TUN-8784: Set JSON encoder options to print formatted JSON when writing diag files

## Summary

The initial implementation produced correct JSON however it was not formatted which would make it harder to read the file by an user.

 Closes TUN-8784

diagnostic/client.go

@@ -159,7 +159,7 @@ func (client *httpClient) GetTunnelConfiguration(ctx context.Context, writer io.
 		return err
 	}
 
-	return copyToWriter(response, writer)
+	return copyJSONToWriter(response, writer)
 }
 
 func (client *httpClient) GetCliConfiguration(ctx context.Context, writer io.Writer) error {
@@ -168,7 +168,7 @@ func (client *httpClient) GetCliConfiguration(ctx context.Context, writer io.Wri
 		return err
 	}
 
-	return copyToWriter(response, writer)
+	return copyJSONToWriter(response, writer)
 }
 
 func copyToWriter(response *http.Response, writer io.Writer) error {
@@ -176,7 +176,29 @@ func copyToWriter(response *http.Response, writer io.Writer) error {
 
 	_, err := io.Copy(writer, response.Body)
 	if err != nil {
-		return fmt.Errorf("error writing metrics: %w", err)
+		return fmt.Errorf("error writing response: %w", err)
+	}
+
+	return nil
+}
+
+func copyJSONToWriter(response *http.Response, writer io.Writer) error {
+	defer response.Body.Close()
+
+	var data interface{}
+
+	decoder := json.NewDecoder(response.Body)
+
+	err := decoder.Decode(&data)
+	if err != nil {
+		return fmt.Errorf("diagnostic client error whilst reading response: %w", err)
+	}
+
+	encoder := newFormattedEncoder(writer)
+
+	err = encoder.Encode(data)
+	if err != nil {
+		return fmt.Errorf("diagnostic client error whilst writing json: %w", err)
 	}
 
 	return nil

diagnostic/diagnostic.go

@@ -40,6 +40,17 @@ type taskResult struct {
 	path   string
 }
 
+func (result taskResult) MarshalJSON() ([]byte, error) {
+	s := map[string]string{
+		"result": result.Result,
+	}
+	if result.Err != nil {
+		s["error"] = result.Err.Error()
+	}
+
+	return json.Marshal(s)
+}
+
 // Struct used to hold the results of different routines executing the network collection.
 type networkCollectionResult struct {
 	name string
@@ -261,7 +272,9 @@ func jsonNetworkInformationWriter(resultMap map[string]networkCollectionResult)
 
 	defer networkDumpHandle.Close()
 
-	err = json.NewEncoder(networkDumpHandle).Encode(jsonMap)
+	encoder := newFormattedEncoder(networkDumpHandle)
+
+	err = encoder.Encode(jsonMap)
 	if err != nil {
 		return "", fmt.Errorf("error encoding network information results: %w", err)
 	}
@@ -279,7 +292,7 @@ func collectFromEndpointAdapter(collect collectToWriterFunc, fileName string) co
 
 		err = collect(ctx, dumpHandle)
 		if err != nil {
-			return "", ErrCreatingTemporaryFile
+			return "", fmt.Errorf("error running collector: %w", err)
 		}
 
 		return dumpHandle.Name(), nil
@@ -300,7 +313,7 @@ func tunnelStateCollectEndpointAdapter(client HTTPClient, tunnel *TunnelState, f
 			tunnel = tunnelResponse
 		}
 
-		encoder := json.NewEncoder(writer)
+		encoder := newFormattedEncoder(writer)
 
 		err := encoder.Encode(tunnel)
 
@@ -421,7 +434,9 @@ func createTaskReport(taskReport map[string]taskResult) (string, error) {
 	}
 	defer dumpHandle.Close()
 
-	err = json.NewEncoder(dumpHandle).Encode(taskReport)
+	encoder := newFormattedEncoder(dumpHandle)
+
+	err = encoder.Encode(taskReport)
 	if err != nil {
 		return "", fmt.Errorf("error encoding task results: %w", err)
 	}

diagnostic/diagnostic_utils.go

@@ -3,6 +3,7 @@ package diagnostic
 import (
 	"archive/zip"
 	"context"
+	"encoding/json"
 	"fmt"
 	"io"
 	"net/url"
@@ -138,3 +139,10 @@ func FindMetricsServer(
 
 	return nil, instances, ErrMultipleMetricsServerFound
 }
+
+// newFormattedEncoder return a JSON encoder with identation
+func newFormattedEncoder(w io.Writer) *json.Encoder {
+	encoder := json.NewEncoder(w)
+	encoder.SetIndent("", "  ")
+	return encoder
+}