Add config get command to print settings values (#2307)

* add "config get" command to print settings values

* use RPC for "config get" and add test cases

* update imports for changed internal layout

* config/get: do not wrap JSON output in YAML

* fix formatting with gofmt

* config/get: unmarshal JSON RPC response

* Apply suggestions from code review

Co-authored-by: Cristian Maglie <c.maglie@bug.st>

* use same default format as "config dump"

* fix import missing after merging review changes remotely

* test (config): fix expected error message with "get <unknown-key>"

---------

Co-authored-by: Cristian Maglie <c.maglie@bug.st>

Author: ardnew

internal/cli/config/config.go

@@ -37,6 +37,7 @@ func NewCommand() *cobra.Command {
 	configCommand.AddCommand(initAddCommand())
 	configCommand.AddCommand(initDeleteCommand())
 	configCommand.AddCommand(initDumpCommand())
+	configCommand.AddCommand(initGetCommand())
 	configCommand.AddCommand(initInitCommand())
 	configCommand.AddCommand(initRemoveCommand())
 	configCommand.AddCommand(initSetCommand())

internal/cli/config/get.go

@@ -0,0 +1,87 @@
+// This file is part of arduino-cli.
+//
+// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
+package config
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+
+	"github.com/arduino/arduino-cli/commands/daemon"
+	"github.com/arduino/arduino-cli/internal/cli/configuration"
+	"github.com/arduino/arduino-cli/internal/cli/feedback"
+	rpc "github.com/arduino/arduino-cli/rpc/cc/arduino/cli/commands/v1"
+	"github.com/sirupsen/logrus"
+	"github.com/spf13/cobra"
+	"gopkg.in/yaml.v3"
+)
+
+func initGetCommand() *cobra.Command {
+	getCommand := &cobra.Command{
+		Use:   "get",
+		Short: tr("Gets a settings key value."),
+		Long:  tr("Gets a settings key value."),
+		Example: "" +
+			"  " + os.Args[0] + " config get logging\n" +
+			"  " + os.Args[0] + " config get daemon.port\n" +
+			"  " + os.Args[0] + " config get board_manager.additional_urls",
+		Args: cobra.MinimumNArgs(1),
+		Run:  runGetCommand,
+		ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+			return configuration.Settings.AllKeys(), cobra.ShellCompDirectiveDefault
+		},
+	}
+	return getCommand
+}
+
+func runGetCommand(cmd *cobra.Command, args []string) {
+	logrus.Info("Executing `arduino-cli config get`")
+
+	svc := daemon.ArduinoCoreServerImpl{}
+	for _, toGet := range args {
+		resp, err := svc.SettingsGetValue(cmd.Context(), &rpc.SettingsGetValueRequest{Key: toGet})
+		if err != nil {
+			feedback.Fatal(tr("Cannot get the configuration key %[1]s: %[2]v", toGet, err), feedback.ErrGeneric)
+		}
+		var result getResult
+		err = json.Unmarshal([]byte(resp.GetJsonData()), &result.resp)
+		if err != nil {
+			// Should never happen...
+			panic(fmt.Sprintf("Cannot parse JSON for key %[1]s: %[2]v", toGet, err))
+		}
+		feedback.PrintResult(result)
+	}
+}
+
+// output from this command may require special formatting.
+// create a dedicated feedback.Result implementation to safely handle
+// any changes to the configuration.Settings struct.
+type getResult struct {
+	resp interface{}
+}
+
+func (gr getResult) Data() interface{} {
+	return gr.resp
+}
+
+func (gr getResult) String() string {
+	gs, err := yaml.Marshal(gr.resp)
+	if err != nil {
+		// Should never happen
+		panic(tr("unable to marshal config to YAML: %v", err))
+	}
+	return string(gs)
+}

internal/integrationtest/config/config_test.go

@@ -818,6 +818,35 @@ func TestDelete(t *testing.T) {
 	require.NotContains(t, configLines, "board_manager")
 }
 
+func TestGet(t *testing.T) {
+	env, cli := integrationtest.CreateArduinoCLIWithEnvironment(t)
+	defer env.CleanUp()
+
+	// Create a config file
+	_, _, err := cli.Run("config", "init", "--dest-dir", ".")
+	require.NoError(t, err)
+
+	// Verifies default state
+	stdout, _, err := cli.Run("config", "dump", "--format", "json", "--config-file", "arduino-cli.yaml")
+	require.NoError(t, err)
+	requirejson.Query(t, stdout, ".config | .daemon | .port", `"50051"`)
+
+	// Get simple key value
+	stdout, _, err = cli.Run("config", "get", "daemon.port", "--format", "json", "--config-file", "arduino-cli.yaml")
+	require.NoError(t, err)
+	requirejson.Contains(t, stdout, `"50051"`)
+
+	// Get structured key value
+	stdout, _, err = cli.Run("config", "get", "daemon", "--format", "json", "--config-file", "arduino-cli.yaml")
+	require.NoError(t, err)
+	requirejson.Contains(t, stdout, `{"port":"50051"}`)
+
+	// Get undefined key
+	_, stderr, err := cli.Run("config", "get", "foo", "--format", "json", "--config-file", "arduino-cli.yaml")
+	require.Error(t, err)
+	requirejson.Contains(t, stderr, `{"error":"Cannot get the configuration key foo: key not found in settings"}`)
+}
+
 func TestInitializationOrderOfConfigThroughFlagAndEnv(t *testing.T) {
 	env, cli := integrationtest.CreateArduinoCLIWithEnvironment(t)
 	defer env.CleanUp()