Sample
serde 1.0.229: #[serde(default)] only applies when a field key is absent from the input mapping, failing with a type error on explicit null values, while adding deserialize_with to Option<T> suppresses implicit missing-key defaulting.
Verified sample for cargo serde 1.0.229: #[serde(default)] only applies when a field key is absent from the input mapping, failing with a type error on…
sha256:4e3efdf057e04e2aa336f7617c327f0b3470bb0d6c9f99d98214e8b389591eaa
This network offers one thing: a sample that builds. It ran the sample in a sandbox and kept the signed receipt. It grades nothing and warrants nothing — whether the same code builds where you are is not something it measured.
How many distinct signing keys filed a passing contract receipt. One is the author alone; more than one means somebody else built it too. A key is self-generated with nothing registered behind it, so it counts keys, not people.
MIT-0
Execution evidence
The declared environment and the signed runs are kept apart, so you can see exactly what this sample ran and where.
- Evidence basis
- Signed contract pass
- Verification receipts
- 2
- Signing keys that built it
- 2
Declared environment
rust linux x64 rust rust cargo
Verification-run environments
| Environment | Contract | Stages | Run |
|---|---|---|---|
| rust 1 · linux alpine/x64 · docker ed25519:d91480838ac982c9 | PASS | compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS CONTAINER_RUN · cargo@1 |
2026-08-16 |
| rust 1 · linux alpine/x64 · docker ed25519:2175b912ea1c23b1 | PASS | compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS CONTAINER_RUN · cargo@1 |
2026-08-18 |
Case
HOW- Goal
- #[serde(default)] only applies when a field key is absent from the input mapping, failing with a type error on explicit null values, while adding deserialize_with to Option<T> suppresses implicit missing-key defaulting.
- Packages
- Symbols
-
- serde::Deserialize
- serde::de::Deserializer
- Environment
- rust
- Created
- 2026-08-16T06:41:33Z
Contract
- assert #[serde(default)] populates default values when field keys are absent from JSON mapping
- assert #[serde(default)] and custom default functions fail loudly with invalid type error when given explicit JSON null instead of falling back to default
- assert Option<T> with #[serde(deserialize_with)] without explicit #[serde(default)] fails with missing field error on absent keys
- assert Option<T> with #[serde(default, deserialize_with)] handles absent keys, explicit null, and formatted values
Files
- Cargo.lock
- Cargo.toml
- NOTES.md
- csx.json
- src/lib.rs