Function prepareDependenciesLayer

pkg/python/python.go:359–403

prepareDependenciesLayer is a helper function that handles the common logic for preparing a dependency layer. It checks for empty requirements, manages the cache, and clears the layer if necessary. It returns a boolean indicating whether the installation should proceed.

(ctx *gcp.Context, l *libcnb.Layer, installerName string, reqs ...string)

// It checks for empty requirements, manages the cache, and clears the layer if necessary.
// It returns a boolean indicating whether the installation should proceed.
func prepareDependenciesLayer(ctx *gcp.Context, l *libcnb.Layer, installerName string, reqs ...string) (bool, error) {
	// Defensive check
	if len(reqs) == 0 {
		ctx.Debugf("No requirements files to install, clearing layer.")
		if err := ctx.ClearLayer(l); err != nil {
			return false, fmt.Errorf("clearing layer %q: %w", l.Name, err)
		}
		return false, nil
	}

	// Caching logic
	currentPythonVersion, err := Version(ctx)
	if err != nil {
		return false, err
	}
	hash, cached, err := cache.HashAndCheck(ctx, l, dependencyHashKey,
		cache.WithFiles(reqs...),
		cache.WithStrings(currentPythonVersion, installerName))
	if err != nil {
		return false, err
	}

	// Check cache expiration to pick up new versions of dependencies that are not pinned.
	expired := cacheExpired(ctx, l)

	if cached && !expired {
		ctx.CacheHit(l.Name)
		return false, nil
	}
	ctx.CacheMiss(l.Name)

	if expired {
		ctx.Debugf("Dependencies cache expired, clearing layer.")
	}
	if err := ctx.ClearLayer(l); err != nil {
		return false, fmt.Errorf("clearing layer %q: %w", l.Name, err)
	}

	// Update layer metadata for caching
	cache.Add(ctx, l, dependencyHashKey, hash)
	ctx.SetMetadata(l, pythonVersionKey, currentPythonVersion)
	ctx.SetMetadata(l, expiryTimestampKey, time.Now().Add(expirationTime).Format(dateFormat))

	return true, nil
}

// compileBytecode is a helper that generates deterministic hash-based pyc files for faster startup.
func compileBytecode(ctx *gcp.Context, path string) error {