Ensure that EnvVarCombineMergeUnique keeps order.

Author: utam0k

pkg/dazzle/combiner.go

@@ -311,14 +311,25 @@ func mergeEnv(base *ociv1.Image, others []*ociv1.Image, vars []EnvVarCombination
 				case EnvVarCombineMerge:
 					envs[k] += ":" + v
 				case EnvVarCombineMergeUnique:
-					vs := make(map[string]struct{})
+					var vs []string
 					for _, s := range strings.Split(envValue, ":") {
-						vs[s] = struct{}{}
+						vs = append(vs, s)
 					}
-					vs[v] = struct{}{}
-					vss := make([]string, 0, len(vs))
-					for s := range vs {
-						vss = append(vss, s)
+					for _, s := range strings.Split(v, ":") {
+						vs = append(vs, s)
+					}
+
+					vss := []string{}
+					flags := make(map[string]bool)
+					for i := len(vs) - 1; i >= 0; i-- {
+						entry := vs[i]
+						if _, value := flags[entry]; !value {
+							flags[entry] = true
+							vss = append(vss, entry)
+						}
+					}
+					for i, j := 0, len(vss)-1; i < j; i, j = i+1, j-1 {
+						vss[i], vss[j] = vss[j], vss[i]
 					}
 					envs[k] = strings.Join(vss, ":")
 				}

pkg/dazzle/combiner_test.go

@@ -0,0 +1,80 @@
+// Copyright © 2020 Gitpod
+
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+package dazzle
+
+import (
+	"testing"
+
+	ociv1 "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+func TestMergeEnv(t *testing.T) {
+	base := ociv1.Image{
+		Config: ociv1.ImageConfig{
+			Env: []string{
+				"PATH=first:second:third:$PATH",
+			},
+		},
+	}
+	others := []*ociv1.Image{
+		{
+			Config: ociv1.ImageConfig{
+				Env: []string{
+					"PATH=fourth:fifth:$PATH",
+				},
+			},
+		},
+		{
+			Config: ociv1.ImageConfig{
+				Env: []string{
+					"PATH=sixth:sixth:$PATH",
+				},
+			},
+		},
+		{
+			Config: ociv1.ImageConfig{
+				Env: []string{
+					"PATH=eighth:seventh:eighth:$PATH",
+				},
+			},
+		},
+	}
+	vars := []EnvVarCombination{
+		{
+			Name:   "PATH",
+			Action: EnvVarCombineMergeUnique,
+		},
+	}
+	envs, err := mergeEnv(&base, others, vars)
+	if err != nil {
+		t.Fatal(err)
+	}
+	expect := []string{"PATH=first:second:third:fourth:fifth:sixth:seventh:eighth:$PATH"}
+	if len(envs) != len(expect) {
+		t.Fatal("unexpected length", len(envs))
+	}
+	for i, env := range envs {
+		if env != expect[i] {
+			t.Fatal("unexpected env", envs)
+		}
+
+	}
+}