anomalyco/sst · error

failed to copy file contents

Error message

failed to copy file contents: %w

What it means

copyFile wraps io.Copy failures (reading src and writing dst streams) with this message. After both files open successfully, the actual byte transfer failed — typically a read error on the source or a write error (disk full, I/O error) on the destination. It is thrown from the same Python runtime copy helper used across build, packaging, and dev sync.

Solutions

1. Check free disk space and quota on the output volume
2. Re-run the deploy/dev sync — transient FS races often resolve on retry
3. Verify the source file is a regular readable file (not a fifo/device/symlink to something unreadable)
4. Inspect the wrapped error text to distinguish read vs write side failure

Example fix

// before
_, err = io.Copy(dstFile, srcFile)
// after
if fi, statErr := os.Stat(src); statErr == nil && !fi.Mode().IsRegular() {
	return fmt.Errorf("skipping non-regular file: %s", src)
}
_, err = io.Copy(dstFile, srcFile)

func regularReadable(path string) error {
	fi, err := os.Stat(path)
	if err != nil {
		return err
	}
	if !fi.Mode().IsRegular() {
		return fmt.Errorf("not a regular file: %s", path)
	}
	f, err := os.Open(path)
	if err != nil {
		return err
	}
	return f.Close()
}

if err := sstBuild(); err != nil {
	if strings.Contains(err.Error(), "failed to copy file contents") {
		// free disk space / re-run; transient FS races typically clear on retry
	}
}

When it happens

Trigger: io.Copy(dstFile, srcFile) errors during copyFile: source file unreadable mid-read (removed, changed permissions, device error) or destination write fails (disk full, quota, I/O error). Reached from ensureDockerfile, flattenPackageToRoot, copySourceFilesSimple, copyDependencyPackages, Run, and syncPythonFiles.

Common situations: Source file deleted or truncated by a watcher/build race while dev sync is copying; filesystem quota or full disk on the build output volume; networked filesystem (NFS/EFS) hiccup; source is a special file (device/fifo) that errors on read.

Related errors

• failed to create destination file
• error walking target directory during cleanup
• failed to copy binary
• failed to copy to
• failed to copy source files

AI-assisted analysis of anomalyco/sst@a0bd20f762 (2026-08-30). Data as JSON: /api/errors/525741f85aa97425. Report an issue: GitHub.

Appendix: source

Thrown at pkg/runtime/python/python.go:411

func copyFile(src, dst string) error {
	if err := os.MkdirAll(filepath.Dir(dst), 0755); err != nil {
		return fmt.Errorf("failed to create directory for %s: %w", dst, err)
	}

	srcFile, err := os.Open(src)
	if err != nil {
		return fmt.Errorf("failed to open source file: %w", err)
	}
	defer srcFile.Close()

	dstFile, err := os.Create(dst)
	if err != nil {
		return fmt.Errorf("failed to create destination file: %w", err)
	}
	defer dstFile.Close()

	if _, err := io.Copy(dstFile, srcFile); err != nil {
		return fmt.Errorf("failed to copy file contents: %w", err)
	}

	return nil
}

// skipContent skips __pycache__, .pyc files, and anything matching isIgnored.
func skipContent(relPath string, info os.FileInfo) bool {
	return isIgnored(relPath)
}

// skipBuildArtifacts skips only dirs that would break workspace package builds.
// Preserves metadata files (pyproject.toml, etc.) needed by uv pip install.
func skipBuildArtifacts(_ string, info os.FileInfo) bool {
	if !info.IsDir() {
		return false
	}
	name := info.Name()
	return name == "__pycache__" || name == ".venv" || name == "node_modules" || name == ".git"

View on GitHub (pinned to a0bd20f762)