Add suggestion to use match_array instead of match for array expectation

danger/specs/Dangerfile

@@ -32,11 +32,22 @@ request specs (and/or feature specs). Please add request specs under
 See https://gitlab.com/groups/gitlab-org/-/epics/5076 for information.
 MSG
 
-has_app_changes = helper.all_changed_files.grep(%r{\A(app|lib|db/(geo/)?(post_)?migrate)/}).any?
-has_ee_app_changes = helper.all_changed_files.grep(%r{\Aee/(app|lib|db/(geo/)?(post_)?migrate)/}).any?
-spec_changes = helper.all_changed_files.grep(%r{\Aspec/})
+MATCH_WITH_ARRAY_REGEX = /(?<exp_word>match|eq)(?<rest>[( ]?\[)/.freeze
+
+SUGGEST_MR_COMMENT = <<~SUGGEST_COMMENT
+```suggestion
+%<suggested_line>s
+
+If order of the result is not important, please consider using `match_array` to avoid flakiness.
+```
+SUGGEST_COMMENT
+
+all_changed_files = helper.all_changed_files
+has_app_changes = all_changed_files.grep(%r{\A(app|lib|db/(geo/)?(post_)?migrate)/}).any?
+has_ee_app_changes = all_changed_files.grep(%r{\Aee/(app|lib|db/(geo/)?(post_)?migrate)/}).any?
+spec_changes = all_changed_files.grep(%r{\Aspec/})
 has_spec_changes = spec_changes.any?
-has_ee_spec_changes = helper.all_changed_files.grep(%r{\Aee/spec/}).any?
+has_ee_spec_changes = all_changed_files.grep(%r{\Aee/spec/}).any?
 new_specs_needed = (gitlab.mr_labels & NO_SPECS_LABELS).empty?
 
 if (has_app_changes || has_ee_app_changes) && !(has_spec_changes || has_ee_spec_changes) && new_specs_needed
@@ -49,6 +60,22 @@ if has_ee_app_changes && has_spec_changes && !(has_app_changes || has_ee_spec_ch
 end
 
 # Forbidding a new file addition under `/spec/controllers` or `/ee/spec/controllers`
-if git.added_files.grep(%r{^(ee/)?spec/controllers/}).any?
+if project_helper.changes.added.files.grep(%r{^(ee/)?spec/controllers/}).any?
   warn CONTROLLER_SPEC_DEPRECATION_MESSAGE
 end
+
+def check_for_match_with_array!
+  (project_helper.changes.added.files + project_helper.changes.modified.files + project_helper.changes.renamed_after.files).grep(%r{\A(ee/)?spec/}).each do |filename|
+    added_lines = helper.changed_lines(filename).grep(/\A\+ /)
+    next unless added_lines.any? { |line| line =~ MATCH_WITH_ARRAY_REGEX }
+
+    spec_file_lines = File.read(filename).lines(chomp: true)
+
+    added_lines.each do |added_line|
+      mr_line = spec_file_lines.find_index(added_line.delete_prefix('+'))
+      markdown(format(SUGGEST_MR_COMMENT, suggested_line: spec_file_lines[mr_line].gsub(MATCH_WITH_ARRAY_REGEX, 'match_array\k<rest>')), file: filename, line: mr_line.succ)
+    end
+  end
+end
+
+check_for_match_with_array!