From 6194e56e13fdc77e46e0bb6cae486ba56a678939 Mon Sep 17 00:00:00 2001
From: Wojciech Graj <me@w-graj.net>
Date: Wed, 18 Feb 2026 19:34:31 +0100
Subject: [PATCH] Add defmt support

---
 .github/workflows/rust.yml |  6 +++---
 Cargo.toml                 |  7 ++++++-
 src/arrayvec.rs            | 23 +++++++++++++++++++++++
 src/lib.rs                 |  2 ++
 src/slicevec.rs            | 11 +++++++++++
 src/tinyvec.rs             | 22 ++++++++++++++++++++++
 6 files changed, 67 insertions(+), 4 deletions(-)

diff --git a/.github/workflows/rust.yml b/.github/workflows/rust.yml
index 4ec05e6..7fd1da7 100644
--- a/.github/workflows/rust.yml
+++ b/.github/workflows/rust.yml
@@ -11,7 +11,7 @@ jobs:
       matrix:
         os: [ubuntu-latest]
         rust:
-        - 1.55.0 # approximate MSRV is Stable -30
+        - 1.60.0 # approximate MSRV is Stable -30
         - stable
         - beta
         - nightly
@@ -28,11 +28,11 @@ jobs:
         toolchain: ${{ matrix.rust }}
     # On MSRV some dev-dependencies don't build so we can't run tests.
     - name: Check MSRV
-      if: matrix.rust == '1.55.0'
+      if: matrix.rust == '1.60.0'
       run: |
         cargo check --features=alloc,std,grab_spare_slice
     - name: Test non nightly
-      if: matrix.rust != '1.55.0' && matrix.rust != 'nightly'
+      if: matrix.rust != '1.60.0' && matrix.rust != 'nightly'
       run: |
         cargo test --features=alloc,std,grab_spare_slice,latest_stable_rust
     - name: Test on Nightly with All Features
diff --git a/Cargo.toml b/Cargo.toml
index 819fd44..5984ecd 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -20,6 +20,8 @@ arbitrary = { version = "1", optional = true }
 borsh = { version = "1.2.0", optional = true, default-features = false }
 # Implements the trait `Array` for `GenericArray` struct.
 generic-array = { version = "1.1.1", optional = true, default-features = false }
+# Provides `Format` implementations
+defmt = { version = "1.0", optional = true }
 
 
 [features]
@@ -76,12 +78,15 @@ experimental_write_impl = []
 real_blackbox = ["criterion/real_blackbox"]
 
 [package.metadata.docs.rs]
-features = ["alloc", "std", "grab_spare_slice", "latest_stable_rust", "serde", "borsh"]
+features = ["alloc", "std", "grab_spare_slice", "latest_stable_rust", "serde", "borsh", "defmt"]
 rustdoc-args = ["--cfg","docs_rs"]
 
 [package.metadata.playground]
 features = ["alloc", "std", "grab_spare_slice", "latest_stable_rust", "serde", "borsh"]
 
+[profile.dev]
+lto = "thin"
+
 [profile.bench]
 debug = 2
 
diff --git a/src/arrayvec.rs b/src/arrayvec.rs
index c55796d..1fbcdc5 100644
--- a/src/arrayvec.rs
+++ b/src/arrayvec.rs
@@ -1422,6 +1422,7 @@ impl<A: Array> From<A> for ArrayVec<A> {
 /// The error type returned when a conversion from a slice to an [`ArrayVec`]
 /// fails.
 #[derive(Debug, Copy, Clone)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub struct TryFromSliceError(());
 
 impl core::fmt::Display for TryFromSliceError {
@@ -1576,6 +1577,17 @@ where
   }
 }
 
+#[cfg(feature = "defmt")]
+#[cfg_attr(docs_rs, doc(cfg(feature = "defmt")))]
+impl<A: Array> defmt::Format for ArrayVecIterator<A>
+where
+  A::Item: defmt::Format,
+{
+  fn format(&self, fmt: defmt::Formatter<'_>) {
+    defmt::write!(fmt, "ArrayVecIterator({:?})", self.as_slice())
+  }
+}
+
 impl<A: Array> IntoIterator for ArrayVec<A> {
   type Item = A::Item;
   type IntoIter = ArrayVecIterator<A>;
@@ -1716,6 +1728,17 @@ where
   }
 }
 
+#[cfg(feature = "defmt")]
+#[cfg_attr(docs_rs, doc(cfg(feature = "defmt")))]
+impl<A: Array> defmt::Format for ArrayVec<A>
+where
+  A::Item: defmt::Format,
+{
+  fn format(&self, fmt: defmt::Formatter<'_>) {
+    defmt::Format::format(self.as_slice(), fmt)
+  }
+}
+
 impl<A: Array> Display for ArrayVec<A>
 where
   A::Item: Display,
diff --git a/src/lib.rs b/src/lib.rs
index 112853c..22f4293 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -52,6 +52,8 @@
 //! * `borsh` provides a `BorshSerialize` and `BorshDeserialize` implementation
 //!   for [`TinyVec`] and [`ArrayVec`] types, provided the inner item also has
 //!   an implementation.
+//! * `defmt` provides a `Format` implementation for all types, provided the
+//!   inner item also has an implementation.
 //!
 //! ## API
 //! The general goal of the crate is that, as much as possible, the vecs here
diff --git a/src/slicevec.rs b/src/slicevec.rs
index bb6b744..d7635d4 100644
--- a/src/slicevec.rs
+++ b/src/slicevec.rs
@@ -894,6 +894,17 @@ where
   }
 }
 
+#[cfg(feature = "defmt")]
+#[cfg_attr(docs_rs, doc(cfg(feature = "defmt")))]
+impl<'s, T> defmt::Format for SliceVec<'s, T>
+where
+  T: defmt::Format,
+{
+  fn format(&self, fmt: defmt::Formatter<'_>) {
+    defmt::Format::format(self.as_slice(), fmt)
+  }
+}
+
 impl<'s, T> Display for SliceVec<'s, T>
 where
   T: Display,
diff --git a/src/tinyvec.rs b/src/tinyvec.rs
index d2bf218..7fff545 100644
--- a/src/tinyvec.rs
+++ b/src/tinyvec.rs
@@ -1553,6 +1553,17 @@ where
   }
 }
 
+#[cfg(feature = "defmt")]
+#[cfg_attr(docs_rs, doc(cfg(feature = "defmt")))]
+impl<A: Array> defmt::Format for TinyVecIterator<A>
+where
+  A::Item: defmt::Format,
+{
+  fn format(&self, fmt: defmt::Formatter<'_>) {
+    defmt::write!(fmt, "TinyVecIterator({:?})", self.as_slice())
+  }
+}
+
 impl<A: Array> IntoIterator for TinyVec<A> {
   type Item = A::Item;
   type IntoIter = TinyVecIterator<A>;
@@ -1680,6 +1691,17 @@ where
   }
 }
 
+#[cfg(feature = "defmt")]
+#[cfg_attr(docs_rs, doc(cfg(feature = "defmt")))]
+impl<A: Array> defmt::Format for TinyVec<A>
+where
+  A::Item: defmt::Format,
+{
+  fn format(&self, fmt: defmt::Formatter<'_>) {
+    defmt::Format::format(self.as_slice(), fmt)
+  }
+}
+
 impl<A: Array> Display for TinyVec<A>
 where
   A::Item: Display,