite()

tracing-core/src/span.rs

@@ -221,11 +221,19 @@ impl<'a> Record<'a> {
 
     /// Records all the fields in this `Record` with the provided [Visitor].
     ///
-    /// [visitor]: super::field::Visit
+    /// [Visitor]: super::field::Visit
     pub fn record(&self, visitor: &mut dyn field::Visit) {
         self.values.record(visitor)
     }
 
+    /// Returns the number of fields that would be visited from this `Record`
+    /// when [`Record::record()`] is called
+    ///
+    /// [`Record::record()`]: Record::record()
+    pub fn record_len(&self) -> usize {
+        self.values.record_len()
+    }
+
     /// Returns `true` if this `Record` contains a value for the given `Field`.
     pub fn contains(&self, field: &field::Field) -> bool {
         self.values.contains(field)

tracing-serde/Cargo.toml

@@ -16,15 +16,16 @@ categories = [
     "encoding",
 ]
 keywords = ["logging", "tracing", "serialization"]
-rust-version = "1.49.0"
+rust-version = "1.51.0"
 
 [features]
 default = ["std"]
 std = ["serde/std", "tracing-core/std"]
 
 [dependencies]
-serde = { version = "1", default-features = false, features = ["alloc"] }
+serde = { version = "1", default-features = false, features = ["alloc", "derive"] }
 tracing-core = { path = "../tracing-core", version = "0.2", default-features = false }
+heapless = { version = "0.7.10", features = ["serde"] }
 
 [dev-dependencies]
 serde_json = "1"