stdenv: pURL - last review suggestion

                }

              ) possibleCPEPartsFuns;

          # search for a PURL in the following order:

          # - locally set

          # - src.meta.PURL

          # - srcs[].meta.PURL (for PURL only)

          purlParts = attrs.meta.identifiers.purlParts or { };

          purlPartsFormatted =

            if purlParts ? type && purlParts ? spec then "pkg:${purlParts.type}/${purlParts.spec}" else null;

          # search for a PURL in the following order:

          purl =

            if purlParts ? type && purlParts ? spec then

              "pkg:${purlParts.type}/${purlParts.spec}"

            # 1) locally set through API

            if purlPartsFormatted != null then

              purlPartsFormatted

            else

              # 2) locally overwritten through meta.identifiers.purl

              (attrs.src.meta.identifiers.purl or null);

          # search for a PURL in the following order:

          purls =

            # 1) locally overwritten through meta.identifiers.purls (e.g. extension of list)

            attrs.meta.identifiers.purls or (

              if purl != null then

                [ purl ]

              # 2) locally set through API

              if purlPartsFormatted != null then

                [ purlPartsFormatted ]

              else

                # 3) src.meta.PURL

                (attrs.src.meta.identifiers.purls or (

                  # some of the srcs may not have a PURL

                  filter (purl: purl != null) (

                    flatten (

                      map

                        # get the PURLs from a single derivation

                        (drv: drv.meta.identifiers.purls or null)

                        # sometimes srcs is a single derivation

                        (flatten (attrs.srcs or [ ]))

                    )

                  )

                  # 4) srcs.meta.PURL

                  if !attrs ? srcs then

                    [ ]

                  else if isList attrs.srcs then

                    concatMap (drv: drv.meta.identifiers.purls or [ ]) attrs.srcs

                  else

                    attrs.srcs.meta.identifiers.purls or [ ]

                )

                )

            );