bug: Field overrides part of anonymous struct in order preserving mode

[oncilla]

Describe the bug

When encoding a struct that includes the anonymous in order preserving mode, the last field of the anonymous struct is overridden with the next field in the parent struct.

When reproducing the problem, I also found out that anonymous pointer types are not encoded at all.

To Reproduce

Following test can be used to reproduce the bug:

func TestMarshalNestedAnonymousStructsBug(t *testing.T) {
	type Basic struct {
		Address string `toml:"address"`
		Port    int    `toml:"port"`
	}
	type Extended struct {
		Basic
		Secret string `toml:"secret"`
	}
	type ExtendedPtr struct {
		*Basic
		Secret string `toml:"secret"`
	}

	expected := `
[config]
  address = ""
  port = 0
  secret = ""
`
	tests := map[string]struct {
		Encoder func(w io.Writer) *Encoder
		Input   interface{}
	}{
		"alphabetical": {
			Encoder: func(w io.Writer) *Encoder { return NewEncoder(w).Order(OrderAlphabetical) },
			Input: struct {
				Config Extended `toml:"config"`
			}{},
		},
		"alphabetical pointer": {
			Encoder: func(w io.Writer) *Encoder { return NewEncoder(w).Order(OrderAlphabetical) },
			Input: struct {
				Config ExtendedPtr `toml:"config"`
			}{},
		},
		"preserve": {
			Encoder: func(w io.Writer) *Encoder { return NewEncoder(w).Order(OrderPreserve) },
			Input: struct {
				Config Extended `toml:"config"`
			}{},
		},
		"preserve pointer": {
			Encoder: func(w io.Writer) *Encoder { return NewEncoder(w).Order(OrderPreserve) },
			Input: struct {
				Config ExtendedPtr `toml:"config"`
			}{},
		},
	}
	for name, test := range tests {
		t.Run(name, func(t *testing.T) {
			var buf bytes.Buffer
			if err := test.Encoder(&buf).Encode(test.Input); err != nil {
				t.Fatalf("unexpected error: %s", err.Error())
			}
			if !bytes.Equal(buf.Bytes(), []byte(expected)) {
				t.Errorf("Bad marshal: expected\n-----\n%s\n-----\ngot\n-----\n%s\n-----\n", expected, buf.String())
			}
		})
	}
}

Output:

--- FAIL: TestMarshalNestedAnonymousStructsBug (0.00s)
    --- FAIL: TestMarshalNestedAnonymousStructsBug/preserve_pointer (0.00s)
        marshal_test.go:2513: Bad marshal: expected
            -----
            
            [config]
              address = ""
              port = 0
              secret = ""
            
            -----
            got
            -----
            
            [config]
              secret = ""
            
            -----
    --- FAIL: TestMarshalNestedAnonymousStructsBug/alphabetical_pointer (0.00s)
        marshal_test.go:2513: Bad marshal: expected
            -----
            
            [config]
              address = ""
              port = 0
              secret = ""
            
            -----
            got
            -----
            
            [config]
              secret = ""
            
            -----
    --- FAIL: TestMarshalNestedAnonymousStructsBug/preserve (0.00s)
        marshal_test.go:2513: Bad marshal: expected
            -----
            
            [config]
              address = ""
              port = 0
              secret = ""
            
            -----
            got
            -----
            
            [config]
              address = ""
              secret = ""
              secret = ""
            
            -----

Expected behavior

No error in the above test case.
I.e., the output for all test cases is:

[config]
  address = ""
  port = 0
  secret = ""

Versions

• go-toml: 88263a0
• go: 1.14
• operating system: Linux

[AllenX2018]

Thanks for reporting!

[AllenX2018]

When encoding a struct that includes the anonymous in order preserving mode, the last field of the anonymous struct is overridden with the next field in the parent struct.

I've fixed this via 34de94e, you can check again with the latest version

When reproducing the problem, I also found out that anonymous pointer types are not encoded at all.

I also check this and I found that's because your pointer is nil. In this case, it can not be dereferenced so it will not be encoded.

[oncilla]

@AllenX2018 Tank you very much for the swift fix. Much appreciated.

I verified it works on the test case I attached to this issue.