Fix usage of loop variable in function closure (#5195)

plugins/processors/strings/strings.go

@@ -72,8 +72,8 @@ const sampleConfig = `
   #   field = "read_count"
   #   suffix = "_count"
 
-  ## Replace substrings within field names
+  ## Replace all non-overlapping instances of old with new
-  # [[processors.strings.trim_suffix]]
+  # [[processors.strings.replace]]
   #   measurement = "*"
   #   old = ":"
   #   new = "_"
@@ -100,8 +100,8 @@ func (c *converter) convertTag(metric telegraf.Metric) {
 		tags[c.Tag] = tv
 	}
 
-	for tag, value := range tags {
+	for key, value := range tags {
-		dest := tag
+		dest := key
 		if c.Tag != "*" && c.Dest != "" {
 			dest = c.Dest
 		}
@@ -122,9 +122,9 @@ func (c *converter) convertField(metric telegraf.Metric) {
 		fields[c.Field] = fv
 	}
 
-	for tag, value := range fields {
+	for key, value := range fields {
-		dest := tag
+		dest := key
-		if c.Tag != "*" && c.Dest != "" {
+		if c.Field != "*" && c.Dest != "" {
 			dest = c.Dest
 		}
 		if fv, ok := value.(string); ok {
@@ -170,6 +170,7 @@ func (s *Strings) initOnce() {
 		s.converters = append(s.converters, c)
 	}
 	for _, c := range s.Trim {
+		c := c
 		if c.Cutset != "" {
 			c.fn = func(s string) string { return strings.Trim(s, c.Cutset) }
 		} else {
@@ -178,6 +179,7 @@ func (s *Strings) initOnce() {
 		s.converters = append(s.converters, c)
 	}
 	for _, c := range s.TrimLeft {
+		c := c
 		if c.Cutset != "" {
 			c.fn = func(s string) string { return strings.TrimLeft(s, c.Cutset) }
 		} else {
@@ -186,6 +188,7 @@ func (s *Strings) initOnce() {
 		s.converters = append(s.converters, c)
 	}
 	for _, c := range s.TrimRight {
+		c := c
 		if c.Cutset != "" {
 			c.fn = func(s string) string { return strings.TrimRight(s, c.Cutset) }
 		} else {
@@ -194,14 +197,17 @@ func (s *Strings) initOnce() {
 		s.converters = append(s.converters, c)
 	}
 	for _, c := range s.TrimPrefix {
+		c := c
 		c.fn = func(s string) string { return strings.TrimPrefix(s, c.Prefix) }
 		s.converters = append(s.converters, c)
 	}
 	for _, c := range s.TrimSuffix {
+		c := c
 		c.fn = func(s string) string { return strings.TrimSuffix(s, c.Suffix) }
 		s.converters = append(s.converters, c)
 	}
 	for _, c := range s.Replace {
+		c := c
 		c.fn = func(s string) string {
 			newString := strings.Replace(s, c.Old, c.New, -1)
 			if newString == "" {

plugins/processors/strings/strings_test.go

@@ -25,24 +25,6 @@ func newM1() telegraf.Metric {
 	return m1
 }
 
-func newM2() telegraf.Metric {
-	m2, _ := metric.New("IIS_log",
-		map[string]string{
-			"verb":           "GET",
-			"resp_code":      "200",
-			"s-computername": "MIXEDCASE_hostname",
-		},
-		map[string]interface{}{
-			"request":       "/mixed/CASE/paTH/?from=-1D&to=now",
-			"cs-host":       "AAAbbb",
-			"ignore_number": int64(200),
-			"ignore_bool":   true,
-		},
-		time.Now(),
-	)
-	return m2
-}
-
 func TestFieldConversions(t *testing.T) {
 	tests := []struct {
 		name   string
@@ -404,9 +386,38 @@ func TestMultipleConversions(t *testing.T) {
 				Tag: "verb",
 			},
 		},
+		Replace: []converter{
+			{
+				Tag: "foo",
+				Old: "a",
+				New: "x",
+			},
+			{
+				Tag: "bar",
+				Old: "b",
+				New: "y",
+			},
+		},
 	}
 
-	processed := plugin.Apply(newM2())
+	m, _ := metric.New("IIS_log",
+		map[string]string{
+			"verb":           "GET",
+			"resp_code":      "200",
+			"s-computername": "MIXEDCASE_hostname",
+			"foo":            "a",
+			"bar":            "b",
+		},
+		map[string]interface{}{
+			"request":       "/mixed/CASE/paTH/?from=-1D&to=now",
+			"cs-host":       "AAAbbb",
+			"ignore_number": int64(200),
+			"ignore_bool":   true,
+		},
+		time.Now(),
+	)
+
+	processed := plugin.Apply(m)
 
 	expectedFields := map[string]interface{}{
 		"request":           "/mixed/case/path/?from=-1d&to=now",
@@ -419,6 +430,8 @@ func TestMultipleConversions(t *testing.T) {
 		"verb":           "GET",
 		"resp_code":      "200",
 		"s-computername": "mixedcase_hostname",
+		"foo":            "x",
+		"bar":            "y",
 	}
 
 	assert.Equal(t, expectedFields, processed[0].Fields())