make AllLocations accept a context (#2518)

The previous implementation would leak a goroutine if the caller of
AllLocations stopped iterating early. Now, accept a context so that the
caller can cancel the AllLocations iterator rather than leak the
goroutine.

Signed-off-by: Will Murphy <will.murphy@anchore.com>

syft/file/cataloger/filemetadata/cataloger.go

@@ -1,6 +1,7 @@
 package filemetadata
 
 import (
+	"context"
 	"fmt"
 
 	"github.com/dustin/go-humanize"
@@ -21,8 +22,10 @@ func NewCataloger() *Cataloger {
 func (i *Cataloger) Catalog(resolver file.Resolver, coordinates ...file.Coordinates) (map[file.Coordinates]file.Metadata, error) {
 	results := make(map[file.Coordinates]file.Metadata)
 	var locations <-chan file.Location
+	ctx, cancel := context.WithCancel(context.TODO())
+	defer cancel()
 	if len(coordinates) == 0 {
-		locations = resolver.AllLocations()
+		locations = resolver.AllLocations(ctx)
 	} else {
 		locations = func() <-chan file.Location {
 			ch := make(chan file.Location)
@@ -35,7 +38,12 @@ func (i *Cataloger) Catalog(resolver file.Resolver, coordinates ...file.Coordina
 						continue
 					}
 					for _, loc := range locs {
-						ch <- loc
+						select {
+						case <-ctx.Done():
+							return
+						case ch <- loc:
+							continue
+						}
 					}
 				}
 			}()

syft/file/cataloger/internal/all_regular_files.go

@@ -1,13 +1,17 @@
 package internal
 
 import (
+	"context"
+
 	stereoscopeFile "github.com/anchore/stereoscope/pkg/file"
 	"github.com/anchore/syft/internal/log"
 	"github.com/anchore/syft/syft/file"
 )
 
 func AllRegularFiles(resolver file.Resolver) (locations []file.Location) {
-	for location := range resolver.AllLocations() {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	for location := range resolver.AllLocations(ctx) {
 		resolvedLocations, err := resolver.FilesByPath(location.RealPath)
 		if err != nil {
 			log.Warnf("unable to resolve %+v: %+v", location, err)

syft/file/mock_resolver.go

@@ -1,6 +1,7 @@
 package file
 
 import (
+	"context"
 	"fmt"
 	"io"
 	"os"
@@ -144,12 +145,17 @@ func (r MockResolver) RelativeFileByPath(_ Location, path string) *Location {
 	return &paths[0]
 }
 
-func (r MockResolver) AllLocations() <-chan Location {
+func (r MockResolver) AllLocations(ctx context.Context) <-chan Location {
 	results := make(chan Location)
 	go func() {
 		defer close(results)
 		for _, l := range r.locations {
-			results <- l
+			select {
+			case <-ctx.Done():
+				return
+			case results <- l:
+				continue
+			}
 		}
 	}()
 	return results

syft/file/resolver.go

@@ -1,6 +1,9 @@
 package file
 
-import "io"
+import (
+	"context"
+	"io"
+)
 
 // Resolver is an interface that encompasses how to get specific file references and file contents for a generic data source.
 type Resolver interface {
@@ -53,7 +56,7 @@ type LocationResolver interface {
 	// The implementation for this may vary, however, generally the following considerations should be made:
 	// - NO symlink resolution should be performed on results
 	// - returns locations for any file or directory
-	AllLocations() <-chan Location
+	AllLocations(ctx context.Context) <-chan Location
 }
 
 type WritableResolver interface {