fix (utils) : [CRW-8603] Use slice of string instead of apimachinery Set to merge events (devfile#1711)

We were previously using apimachinery Set that is internally based on Map, an unordered data structure.
Due to this we were losing the original insertion order defined in the devfile while merging it, List()
call returns the elements in non-deterministic order, as it internally ranges over the map.

Use string slice to preserve insertion order of all event types.

Signed-off-by: Rohan Kumar <rohaan@redhat.com>

Author: rohanKanojia

pkg/utils/overriding/merging.go

@@ -108,19 +108,19 @@ func MergeDevWorkspaceTemplateSpec(
 		}
 	}
 
-	preStartCommands := sets.String{}
-	postStartCommands := sets.String{}
-	preStopCommands := sets.String{}
-	postStopCommands := sets.String{}
+	var preStartCommands []string
+	var postStartCommands []string
+	var preStopCommands []string
+	var postStopCommands []string
 	for _, content := range allContents {
 		if content.Events != nil {
 			if result.Events == nil {
 				result.Events = &dw.Events{}
 			}
-			preStartCommands = preStartCommands.Union(sets.NewString(content.Events.PreStart...))
-			postStartCommands = postStartCommands.Union(sets.NewString(content.Events.PostStart...))
-			preStopCommands = preStopCommands.Union(sets.NewString(content.Events.PreStop...))
-			postStopCommands = postStopCommands.Union(sets.NewString(content.Events.PostStop...))
+			preStartCommands = UnionStrings(preStartCommands, content.Events.PreStart)
+			postStartCommands = UnionStrings(postStartCommands, content.Events.PostStart)
+			preStopCommands = UnionStrings(preStopCommands, content.Events.PreStop)
+			postStopCommands = UnionStrings(postStopCommands, content.Events.PostStop)
 		}
 
 		if len(content.Variables) > 0 {
@@ -147,10 +147,10 @@ func MergeDevWorkspaceTemplateSpec(
 	}
 
 	if result.Events != nil {
-		result.Events.PreStart = preStartCommands.List()
-		result.Events.PostStart = postStartCommands.List()
-		result.Events.PreStop = preStopCommands.List()
-		result.Events.PostStop = postStopCommands.List()
+		result.Events.PreStart = preStartCommands
+		result.Events.PostStart = postStartCommands
+		result.Events.PreStop = preStopCommands
+		result.Events.PostStop = postStopCommands
 	}
 
 	return &result, nil

pkg/utils/overriding/merging_test.go

@@ -134,3 +134,24 @@ func TestMergingOnlyParent(t *testing.T) {
 		assert.Equal(t, &expectedDWT, gotDWT)
 	}
 }
+
+func TestMergePostStartInOrder(t *testing.T) {
+	// Given
+	baseFile := "test-fixtures/merges/multiple-post-start/main.yaml"
+	parentFile := "test-fixtures/merges/multiple-post-start/plugin.yaml"
+	resultFile := "test-fixtures/merges/multiple-post-start/result.yaml"
+
+	baseDWT := dw.DevWorkspaceTemplateSpecContent{}
+	parentDWT := dw.DevWorkspaceTemplateSpecContent{}
+	expectedDWT := dw.DevWorkspaceTemplateSpecContent{}
+
+	readFileToStruct(t, baseFile, &baseDWT)
+	readFileToStruct(t, parentFile, &parentDWT)
+	readFileToStruct(t, resultFile, &expectedDWT)
+
+	// When + Then
+	gotDWT, err := MergeDevWorkspaceTemplateSpec(&baseDWT, &parentDWT)
+	if assert.NoError(t, err) {
+		assert.Equal(t, &expectedDWT, gotDWT)
+	}
+}

pkg/utils/overriding/test-fixtures/merges/events-merge/result.yaml

@@ -1,32 +1,31 @@
 events:
   preStart:
-    - "preStartFromMainContent"
     - "preStartFromParent"
     - "preStartFromPlugin"
+    - "preStartFromMainContent"
   preStop:
-    - "preStopFromMainContent"
     - "preStopFromParent"
     - "preStopFromPlugin"
+    - "preStopFromMainContent"
   postStart:
-    - "postStartFromMainContent"
     - "postStartFromParent"
     - "postStartFromPlugin"
+    - "postStartFromMainContent"
   postStop:
-    - "postStopFromMainContent"
     - "postStopFromParent"
     - "postStopFromPlugin"
+    - "postStopFromMainContent"
 
 # Note:
 #
 # The command Id are merged *per-event type*
 # from the commands of the corresponding event type
-# in parent, plugins and devfile main content. 
+# in parent, plugins and devfile main content.
 #
-# The command Ids in each event type are unordered sets.
-# Only event types are ordered; no guarantee is provided that
-# Commands inside an event type will be executed in the order
-# they appear in the list.
+# The command Ids in each event type are string slices.
+# While merging original insertion order of events would
+# be preserved.
 #
 # However in the test results, as it will happen usually,
-# command ids of a given event type will simply be ordered
-# in alphabetical order. 
+# command ids of a given event type will be merged preserving
+# insertion order in source devfiles.

pkg/utils/overriding/test-fixtures/merges/multiple-post-start/main.yaml

@@ -0,0 +1,9 @@
+parent:
+  uri: "anyParent"
+components:
+  - plugin:
+      uri: "aCustomLocation"
+    name: "the-only-plugin"
+events:
+  postStart:
+    - "init-che-code-command"

pkg/utils/overriding/test-fixtures/merges/multiple-post-start/plugin.yaml

@@ -0,0 +1,5 @@
+events:
+  postStart:
+    - "event-one"
+    - "event-two"
+    - "event-three"

pkg/utils/overriding/test-fixtures/merges/multiple-post-start/result.yaml

@@ -0,0 +1,9 @@
+events:
+  preStart: []
+  preStop: []
+  postStop: []
+  postStart:
+    - "event-one"
+    - "event-two"
+    - "event-three"
+    - "init-che-code-command"

pkg/utils/overriding/utils.go

@@ -32,3 +32,34 @@ func handleUnmarshal(j []byte) (map[string]interface{}, error) {
 	}
 	return m, nil
 }
+
+// UnionStrings returns the union of two string slices, preserving the order
+// of first occurrence and removing duplicates.
+//
+// Elements from the first slice `a` are added in order. Elements from the second
+// slice `b` are appended only if they do not already exist in `a`.
+//
+// The returned slice is guaranteed to be non-nil, even if both input slices are nil.
+//
+// Example:
+//
+//	UnionStrings([]string{"a", "b"}, []string{"b", "c"})
+//	// Returns: []string{"a", "b", "c"}
+func UnionStrings(a, b []string) []string {
+	alreadyExistsInList := make(map[string]bool)
+	result := make([]string, 0)
+
+	for _, s := range a {
+		if !alreadyExistsInList[s] {
+			alreadyExistsInList[s] = true
+			result = append(result, s)
+		}
+	}
+	for _, s := range b {
+		if !alreadyExistsInList[s] {
+			alreadyExistsInList[s] = true
+			result = append(result, s)
+		}
+	}
+	return result
+}

pkg/utils/overriding/utils_test.go

@@ -0,0 +1,100 @@
+//
+//
+// Copyright Red Hat
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package overriding
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestUnionStrings(t *testing.T) {
+	tests := []struct {
+		name     string
+		a        []string
+		b        []string
+		expected []string
+	}{
+		{
+			name:     "both empty",
+			a:        []string{},
+			b:        []string{},
+			expected: []string{},
+		},
+		{
+			name:     "first is nil, second is empty",
+			a:        nil,
+			b:        []string{},
+			expected: []string{},
+		},
+		{
+			name:     "first is empty, second is nil",
+			a:        []string{},
+			b:        nil,
+			expected: []string{},
+		},
+		{
+			name:     "both are nil",
+			a:        nil,
+			b:        nil,
+			expected: []string{},
+		},
+		{
+			name:     "no overlap",
+			a:        []string{"x", "y"},
+			b:        []string{"a", "b"},
+			expected: []string{"x", "y", "a", "b"},
+		},
+		{
+			name:     "partial overlap",
+			a:        []string{"a", "b"},
+			b:        []string{"b", "c"},
+			expected: []string{"a", "b", "c"},
+		},
+		{
+			name:     "duplicate in same slice",
+			a:        []string{"a", "a", "b"},
+			b:        []string{"b", "c"},
+			expected: []string{"a", "b", "c"},
+		},
+		{
+			name:     "only duplicates",
+			a:        []string{"a", "b"},
+			b:        []string{"a", "b"},
+			expected: []string{"a", "b"},
+		},
+		{
+			name:     "preserves order",
+			a:        []string{"c", "a"},
+			b:        []string{"b", "a", "d"},
+			expected: []string{"c", "a", "b", "d"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			actual := UnionStrings(tt.a, tt.b)
+
+			if actual == nil {
+				t.Errorf("expected non-nil slice, got nil")
+			}
+
+			if !reflect.DeepEqual(actual, tt.expected) {
+				t.Errorf("UnionStrings(%v, %v) = %v; want %v", tt.a, tt.b, actual, tt.expected)
+			}
+		})
+	}
+}