Rework tree from map (#139)

* Make TreeFromMap reflect to construct tree
* Fix wording of invalid value type in writeTo

Fixes #138, #139, #134 

⚠️ TreeFromMap signature changed to `TreeFromMap(map[string]interface{}) (*TomlTree, error)`

tomltree_create_test.go

@@ -0,0 +1,95 @@
+package toml
+
+import (
+	"testing"
+	"time"
+)
+
+func validate(t *testing.T, path string, object interface{}) {
+	switch o := object.(type) {
+	case *TomlTree:
+		for key, tree := range o.values {
+			validate(t, path+"."+key, tree)
+		}
+	case []*TomlTree:
+		for index, tree := range o {
+			validate(t, path+"."+string(index), tree)
+		}
+	case *tomlValue:
+		switch o.value.(type) {
+		case int64, uint64, bool, string, float64, time.Time,
+			[]int64, []uint64, []bool, []string, []float64, []time.Time:
+			return // ok
+		default:
+			t.Fatalf("tomlValue at key %s containing incorrect type %T", path, o.value)
+		}
+	default:
+		t.Fatalf("value at key %s is of incorrect type %T", path, object)
+	}
+	t.Log("validation ok", path)
+}
+
+func validateTree(t *testing.T, tree *TomlTree) {
+	validate(t, "", tree)
+}
+
+func TestTomlTreeCreateToTree(t *testing.T) {
+	data := map[string]interface{}{
+		"a_string": "bar",
+		"an_int":   42,
+		"time":     time.Now(),
+		"int8":     int8(2),
+		"int16":    int16(2),
+		"int32":    int32(2),
+		"uint8":    uint8(2),
+		"uint16":   uint16(2),
+		"uint32":   uint32(2),
+		"float32":  float32(2),
+		"a_bool":   false,
+		"nested": map[string]interface{}{
+			"foo": "bar",
+		},
+		"array":       []string{"a", "b", "c"},
+		"array_uint":  []uint{uint(1), uint(2)},
+		"array_table": []map[string]interface{}{map[string]interface{}{"sub_map": 52}},
+		"array_times": []time.Time{time.Now(), time.Now()},
+		"map_times":   map[string]time.Time{"now": time.Now()},
+	}
+	tree, err := TreeFromMap(data)
+	if err != nil {
+		t.Fatal("unexpected error:", err)
+	}
+	validateTree(t, tree)
+}
+
+func TestTomlTreeCreateToTreeInvalidLeafType(t *testing.T) {
+	_, err := TreeFromMap(map[string]interface{}{"foo": t})
+	expected := "cannot convert type *testing.T to TomlTree"
+	if err.Error() != expected {
+		t.Fatalf("expected error %s, got %s", expected, err.Error())
+	}
+}
+
+func TestTomlTreeCreateToTreeInvalidMapKeyType(t *testing.T) {
+	_, err := TreeFromMap(map[string]interface{}{"foo": map[int]interface{}{2: 1}})
+	expected := "map key needs to be a string, not int"
+	if err.Error() != expected {
+		t.Fatalf("expected error %s, got %s", expected, err.Error())
+	}
+}
+
+func TestTomlTreeCreateToTreeInvalidArrayMemberType(t *testing.T) {
+	_, err := TreeFromMap(map[string]interface{}{"foo": []*testing.T{t}})
+	expected := "cannot convert type *testing.T to TomlTree"
+	if err.Error() != expected {
+		t.Fatalf("expected error %s, got %s", expected, err.Error())
+	}
+}
+
+func TestTomlTreeCreateToTreeInvalidTableGroupType(t *testing.T) {
+	_, err := TreeFromMap(map[string]interface{}{"foo": []map[string]interface{}{map[string]interface{}{"hello": t}}})
+	expected := "cannot convert type *testing.T to TomlTree"
+	if err.Error() != expected {
+		t.Fatalf("expected error %s, got %s", expected, err.Error())
+	}
+}