docker context rm: allow --force to ignore non-existing contexts

Before this change, running `docker context rm --force` would fail if the context
did not exist. This behavior was different from other commands, which allowed
ignoring non-existing objects.

For example; when trying to remove a non-existing volume, the command would
fail without "force":

```bash
docker volume rm nosuchvolume
Error: No such volume: nosuchvolume
echo $?
1
```

But using the `-f` / `--force` option would make the command complete successfully
(the error itself is still printed for informational purposes);

```bash
docker volume rm -f nosuchvolume
nosuchvolume
echo $?
0
```

With this patch, `docker context rm` behaves the same:

```bash
docker context rm nosuchcontext
context "nosuchcontext" does not exist
echo $?
1
```

```bash
docker context rm -f nosuchcontext
nosuchcontext
echo $?
0
```

This patch also simplifies how we check if the context exists; previously we
would try to read the context's metadata; this could fail if a context was
corrupted, or if an empty directory was present. This patch now only checks
if the directory exists, without first validating the context's data.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cli/command/context/remove.go

@@ -1,12 +1,14 @@
 package context
 
 import (
-	"errors"
 	"fmt"
+	"os"
 	"strings"
 
 	"github.com/docker/cli/cli"
 	"github.com/docker/cli/cli/command"
+	"github.com/docker/docker/errdefs"
+	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 )
 
@@ -50,9 +52,6 @@ func RunRemove(dockerCli command.Cli, opts RemoveOptions, names []string) error
 }
 
 func doRemove(dockerCli command.Cli, name string, isCurrent, force bool) error {
-	if _, err := dockerCli.ContextStore().GetMetadata(name); err != nil {
-		return err
-	}
 	if isCurrent {
 		if !force {
 			return errors.New("context is in use, set -f flag to force remove")
@@ -64,5 +63,23 @@ func doRemove(dockerCli command.Cli, name string, isCurrent, force bool) error {
 			return err
 		}
 	}
+
+	if !force {
+		if err := checkContextExists(dockerCli, name); err != nil {
+			return err
+		}
+	}
 	return dockerCli.ContextStore().Remove(name)
 }
+
+// checkContextExists returns an error if the context directory does not exist.
+func checkContextExists(dockerCli command.Cli, name string) error {
+	contextDir := dockerCli.ContextStore().GetStorageInfo(name).MetadataPath
+	_, err := os.Stat(contextDir)
+	if os.IsNotExist(err) {
+		return errdefs.NotFound(errors.Errorf("context %q does not exist", name))
+	}
+	// Ignore other errors; if relevant, they will produce an error when
+	// performing the actual delete.
+	return nil
+}

cli/command/context/remove_test.go

@@ -27,6 +27,9 @@ func TestRemoveNotAContext(t *testing.T) {
 	createTestContext(t, cli, "other")
 	err := RunRemove(cli, RemoveOptions{}, []string{"not-a-context"})
 	assert.ErrorContains(t, err, `context "not-a-context" does not exist`)
+
+	err = RunRemove(cli, RemoveOptions{Force: true}, []string{"not-a-context"})
+	assert.NilError(t, err)
 }
 
 func TestRemoveCurrent(t *testing.T) {