{"record":{"id":"d52029b158535f70","repo":"golang/go","slug":"internal-error-constructing-http-head-request-v","errorCode":null,"errorMessage":"internal error constructing HTTP HEAD request: %v\n","messagePattern":"internal error constructing HTTP HEAD request: (.+?)\n","errorType":"error_code","errorClass":null,"httpStatus":null,"severity":"error","filePath":"src/cmd/go/internal/auth/gitauth.go","lineNumber":62,"sourceCode":"\t}\n\tcmd := exec.Command(\"git\", \"credential\", \"fill\")\n\tcmd.Dir = dir\n\tcmd.Stdin = strings.NewReader(fmt.Sprintf(\"url=%s\\n\", url))\n\tout, err := cmd.CombinedOutput()\n\tif err != nil {\n\t\treturn \"\", nil, fmt.Errorf(\"'git credential fill' failed (url=%s): %w\\n%s\", url, err, out)\n\t}\n\tparsedPrefix, username, password := parseGitAuth(out)\n\tif parsedPrefix == \"\" {\n\t\treturn \"\", nil, fmt.Errorf(\"'git credential fill' failed for url=%s, could not parse url\\n\", url)\n\t}\n\t// Check that the URL Git gave us is a prefix of the one we requested.\n\tif !strings.HasPrefix(url, parsedPrefix) {\n\t\treturn \"\", nil, fmt.Errorf(\"requested a credential for %s, but 'git credential fill' provided one for %s\\n\", url, parsedPrefix)\n\t}\n\treq, err := http.NewRequest(\"HEAD\", parsedPrefix, nil)\n\tif err != nil {\n\t\treturn \"\", nil, fmt.Errorf(\"internal error constructing HTTP HEAD request: %v\\n\", err)\n\t}\n\treq.SetBasicAuth(username, password)\n\t// Asynchronously validate the provided credentials using a HEAD request,\n\t// allowing the git credential helper to update its cache without blocking.\n\t// This avoids repeatedly prompting the user for valid credentials.\n\t// This is a best-effort update; the primary validation will still occur\n\t// with the caller's client.\n\t// The request is intercepted for testing purposes to simulate interactions\n\t// with the credential helper.\n\tintercept.Request(req)\n\tgo updateGitCredentialHelper(client, req, out)\n\n\t// Return the parsed prefix and headers, even if credential validation fails.\n\t// The caller is responsible for the primary validation.\n\treturn parsedPrefix, req.Header, nil\n}\n\n// parseGitAuth parses the output of 'git credential fill', extracting","sourceCodeStart":44,"sourceCodeEnd":80,"githubUrl":"https://github.com/golang/go/blob/b6b368adc57c96c3151d224d172029f233ead2c3/src/cmd/go/internal/auth/gitauth.go#L44-L80","documentation":"Returned by runGitAuth when `http.NewRequest(\"HEAD\", parsedPrefix, nil)` fails. http.NewRequest only errors on a bad method or a URL that url.Parse rejects; for an https URL that has already been prefix-validated against the request, this is effectively an internal/defensive failure. In practice it indicates parsedPrefix contains characters url.Parse rejects despite passing the earlier HasPrefix check.","triggerScenarios":"parsedPrefix is a non-empty string that nonetheless fails url.Parse (e.g. contains control characters, invalid percent-encoding, or whitespace). Near-impossible given git output was already validated.","commonSituations":"Not expected for end users. Would indicate a bug in parseGitAuth producing a malformed prefix, or git output with unusual control characters.","solutions":["Report as a Go issue, attaching the `git credential fill` output (redact secrets).","If maintaining a fork, sanitize parsedPrefix (e.g. strip control chars) before constructing the request."],"exampleFix":null,"handlingStrategy":"validation","validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":["This is an internal/defensive error; not expected for end users.","If encountered, report a Go issue with the (redacted) git credential output."],"tags":["go-toolchain","goauth","git","authentication","internal","unreachable"],"analyzedSha":"b6b368adc57c96c3151d224d172029f233ead2c3","analyzedAt":"2026-08-12T00:22:02.250Z","schemaVersion":2},"datasetVersion":"2026-08-12T08:17:17.861Z"}