fix: tidyup code quality warnings (#1887)

- Merge variable declaration with assignment
- Simplify `switch` cases with type assertion
- Remove unnecessary wrapping of function call
- Fix unnecessary typecasting on `bytes.Buffer`
- Remove unnecessary guard around map
- Fix check for empty string
- Fix Yoda conditions

admin.go

@@ -549,11 +549,7 @@ func (ca *clusterAdmin) DeleteRecords(topic string, partitionOffsets map[int32]i
 		if err != nil {
 			return err
 		}
-		if _, ok := partitionPerBroker[broker]; ok {
-			partitionPerBroker[broker] = append(partitionPerBroker[broker], partition)
-		} else {
-			partitionPerBroker[broker] = []int32{partition}
-		}
+		partitionPerBroker[broker] = append(partitionPerBroker[broker], partition)
 	}
 	errs := make([]error, 0)
 	for broker, partitions := range partitionPerBroker {

alter_partition_reassignments_response_test.go

@@ -26,9 +26,7 @@ var (
 )
 
 func TestAlterPartitionReassignmentResponse(t *testing.T) {
-	var response *AlterPartitionReassignmentsResponse
-
-	response = &AlterPartitionReassignmentsResponse{
+	var response *AlterPartitionReassignmentsResponse = &AlterPartitionReassignmentsResponse{
 		ThrottleTimeMs: int32(10000),
 		Version:        int16(0),
 	}

client.go

@@ -475,7 +475,7 @@ func (client *client) RefreshMetadata(topics ...string) error {
 	// error. This handles the case by returning an error instead of sending it
 	// off to Kafka. See: https://github.com/Shopify/sarama/pull/38#issuecomment-26362310
 	for _, topic := range topics {
-		if len(topic) == 0 {
+		if topic == "" {
 			return ErrInvalidTopic // this is the error that 0.8.2 and later correctly return
 		}
 	}
@@ -892,7 +892,7 @@ func (client *client) tryRefreshMetadata(topics []string, attemptsRemaining int,
 			req.Version = 1
 		}
 		response, err := broker.GetMetadata(req)
-		switch err.(type) {
+		switch err := err.(type) {
 		case nil:
 			allKnownMetaData := len(topics) == 0
 			// valid response, use it
@@ -909,12 +909,12 @@ func (client *client) tryRefreshMetadata(topics []string, attemptsRemaining int,
 
 		case KError:
 			// if SASL auth error return as this _should_ be a non retryable err for all brokers
-			if err.(KError) == ErrSASLAuthenticationFailed {
+			if err == ErrSASLAuthenticationFailed {
 				Logger.Println("client/metadata failed SASL authentication")
 				return err
 			}
 
-			if err.(KError) == ErrTopicAuthorizationFailed {
+			if err == ErrTopicAuthorizationFailed {
 				Logger.Println("client is not authorized to access this topic. The topics were: ", topics)
 				return err
 			}

client_test.go

@@ -61,7 +61,7 @@ func TestCachedPartitions(t *testing.T) {
 	// Verify we actually use the cache at all!
 	tmp[allPartitions] = []int32{1, 2, 3, 4}
 	client.cachedPartitionsResults["my_topic"] = tmp
-	if 4 != len(client.cachedPartitions("my_topic", allPartitions)) {
+	if len(client.cachedPartitions("my_topic", allPartitions)) != 4 {
 		t.Fatal("Not using the cache!")
 	}
 

examples/http_server/http_server_test.go

@@ -42,7 +42,7 @@ func TestCollectSuccessfully(t *testing.T) {
 		t.Errorf("Expected HTTP status 200, found %d", res.Code)
 	}
 
-	if string(res.Body.Bytes()) != "Your data is stored with unique identifier important/0/1" {
+	if res.Body.String() != "Your data is stored with unique identifier important/0/1" {
 		t.Error("Unexpected response body", res.Body)
 	}
 }

examples/sasl_scram_client/scram_client.go

@@ -3,13 +3,12 @@ package main
 import (
 	"crypto/sha256"
 	"crypto/sha512"
-	"hash"
 
 	"github.com/xdg/scram"
 )
 
-var SHA256 scram.HashGeneratorFcn = func() hash.Hash { return sha256.New() }
-var SHA512 scram.HashGeneratorFcn = func() hash.Hash { return sha512.New() }
+var SHA256 scram.HashGeneratorFcn = sha256.New
+var SHA512 scram.HashGeneratorFcn = sha512.New
 
 type XDGSCRAMClient struct {
 	*scram.Client

list_partition_reassignments_request_test.go

@@ -14,9 +14,7 @@ var (
 )
 
 func TestListPartitionReassignmentRequest(t *testing.T) {
-	var request *ListPartitionReassignmentsRequest
-
-	request = &ListPartitionReassignmentsRequest{
+	var request *ListPartitionReassignmentsRequest = &ListPartitionReassignmentsRequest{
 		TimeoutMs: int32(10000),
 		Version:   int16(0),
 	}

list_partition_reassignments_response_test.go

@@ -19,9 +19,7 @@ var (
 )
 
 func TestListPartitionReassignmentResponse(t *testing.T) {
-	var response *ListPartitionReassignmentsResponse
-
-	response = &ListPartitionReassignmentsResponse{
+	var response *ListPartitionReassignmentsResponse = &ListPartitionReassignmentsResponse{
 		ThrottleTimeMs: int32(10000),
 		Version:        int16(0),
 	}