fix: labels field is nil in values interpolation (#24501) (#24502)

Signed-off-by: tonychg <tonychg7@pm.me>

applicationset/generators/pull_request.go

@@ -119,15 +119,15 @@ func (g *PullRequestGenerator) GenerateParams(appSetGenerator *argoprojiov1alpha
 			"author":             pull.Author,
 		}
 
-		err := appendTemplatedValues(appSetGenerator.PullRequest.Values, paramMap, applicationSetInfo.Spec.GoTemplate, applicationSetInfo.Spec.GoTemplateOptions)
-		if err != nil {
-			return nil, fmt.Errorf("failed to append templated values: %w", err)
-		}
-
 		// PR lables will only be supported for Go Template appsets, since fasttemplate will be deprecated.
 		if applicationSetInfo != nil && applicationSetInfo.Spec.GoTemplate {
 			paramMap["labels"] = pull.Labels
 		}
+
+		err := appendTemplatedValues(appSetGenerator.PullRequest.Values, paramMap, applicationSetInfo.Spec.GoTemplate, applicationSetInfo.Spec.GoTemplateOptions)
+		if err != nil {
+			return nil, fmt.Errorf("failed to append templated values: %w", err)
+		}
 		params = append(params, paramMap)
 	}
 	return params, nil

applicationset/generators/pull_request_test.go

@@ -277,6 +277,51 @@ func TestPullRequestGithubGenerateParams(t *testing.T) {
 				},
 			},
 		},
+		{
+			selectFunc: func(context.Context, *argoprojiov1alpha1.PullRequestGenerator, *argoprojiov1alpha1.ApplicationSet) (pullrequest.PullRequestService, error) {
+				return pullrequest.NewFakeService(
+					ctx,
+					[]*pullrequest.PullRequest{
+						{
+							Number:       1,
+							Title:        "title1",
+							Branch:       "my_branch",
+							TargetBranch: "master",
+							HeadSHA:      "abcd",
+							Author:       "testName",
+							Labels:       []string{"preview", "preview:team1"},
+						},
+					},
+					nil,
+				)
+			},
+			values: map[string]string{
+				"preview_env": "{{ regexFind \"(team1|team2)\" (.labels | join \",\") }}",
+			},
+			expected: []map[string]any{
+				{
+					"number":             "1",
+					"title":              "title1",
+					"branch":             "my_branch",
+					"branch_slug":        "my-branch",
+					"target_branch":      "master",
+					"target_branch_slug": "master",
+					"head_sha":           "abcd",
+					"head_short_sha":     "abcd",
+					"head_short_sha_7":   "abcd",
+					"author":             "testName",
+					"labels":             []string{"preview", "preview:team1"},
+					"values":             map[string]string{"preview_env": "team1"},
+				},
+			},
+			expectedErr: nil,
+			applicationSet: argoprojiov1alpha1.ApplicationSet{
+				Spec: argoprojiov1alpha1.ApplicationSetSpec{
+					// Application set is using fasttemplate.
+					GoTemplate: true,
+				},
+			},
+		},
 	}
 
 	for _, c := range cases {