algocfg: Add print option to algocfg.

cmd/algocfg/profileCommand.go

@@ -92,6 +92,7 @@
 	rootCmd.AddCommand(profileCmd)
 	profileCmd.AddCommand(setProfileCmd)
 	setProfileCmd.Flags().BoolVarP(&forceUpdate, "yes", "y", false, "Force updates to be written")
+	profileCmd.AddCommand(printProfileCmd)
 	profileCmd.AddCommand(listProfileCmd)
 }
 
@@ -133,6 +134,23 @@
 	},
 }
 
+var printProfileCmd = &cobra.Command{
+	Use:   "print",
+	Short: "Print config.json to stdout.",
+	Args:  cobra.ExactArgs(1),
+	Run: func(cmd *cobra.Command, args []string) {
+		cfg, err := getConfigForArg(args[0])
+		if err != nil {
+			reportErrorf("%v", err)
+		}
+		err = codecs.WriteNonDefaultValues(os.Stdout, cfg, config.GetDefaultLocal(), nil)
+		if err != nil {
+			reportErrorf("Error writing config file to stdout: %s", err)
+		}
+		fmt.Fprintf(os.Stdout, "\n")
+	},
+}
+
 var setProfileCmd = &cobra.Command{
 	Use:   "set",
 	Short: "Set config.json file from a profile.",
@@ -157,7 +175,7 @@
 					return
 				}
 			}
-			err = codecs.SaveNonDefaultValuesToFile(file, cfg, config.GetDefaultLocal(), nil, true)
+			err = codecs.SaveNonDefaultValuesToFile(file, cfg, config.GetDefaultLocal(), nil)
 			if err != nil {
 				reportErrorf("Error saving updated config file '%s' - %s", file, err)
 			}

cmd/algocfg/resetCommand.go

@@ -63,7 +63,7 @@
 			}
 
 			file := filepath.Join(dataDir, config.ConfigFilename)
-			err = codecs.SaveNonDefaultValuesToFile(file, cfg, defaults, nil, true)
+			err = codecs.SaveNonDefaultValuesToFile(file, cfg, defaults, nil)
 			if err != nil {
 				reportWarnf("Error saving updated config file '%s' - %s", file, err)
 				anyError = true

cmd/algocfg/setCommand.go

@@ -66,7 +66,7 @@
 			}
 
 			file := filepath.Join(dataDir, config.ConfigFilename)
-			err = codecs.SaveNonDefaultValuesToFile(file, cfg, config.GetDefaultLocal(), nil, true)
+			err = codecs.SaveNonDefaultValuesToFile(file, cfg, config.GetDefaultLocal(), nil)
 			if err != nil {
 				reportWarnf("Error saving updated config file '%s' - %s", file, err)
 				anyError = true

config/localTemplate.go

@@ -652,7 +652,7 @@ func (cfg Local) SaveAllToDisk(root string) error {
 func (cfg Local) SaveToFile(filename string) error {
 	var alwaysInclude []string
 	alwaysInclude = append(alwaysInclude, "Version")
-	return codecs.SaveNonDefaultValuesToFile(filename, cfg, defaultLocal, alwaysInclude, true)
+	return codecs.SaveNonDefaultValuesToFile(filename, cfg, defaultLocal, alwaysInclude)
 }
 
 // DNSSecuritySRVEnforced returns true if SRV response verification enforced

util/codecs/json.go

@@ -18,6 +18,7 @@
 
 import (
 	"bufio"
+	"bytes"
 	"encoding/json"
 	"fmt"
 	"io"
@@ -48,55 +49,44 @@
 	return
 }
 
+func writeBytes(writer io.Writer, object interface{}, prettyFormat bool) error {
+	var enc *json.Encoder
+	if prettyFormat {
+		enc = NewFormattedJSONEncoder(writer)
+	} else {
+		enc = json.NewEncoder(writer)
+	}
+	return enc.Encode(object)
+}
+
 // SaveObjectToFile implements the common pattern for saving an object to a file as json
 func SaveObjectToFile(filename string, object interface{}, prettyFormat bool) error {
 	f, err := os.Create(filename)
 	if err != nil {
 		return err
 	}
 	defer f.Close()
-	var enc *json.Encoder
-	if prettyFormat {
-		enc = NewFormattedJSONEncoder(f)
-	} else {
-		enc = json.NewEncoder(f)
-	}
-	err = enc.Encode(object)
-	return err
+	return writeBytes(f, object, prettyFormat)
 }
 
-// SaveNonDefaultValuesToFile saves an object to a file as json, but only fields that are not
+// WriteNonDefaultValues writes object to a writer as json, but only fields that are not
 // currently set to be the default value.
 // Optionally, you can specify an array of field names to always include.
-func SaveNonDefaultValuesToFile(filename string, object, defaultObject interface{}, ignore []string, prettyFormat bool) error {
-	// Serialize object to temporary file.
-	// Read file into string array
+func WriteNonDefaultValues(writer io.Writer, object, defaultObject interface{}, ignore []string) error {
 	// Iterate one line at a time, parse Name
 	// If ignore contains Name, don't delete
 	// Use reflection to compare object[Name].value == defaultObject[Name].value
 	// If same, delete line from array
 	// When done, ensure last value line doesn't include comma
 	// Write string array to file.
 
-	file, err := os.CreateTemp("", "encsndv")
-	if err != nil {
-		return err
-	}
-	name := file.Name()
-	file.Close()
-
-	defer os.Remove(name)
-	// Save object to file pretty-formatted so we can read one value-per-line
-	err = SaveObjectToFile(name, object, true)
+	var buf bytes.Buffer
+	err := writeBytes(&buf, object, true)
 	if err != nil {
 		return err
 	}
+	content := buf.Bytes()
 
-	// Read lines from encoded file into string array
-	content, err := os.ReadFile(name)
-	if err != nil {
-		return err
-	}
 	valueLines := strings.Split(string(content), "\n")
 
 	// Create maps of the name->value pairs for the object and the defaults
@@ -155,19 +145,30 @@
 		}
 	}
 
+	combined := strings.Join(newFile, "\n")
+	combined = strings.TrimRight(combined, "\r\n ")
+	_, err = writer.Write([]byte(combined))
+	return err
+}
+
+// SaveNonDefaultValuesToFile saves an object to a file as json, but only fields that are not
+// currently set to be the default value.
+// Optionally, you can specify an array of field names to always include.
+func SaveNonDefaultValuesToFile(filename string, object, defaultObject interface{}, ignore []string) error {
 	outFile, err := os.Create(filename)
 	if err != nil {
 		return err
 	}
 	defer outFile.Close()
 	writer := bufio.NewWriter(outFile)
-	combined := strings.Join(newFile, "\n")
-	combined = strings.TrimRight(combined, "\r\n ")
-	_, err = writer.WriteString(combined)
-	if err == nil {
-		writer.Flush()
+
+	err = WriteNonDefaultValues(writer, object, defaultObject, ignore)
+	if err != nil {
+		return err
 	}
-	return err
+
+	writer.Flush()
+	return nil
 }
 
 func extractValueName(line string) (name string) {

util/codecs/json_test.go

@@ -17,9 +17,13 @@
 package codecs
 
 import (
-	"github.com/algorand/go-algorand/test/partitiontest"
-	"github.com/stretchr/testify/require"
+	"bytes"
 	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/algorand/go-algorand/test/partitiontest"
 )
 
 type testValue struct {
@@ -30,6 +34,7 @@ type testValue struct {
 
 func TestIsDefaultValue(t *testing.T) {
 	partitiontest.PartitionTest(t)
+	t.Parallel()
 
 	a := require.New(t)
 
@@ -52,3 +57,75 @@ func TestIsDefaultValue(t *testing.T) {
 	a.False(isDefaultValue("Int", objectValues, defaultValues))
 	a.True(isDefaultValue("Missing", objectValues, defaultValues))
 }
+
+func TestWriteNonDefaultValue(t *testing.T) {
+	partitiontest.PartitionTest(t)
+	t.Parallel()
+
+	type TestType struct {
+		Version       uint32
+		Archival      bool
+		GossipFanout  int
+		NetAddress    string
+		ReconnectTime time.Duration
+	}
+
+	defaultObject := TestType{
+		Version:       1,
+		Archival:      true,
+		GossipFanout:  50,
+		NetAddress:    "Denver",
+		ReconnectTime: 60 * time.Second,
+	}
+
+	testcases := []struct {
+		name   string
+		in     TestType
+		out    string
+		ignore []string
+	}{
+		{
+			name: "all defaults",
+			in:   defaultObject,
+			out: `{
+}`,
+		}, {
+			name: "some defaults",
+			in: TestType{
+				Version:       1,
+				Archival:      false,
+				GossipFanout:  25,
+				NetAddress:    "Denver",
+				ReconnectTime: 60 * time.Nanosecond,
+			},
+			out: `{
+	"Archival": false,
+	"GossipFanout": 25,
+	"ReconnectTime": 60
+}`,
+		}, {
+			name:   "ignore",
+			in:     defaultObject,
+			ignore: []string{"Version", "Archival", "GossipFanout", "NetAddress", "ReconnectTime"},
+			out: `{
+	"Version": 1,
+	"Archival": true,
+	"GossipFanout": 50,
+	"NetAddress": "Denver",
+	"ReconnectTime": 60000000000
+}`,
+		},
+	}
+
+	for _, tc := range testcases {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			a := require.New(t)
+			var writer bytes.Buffer
+			err := WriteNonDefaultValues(&writer, tc.in, defaultObject, tc.ignore)
+			a.NoError(err)
+			a.Equal(tc.out, writer.String())
+		})
+	}
+}