fix: add map with pointer value support (#76)

diff_pointer.go

@@ -17,12 +17,18 @@ func (d *Differ) diffPtr(path []string, a, b reflect.Value, parent interface{})
 			if !b.IsNil() {
 				return d.diff(path, reflect.ValueOf(nil), reflect.Indirect(b), parent)
 			}
+
+			d.cl.Add(CREATE, path, nil, exportInterface(b), parent)
+			return nil
 		}
 
 		if b.Kind() == reflect.Invalid {
 			if !a.IsNil() {
 				return d.diff(path, reflect.Indirect(a), reflect.ValueOf(nil), parent)
 			}
+
+			d.cl.Add(DELETE, path, exportInterface(a), nil, parent)
+			return nil
 		}
 
 		return ErrTypeMismatch

patch.go

@@ -188,6 +188,14 @@ func (d *Differ) renderChangeTarget(c *ChangeValue) {
 
 	//walking a path means dealing with real elements
 	case reflect.Interface, reflect.Ptr:
+		if c.target.IsNil() {
+			n := reflect.New(c.target.Type().Elem())
+			c.target.Set(n)
+			c.target = &n
+			d.renderChangeTarget(c)
+			return
+		}
+
 		el := c.target.Elem()
 		c.target = &el
 		c.ClearFlag(FlagInvalidTarget)

patch_test.go

@@ -304,6 +304,34 @@ func TestPatch(t *testing.T) {
 		assert.False(t, patchLog.HasErrors())
 	})
 
+	t.Run("map-to-pointer", func(t *testing.T) {
+		t1 := make(map[string]*tmstruct)
+		t2 := map[string]*tmstruct{"after": {Foo: "val"}}
+
+		changelog, err := diff.Diff(t1, t2)
+		assert.NoError(t, err)
+
+		patchLog := diff.Patch(changelog, &t1)
+		assert.False(t, patchLog.HasErrors())
+
+		assert.True(t, len(t2) == len(t1))
+		assert.Equal(t, t1["after"], &tmstruct{Foo: "val"})
+	})
+
+	t.Run("map-to-nil-pointer", func(t *testing.T) {
+		t1 := make(map[string]*tmstruct)
+		t2 := map[string]*tmstruct{"after": nil}
+
+		changelog, err := diff.Diff(t1, t2)
+		assert.NoError(t, err)
+
+		patchLog := diff.Patch(changelog, &t1)
+		assert.False(t, patchLog.HasErrors())
+
+		assert.Equal(t, len(t2), len(t1))
+		assert.Nil(t, t1["after"])
+	})
+
 	t.Run("pointer-with-converted-type", func(t *testing.T) {
 		type tps struct {
 			S *int