CodeSampleX

Sample

sigs.k8s.io/yaml v1.4.0: Show that unknown fields are accepted by default when using `sigs.k8s.io/yaml.Unmarshal`

Verified sample for golang sigs.k8s.io/yaml v1.4.0: Show that unknown fields are accepted by default when using `sigs.k8s.io/yaml.Unmarshal`. The contract…

sha256:31bb1662a7e52a6917ae49a60054435cf7896f3677ef04c2dbd3e0e314827ca5

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
3
Signing keys that built it
3
Declared environment go linux x64 go go golang

Verification-run environments

Environment Contract Stages Run
go 1.26 · linux alpine/x64 · docker ed25519:d91480838ac982c9 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · golang@1		 2026-08-16
go 1.26 · linux alpine/x64 · docker ed25519:2175b912ea1c23b1 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · golang@1		 2026-08-18
go 1.26 · linux alpine/x64 · docker ed25519:c1973797be207ac4 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · golang@1golang:1.26-alpine@sha256:28d89ee9cc0f…		 2026-09-08

Case

HOW
Goal
Show that unknown fields are accepted by default when using `sigs.k8s.io/yaml.Unmarshal`
Packages
Symbols
  • sigs.k8s.io/yaml.Unmarshal
  • sigs.k8s.io/yaml.DisallowUnknownFields
Environment
go
Created
2026-08-16T13:18:55Z

Contract

  1. assert Unmarshal succeeds when decoding `name: main unknown: value` into `decodeTarget` without options
  2. assert the known `name` field decodes to `main` when unknown fields are present
  3. assert adding `yaml.DisallowUnknownFields` as the JSON option makes the same input fail

Files

  • NOTES.md
  • csx.json
  • go.mod
  • go.sum
  • unknown_field_default_test.go

Download the source artifact (tar.gz)

Source

NOTES.md
search_known_solution returned this hit:
case:sha256:52a3759d69a50a82cd8484876ab1475170e7f951f706d6c06982182b4061b8b6 (goal: JSON-tag precedence over yaml tags in `sigs.k8s.io/yaml`).

Using that sample as-is would miss this trap: `Unmarshal` does **not** enforce unknown-field rejection by default, so code that assumes strictness fails immediately with a passing build on unknown input instead of failing fast.
csx.json
{"case":{"believed":"A caller expects unknown YAML keys to be rejected by default when decoding into a typed struct.","caseId":"case:sha256:3c8f69bddbb54bd3bcead652e0657398830390f3969468693d0119ec23a94a24","contract":["assert Unmarshal succeeds when decoding `name: main\nunknown: value` into `decodeTarget` without options","assert the known `name` field decodes to `main` when unknown fields are present","assert adding `yaml.DisallowUnknownFields` as the JSON option makes the same input fail"],"goal":"Show that unknown fields are accepted by default when using `sigs.k8s.io/yaml.Unmarshal`","kind":"HOW","packages":["pkg:golang/sigs.k8s.io/yaml@v1.4.0"],"schemaVersion":1,"symbols":["sigs.k8s.io/yaml.Unmarshal","sigs.k8s.io/yaml.DisallowUnknownFields"]},"contractCommand":["go","test","./..."],"environment":{"arch":"x64","ecosystem":"golang","executionContext":"go","language":"go","os":"linux","packageManager":"golang","runtime":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/sigs.k8s.io/yaml@v1.4.0"],"schemaVersion":1,"symbols":["sigs.k8s.io/yaml.Unmarshal","sigs.k8s.io/yaml.DisallowUnknownFields"],"verifierAdapter":"golang@1"}
go.mod
module example

go 1.22.0

require sigs.k8s.io/yaml v1.4.0
go.sum
github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
sigs.k8s.io/yaml v1.4.0 h1:Mk1wCc2gy/F0THH0TAp1QYyJNzRm2KCLy3o5ASXVI5E=
sigs.k8s.io/yaml v1.4.0/go.mod h1:Ejl7/uTz7PSA4eKMyQCUTnhZYNmLIl+5c2lQPGR2BPY=
unknown_field_default_test.go
package example

import (
	"testing"

	yaml "sigs.k8s.io/yaml"
)

type decodeTarget struct {
	Name string `json:"name"`
}

func TestUnmarshalAllowsUnknownByDefault(t *testing.T) {
	const data = "name: main\nunknown: value\n"
	var got decodeTarget

	if err := yaml.Unmarshal([]byte(data), &got); err != nil {
		t.Fatalf("unexpected error: %v", err)
	}

	if got.Name != "main" {
		t.Fatalf("expected name=%q, got %q", "main", got.Name)
	}
}

func TestUnmarshalDisallowUnknownFieldsFails(t *testing.T) {
	const data = "name: main\nunknown: value\n"
	var got decodeTarget

	if err := yaml.Unmarshal([]byte(data), &got, yaml.DisallowUnknownFields); err == nil {
		t.Fatalf("expected decode failure for unknown field when DisallowUnknownFields is supplied")
	}
}

Origin Seeder

csx-seed