Allow strings "true", "false", "1" and "0" to be used where booleans are expected

There is precedent for allowing strings containing digits where numbers are expected,
and so this extends that to also allow for boolean values to be given as strings.

This applies only to callers going through the decoder API. Direct access via the AST
will reflect exactly what was given in the input configuration.

decoder.go

@@ -117,10 +117,17 @@ func (d *decoder) decode(name string, node ast.Node, result reflect.Value) error
 func (d *decoder) decodeBool(name string, node ast.Node, result reflect.Value) error {
 	switch n := node.(type) {
 	case *ast.LiteralType:
-		if n.Token.Type == token.BOOL {
-			v, err := strconv.ParseBool(n.Token.Text)
-			if err != nil {
-				return err
+		switch n.Token.Type {
+		case token.BOOL, token.STRING, token.NUMBER:
+			var v bool
+			s := strings.ToLower(strings.Replace(n.Token.Text, "\"", "", -1))
+			switch s {
+			case "1", "true":
+				v = true
+			case "0", "false":
+				v = false
+			default:
+				return fmt.Errorf("decodeBool: Unknown value for boolean: %s", n.Token.Text)
 			}
 
 			result.Set(reflect.ValueOf(v))

decoder_test.go

@@ -794,6 +794,51 @@ func TestDecode_interfaceNonPointer(t *testing.T) {
 	}
 }
 
+func TestDecode_boolString(t *testing.T) {
+	var value struct {
+		Boolean bool
+	}
+
+	err := Decode(&value, testReadFile(t, "basic_bool_string.hcl"))
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if value.Boolean != true {
+		t.Fatalf("bad: %#v", value.Boolean)
+	}
+}
+
+func TestDecode_boolInt(t *testing.T) {
+	var value struct {
+		Boolean bool
+	}
+
+	err := Decode(&value, testReadFile(t, "basic_bool_int.hcl"))
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if value.Boolean != true {
+		t.Fatalf("bad: %#v", value.Boolean)
+	}
+}
+
+func TestDecode_bool(t *testing.T) {
+	var value struct {
+		Boolean bool
+	}
+
+	err := Decode(&value, testReadFile(t, "basic_bool.hcl"))
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if value.Boolean != true {
+		t.Fatalf("bad: %#v", value.Boolean)
+	}
+}
+
 func TestDecode_intString(t *testing.T) {
 	var value struct {
 		Count int

test-fixtures/basic_bool.hcl

@@ -0,0 +1 @@
+boolean = true

test-fixtures/basic_bool_int.hcl

@@ -0,0 +1 @@
+boolean = 1

test-fixtures/basic_bool_string.hcl

@@ -0,0 +1 @@
+boolean = "trUe"