{"record":{"id":"0bc9fb1ee3a7eb92","repo":"kubernetes/kops","slug":"path-type-t-for-q-does-not-implement-writetowith","errorCode":null,"errorMessage":"path type %T for %q does not implement WriteToWithContext","messagePattern":"path type %T for %q does not implement WriteToWithContext","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"upup/pkg/fi/http.go","lineNumber":113,"sourceCode":"\n\talgorithm := hashing.HashAlgorithmSHA256\n\tif hash != nil {\n\t\talgorithm = hash.Algorithm\n\t}\n\thasher := algorithm.NewHasher()\n\twriter := io.MultiWriter(dest, hasher)\n\n\tswitch u.Scheme {\n\tcase \"gs\", \"s3\", \"azureblob\":\n\t\t// vfs resolves the bucket and signs the request with the ambient cloud credentials,\n\t\t// such as the instance identity.\n\t\tp, err := vfs.Context.BuildVfsPath(desturl)\n\t\tif err != nil {\n\t\t\treturn nil, fmt.Errorf(\"building path for %q: %w\", desturl, err)\n\t\t}\n\t\tcloudPath, ok := p.(vfs.WriterToWithContext)\n\t\tif !ok {\n\t\t\treturn nil, fmt.Errorf(\"path type %T for %q does not implement WriteToWithContext\", p, desturl)\n\t\t}\n\t\tif _, err := cloudPath.WriteToWithContext(ctx, writer); err != nil {\n\t\t\treturn nil, fmt.Errorf(\"error downloading content from %q: %w\", desturl, err)\n\t\t}\n\tdefault:\n\t\treader, err := OpenURL(desturl)\n\t\tif err != nil {\n\t\t\treturn nil, err\n\t\t}\n\t\tdefer reader.Close()\n\n\t\tif _, err := io.Copy(writer, reader); err != nil {\n\t\t\treturn nil, fmt.Errorf(\"error downloading HTTP content from %q: %v\", desturl, err)\n\t\t}\n\t}\n\n\tactual := &hashing.Hash{\n\t\tAlgorithm: algorithm,","sourceCodeStart":95,"sourceCodeEnd":131,"githubUrl":"https://github.com/kubernetes/kops/blob/4c8573c808a73d578c5eadc86d410646ea0b0d73/upup/pkg/fi/http.go#L95-L131","documentation":"After building the vfs.Path for a gs/s3/azureblob URL, the code asserts the concrete type implements vfs.WriterToWithContext. If a path type lacks this interface, downloads cannot be streamed and this error names the type and URL. This is an internal capability mismatch, typically from an unsupported/custom vfs path implementation.","triggerScenarios":"A type assertion p.(vfs.WriterToWithContext) fails for a cloud-storage path — i.e. a vfs path implementation that does not support context-aware streaming writes.","commonSituations":"Custom or older vfs path types registered for the scheme; using a forked/modified kops where a new vfs backend lacks WriteToWithContext.","solutions":["Note the %T type in the error to identify which path implementation is used","Confirm you are on an unmodified, current kops build","If custom vfs code is involved, implement vfs.WriterToWithContext on that path type","Work around by serving the file over an HTTP(S) URL instead"],"exampleFix":"// before\ntype myPath struct{...} // no WriteToWithContext\n// after\nfunc (p *myPath) WriteToWithContext(ctx context.Context, w io.Writer) (int64, error) { ... }","handlingStrategy":"type-guard","validationCode":null,"typeGuard":"func supportsStreaming(p vfs.Path) bool {\n    _, ok := p.(vfs.WriterToWithContext)\n    return ok\n}","tryCatchPattern":"if _, err := fi.DownloadURL(ctx, assetURL, dest, nil); err != nil {\n    if strings.Contains(err.Error(), \"does not implement WriteToWithContext\") {\n        return fmt.Errorf(\"vfs path for %s lacks streaming support; use an HTTPS mirror\", assetURL)\n    }\n    return err\n}","preventionTips":["Use stock kops builds; avoid forks that add custom vfs path types","Keep kops updated so all vfs backends implement streaming writes","Prefer HTTPS mirrors when a backend's streaming support is uncertain"],"tags":["vfs","interface","download"],"backgroundTag":"interface-not-implemented","analyzedSha":"4c8573c808a73d578c5eadc86d410646ea0b0d73","analyzedAt":"2026-09-05T04:13:19.212Z","contentChangedAt":"2026-09-05T04:13:19.212Z","schemaVersion":2},"datasetVersion":"2026-09-12T07:17:12.445Z"}