Newer noncurrent versions (#13815)

- Rename MaxNoncurrentVersions tag to NewerNoncurrentVersions

Note: We apply overlapping NewerNoncurrentVersions rules such that 
we honor the highest among applicable limits. e.g if 2 overlapping rules 
are configured with 2 and 3 noncurrent versions to be retained, we 
will retain 3.

- Expire newer noncurrent versions after noncurrent days
- MinIO extension: allow noncurrent days to be zero, allowing expiry 
  of noncurrent version as soon as more than configured 
  NewerNoncurrentVersions are present.
- Allow NewerNoncurrentVersions rules on object-locked buckets
- No x-amz-expiration when NewerNoncurrentVersions configured
- ComputeAction should skip rules with NewerNoncurrentVersions > 0
- Add unit tests for lifecycle.ComputeAction
- Support lifecycle rules with MaxNoncurrentVersions
- Extend ExpectedExpiryTime to work with zero days
- Fix all-time comparisons to be relative to UTC

internal/bucket/lifecycle/noncurrentversion.go

@@ -24,10 +24,10 @@ import (
 
 // NoncurrentVersionExpiration - an action for lifecycle configuration rule.
 type NoncurrentVersionExpiration struct {
-	XMLName               xml.Name       `xml:"NoncurrentVersionExpiration"`
-	NoncurrentDays        ExpirationDays `xml:"NoncurrentDays,omitempty"`
-	MaxNoncurrentVersions int            `xml:"MaxNoncurrentVersions,omitempty"`
-	set                   bool
+	XMLName                 xml.Name       `xml:"NoncurrentVersionExpiration"`
+	NoncurrentDays          ExpirationDays `xml:"NoncurrentDays,omitempty"`
+	NewerNoncurrentVersions int            `xml:"NewerNoncurrentVersions,omitempty"`
+	set                     bool
 }
 
 // MarshalXML if non-current days not set to non zero value
@@ -41,20 +41,35 @@ func (n NoncurrentVersionExpiration) MarshalXML(e *xml.Encoder, start xml.StartE
 
 // UnmarshalXML decodes NoncurrentVersionExpiration
 func (n *NoncurrentVersionExpiration) UnmarshalXML(d *xml.Decoder, startElement xml.StartElement) error {
-	type noncurrentVersionExpirationWrapper NoncurrentVersionExpiration
-	var val noncurrentVersionExpirationWrapper
+	// To handle xml with MaxNoncurrentVersions from older MinIO releases.
+	// note: only one of MaxNoncurrentVersions or NewerNoncurrentVersions would be present.
+	type noncurrentExpiration struct {
+		XMLName                 xml.Name       `xml:"NoncurrentVersionExpiration"`
+		NoncurrentDays          ExpirationDays `xml:"NoncurrentDays,omitempty"`
+		NewerNoncurrentVersions int            `xml:"NewerNoncurrentVersions,omitempty"`
+		MaxNoncurrentVersions   int            `xml:"MaxNoncurrentVersions,omitempty"`
+	}
+
+	var val noncurrentExpiration
 	err := d.DecodeElement(&val, &startElement)
 	if err != nil {
 		return err
 	}
-	*n = NoncurrentVersionExpiration(val)
+	if val.MaxNoncurrentVersions > 0 {
+		val.NewerNoncurrentVersions = val.MaxNoncurrentVersions
+	}
+	*n = NoncurrentVersionExpiration{
+		XMLName:                 val.XMLName,
+		NoncurrentDays:          val.NoncurrentDays,
+		NewerNoncurrentVersions: val.NewerNoncurrentVersions,
+	}
 	n.set = true
 	return nil
 }
 
 // IsNull returns if both NoncurrentDays and NoncurrentVersions are empty
 func (n NoncurrentVersionExpiration) IsNull() bool {
-	return n.IsDaysNull() && n.MaxNoncurrentVersions == 0
+	return n.IsDaysNull() && n.NewerNoncurrentVersions == 0
 }
 
 // IsDaysNull returns true if days field is null
@@ -69,16 +84,13 @@ func (n NoncurrentVersionExpiration) Validate() error {
 	}
 	val := int(n.NoncurrentDays)
 	switch {
-	case val == 0 && n.MaxNoncurrentVersions == 0:
+	case val == 0 && n.NewerNoncurrentVersions == 0:
 		// both fields can't be zero
 		return errXMLNotWellFormed
 
-	case val > 0 && n.MaxNoncurrentVersions > 0:
-		// both tags can't be non-zero simultaneously
-		return errLifecycleInvalidNoncurrentExpiration
-
-	case val < 0, n.MaxNoncurrentVersions < 0:
+	case val < 0, n.NewerNoncurrentVersions < 0:
 		// negative values are not supported
+		return errXMLNotWellFormed
 	}
 	return nil
 }