railpack

1package buildkit2 3import (4	"github.com/containerd/platforms"5	specs "github.com/opencontainers/image-spec/specs-go/v1"6)7 8// ParsePlatformWithDefaults parses a platform string and returns the corresponding specs.Platform.9// If the input is empty, it defaults to a Linux platform that matches the host architecture.10//11// This function handles the common case where we need to map host platforms to container platforms.12// We cannot use platforms.DefaultSpec() directly because it returns the host platform13// (e.g., darwin/arm64/v8 on macOS), but container base images only support Linux platforms.14// Instead, we map the host architecture to the corresponding Linux container platform15// to provide optimal performance while ensuring compatibility with container runtimes.16//17// Examples:18//   - "" -> linux/amd64 (on Intel hosts) or linux/arm64/v8 (on ARM hosts)19//   - "linux/amd64" -> linux/amd6420//   - "linux/arm64" -> linux/arm6421//   - "linux/arm64/v8" -> linux/arm64/v822func ParsePlatformWithDefaults(platformStr string) (specs.Platform, error) {23	if platformStr == "" {24		// Default to Linux platform for container builds25		// We cannot use platforms.DefaultSpec() directly because it returns the host platform26		// (e.g., darwin/arm64/v8 on macOS), but container base images only support Linux platforms.27		// Instead, we map the host architecture to the corresponding Linux container platform28		// to provide optimal performance while ensuring compatibility with container runtimes.29		hostPlatform := platforms.DefaultSpec()30		if hostPlatform.Architecture == "arm64" {31			return specs.Platform{OS: "linux", Architecture: "arm64", Variant: "v8"}, nil32		} else {33			return specs.Platform{OS: "linux", Architecture: "amd64"}, nil34		}35	}36 37	// Parse the user-specified platform string38	return platforms.Parse(platformStr)39}40