Supporting Private GitHub repos and other artifact stores

internal/download/fetch.go

@@ -18,6 +18,8 @@ import (
 	"io"
 	"net/http"
 	"os"
+	"os/exec"
+	"strings"
 
 	"github.com/pkg/errors"
 	"k8s.io/klog/v2"
@@ -56,3 +58,63 @@ func (f fileFetcher) Get(_ string) (io.ReadCloser, error) {
 
 // NewFileFetcher returns a local file reader.
 func NewFileFetcher(path string) Fetcher { return fileFetcher{f: path} }
+
+var _ Fetcher = CommandFetcher{}
+
+// CommandFetcher is used to run a command to receive a file as stdout
+type CommandFetcher struct{}
+
+func (CommandFetcher) Get(cmd string) (io.ReadCloser, error) {
+	var stream io.ReadCloser
+
+	// Create tempFile for loading the plugin artifact
+	tempFile, err := os.CreateTemp("", "")
+	if err != nil {
+		return stream, err
+	}
+	defer klog.V(2).Infof("Removed temp file at %q", tempFile.Name())
+	defer os.Remove(tempFile.Name())
+
+	klog.V(2).Infof("Created temp file for command output at %q", tempFile.Name())
+
+	// Intentionally not closing the stream object in this function!
+	// The open file to tempFile will remain readable until the last process
+	// releases it. Another function is responsible for closing the
+	// io.ReaderCloser.
+	stream, err = os.Open(tempFile.Name())
+	if err != nil {
+		return stream, err
+	}
+
+	// HACK REMOVEME TESTING ONLY
+	// This is a workaround to accept command within the `uri` key of the krew
+	// plugin spec. An alternative solution, which is likely more optimal, is
+	// adding a new field to the spec for `downloadCommand` or similarly named
+	// key which would contain a command to run. This hack was put in place to
+	// test the rough implementation of loading a plugin from the stdout of a
+	// command.
+	cmd = strings.Replace(cmd, "cmd://", "", 1)
+
+	// TODO Improve splitting, this implementation has issues with newlines and
+	// qoutes in the cmd string.
+	c := strings.Split(cmd, " ")
+	runner := exec.Command(c[0], c[1:]...)
+
+	// NOTE Attempted to pass runner.Stdout() as an io.ReaderCloser but the io
+	// closes as soon as the application finishes running, which cannot extend
+	// reading beyond this function. Instead opted to push this into a tempFile
+	// on the local filesystem.
+	// Send stdout to tempFile for later ingestion
+	runner.Stdout = tempFile
+
+	klog.V(2).Infof("Running command %q", cmd)
+	if err := runner.Run(); err != nil {
+		// TODO It would be helpful to have more diagnostic information like the
+		// stdout and stderr of the command if Run() fails to exit 0. Right now the
+		// Command err just says things like `exited code 1` or similarly vague
+		// output. Could use klog.V(N)... to log output with verbosity.
+		return stream, errors.Wrapf(err, "failed to run command: %s", cmd)
+	}
+
+	return stream, err
+}

internal/installation/install.go

@@ -140,7 +140,7 @@ func applyDefaults(platform *index.Platform) {
 // while validating its checksum with the provided sha256sum, and extracts its contents to extractDir that must be.
 // created.
 func downloadAndExtract(extractDir, uri, sha256sum, overrideFile string) error {
-	var fetcher download.Fetcher = download.HTTPFetcher{}
+	var fetcher download.Fetcher = uriFetcherSelector(uri)
 	if overrideFile != "" {
 		fetcher = download.NewFileFetcher(overrideFile)
 	}
@@ -150,6 +150,33 @@ func downloadAndExtract(extractDir, uri, sha256sum, overrideFile string) error {
 	return errors.Wrap(err, "failed to unpack the plugin archive")
 }
 
+// uriFetcherSelector returns a Fetcher based on uri scheme
+// HACK Do not ship, strictly for testing. This was a dummy implementation to
+// select the "Fetcher" interface based on the contents of `uri` spec key. An
+// alternative approach would be to have another key like `downloadCommand` or
+// even a more deep spec which could include things like environment vars, etc.
+// Alternatively, if this is a desirable pattern, you could add real schemes
+// like gs:// and s3:// which could invoke supported upstream cloud provider
+// SDKs.
+func uriFetcherSelector(uri string) (f download.Fetcher) {
+	switch {
+	case strings.HasPrefix(uri, "http://"):
+		f = download.HTTPFetcher{}
+	case strings.HasPrefix(uri, "https://"):
+		f = download.HTTPFetcher{}
+	case strings.HasPrefix(uri, "cmd://"):
+		f = download.CommandFetcher{}
+	case strings.HasPrefix(uri, "file://"):
+		// HACK This is just an example of natively supporting a local file
+		// artifact in the uri field.
+		f = download.NewFileFetcher(strings.Replace(uri, "file://", "", 1))
+	default:
+		// Alternatives could be to send a user error here
+		f = download.HTTPFetcher{}
+	}
+	return f
+}
+
 // Uninstall will uninstall a plugin.
 func Uninstall(p environment.Paths, name string) error {
 	if name == constants.KrewPluginName {