fix: display the correct response for coder list (#16547)

Closes https://github.com/coder/coder/issues/16312

We intend to modify the behavior of the CLI handler based on the
specified output format. However, the output format is currently only
accessible within the `OutputFormatter` structure. Therefore, I propose
extending `OutputFormatter` by introducing a public `FormatID` method,
which will allow us to retrieve the format identifier and use it to
customize the behavior of the CLI handler accordingly.

cli/list_test.go

@@ -74,4 +74,30 @@ func TestList(t *testing.T) {
 		require.NoError(t, json.Unmarshal(out.Bytes(), &workspaces))
 		require.Len(t, workspaces, 1)
 	})
+
+	t.Run("NoWorkspacesJSON", func(t *testing.T) {
+		t.Parallel()
+		client := coderdtest.New(t, nil)
+		owner := coderdtest.CreateFirstUser(t, client)
+		member, _ := coderdtest.CreateAnotherUser(t, client, owner.OrganizationID)
+
+		inv, root := clitest.New(t, "list", "--output=json")
+		clitest.SetupConfig(t, member, root)
+
+		ctx, cancelFunc := context.WithTimeout(context.Background(), testutil.WaitLong)
+		defer cancelFunc()
+
+		stdout := bytes.NewBuffer(nil)
+		stderr := bytes.NewBuffer(nil)
+		inv.Stdout = stdout
+		inv.Stderr = stderr
+		err := inv.WithContext(ctx).Run()
+		require.NoError(t, err)
+
+		var workspaces []codersdk.Workspace
+		require.NoError(t, json.Unmarshal(stdout.Bytes(), &workspaces))
+		require.Len(t, workspaces, 0)
+
+		require.Len(t, stderr.Bytes(), 0)
+	})
 }