support legacy boolean but warn user about incompatibility

Signed-off-by: Nicolas De Loof <[email protected]>

Author: ndeloof

interpolation/interpolation.go

@@ -72,7 +72,7 @@ func recursiveInterpolate(value interface{}, path Path, opts Options) (interface
 	switch value := value.(type) {
 	case string:
 		newValue, err := opts.Substitute(value, template.Mapping(opts.LookupValue))
-		if err != nil || newValue == value {
+		if err != nil {
 			return value, newPathError(path, err)
 		}
 		caster, ok := opts.getCasterForPath(path)

loader/interpolate.go

@@ -22,6 +22,7 @@ import (
 
 	interp "github.com/compose-spec/compose-go/interpolation"
 	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
 )
 
 var interpolateTypeCastMapping = map[interp.Path]interp.Cast{
@@ -114,9 +115,15 @@ func toFloat32(value string) (interface{}, error) {
 // should match http://yaml.org/type/bool.html
 func toBoolean(value string) (interface{}, error) {
 	switch strings.ToLower(value) {
-	case "y", "yes", "true", "on":
+	case "true":
 		return true, nil
-	case "n", "no", "false", "off":
+	case "false":
+		return false, nil
+	case "y", "yes", "on":
+		logrus.Warnf("%q for boolean is not supported by YAML 1.2, please use `true`", value)
+		return true, nil
+	case "n", "no", "off":
+		logrus.Warnf("%q for boolean is not supported by YAML 1.2, please use `false`", value)
 		return false, nil
 	default:
 		return nil, errors.Errorf("invalid boolean: %s", value)

loader/loader_test.go

@@ -2126,6 +2126,17 @@ services:
 	assert.ErrorContains(t, err, "services.test.build.ssh must be a mapping")
 }
 
+func TestLoadLegacyBoolean(t *testing.T) {
+	actual, err := loadYAML(`
+name: load-legacy-boolean
+services:
+  test:
+    init: yes # used to be a valid YAML bool, removed in YAML 1.2 
+`)
+	assert.NilError(t, err)
+	assert.Check(t, *actual.Services[0].Init)
+}
+
 func TestLoadSSHWithDefaultValueInBuildConfig(t *testing.T) {
 	actual, err := loadYAML(`
 name: load-ssh-with-default-value-in-build-config