tweak the way ImageWithoutImports is handled

private/bufpkg/bufimage/bufimage.go

@@ -480,7 +480,9 @@ func ImageWithoutImports(image Image) Image {
 			newImageFiles = append(newImageFiles, imageFile)
 		}
 	}
-	return newImageNoValidate(newImageFiles)
+	// We preserve the original resolver because a resolver can't
+	// be successfully created without the image's dependencies.
+	return newImageNoValidate(newImageFiles, image.Resolver())
 }
 
 // ImageWithOnlyPaths returns a copy of the Image that only includes the files

private/bufpkg/bufimage/image.go

@@ -74,7 +74,11 @@ func newImage(files []ImageFile, reorder bool, resolver protoencoding.Resolver)
 		files = orderImageFiles(files, pathToImageFile)
 	}
 	if resolver == nil {
-		resolver = resolverForImageFiles(files)
+		fileDescriptorProtos := make([]*descriptorpb.FileDescriptorProto, len(files))
+		for i := range files {
+			fileDescriptorProtos[i] = files[i].FileDescriptorProto()
+		}
+		resolver = protoencoding.NewLazyResolver(fileDescriptorProtos...)
 	}
 	return &image{
 		files:           files,
@@ -83,7 +87,7 @@ func newImage(files []ImageFile, reorder bool, resolver protoencoding.Resolver)
 	}, nil
 }
 
-func newImageNoValidate(files []ImageFile) *image {
+func newImageNoValidate(files []ImageFile, resolver protoencoding.Resolver) *image {
 	pathToImageFile := make(map[string]ImageFile, len(files))
 	for _, file := range files {
 		path := file.Path()
@@ -92,7 +96,7 @@ func newImageNoValidate(files []ImageFile) *image {
 	return &image{
 		files:           files,
 		pathToImageFile: pathToImageFile,
-		resolver:        resolverForImageFiles(files),
+		resolver:        resolver,
 	}
 }
 
@@ -152,11 +156,3 @@ func orderImageFilesRec(
 	}
 	return append(outputImageFiles, inputImageFile)
 }
-
-func resolverForImageFiles(files []ImageFile) protoencoding.Resolver {
-	fileDescriptorProtos := make([]*descriptorpb.FileDescriptorProto, len(files))
-	for i := range files {
-		fileDescriptorProtos[i] = files[i].FileDescriptorProto()
-	}
-	return protoencoding.NewLazyResolver(fileDescriptorProtos...)
-}