refactor: centralise "match if nil" logic

Author: tri-adam

pkg/sif/image.go

@@ -32,11 +32,7 @@ func (f *OCIFileImage) Image(m match.Matcher, _ ...Option) (v1.Image, error) {
 		return nil, err
 	}
 
-	if m == nil {
-		m = matchAll
-	}
-
-	matches, err := partial.FindImages(ri, m)
+	matches, err := partial.FindImages(ri, matchAllIfNil(m))
 	if err != nil {
 		return nil, err
 	}

pkg/sif/index.go

@@ -76,11 +76,7 @@ func (f *OCIFileImage) Index(m match.Matcher, _ ...Option) (v1.ImageIndex, error
 		return nil, err
 	}
 
-	if m == nil {
-		m = matchAll
-	}
-
-	matches, err := partial.FindIndexes(ri, m)
+	matches, err := partial.FindIndexes(ri, matchAllIfNil(m))
 	if err != nil {
 		return nil, err
 	}

pkg/sif/manifest.go

@@ -1,3 +1,7 @@
+// Copyright 2024 Sylabs Inc. All rights reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+
 package sif
 
 import (

pkg/sif/match.go

@@ -8,6 +8,7 @@ import (
 	"errors"
 
 	v1 "github.com/google/go-containerregistry/pkg/v1"
+	"github.com/google/go-containerregistry/pkg/v1/match"
 )
 
 var (
@@ -16,3 +17,11 @@ var (
 )
 
 func matchAll(v1.Descriptor) bool { return true }
+
+// matchAllIfNil returns m if not nil, or a Matcher that matches all descriptors otherwise.
+func matchAllIfNil(m match.Matcher) match.Matcher {
+	if m != nil {
+		return m
+	}
+	return matchAll
+}

pkg/sif/update.go

@@ -471,11 +471,7 @@ func (f *OCIFileImage) RemoveManifests(matcher match.Matcher) error {
 		return err
 	}
 
-	if matcher == nil {
-		matcher = matchAll
-	}
-
-	return f.UpdateRootIndex(mutate.RemoveManifests(ri, matcher))
+	return f.UpdateRootIndex(mutate.RemoveManifests(ri, matchAllIfNil(matcher)))
 }
 
 // ReplaceImage writes img to the SIF, replacing any existing manifest that is
@@ -505,16 +501,12 @@ func (f *OCIFileImage) replace(add mutate.Appendable, matcher match.Matcher, opt
 		}
 	}
 
-	if matcher == nil {
-		matcher = matchAll
-	}
-
 	ri, err := f.RootIndex()
 	if err != nil {
 		return err
 	}
 
-	ri = mutate.RemoveManifests(ri, matcher)
+	ri = mutate.RemoveManifests(ri, matchAllIfNil(matcher))
 
 	ri, err = appendToIndex(ri, add, ao)
 	if err != nil {