{"id":"8ba148d850763c62","repo":"gofiber/fiber","slug":"failed-to-open-w","errorCode":null,"errorMessage":"failed to open: %w","messagePattern":"failed to open: %w","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"helpers.go","lineNumber":155,"sourceCode":"\tvalue := reflect.NewAt(field.Type(), unsafe.Pointer(field.UnsafeAddr())).Elem() //nolint:gosec // Access to unexported field is required for listeners that don't expose TLS config methods.\n\tif !value.IsValid() {\n\t\treturn nil\n\t}\n\n\tcfg, ok := value.Interface().(*tls.Config)\n\tif !ok {\n\t\treturn nil\n\t}\n\n\treturn cfg\n}\n\n// readContent opens a named file and read content from it\nfunc readContent(rf io.ReaderFrom, name string) (int64, error) {\n\t// Read file\n\tf, err := os.Open(filepath.Clean(name))\n\tif err != nil {\n\t\treturn 0, fmt.Errorf(\"failed to open: %w\", err)\n\t}\n\tdefer func() {\n\t\tif err = f.Close(); err != nil {\n\t\t\tlog.Errorf(\"Error closing file: %s\", err)\n\t\t}\n\t}()\n\tn, readErr := rf.ReadFrom(f)\n\tif readErr != nil {\n\t\treturn n, fmt.Errorf(\"failed to read: %w\", readErr)\n\t}\n\treturn n, nil\n}\n\n// quoteEscapeMask marks the lanes of w holding bytes quoteRawString must\n// escape: '\\\\', '\"', any C0 control (including HTAB), or DEL. Lanes >= 0x80\n// are never marked; non-ASCII bytes pass through verbatim. This is\n// utils.IndexNonQuotable's RFC 9110 set widened by HTAB, which the RFC\n// permits as qdtext but this function has always percent-encoded.","sourceCodeStart":137,"sourceCodeEnd":173,"githubUrl":"https://github.com/gofiber/fiber/blob/9a4c7e57fe0b080a04235d28a4b0d2b4b353d58c/helpers.go#L137-L173","documentation":"Returned by the internal readContent helper when os.Open fails to open the named file. readContent is used to load file content into an io.ReaderFrom (e.g. reading a template file for rendering in res.go). The error wraps the underlying os.PathError so the caller sees both the 'failed to open' context and the OS reason.","triggerScenarios":"Rendering a template via c.Render() with a template name/path that does not exist on disk, or where the process lacks read permission on the template file. readContent(buf, name) calls os.Open(filepath.Clean(name)) which returns ENOENT or EACCES.","commonSituations":"Wrong working directory so the relative template path resolves incorrectly, missing template file in the deployment artifact, file permission bits stripping read access, or a typo in the template name passed to c.Render().","solutions":["Verify the file path exists and is readable by the process (check with ls -l on the path).","Use absolute paths or ensure the working directory is set correctly in the deployment.","Confirm the template file is included in the Docker image / build artifact.","Fix filesystem permissions so the process owner can read the file."],"exampleFix":"// before\nc.Render(\"views/user.tmpl\", bind) // file missing\n\n// after\n// ensure 'views/user.tmpl' exists at the expected path, or register a template engine\nc.Render(\"views/user.tmpl\", bind)","handlingStrategy":"validation","validationCode":"// Ensure a template file is readable before rendering\nif _, err := os.Stat(filepath.Clean(name)); err != nil {\n    return fmt.Errorf(\"template not accessible %q: %w\", name, err)\n}","typeGuard":null,"tryCatchPattern":"if err := c.Render(name, bind); err != nil {\n    if strings.Contains(err.Error(), \"failed to open\") {\n        return c.Status(fiber.StatusNotFound).SendString(\"template not found\")\n    }\n    return err\n}","preventionTips":["Use absolute paths or set the working directory explicitly in production.","Include template files in the build artifact / Docker image.","Preload and validate templates at startup.","Verify read permissions for the process owner."],"tags":["filesystem","template","render","go"],"analyzedSha":"9a4c7e57fe0b080a04235d28a4b0d2b4b353d58c","analyzedAt":"2026-08-04T21:44:03.395Z","schemaVersion":2}