decoder: strict mode (#512)

strict.go

@@ -0,0 +1,79 @@
+package toml
+
+import (
+	"github.com/pelletier/go-toml/v2/internal/ast"
+	"github.com/pelletier/go-toml/v2/internal/tracker"
+)
+
+type strict struct {
+	Enabled bool
+
+	// Tracks the current key being processed.
+	key tracker.KeyTracker
+
+	missing []decodeError
+}
+
+func (s *strict) EnterTable(node ast.Node) {
+	if !s.Enabled {
+		return
+	}
+	s.key.UpdateTable(node)
+}
+
+func (s *strict) EnterArrayTable(node ast.Node) {
+	if !s.Enabled {
+		return
+	}
+	s.key.UpdateArrayTable(node)
+}
+
+func (s *strict) EnterKeyValue(node ast.Node) {
+	if !s.Enabled {
+		return
+	}
+	s.key.Push(node)
+}
+
+func (s *strict) ExitKeyValue(node ast.Node) {
+	if !s.Enabled {
+		return
+	}
+	s.key.Pop(node)
+}
+
+func (s *strict) MissingTable(node ast.Node) {
+	if !s.Enabled {
+		return
+	}
+	s.missing = append(s.missing, decodeError{
+		highlight: keyLocation(node),
+		message:   "missing table",
+		key:       s.key.Key(),
+	})
+}
+
+func (s *strict) MissingField(node ast.Node) {
+	if !s.Enabled {
+		return
+	}
+	s.missing = append(s.missing, decodeError{
+		highlight: keyLocation(node),
+		message:   "missing field",
+		key:       s.key.Key(),
+	})
+}
+
+func (s *strict) Error(doc []byte) error {
+	if !s.Enabled || len(s.missing) == 0 {
+		return nil
+	}
+
+	err := &StrictMissingError{
+		Errors: make([]DecodeError, 0, len(s.missing)),
+	}
+	for _, derr := range s.missing {
+		err.Errors = append(err.Errors, *wrapDecodeError(doc, &derr))
+	}
+	return err
+}