opam 2.1beta: upgrade from opam 1.x fails with backtrace

[avsm]

While bisecting a build issue, I reverted back to an old opam repo with opam 2.1beta and got:

$ cd opam-repository && git checkout 437319f58e6ee094608d0964f5ec76819ba33d59
$ opam update
<><> Updating package repositories ><><><><><><><><><><><><><><><><><><><><>  🐫 
[default] no changes from file:///Users/avsm/src/git/ocaml/opam-repository
[NOTE] Repository at file:///Users/avsm/src/git/ocaml/opam-repository doesn't define its version, assuming it's 1.2.

<><> Upgrading repositories from older opam format ><><><><><><><><><><><><>  🐫 
Upgrading repository "default"...
Fetching patches of ocaml-variants.3.07+1 to check their hashes...
Fetching patches of ocaml-variants.3.07+2 to check their hashes...
Fetching patches of ocaml-base-compiler.3.11.2 to check their hashes...
Fetching patches of ocaml-base-compiler.3.12.0 to check their hashes...
Fetching patches of ocaml-variants.4.00.0+fp to check their hashes...
Fetching patches of ocaml-base-compiler.4.00.1 to check their hashes...
Fetching patches of ocaml-variants.4.00.1+annot to check their hashes...
Fetching patches of ocaml-variants.4.00.1+debug-runtime to check their hashes...
Fetching patches of ocaml-variants.4.00.1+french to check their hashes...
Fetching patches of ocaml-variants.4.00.1+raspberrypi to check their hashes...
Fetching patches of ocaml-base-compiler.4.01.0 to check their hashes...
Fetching patches of ocaml-variants.4.01.0+32bit to check their hashes...
Fetching patches of ocaml-variants.4.01.0+BER to check their hashes...
Fetching patches of ocaml-variants.4.01.0+PIC to check their hashes...
Fetching patches of ocaml-variants.4.01.0+armv6-freebsd to check their hashes...
Fetching patches of ocaml-variants.4.01.0+fp to check their hashes...
Fetching patches of ocaml-variants.4.01.0+open-types to check their hashes...
Fetching patches of ocaml-variants.4.01.0+profile to check their hashes...
Fetching patches of ocaml-variants.4.02.0+improved-errors to check their hashes...
Fetching patches of ocaml-variants.4.02.3+termux to check their hashes...
Fetching patches of ocaml-variants.4.03.0+termux to check their hashes...
Fetching patches of ocaml-variants.4.04.0+termux to check their hashes...
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/aacplus/aacplus.0.2.1/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/aacplus/aacplus.0.2.2/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/conf-libsvm/conf-libsvm.3/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/conf-libsvm/conf-libsvm.3/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/conf-libuv/conf-libuv.1/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/conf-mecab/conf-mecab.0.996/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/conf-mecab/conf-mecab.0.996/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/conf-zmq/conf-zmq.0.1/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/efl/efl.1.8.1/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/efl/efl.1.8.2/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/efl/efl.1.8.3/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/efl/efl.1.8.4/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/efl/efl.1.9.0/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/efl/efl.1.9.1/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/efl/efl.1.9.2/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/efl/efl.1.10.0/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/efl/efl.1.10.1/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/efl/efl.1.11.0/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/efl/efl.1.11.1/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/efl/efl.1.12.0/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/efl/efl.1.13.0/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/efl/efl.1.17.0/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/efl/efl.1.18.0/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/iocaml-kernel/iocaml-kernel.0.4.0/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/ivy/ivy.1.2.2/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/ivy/ivy.1.3.1/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/llvm/llvm.3.4/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/llvm/llvm.3.5/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/llvm/llvm.3.6/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/llvm/llvm.3.7/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/lz4/lz4.1.0.0/opam: "source" tag
[WARNING] Ignored depext in /private/var/folders/15/h4lnc3_n4tj_2m9vzkqfx8qm0000gn/T/opam-34337-78da6c/default/packages/lz4/lz4.1.0.1/opam: "source" tag
Fatal error: hd
Backtrace:
  Raised at Stdlib.failwith in file "stdlib.ml", line 29, characters 17-33
  Called from Stdlib__list.hd in file "list.ml" (inlined), line 30, characters 10-23
  Called from OpamFile.Syntax.to_string_with_preserved_format.item_var_str in file "src/format/opamFile.ml", line 880, characters 34-68
  Called from Stdlib__list.fold_left in file "list.ml", line 121, characters 24-34
  Called from OpamFile.Syntax.to_string_with_preserved_format in file "src/format/opamFile.ml", line 901, characters 8-1023
  Called from OpamFile.OPAMSyntax.to_string_with_preserved_format in file "src/format/opamFile.ml" (inlined), line 3021, characters 4-137
  Called from OpamFile.OPAMSyntax.write_with_preserved_format in file "src/format/opamFile.ml", line 3028, characters 6-89
  Called from OpamAdminRepoUpgrade.do_upgrade.(fun) in file "src/client/opamAdminRepoUpgrade.ml", line 426, characters 11-67
  Called from Stdlib__map.Make.iter in file "map.ml", line 297, characters 20-25
  Called from Stdlib__map.Make.iter in file "map.ml", line 297, characters 10-18
  Called from Stdlib__map.Make.iter in file "map.ml", line 297, characters 10-18
  Called from Stdlib__map.Make.iter in file "map.ml", line 297, characters 10-18
  Called from Stdlib__map.Make.iter in file "map.ml", line 297, characters 10-18
  Called from Stdlib__map.Make.iter in file "map.ml", line 297, characters 10-18
  Called from OpamAdminRepoUpgrade.do_upgrade in file "src/client/opamAdminRepoUpgrade.ml", line 414, characters 2-1023
  Called from OpamRepositoryCommand.update_with_auto_upgrade.(fun) in file "src/client/opamRepositoryCommand.ml", line 258, characters 11-52
  Called from Stdlib__list.fold_left in file "list.ml", line 121, characters 24-34
  Called from OpamRepositoryCommand.update_with_auto_upgrade in file "src/client/opamRepositoryCommand.ml", line 233, characters 4-1023
  Called from OpamFilename.with_flock_upgrade in file "src/core/opamFilename.ml", line 428, characters 14-45
  Re-raised at OpamStd.Exn.finalise in file "src/core/opamStd.ml", line 1362, characters 4-38
  Called from OpamStd.Op.(@@) in file "src/core/opamStd.ml" (inlined), line 1373, characters 17-20
  Called from OpamRepositoryState.with_write_lock in file "src/state/opamRepositoryState.ml", line 264, characters 4-148
  Called from OpamStd.Op.(@@) in file "src/core/opamStd.ml" (inlined), line 1373, characters 17-20
  Called from OpamClient.update in file "src/client/opamClient.ml", line 624, characters 6-186
  Called from OpamCommands.update.update.(fun) in file "src/client/opamCommands.ml", line 1880, characters 6-149
  Called from OpamGlobalState.with_ in file "src/state/opamGlobalState.ml", line 167, characters 14-18
  Re-raised at OpamStd.Exn.finalise in file "src/core/opamStd.ml", line 1362, characters 4-38
  Called from Cmdliner_term.app.(fun) in file "src_ext/cmdliner/src/cmdliner_term.ml", line 27, characters 19-24
  Called from Cmdliner.Term.run in file "src_ext/cmdliner/src/cmdliner.ml", line 118, characters 32-39
  Called from Cmdliner.Term.term_eval in file "src_ext/cmdliner/src/cmdliner.ml", line 148, characters 18-36
  Called from Cmdliner.Term.eval_choice in file "src_ext/cmdliner/src/cmdliner.ml", line 266, characters 22-48
  Called from OpamCliMain.run.(fun) in file "src/client/opamCliMain.ml", line 345, characters 8-60
  Called from OpamCliMain.main_catch_all in file "src/client/opamCliMain.ml", line 247, characters 6-10

[avsm]

Same thing happens with opam admin upgrade on the opam-repo, so it's easier to repro with just that.

[dra27]

It's a bug in the preserved format rewriter - just working on a fix

[dra27]

Concretely, ocamlbuild contains depends: [ ]