Merge pull request #281 from semrekkers/issue-238

mitchellh · web-flow · commit 5a2eb615e9aa · 2022-04-20T15:27:15.000-07:00
Fix empty keyName when decoding struct -&gt; map with omitempty
diff --git a/mapstructure.go b/mapstructure.go
@@ -957,7 +957,9 @@ func (d *Decoder) decodeMapFromStruct(name string, dataVal reflect.Value, val re
 					return fmt.Errorf("cannot squash non-struct type '%s'", v.Type())
 				}
 			}
-			keyName = tagValue[:index]
+			if keyNameTagValue := tagValue[:index]; keyNameTagValue != "" {
+				keyName = keyNameTagValue
+			}
 		} else if len(tagValue) > 0 {
 			if tagValue == "-" {
 				continue
diff --git a/mapstructure_bugs_test.go b/mapstructure_bugs_test.go
@@ -1,6 +1,7 @@
 package mapstructure
 
 import (
+	"fmt"
 	"reflect"
 	"testing"
 	"time"
@@ -601,3 +602,25 @@ func TestMapSquash(t *testing.T) {
 		t.Fatal("expected false")
 	}
 }
+
+// GH-238: Empty key name when decoding map from struct with only omitempty flag
+func TestMapOmitEmptyWithEmptyFieldnameInTag(t *testing.T) {
+	type Struct struct {
+		Username string `mapstructure:",omitempty"`
+		Age      int    `mapstructure:",omitempty"`
+	}
+
+	s := Struct{
+		Username: "Joe",
+	}
+	var m map[string]interface{}
+
+	if err := Decode(s, &m); err != nil {
+		t.Fatal(err)
+	}
+
+	expect := "map[Username:Joe]"
+	if got := fmt.Sprintf("%+v", m); expect != got {
+		t.Fatalf("expect %q, got: %s", expect, got)
+	}
+}

Original file line number	Diff line number	Diff line change
`@@ -957,7 +957,9 @@ func (d *Decoder) decodeMapFromStruct(name string, dataVal reflect.Value, val re`
`957`	`957`	`return fmt.Errorf("cannot squash non-struct type '%s'", v.Type())`
`958`	`958`	`}`
`959`	`959`	`}`
`960`		`- keyName = tagValue[:index]`
	`960`	`+ if keyNameTagValue := tagValue[:index]; keyNameTagValue != "" {`
	`961`	`+ keyName = keyNameTagValue`
	`962`	`+ }`
`961`	`963`	`} else if len(tagValue) > 0 {`
`962`	`964`	`if tagValue == "-" {`
`963`	`965`	`continue`