add "field_tags" to json parser config

internal/config/config.go

@@ -1261,6 +1261,18 @@ func buildParser(name string, tbl *ast.Table) (parsers.Parser, error) {
 		}
 	}
 
+	if node, ok := tbl.Fields["field_keys"]; ok {
+		if kv, ok := node.(*ast.KeyValue); ok {
+			if ary, ok := kv.Value.(*ast.Array); ok {
+				for _, elem := range ary.Value {
+					if str, ok := elem.(*ast.String); ok {
+						c.FieldKeys = append(c.FieldKeys, str.Value)
+					}
+				}
+			}
+		}
+	}
+
 	if node, ok := tbl.Fields["data_type"]; ok {
 		if kv, ok := node.(*ast.KeyValue); ok {
 			if str, ok := kv.Value.(*ast.String); ok {
@@ -1344,6 +1356,7 @@ func buildParser(name string, tbl *ast.Table) (parsers.Parser, error) {
 	delete(tbl.Fields, "separator")
 	delete(tbl.Fields, "templates")
 	delete(tbl.Fields, "tag_keys")
+	delete(tbl.Fields, "field_keys")
 	delete(tbl.Fields, "data_type")
 	delete(tbl.Fields, "collectd_auth_file")
 	delete(tbl.Fields, "collectd_security_level")

internal/config/config_test.go

@@ -143,7 +143,7 @@ func TestConfig_LoadDirectory(t *testing.T) {
 		"Testdata did not produce correct memcached metadata.")
 
 	ex := inputs.Inputs["exec"]().(*exec.Exec)
-	p, err := parsers.NewJSONParser("exec", nil, nil)
+	p, err := parsers.NewJSONParser("exec", nil, nil, nil)
 	assert.NoError(t, err)
 	ex.SetParser(p)
 	ex.Command = "/usr/bin/myothercollector --foo=bar"