From 9b5b03d1e03b20a80c0a0c92866136d4243e5f4a Mon Sep 17 00:00:00 2001
From: Achilleas Tzenetopoulos <atzenetopoulos@gmail.com>
Date: Wed, 27 Jan 2021 01:49:34 +0200
Subject: [PATCH] list volumes before pruning

Signed-off-by: Achilleas Tzenetopoulos <atzenetopoulos@gmail.com>
---
 cmd/podman/volumes/prune.go  | 52 +++++++++++++++++++++++++++++++-----
 test/system/160-volumes.bats | 15 +++++++++++
 2 files changed, 61 insertions(+), 6 deletions(-)

diff --git a/cmd/podman/volumes/prune.go b/cmd/podman/volumes/prune.go
index 0f3ba9ef66d5..39ad2735bc95 100644
--- a/cmd/podman/volumes/prune.go
+++ b/cmd/podman/volumes/prune.go
@@ -49,16 +49,46 @@ func init() {
 
 func prune(cmd *cobra.Command, args []string) error {
 	var (
-		pruneOptions = entities.VolumePruneOptions{}
+		pruneOptions  = entities.VolumePruneOptions{}
+		listOptions   = entities.VolumeListOptions{}
+		unusedOptions = entities.VolumeListOptions{}
 	)
 	// Prompt for confirmation if --force is not set
 	force, err := cmd.Flags().GetBool("force")
 	if err != nil {
 		return err
 	}
+	pruneOptions.Filters, err = filters.ParseFilterArgumentsIntoFilters(filter)
 	if !force {
 		reader := bufio.NewReader(os.Stdin)
-		fmt.Println("WARNING! This will remove all volumes not used by at least one container.")
+		fmt.Println("WARNING! This will remove all volumes not used by at least one container. The following volumes will be removed:")
+		if err != nil {
+			return err
+		}
+		listOptions.Filter, err = filters.ParseFilterArgumentsIntoFilters(filter)
+		if err != nil {
+			return err
+		}
+		// filter all the dangling volumes
+		unusedOptions.Filter = make(map[string][]string, 1)
+		unusedOptions.Filter["dangling"] = []string{"true"}
+		unusedVolumes, err := registry.ContainerEngine().VolumeList(context.Background(), unusedOptions)
+		if err != nil {
+			return err
+		}
+		// filter volumes based on user input
+		filteredVolumes, err := registry.ContainerEngine().VolumeList(context.Background(), listOptions)
+		if err != nil {
+			return err
+		}
+		finalVolumes := getIntersection(unusedVolumes, filteredVolumes)
+		if len(finalVolumes) < 1 {
+			fmt.Println("No dangling volumes found")
+			return nil
+		}
+		for _, fv := range finalVolumes {
+			fmt.Println(fv.Name)
+		}
 		fmt.Print("Are you sure you want to continue? [y/N] ")
 		answer, err := reader.ReadString('\n')
 		if err != nil {
@@ -68,13 +98,23 @@ func prune(cmd *cobra.Command, args []string) error {
 			return nil
 		}
 	}
-	pruneOptions.Filters, err = filters.ParseFilterArgumentsIntoFilters(filter)
-	if err != nil {
-		return err
-	}
 	responses, err := registry.ContainerEngine().VolumePrune(context.Background(), pruneOptions)
 	if err != nil {
 		return err
 	}
 	return utils.PrintVolumePruneResults(responses, false)
 }
+
+func getIntersection(a, b []*entities.VolumeListReport) []*entities.VolumeListReport {
+	var intersection []*entities.VolumeListReport
+	hash := make(map[string]bool, len(a))
+	for _, aa := range a {
+		hash[aa.Name] = true
+	}
+	for _, bb := range b {
+		if hash[bb.Name] {
+			intersection = append(intersection, bb)
+		}
+	}
+	return intersection
+}
diff --git a/test/system/160-volumes.bats b/test/system/160-volumes.bats
index 0b7aab2fb624..4952eafc2ff0 100644
--- a/test/system/160-volumes.bats
+++ b/test/system/160-volumes.bats
@@ -214,6 +214,13 @@ EOF
         run_podman volume create $vol
     done
 
+    # Create two additional labeled volumes
+    for i in 5 6; do
+        vol=myvol${i}$(random_string)
+        v[$i]=$vol
+        run_podman volume create $vol --label "mylabel"
+    done
+
     # (Assert that output is formatted, not a one-line blob: #8011)
     run_podman volume inspect ${v[1]}
     if [[ "${#lines[*]}" -lt 10 ]]; then
@@ -225,6 +232,14 @@ EOF
     run_podman run --name c2 --volume ${v[2]}:/vol2 -v ${v[3]}:/vol3 \
                $IMAGE date
 
+    # List available volumes for pruning after using 1,2,3
+    run_podman volume prune <<< N
+    is "$(echo $(sort <<<${lines[@]:1:3}))" "${v[4]} ${v[5]} ${v[6]}" "volume prune, with 1,2,3 in use, lists 4,5,6"
+
+    # List available volumes for pruning after using 1,2,3 and filtering; see #8913
+    run_podman volume prune --filter label=mylabel <<< N
+    is "$(echo $(sort <<<${lines[@]:1:2}))" "${v[5]} ${v[6]}" "volume prune, with 1,2,3 in use and 4 filtered out, lists 5,6"
+
     # prune should remove v4
     run_podman volume prune --force
     is "$output" "${v[4]}" "volume prune, with 1, 2, 3 in use, deletes only 4"