feat: Implement DataSize for Principal

CHANGELOG.md

@@ -2,6 +2,13 @@
 
 ## Unreleased
 
+## 2026-02-27
+
+### Candid 0.10.24
+
+* Non-breaking changes:
+  + Implement `DataSize` for `Principal`, enabling `Principal` as an element type in `BoundedVec`
+
 ## 2026-02-20
 
 ### Candid 0.10.23

rust/candid/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "candid"
 # sync with the version in `candid_derive/Cargo.toml`
-version = "0.10.23"
+version = "0.10.24"
 edition = "2021"
 rust-version.workspace = true
 authors = ["DFINITY Team"]
@@ -16,7 +16,7 @@ keywords = ["internet-computer", "idl", "candid", "dfinity"]
 include = ["src", "Cargo.toml", "LICENSE", "README.md"]
 
 [dependencies]
-candid_derive = { path = "../candid_derive", version = "=0.10.23" }
+candid_derive = { path = "../candid_derive", version = "=0.10.24" }
 ic_principal = { path = "../ic_principal", version = "0.1.0" }
 binread = { version = "2.2", features = ["debug_template"] }
 byteorder = "1.5.0"

rust/candid/src/types/bounded_vec.rs

@@ -367,9 +367,6 @@ mod tests {
 }
 
 mod data_size {
-    // We implement a standalone trait `DataSize` here and use it
-    // instead of `CountBytes`.
-
     /// Trait to reasonably estimate the memory usage of a value in bytes.
     ///
     /// Default implementation returns zero.
@@ -416,6 +413,12 @@ mod data_size {
         }
     }
 
+    impl DataSize for ic_principal::Principal {
+        fn data_size(&self) -> usize {
+            self.as_slice().len()
+        }
+    }
+
     #[cfg(test)]
     mod tests {
         use super::*;

rust/candid_derive/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "candid_derive"
 # sync with the version in `candid/Cargo.toml`
-version = "0.10.23"
+version = "0.10.24"
 edition = "2021"
 rust-version.workspace = true
 authors = ["DFINITY Team"]

rust/ic_principal/tests/principal.rs

@@ -314,3 +314,22 @@ fn rangemap_steplite_impl_works() {
     assert!(set.contains(&p2));
     assert!(!set.contains(&Principal::from_slice(&[0, 1, 4, 0])));
 }
+
+#[test]
+fn as_slice_len_principal() {
+    let anonymous_principal = Principal::anonymous();
+    assert_eq!(anonymous_principal.as_slice().len(), 1);
+
+    let management_canister = Principal::management_canister();
+    assert_eq!(management_canister.as_slice().len(), 0);
+
+    let key = b"42";
+    let self_authenticating = Principal::self_authenticating(key);
+    assert_eq!(self_authenticating.as_slice().len(), 29);
+
+    let from_slice = Principal::from_slice(&TEST_CASE_BYTES);
+    assert_eq!(from_slice.as_slice().len(), 9);
+
+    let from_text = Principal::from_text(TEST_CASE_TEXT).unwrap();
+    assert_eq!(from_text.as_slice().len(), 9);
+}