cmd/create: Don't block user interaction while fetching the image size

It takes 'skopeo inspect' a few seconds to fetch the image size from the
remote registry, and while that happens the user can't interact with the
image download prompt:
  $ toolbox create
  Image required to create toolbox container.
  <wait for a few seconds>
  Download registry.fedoraproject.org/fedora-toolbox:39 (359.8MB)? [y/N]:

This feels awkward because it's not clear to the user what's going on
during those few seconds.  Moreover, while knowing the image size can be
convenient at times, for example when disk space and network bandwidth
are limited, it's not always important.

It will be better if 'skopeo inspect' ran in the background, while
waiting for the user to respond to the image download prompt, and once
the image size has been fetched, the prompt can be updated to include
it.

So, initially:
  $ toolbox create
  Image required to create toolbox container.
  Download registry.fedoraproject.org/fedora-toolbox:39 (...)? [y/N]:

... and then once the size is available:
  $ toolbox create
  Image required to create toolbox container.
  Download registry.fedoraproject.org/fedora-toolbox:39 (359.8MB)? [y/N]:

If skopeo(1) is missing or too old, then the prompt can continue without
the size, as it did before:
  $ toolbox create
  Image required to create toolbox container.
  Download registry.fedoraproject.org/fedora-toolbox:39 [y/N]:

The use of the context.Cause and context.WithCancelCause functions [1]
requires Go >= 1.20.  Bumping the Go version in src/go.mod then requires
a 'go mod tidy'.  Otherwise, it leads to:
  $ meson compile -C builddir --verbose
  /home/rishi/devel/containers/git/toolbox/src/go-build-wrapper
    /home/rishi/devel/containers/git/toolbox/src
    /home/rishi/devel/containers/git/toolbox/builddir src/toolbox
    0.0.99.4 cc /lib64/ld-linux-x86-64.so.2 false
  go: updates to go.mod needed; to update it:
          go mod tidy
  ninja: build stopped: subcommand failed.

[1] https://pkg.go.dev/context

#752
#1263

.github/workflows/ubuntu-tests.yaml

@@ -44,7 +44,7 @@ jobs:
             fish \
             gcc \
             go-md2man \
-            golang \
+            golang-1.20 \
             meson \
             ninja-build \
             openssl \
@@ -54,6 +54,16 @@ jobs:
             systemd \
             udisks2
 
+      - name: Set up PATH for Go 1.20
+        run: |
+          echo 'PATH=/usr/lib/go-1.20/bin:$PATH' >> "$GITHUB_ENV"
+          cat "$GITHUB_ENV"
+
+      - name: Debug
+        run: |
+          echo "$PATH"
+          cat "$GITHUB_ENV"
+
       - name: Checkout Bats
         uses: actions/checkout@v3
         with:

src/cmd/create.go

@@ -576,8 +576,7 @@ func getFullyQualifiedImageFromRepoTags(image string) (string, error) {
 	return imageFull, nil
 }
 
-func getImageSizeFromRegistry(imageFull string) (string, error) {
-	ctx := context.Background()
+func getImageSizeFromRegistry(ctx context.Context, imageFull string) (string, error) {
 	image, err := skopeo.Inspect(ctx, imageFull)
 	if err != nil {
 		return "", err
@@ -601,6 +600,23 @@ func getImageSizeFromRegistry(imageFull string) (string, error) {
 	return imageSizeHuman, nil
 }
 
+func getImageSizeFromRegistryAsync(ctx context.Context, imageFull string) (<-chan string, <-chan error) {
+	retValCh := make(chan string)
+	errCh := make(chan error)
+
+	go func() {
+		imageSize, err := getImageSizeFromRegistry(ctx, imageFull)
+		if err != nil {
+			errCh <- err
+			return
+		}
+
+		retValCh <- imageSize
+	}()
+
+	return retValCh, errCh
+}
+
 func getServiceSocket(serviceName string, unitName string) (string, error) {
 	logrus.Debugf("Resolving path to the %s socket", serviceName)
 
@@ -713,18 +729,7 @@ func pullImage(image, release, authFile string) (bool, error) {
 	}
 
 	if promptForDownload {
-		fmt.Println("Image required to create toolbox container.")
-
-		var prompt string
-
-		if imageSize, err := getImageSizeFromRegistry(imageFull); err != nil {
-			logrus.Debugf("Getting image size failed: %s", err)
-			prompt = fmt.Sprintf("Download %s? [y/N]:", imageFull)
-		} else {
-			prompt = fmt.Sprintf("Download %s (%s)? [y/N]:", imageFull, imageSize)
-		}
-
-		shouldPullImage = askForConfirmation(prompt)
+		shouldPullImage = showPromptForDownload(imageFull)
 	}
 
 	if !shouldPullImage {
@@ -756,6 +761,138 @@ func pullImage(image, release, authFile string) (bool, error) {
 	return true, nil
 }
 
+func showPromptForDownload(imageFull string) bool {
+	fmt.Println("Image required to create toolbox container.")
+
+	prompt := fmt.Sprintf("Download %s ( ... MB)? [y/N]:", imageFull)
+
+	parentCtx := context.Background()
+	askCtx, askCancel := context.WithCancelCause(parentCtx)
+	defer askCancel(errors.New("clean-up"))
+
+	askCh, askErrCh := askForConfirmationAsync(askCtx, prompt, false)
+
+	imageSizeCtx, imageSizeCancel := context.WithCancelCause(parentCtx)
+	defer imageSizeCancel(errors.New("clean-up"))
+
+	imageSizeCh, imageSizeErrCh := getImageSizeFromRegistryAsync(imageSizeCtx, imageFull)
+
+	var imageSize string
+	var shouldPullImage bool
+
+	select {
+	case val := <-askCh:
+		shouldPullImage = val
+		cause := fmt.Errorf("%w: received confirmation without image size", context.Canceled)
+		imageSizeCancel(cause)
+	case err := <-askErrCh:
+		shouldPullImage = false
+		cause := fmt.Errorf("failed to ask for confirmation without image size: %w", err)
+		imageSizeCancel(cause)
+	case val := <-imageSizeCh:
+		imageSize = val
+		cause := fmt.Errorf("%w: received image size", context.Canceled)
+		askCancel(cause)
+	case err := <-imageSizeErrCh:
+		cause := fmt.Errorf("failed to get image size: %w", err)
+		askCancel(cause)
+	}
+
+	if imageSizeCtx.Err() != nil && askCtx.Err() == nil {
+		cause := context.Cause(imageSizeCtx)
+		logrus.Debugf("Show prompt for download: image size canceled: %s", cause)
+		return shouldPullImage
+	}
+
+	var done bool
+
+	if imageSizeCtx.Err() == nil && askCtx.Err() != nil {
+		select {
+		case val := <-askCh:
+			logrus.Debugf("Show prompt for download: received pending confirmation without image size")
+			shouldPullImage = val
+			done = true
+		case err := <-askErrCh:
+			logrus.Debugf("Show prompt for download: failed to ask for confirmation without image size: %s",
+				err)
+		}
+	} else {
+		panic("code should not be reached")
+	}
+
+	cause := context.Cause(askCtx)
+	logrus.Debugf("Show prompt for download: ask canceled: %s", cause)
+
+	if done {
+		return shouldPullImage
+	}
+
+	var restoreCursor bool
+
+	if errors.Is(cause, context.Canceled) {
+		imageSizeLen := len(imageSize)
+		var padding1 int
+		var padding2 int
+		var padding3 int
+		var padding4 int
+
+		if imageSizeLen < 7 {
+			padding4 = 7 - imageSizeLen
+		}
+
+		if padding4 > 1 {
+			padding3 = padding4 - 1
+			padding4 = 1
+		}
+
+		if padding3 > 1 {
+			padding2 = padding3 - 1
+			padding3 = 1
+		}
+
+		if padding2 > 1 {
+			padding1 = padding2 - 1
+			padding2 = 1
+		}
+
+		prompt = fmt.Sprintf("Download %s (%*s%s%*s)? %*s[y/N]:%*s",
+			imageFull,
+			padding1, "",
+			imageSize,
+			padding2, "",
+			padding3, "",
+			padding4, "")
+
+		// Save the cursor position.
+		fmt.Printf("\033[s")
+
+		restoreCursor = true
+	} else {
+		prompt = fmt.Sprintf("Download %s? [y/N]:", imageFull)
+
+		// Delete entire line regardless of cursor position.
+		fmt.Printf("\033[2K")
+	}
+
+	fmt.Printf("\r")
+
+	askAgainCtx, askAgainCancel := context.WithCancelCause(parentCtx)
+	defer askAgainCancel(errors.New("clean-up"))
+
+	askAgainCh, askAgainErrCh := askForConfirmationAsync(askAgainCtx, prompt, restoreCursor)
+
+	select {
+	case val := <-askAgainCh:
+		logrus.Debug("Show prompt for download: received confirmation with image size")
+		shouldPullImage = val
+	case err := <-askAgainErrCh:
+		logrus.Debugf("Show prompt for download: failed to ask for confirmation with image size: %s", err)
+		shouldPullImage = false
+	}
+
+	return shouldPullImage
+}
+
 // systemdNeedsEscape checks whether a byte in a potential dbus ObjectPath needs to be escaped
 func systemdNeedsEscape(i int, b byte) bool {
 	// Escape everything that is not a-z-A-Z-0-9

src/go.mod

@@ -1,6 +1,6 @@
 module github.com/containers/toolbox
 
-go 1.14
+go 1.20
 
 require (
 	github.com/HarryMichal/go-version v1.0.1
@@ -16,3 +16,25 @@ require (
 	golang.org/x/sys v0.1.0
 	golang.org/x/term v0.0.0-20210927222741-03fcf44c2211
 )
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/fatih/color v1.13.0 // indirect
+	github.com/hashicorp/hcl v1.0.0 // indirect
+	github.com/inconshreveable/mousetrap v1.0.0 // indirect
+	github.com/magiconair/properties v1.8.5 // indirect
+	github.com/mattn/go-colorable v0.1.12 // indirect
+	github.com/mattn/go-isatty v0.0.14 // indirect
+	github.com/mitchellh/mapstructure v1.4.3 // indirect
+	github.com/pelletier/go-toml v1.9.4 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/spf13/afero v1.6.0 // indirect
+	github.com/spf13/cast v1.4.1 // indirect
+	github.com/spf13/jwalterweatherman v1.1.0 // indirect
+	github.com/spf13/pflag v1.0.5 // indirect
+	github.com/subosito/gotenv v1.2.0 // indirect
+	golang.org/x/text v0.3.7 // indirect
+	gopkg.in/ini.v1 v1.66.2 // indirect
+	gopkg.in/yaml.v2 v2.4.0 // indirect
+	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b // indirect
+)

src/go.sum

@@ -203,7 +203,6 @@ github.com/googleapis/gax-go/v2 v2.1.0/go.mod h1:Q3nei7sK6ybPYH7twZdmQpAd1MKb7pf
 github.com/googleapis/gax-go/v2 v2.1.1/go.mod h1:hddJymUZASv3XPyGkUpKj8pPO47Rmb0eJc8R6ouapiM=
 github.com/grpc-ecosystem/grpc-gateway v1.16.0/go.mod h1:BDjrQk3hbvj6Nolgz8mAMFbcEtjT1g+wF4CSlocrBnw=
 github.com/hashicorp/consul/api v1.11.0/go.mod h1:XjsvQN+RJGWI2TWy1/kqaE16HrR2J/FWgkYjdZQsX9M=
-github.com/hashicorp/consul/api v1.12.0/go.mod h1:6pVBMo0ebnYdt2S3H87XhekM/HHrUoTD2XXb/VrZVy0=
 github.com/hashicorp/consul/sdk v0.8.0/go.mod h1:GBvyrGALthsZObzUGsfgHZQDXjg4lOjagTIwIR1vPms=
 github.com/hashicorp/errwrap v1.0.0/go.mod h1:YH+1FKiLXxHSkmPseP+kNlulaMuP3n2brvKWEqk/Jc4=
 github.com/hashicorp/go-cleanhttp v0.5.0/go.mod h1:JpRdi6/HCYpAwUzNwuwqhbovhLtngrth3wmdIIUrZ80=
@@ -319,7 +318,6 @@ github.com/rogpeppe/go-internal v1.3.0/go.mod h1:M8bDsm7K2OlrFYOpmOWEs/qY81heoFR
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
 github.com/ryanuber/columnize v0.0.0-20160712163229-9b3edd62028f/go.mod h1:sm1tb6uqfes/u+d4ooFouqFdy9/2g9QGwK3SQygK0Ts=
 github.com/sagikazarmark/crypt v0.3.0/go.mod h1:uD/D+6UF4SrIR1uGEv7bBNkNqLGqUr43MRiaGWX1Nig=
-github.com/sagikazarmark/crypt v0.4.0/go.mod h1:ALv2SRj7GxYV4HO9elxH9nS6M9gW+xDNxqmyJ6RfDFM=
 github.com/sean-/seed v0.0.0-20170313163322-e2103e2c3529/go.mod h1:DxrIzT+xaE7yg65j358z/aeFdxmN0P9QXhEzd20vsDc=
 github.com/sirupsen/logrus v1.2.0/go.mod h1:LxeOpSwHxABJmUn/MG1IvRgCAasNZTLOkJPxbbu5VWo=
 github.com/sirupsen/logrus v1.4.2/go.mod h1:tLMulIdttU9McNUspp0xgXVQah82FyeX6MwdIuYE2rE=
@@ -551,7 +549,6 @@ golang.org/x/sys v0.0.0-20210927094055-39ccf1dd6fa6/go.mod h1:oPkhp1MJrh7nUepCBc
 golang.org/x/sys v0.0.0-20211007075335-d3039528d8ac/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20211124211545-fe61309f8881/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20211205182925-97ca703d548d/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20211210111614-af8b64212486/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.1.0 h1:kunALQeHf1/185U1i0GOB/fy1IPRDDpuoOOqRReG57U=
 golang.org/x/sys v0.1.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
@@ -660,7 +657,6 @@ google.golang.org/api v0.57.0/go.mod h1:dVPlbZyBo2/OjBpmvNdpn2GRm6rPy75jyU7bmhdr
 google.golang.org/api v0.59.0/go.mod h1:sT2boj7M9YJxZzgeZqXogmhfmRWDtPzT31xkieUbuZU=
 google.golang.org/api v0.61.0/go.mod h1:xQRti5UdCmoCEqFxcz93fTl338AVqDgyaDRuOZ3hg9I=
 google.golang.org/api v0.62.0/go.mod h1:dKmwPCydfsad4qCH08MSdgWjfHOyfpd4VtDGgRFdavw=
-google.golang.org/api v0.63.0/go.mod h1:gs4ij2ffTRXwuzzgJl/56BdwJaA194ijkfn++9tDuPo=
 google.golang.org/appengine v1.1.0/go.mod h1:EbEs0AVv82hx2wNQdGPgUI5lhzA/G0D9YwlJXL52JkM=
 google.golang.org/appengine v1.4.0/go.mod h1:xpcJRLb0r/rnEns0DIKYYv+WjYCduHsrkT7/EB5XEv4=
 google.golang.org/appengine v1.5.0/go.mod h1:xpcJRLb0r/rnEns0DIKYYv+WjYCduHsrkT7/EB5XEv4=
@@ -758,7 +754,6 @@ google.golang.org/grpc v1.39.1/go.mod h1:PImNr+rS9TWYb2O4/emRugxiyHZ5JyHW5F+RPnD
 google.golang.org/grpc v1.40.0/go.mod h1:ogyxbiOoUXAkP+4+xa6PZSE9DZgIHtSpzjDTB9KAK34=
 google.golang.org/grpc v1.40.1/go.mod h1:ogyxbiOoUXAkP+4+xa6PZSE9DZgIHtSpzjDTB9KAK34=
 google.golang.org/grpc v1.42.0/go.mod h1:k+4IHHFw41K8+bbowsex27ge2rCb65oeWqe4jJ590SU=
-google.golang.org/grpc v1.43.0/go.mod h1:k+4IHHFw41K8+bbowsex27ge2rCb65oeWqe4jJ590SU=
 google.golang.org/grpc/cmd/protoc-gen-go-grpc v1.1.0/go.mod h1:6Kw0yEErY5E/yWrBtf03jp27GLLJujG4z/JK95pnjjw=
 google.golang.org/protobuf v0.0.0-20200109180630-ec00e32a8dfd/go.mod h1:DFci5gLYBciE7Vtevhsrf46CRTquxDuWsQurQQe4oz8=
 google.golang.org/protobuf v0.0.0-20200221191635-4d8936d0db64/go.mod h1:kwYJMbMJ01Woi6D6+Kah6886xMZcty6N08ah7+eCXa0=