{"record":{"id":"3e4df4efa0eb22e7","repo":"apache/beam","slug":"error-re-encoding-characteristic-for-variant-v-handler-v-v","errorCode":null,"errorMessage":"error re-encoding characteristic for variant %v handler %v: %v","messagePattern":"error re-encoding characteristic for variant (.+?) handler (.+?): (.+?)","errorType":"panic","errorClass":null,"httpStatus":null,"severity":"error","filePath":"sdks/go/pkg/beam/runners/prism/internal/config/config.go","lineNumber":204,"sourceCode":"\terr := &unknownHandlersErr{}\n\thandlers := map[string]struct{}{}\n\tfor v, hs := range r.variations {\n\t\tfor hk, hyn := range hs.Handlers {\n\t\t\thandlers[hk] = struct{}{}\n\n\t\t\tmd, ok := r.metadata[hk]\n\t\t\tif !ok {\n\t\t\t\terr.add(hk, v)\n\t\t\t\tcontinue\n\t\t\t}\n\n\t\t\t// Validate that handler config so we can give a good error message now.\n\t\t\t// We re-encode, then decode, since then we don't need to re-implement\n\t\t\t// the existing Known fields. Sadly, this doens't persist through\n\t\t\t// yaml.Node fields.\n\t\t\thb, err := yaml.Marshal(hyn)\n\t\t\tif err != nil {\n\t\t\t\tpanic(fmt.Sprintf(\"error re-encoding characteristic for variant %v handler %v: %v\", v, hk, err))\n\t\t\t}\n\t\t\tbuf := bytes.NewBuffer(hb)\n\t\t\tdec := yaml.NewDecoder(buf)\n\t\t\tdec.KnownFields(true)\n\t\t\trt := md.ConfigCharacteristic()\n\t\t\trtv := reflect.New(rt)\n\t\t\tif err := dec.Decode(rtv.Interface()); err != nil {\n\t\t\t\treturn fmt.Errorf(\"error decoding characteristic strictly for variant %v handler %v: %v\", v, hk, err)\n\t\t\t}\n\n\t\t}\n\t}\n\n\tif err.valid() {\n\t\treturn err\n\t}\n\n\tr.variantIDs = maps.Keys(r.variations)","sourceCodeStart":186,"sourceCodeEnd":222,"githubUrl":"https://github.com/apache/beam/blob/12126d8942aaf848030c478b4c6a28c6af861c66/sdks/go/pkg/beam/runners/prism/internal/config/config.go#L186-L222","documentation":"During LoadFromYaml, each handler config YAML node is re-encoded with yaml.Marshal and then re-decoded with KnownFields(true) to validate it against the characteristic's type. If the re-encode step fails (rare, since the node came from valid YAML), prism panics.","triggerScenarios":"yaml.Marshal(hyn) returns an error while re-encoding a handler's yaml.Node during config load — typically only with invalid/marshaling-incompatible node content injected programmatically rather than parsed from a file.","commonSituations":"Building config nodes programmatically with unsupported content; corrupt or non-standard YAML nodes; library version differences in go-yaml behavior for exotic node types.","solutions":["Validate the YAML file parses cleanly with a standard YAML parser before loading","Simplify exotic YAML constructs (anchors/aliases, tags) to plain mappings","Load config from a normal file rather than constructing yaml.Node values manually","Check go-yaml library version compatibility"],"exampleFix":"// before: exotic yaml the marshaler chokes on\nhandler: !custom-tag {a: 1}\n// after: plain yaml\nhandler:\n  a: 1","handlingStrategy":"validation","validationCode":"if _, err := yaml.Marshal(hyn); err != nil { return fmt.Errorf(\"handler node not marshalable: %w\", err) }","typeGuard":null,"tryCatchPattern":"defer func() { if r := recover(); r != nil { err = fmt.Errorf(\"config re-encode failed: %v\", r) } }()","preventionTips":["Keep handler YAML as plain mappings without exotic tags/anchors","Parse config from files rather than constructing yaml.Node in code","Test configs with go-yaml's KnownFields decoding locally first"],"tags":["go","beam","prism","config","yaml","panic"],"backgroundTag":"yaml-parse-error","analyzedSha":"12126d8942aaf848030c478b4c6a28c6af861c66","analyzedAt":"2026-09-13T01:50:10.254Z","contentChangedAt":"2026-09-13T01:50:10.254Z","schemaVersion":2},"datasetVersion":"2026-09-20T03:17:13.778Z"}