gofr-dev/gofr · error

%w: S3 file is empty

Error message

%w: S3 file is empty

What it means

This error wraps ErrNilResponse: during (*S3File).Read, the GetObject call succeeded but the response body was nil, so the S3 file appears empty/unreadable and the read is aborted with 0 bytes. The wrapper message names the wrapped sentinel, so errors.Is(err, s3.ErrNilResponse) matches it.

Source

Thrown at pkg/gofr/datasource/file/s3/file.go:153

	// empty objects and backends that reject "bytes=0-" behave as before.
	if f.offset > 0 {
		input.Range = aws.String(fmt.Sprintf("bytes=%d-", f.offset))
	}

	res, err := f.conn.GetObject(context.TODO(), input)
	if err != nil {
		msg = fmt.Sprintf("Failed to retrieve %q: %v", fileName, err)
		return 0, err
	}

	// Close the body from any previous read before replacing it, otherwise the
	// earlier HTTP connection leaks.
	f.closeBody()

	f.body = res.Body
	if f.body == nil {
		msg = fmt.Sprintf("File %q is nil", fileName)
		return 0, fmt.Errorf("%w: S3 file is empty", ErrNilResponse)
	}

	// If a byte range was requested (offset > 0) but the backend replied with the
	// whole object (no Content-Range), io.ReadFull would fill p from byte 0 and
	// silently serve the wrong bytes. Refuse rather than corrupt the read.
	if f.offset > 0 && res.ContentRange == nil {
		f.closeBody()
		f.body = nil
		msg = fmt.Sprintf("Range request for %q not honored by backend", fileName)

		return 0, ErrRangeNotHonored
	}

	// normalizeReadFull fills p completely unless the object ends first, reporting
	// a short fill as io.EOF along with the real byte count — honoring the io.Reader
	// contract that n reflects the number of bytes actually read.
	n, err = normalizeReadFull(f.body, p)
	if err != nil && !errors.Is(err, io.EOF) {

View on GitHub (pinned to 187eb24962)

Solutions

1. Confirm the object is fully retrievable with the AWS CLI and that the bucket/key are correct.
2. Fix or upgrade the S3-compatible backend/proxy so GetObject always streams a body on 200.
3. Populate Body in any mock/test client used with this datasource.
4. Check errors.Is(err, s3.ErrNilResponse) in your error handling and retry or fail the read explicitly.

Example fix

// handling
if err != nil {
    if errors.Is(err, s3datasource.ErrNilResponse) {
        // backend returned no body; retry or surface a 5xx
    }
}

n, err := f.Read(buf)
if err != nil && errors.Is(err, s3datasource.ErrNilResponse) {
    // treat as failed read; retry or surface backend health issue
    return fmt.Errorf("read %s: %w", name, err)
}

When it happens

Trigger: Any Read() call on an S3File where the backend returns a GetObjectOutput with a nil Body — malformed backend responses, incomplete mocks, or SDK/backend contract mismatches.

Common situations: S3-compatible stores (MinIO/SeaweedFS) returning degraded 200 responses; test stubs of GetObjectOutput without Body; intermittent proxy failures stripping the body.

Related errors

• response retrieved is nil
• errFileNotOpenForReading
• s3 backend did not honor the requested byte range
• %w: negative offset %d
• out of range

AI-assisted analysis of gofr-dev/gofr@187eb24962 (2026-09-01). Data as JSON: /api/errors/2ca74360c2db2385. Report an issue: GitHub.