Sample
Configure YAML decoding with yaml.AllowDuplicateMapKey to permit duplicate mapping keys and retain the latest value instead of failing with a syntax error
sha256:5dac961373b18c0b0dbf6de249512818668244b0f0d0efae8f309c2f73f303de
PUBLISHED
L3_CONTRACT_PASS
MIT-0
Execution evidence
Declared environment and signed verification runs are separated so you can see exactly what this sample proves.
Evidence basisSigned contract pass
Verification receipts1
Verification levelL3_CONTRACT_PASS
Declared environment
- Execution context
- go
- Operating system
- linux
- Architecture
- x64
- Runtime
- go
- Language
- go
- Package manager
- go
Verification-run environments
- Execution context
- go 1.26
- Operating system
- linux alpine · musl
- Architecture
- x64
- Runtime
- go 1.26
- Language
- go
- Package manager
- go
- Execution
- container · docker
CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · golang@1 · 2026-08-17
Case
- Goal
- Configure YAML decoding with yaml.AllowDuplicateMapKey to permit duplicate mapping keys and retain the latest value instead of failing with a syntax error HOW
- Packages
-
github.com/goccy/go-yaml v1.19.2
- Environment
- go
- Created
- 2026-08-17T14:04:27Z
Commonly assumed
yaml.Unmarshal silently accepts duplicate mapping keys and overwrites earlier occurrences with later ones.
The sample's author recorded this as what a developer or model would expect here. The contract below is what actually ran.
Contract
- assert yaml.Unmarshal rejects duplicate mapping keys with a SyntaxError by default, leaving destination values empty
- assert yaml.UnmarshalWithOptions with yaml.AllowDuplicateMapKey succeeds and retains the latest key value in document order
- assert yaml.NewDecoder with yaml.AllowDuplicateMapKey succeeds on streaming readers with duplicate mapping keys
- assert yaml.AllowDuplicateMapKey applies identically to nested struct fields and map targets
Files
- NOTES.md
- csx.json
- go.mod
- go.sum
- yaml_duplicate_key_test.go
Download the source artifact (tar.gz)
Origin Seeder
csx-seed
Verification receipts
- go 1.26 · linux alpine/x64 · docker · CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · golang@1 · 2026-08-17 · ed25519:d91480838ac982c9