preserve input order of filtered resources (#24)

fixes #23

pkg/filter/filter.go

@@ -1,6 +1,8 @@
 package filter
 
 import (
+	"sort"
+
 	"github.com/ryane/kfilt/pkg/resource"
 )
 
@@ -23,6 +25,11 @@ func (f *Filter) Filter(resources []resource.Resource) ([]resource.Resource, err
 	var err error
 	filtered := append([]resource.Resource{}, resources...)
 
+	ordermap := map[string]int{}
+	for i, res := range resources {
+		ordermap[res.ID()] = i
+	}
+
 	// excludes
 	for _, matcher := range f.Exclude {
 		filtered, err = exclude(filtered, matcher)
@@ -51,6 +58,10 @@ func (f *Filter) Filter(resources []resource.Resource) ([]resource.Resource, err
 		filtered = included
 	}
 
+	sort.Slice(filtered, func(i, j int) bool {
+		return ordermap[filtered[i].ID()] < ordermap[filtered[j].ID()]
+	})
+
 	return filtered, nil
 }
 

pkg/filter/filter_test.go

@@ -172,6 +172,24 @@ func TestFilter(t *testing.T) {
 			},
 			noError,
 		},
+		{
+			"preserve order of returned resources",
+			excludeMatchers{},
+			includeMatchers{
+				{
+					Kind: "Pod",
+				},
+				{
+					Kind: "ServiceAccount",
+				},
+			},
+			expectIDs{
+				"/v1:serviceaccount::test-sa",
+				"/v1:serviceaccount::test-sa-2",
+				"/v1:pod:test-ns:test-pod",
+			},
+			noError,
+		},
 		{
 			"label key/value selector",
 			excludeMatchers{},
@@ -277,32 +295,34 @@ func TestFilter(t *testing.T) {
 	}
 
 	for _, test := range tests {
-		f := filter.New()
-		for _, m := range test.include {
-			f.AddInclude(m)
-		}
-		for _, m := range test.exclude {
-			f.AddExclude(m)
-		}
-
-		results, err := f.Filter(input)
-		if !test.expectedError(err) {
-			t.Errorf("unexpected error for %s: %v", test.name, err)
-			t.FailNow()
-		}
+		t.Run(test.name, func(t *testing.T) {
+			f := filter.New()
+			for _, m := range test.include {
+				f.AddInclude(m)
+			}
+			for _, m := range test.exclude {
+				f.AddExclude(m)
+			}
 
-		if len(results) != len(test.expectIDs) {
-			t.Errorf("%s: expected %d results, got %d\nincludes: %+v, excludes: %+v\nresults: %v", test.name, len(test.expectIDs), len(results), f.Include, f.Exclude, resourceIDs(results))
-			t.FailNow()
-		}
+			results, err := f.Filter(input)
+			if !test.expectedError(err) {
+				t.Errorf("unexpected error for %s: %v", test.name, err)
+				t.FailNow()
+			}
 
-		for i, res := range results {
-			id := res.ID()
-			if id != test.expectIDs[i] {
-				t.Errorf("%s: expected %s, got %s\nincludes: %v, excludes: %v", test.name, test.expectIDs[i], id, f.Include, f.Exclude)
+			if len(results) != len(test.expectIDs) {
+				t.Errorf("%s: expected %d results, got %d\nincludes: %+v, excludes: %+v\nresults: %v", test.name, len(test.expectIDs), len(results), f.Include, f.Exclude, resourceIDs(results))
 				t.FailNow()
 			}
-		}
+
+			for i, res := range results {
+				id := res.ID()
+				if id != test.expectIDs[i] {
+					t.Errorf("%s: expected %s, got %s\nincludes: %v, excludes: %v", test.name, test.expectIDs[i], id, f.Include, f.Exclude)
+					t.FailNow()
+				}
+			}
+		})
 	}
 }