shell completion for paths inside the image/container

Add shell completion for paths inside the container or image. Currently
podman run IMAGE [TAB] only uses the default shell completion which
suggests paths on the host. This is fine for some cases but often the
user wants a path which only exists in the image/container.

This commits adds support for that. Both podman create/run can now
complete the paths from the image, podman cp ctr:... now completes paths
from the actual container.

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

2 files changed, 186 insertions, 22 deletions

diff --git a/cmd/podman/common/completion.go b/cmd/podman/common/completion.go
index 3720e9608..5eef5f982 100644
--- a/cmd/podman/common/completion.go
+++ b/cmd/podman/common/completion.go
@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"fmt"
 	"os"
+	"path"
 	"reflect"
 	"strconv"
 	"strings"
@@ -21,6 +22,7 @@ import (
 	"github.com/containers/podman/v4/pkg/signal"
 	systemdDefine "github.com/containers/podman/v4/pkg/systemd/define"
 	"github.com/containers/podman/v4/pkg/util"
+	securejoin "github.com/cyphar/filepath-securejoin"
 	"github.com/spf13/cobra"
 )
 
@@ -282,6 +284,61 @@ func getNetworks(cmd *cobra.Command, toComplete string, cType completeType) ([]s
 	return suggestions, cobra.ShellCompDirectiveNoFileComp
 }
 
+func getPathCompletion(root string, toComplete string) []string {
+	if toComplete == "" {
+		toComplete = "/"
+	}
+	// Important: securejoin is required to make sure we never leave the root mount point
+	userpath, err := securejoin.SecureJoin(root, toComplete)
+	if err != nil {
+		cobra.CompErrorln(err.Error())
+		return nil
+	}
+	var base string
+	f, err := os.Open(userpath)
+	if err != nil {
+		// Do not use path.Dir() since this cleans the paths which
+		// then no longer matches the user input.
+		userpath, base = path.Split(userpath)
+		toComplete, _ = path.Split(toComplete)
+		f, err = os.Open(userpath)
+		if err != nil {
+			return nil
+		}
+	}
+	stat, err := f.Stat()
+	if err != nil {
+		cobra.CompErrorln(err.Error())
+		return nil
+	}
+	if !stat.IsDir() {
+		// nothing to complete since it is no dir
+		return nil
+	}
+	entries, err := f.ReadDir(-1)
+	if err != nil {
+		cobra.CompErrorln(err.Error())
+		return nil
+	}
+	completions := make([]string, 0, len(entries))
+	for _, e := range entries {
+		if strings.HasPrefix(e.Name(), base) {
+			completions = append(completions, simplePathJoinUnix(toComplete, e.Name()))
+		}
+	}
+	return completions
+}
+
+// simplePathJoinUnix joins to path components by adding a slash only if p1 doesn't end with one.
+// We cannot use path.Join() for the completions logic because this one always calls Clean() on
+// the path which changes it from the input.
+func simplePathJoinUnix(p1, p2 string) string {
+	if p1[len(p1)-1] == '/' {
+		return p1 + p2
+	}
+	return p1 + "/" + p2
+}
+
 // validCurrentCmdLine validates the current cmd line
 // It utilizes the Args function from the cmd struct
 // In most cases the Args function validates the args length but it
@@ -523,8 +580,32 @@ func AutocompleteCreateRun(cmd *cobra.Command, args []string, toComplete string)
 		}
 		return getImages(cmd, toComplete)
 	}
-	// TODO: add path completion for files in the image
-	return nil, cobra.ShellCompDirectiveDefault
+	// Mount the image and provide path completion
+	engine, err := setupImageEngine(cmd)
+	if err != nil {
+		cobra.CompErrorln(err.Error())
+		return nil, cobra.ShellCompDirectiveDefault
+	}
+
+	resp, err := engine.Mount(registry.Context(), []string{args[0]}, entities.ImageMountOptions{})
+	if err != nil {
+		cobra.CompErrorln(err.Error())
+		return nil, cobra.ShellCompDirectiveDefault
+	}
+	defer func() {
+		_, err := engine.Unmount(registry.Context(), []string{args[0]}, entities.ImageUnmountOptions{})
+		if err != nil {
+			cobra.CompErrorln(err.Error())
+		}
+	}()
+	if len(resp) != 1 {
+		return nil, cobra.ShellCompDirectiveDefault
+	}
+
+	// So this uses ShellCompDirectiveDefault to also still provide normal shell
+	// completion in case no path matches. This is useful if someone tries to get
+	// completion for paths that are not available in the image, e.g. /proc/...
+	return getPathCompletion(resp[0].Path, toComplete), cobra.ShellCompDirectiveDefault | cobra.ShellCompDirectiveNoSpace
 }
 
 // AutocompleteRegistries - Autocomplete registries.
@@ -572,14 +653,39 @@ func AutocompleteCpCommand(cmd *cobra.Command, args []string, toComplete string)
 		return nil, cobra.ShellCompDirectiveNoFileComp
 	}
 	if len(args) < 2 {
+		if i := strings.IndexByte(toComplete, ':'); i > -1 {
+			// Looks like the user already set the container.
+			// Lets mount it and provide path completion for files in the container.
+			engine, err := setupContainerEngine(cmd)
+			if err != nil {
+				cobra.CompErrorln(err.Error())
+				return nil, cobra.ShellCompDirectiveDefault
+			}
+
+			resp, err := engine.ContainerMount(registry.Context(), []string{toComplete[:i]}, entities.ContainerMountOptions{})
+			if err != nil {
+				cobra.CompErrorln(err.Error())
+				return nil, cobra.ShellCompDirectiveDefault
+			}
+			defer func() {
+				_, err := engine.ContainerUnmount(registry.Context(), []string{toComplete[:i]}, entities.ContainerUnmountOptions{})
+				if err != nil {
+					cobra.CompErrorln(err.Error())
+				}
+			}()
+			if len(resp) != 1 {
+				return nil, cobra.ShellCompDirectiveDefault
+			}
+			return prefixSlice(toComplete[:i+1], getPathCompletion(resp[0].Path, toComplete[i+1:])), cobra.ShellCompDirectiveDefault | cobra.ShellCompDirectiveNoSpace
+		}
+		// Suggest containers when they match the input otherwise normal shell completion is used
 		containers, _ := getContainers(cmd, toComplete, completeDefault)
 		for _, container := range containers {
-			// TODO: Add path completion for inside the container if possible
 			if strings.HasPrefix(container, toComplete) {
-				return containers, cobra.ShellCompDirectiveNoSpace
+				return suffixCompSlice(":", containers), cobra.ShellCompDirectiveNoSpace
 			}
 		}
-		// else complete paths
+		// else complete paths on the host
 		return nil, cobra.ShellCompDirectiveDefault
 	}
 	// don't complete more than 2 args
diff --git a/test/system/600-completion.bats b/test/system/600-completion.bats
index 018e95e78..2de9b1ae1 100644
--- a/test/system/600-completion.bats
+++ b/test/system/600-completion.bats
@@ -8,6 +8,16 @@
 
 load helpers
 
+function setup() {
+    # $PODMAN may be a space-separated string, e.g. if we include a --url.
+    local -a podman_as_array=($PODMAN)
+    # __completeNoDesc must be the first arg if we running the completion cmd
+    # set the var for the run_completion function
+    PODMAN_COMPLETION="${podman_as_array[0]} __completeNoDesc ${podman_as_array[@]:1}"
+
+    basic_setup
+}
+
 # Returns true if we are able to podman-pause
 function _can_pause() {
     # Even though we're just trying completion, not an actual unpause,
@@ -88,8 +98,14 @@ function check_shell_completion() {
                         continue 2
                     fi
 
+                    name=$random_container_name
+                    # special case podman cp suggest containers names with a colon
+                    if [[ $cmd = "cp" ]]; then
+                        name="$name:"
+                    fi
+
                     run_completion "$@" $cmd "${extra_args[@]}" ""
-                    is "$output" ".*-$random_container_name${nl}" \
+                    is "$output" ".*-$name${nl}" \
                        "$* $cmd: actual container listed in suggestions"
 
                     match=true
@@ -175,7 +191,7 @@ function check_shell_completion() {
                         _check_completion_end NoSpace
                     else
                         _check_completion_end Default
-                        assert "${#lines[@]}" -eq 2 "$* $cmd: Suggestions are in the output"
+                        _check_no_suggestions
                     fi
                     ;;
 
@@ -205,16 +221,7 @@ function check_shell_completion() {
         if [[ ! ${args##* } =~ "..." ]]; then
             run_completion "$@" $cmd "${extra_args[@]}" ""
             _check_completion_end NoFileComp
-            if [ ${#lines[@]} -gt 2 ]; then
-                # checking for line count is not enough since we may include additional debug output
-                # lines starting with [Debug] are allowed
-                i=0
-                length=$(( ${#lines[@]} - 2 ))
-                while [[ i -lt length ]]; do
-                    assert "${lines[$i]:0:7}" == "[Debug]" "Suggestions are in the output"
-                    i=$(( i + 1 ))
-                done
-            fi
+            _check_no_suggestions
         fi
 
     done
@@ -231,6 +238,24 @@ function _check_completion_end() {
     is "${lines[-1]}" "Completion ended with directive: ShellCompDirective$1" "Completion has wrong ShellCompDirective set"
 }
 
+# Check that there are no suggestions in the output.
+# We could only check stdout and not stderr but this is not possible with bats.
+# By default we always have two extra lines at the end for the ShellCompDirective.
+# Then we could also have other extra lines for debugging, they will always start
+# with [Debug], e.g. `[Debug] [Error] no container with name or ID "t12" found: no such container`.
+function _check_no_suggestions() {
+    if [ ${#lines[@]} -gt 2 ]; then
+        # Checking for line count is not enough since we may include additional debug output.
+        # Lines starting with [Debug] are allowed.
+        local i=0
+        length=$((${#lines[@]} - 2))
+        while [[ i -lt length ]]; do
+            assert "${lines[$i]:0:7}" == "[Debug]"  "Unexpected non-Debug output line: ${lines[$i]}"
+            i=$((i + 1))
+        done
+    fi
+}
+
 
 @test "podman shell completion test" {
 
@@ -280,11 +305,6 @@ function _check_completion_end() {
     # create secret
     run_podman secret create $random_secret_name $secret_file
 
-    # $PODMAN may be a space-separated string, e.g. if we include a --url.
-    local -a podman_as_array=($PODMAN)
-    # __completeNoDesc must be the first arg if we running the completion cmd
-    PODMAN_COMPLETION="${podman_as_array[0]} __completeNoDesc ${podman_as_array[@]:1}"
-
     # Called with no args -- start with 'podman --help'. check_shell_completion() will
     # recurse for any subcommands.
     check_shell_completion
@@ -316,3 +336,41 @@ function _check_completion_end() {
     done <<<"$output"
 
 }
+
+@test "podman shell completion for paths in container/image" {
+    skip_if_remote "mounting via remote does not work"
+    for cmd in create run; do
+        run_completion $cmd $IMAGE ""
+        assert "$output" =~ ".*^/etc\$.*^/home\$.*^/root\$.*" "root directories suggested (cmd: podman $cmd)"
+
+        # check completion for subdirectory
+        run_completion $cmd $IMAGE "/etc"
+        # It should be safe to assume the os-release file always exists in $IMAGE
+        assert "$output" =~ ".*^/etc/os-release\$.*" "/etc files suggested (cmd: podman $cmd /etc)"
+        # check completion for partial file name
+        run_completion $cmd $IMAGE "/etc/os-"
+        assert "$output" =~ ".*^/etc/os-release\$.*" "/etc files suggested (cmd: podman $cmd /etc/os-)"
+
+        # check completion with relative path components
+        # It is important the we will still use the image root and not escape to the host
+        run_completion $cmd $IMAGE "../../"
+        assert "$output" =~ ".*^../../etc\$.*^../../home\$.*" "relative root directories suggested (cmd: podman $cmd ../../)"
+    done
+
+    random_name=$(random_string 30)
+    random_file=$(random_string 30)
+    run_podman run --name $random_name $IMAGE touch /tmp/$random_file
+
+    # check completion for podman cp
+    run_completion cp ""
+    assert "$output" =~ ".*^$random_name\:\$.*" "podman cp suggest container names"
+
+    run_completion cp "$random_name:"
+    assert "$output" =~ ".*^$random_name\:/etc\$.*" "podman cp suggest paths in container"
+
+    run_completion cp "$random_name:/tmp"
+    assert "$output" =~ ".*^$random_name\:/tmp/$random_file\$.*" "podman cp suggest custom file in container"
+
+    # cleanup container
+    run_podman rm $random_name
+}