Implicit metapackages causing IndexError via parse/raw warning

[ndevenish]

Checklist

• I added a descriptive title
• I searched open reports and couldn't find a duplicate

What happened?

Ran into an issue trying to render a package (recipe) with conda-smithy; Filed conda-forge/conda-smithy#2306, but seems to be coming from conda-build. Trace:

Traceback (most recent call last):
  File "/Users/nickd/.local/bin/conda-smithy", line 10, in <module>
    sys.exit(main())
             ^^^^^^
  File "/Users/nickd/.condax/conda-smithy/lib/python3.12/site-packages/conda_smithy/cli.py", line 767, in main
    args.subcommand_func(args)
  File "/Users/nickd/.condax/conda-smithy/lib/python3.12/site-packages/conda_smithy/cli.py", line 608, in __call__
    self._call(args, tmpdir)
  File "/Users/nickd/.condax/conda-smithy/lib/python3.12/site-packages/conda_smithy/cli.py", line 613, in _call
    configure_feedstock.main(
  File "/Users/nickd/.condax/conda-smithy/lib/python3.12/site-packages/conda_smithy/configure_feedstock.py", line 2920, in main
    render_azure(env, config, forge_dir, return_metadata=True)
  File "/Users/nickd/.condax/conda-smithy/lib/python3.12/site-packages/conda_smithy/configure_feedstock.py", line 1935, in render_azure
    return _render_ci_provider(
           ^^^^^^^^^^^^^^^^^^^^
  File "/Users/nickd/.condax/conda-smithy/lib/python3.12/site-packages/conda_smithy/configure_feedstock.py", line 1237, in _render_ci_provider
    dump_subspace_config_files(
  File "/Users/nickd/.condax/conda-smithy/lib/python3.12/site-packages/conda_smithy/configure_feedstock.py", line 783, in dump_subspace_config_files
    configs, top_level_loop_vars = _collapse_subpackage_variants(
                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/nickd/.condax/conda-smithy/lib/python3.12/site-packages/conda_smithy/configure_feedstock.py", line 577, in _collapse_subpackage_variants
    meta.get_used_loop_vars(force_top_level=True) for meta in list_of_metas
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/nickd/.condax/conda-smithy/lib/python3.12/site-packages/conda_build/metadata.py", line 2807, in get_used_loop_vars
    used_vars = self.get_used_vars(
                ^^^^^^^^^^^^^^^^^^^
  File "/Users/nickd/.condax/conda-smithy/lib/python3.12/site-packages/conda_build/metadata.py", line 2905, in get_used_vars
    meta_yaml_reqs = self._get_used_vars_meta_yaml(
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/nickd/.condax/conda-smithy/lib/python3.12/site-packages/conda_build/metadata.py", line 2980, in _get_used_vars_meta_yaml
    reqs_text, recipe_text = self._get_used_vars_meta_yaml_helper(
                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/nickd/.condax/conda-smithy/lib/python3.12/site-packages/conda_build/metadata.py", line 2963, in _get_used_vars_meta_yaml_helper
    ) + self.extract_single_output_text(
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/nickd/.condax/conda-smithy/lib/python3.12/site-packages/conda_build/metadata.py", line 2321, in extract_single_output_text
    output = output_matches[output_index] if output_matches else ""
             ~~~~~~~~~~~~~~^^^^^^^^^^^^^^
IndexError: list index out of range

The problem seems to come from the situation warned about in

conda-build/conda_build/metadata.py

Lines 2294 to 2301 in 0eb74e1

	if len(output_matches) != len(outputs):
	# See https://github.com/conda/conda-build/issues/5571
	utils.get_logger(__name__).warning(
	"Number of parsed outputs does not match detected raw metadata blocks. "
	"Identified output block may be wrong! "
	"If you are using Jinja conditionals to include or exclude outputs, "
	"consider using `skip: true # [condition]` instead."
	)

The output_matches as parsed from recipe_text:

conda-build/conda_build/metadata.py

Lines 2286 to 2287 in 0eb74e1

	recipe_text = self.extract_outputs_text(apply_selectors=apply_selectors)
	output_matches = output_re.findall(recipe_text)

only has three matches because recipe_text only includes the outputs: section, not the implicit metapackage from the top-level requirement (as documented here). So when the block below tries to output_matches[output_index] it fails because output_index == len(output_matches) (e.g. higher index).

This warning was added in 74dc428, and possibly #5655 is a symptom; if it's only counting output: sections now, then the lengths won't match but perhaps it can still find the zeroth package?

Moving to an explicit metapackage made the problem go away: conda-forge/hdf5-external-filter-plugins-feedstock@c0c9243

Conda Info

libmamba version : 2.1.0
          mamba version : 2.1.0
           curl version : libcurl/8.13.0 OpenSSL/3.5.0 (SecureTransport) zlib/1.3.1 zstd/1.5.7 libssh2/1.11.1 nghttp2/1.64.0
     libarchive version : libarchive 3.7.7 zlib/1.3.1 liblzma/5.6.3 bz2lib/1.0.8 liblz4/1.10.0 libzstd/1.5.6
       envs directories : /Users/nickd/.condax/mamba/envs
          package cache : /Users/nickd/.condax/mamba/pkgs
                          /Users/nickd/.mamba/pkgs
            environment : /Users/nickd/.condax/conda-smithy
           env location : /Users/nickd/.condax/conda-smithy
      user config files : /Users/nickd/.mambarc
 populated config files : /Users/nickd/.condax/conda-smithy/condarc
                          /Users/nickd/.condarc
                          /Users/nickd/.condax/mamba/condarc
       virtual packages : __unix=0=0
                          __osx=15.3.2=0
                          __archspec=1=arm64
               channels : https://conda.anaconda.org/conda-forge/noarch
                          https://conda.anaconda.org/conda-forge/osx-arm64
                          https://repo.anaconda.com/pkgs/main/noarch
                          https://repo.anaconda.com/pkgs/main/osx-arm64
                          https://repo.anaconda.com/pkgs/r/noarch
                          https://repo.anaconda.com/pkgs/r/osx-arm64
                          https://conda.anaconda.org/nodefaults/noarch
                          https://conda.anaconda.org/nodefaults/osx-arm64
       base environment : /Users/nickd/.condax/mamba
               platform : osx-arm64

Conda Config

Conda list

List of packages in environment: "/Users/nickd/.condax/conda-smithy"

  Name                        Version              Build               Channel
────────────────────────────────────────────────────────────────────────────────────
  anyio                       4.9.0                pyh29332c3_0        conda-forge
  archspec                    0.2.5                pyhd8ed1ab_0        conda-forge
  attrs                       25.3.0               pyh71513ae_0        conda-forge
  backports                   1.0                  pyhd8ed1ab_5        conda-forge
  backports.strenum           1.3.1                haf276df_2          conda-forge
  backports.tarfile           1.2.0                pyhd8ed1ab_1        conda-forge
  beautifulsoup4              4.13.4               pyha770c72_0        conda-forge
  blinker                     1.9.0                pyhff2d567_0        conda-forge
  boltons                     24.0.0               pyhd8ed1ab_1        conda-forge
  boolean.py                  5.0                  pyhd8ed1ab_0        conda-forge
  brotli-python               1.1.0                py312hde4cb15_2     conda-forge
  bzip2                       1.0.8                h99b78c6_7          conda-forge
  c-ares                      1.34.5               h5505292_0          conda-forge
  ca-certificates             2025.1.31            hbd8a1cb_1          conda-forge
  cctools                     1010.6               hb4fb6a3_6          conda-forge
  cctools_osx-arm64           1010.6               h3b4f5d3_6          conda-forge
  certifi                     2025.1.31            pyhd8ed1ab_0        conda-forge
  cffi                        1.17.1               py312h0fad829_0     conda-forge
  chardet                     5.2.0                pyhd8ed1ab_3        conda-forge
  charset-normalizer          3.4.1                pyhd8ed1ab_0        conda-forge
  cirun                       0.30                 pyhd8ed1ab_1        conda-forge
  click                       8.1.8                pyh707e725_0        conda-forge
  colorama                    0.4.6                pyhd8ed1ab_1        conda-forge
  conda                       25.3.1               py312h81bd7bf_1     conda-forge
  conda-build                 25.4.2               py312h81bd7bf_0     conda-forge
  conda-forge-pinning         2025.04.23.13.34.55  hd8ed1ab_0          conda-forge
  conda-index                 0.6.0                pyhd8ed1ab_0        conda-forge
  conda-libmamba-solver       25.3.0               pyhd8ed1ab_0        conda-forge
  conda-package-handling      2.4.0                pyh7900ff3_2        conda-forge
  conda-package-streaming     0.11.0               pyhd8ed1ab_1        conda-forge
  conda-smithy                3.47.2               unix_pyhd81877a_0   conda-forge
  cpp-expected                1.1.0                h177bc72_1          conda-forge
  cryptography                44.0.2               py312hf9bd80e_0     conda-forge
  deprecated                  1.2.18               pyhd8ed1ab_0        conda-forge
  distlib                     0.3.9                pyhd8ed1ab_1        conda-forge
  distro                      1.9.0                pyhd8ed1ab_1        conda-forge
  editables                   0.5                  pyhd8ed1ab_1        conda-forge
  evalidate                   2.0.3                pyh29332c3_1        conda-forge
  exceptiongroup              1.2.2                pyhd8ed1ab_1        conda-forge
  filelock                    3.18.0               pyhd8ed1ab_0        conda-forge
  fmt                         11.1.4               h440487c_1          conda-forge
  frozendict                  2.4.6                py312h0bf5046_0     conda-forge
  git                         2.49.0               pl5321hd71a902_0    conda-forge
  gitdb                       4.0.12               pyhd8ed1ab_0        conda-forge
  gitpython                   3.1.44               pyhff2d567_0        conda-forge
  gmp                         6.3.0                h7bae524_2          conda-forge
  h11                         0.14.0               pyhd8ed1ab_1        conda-forge
  h2                          4.2.0                pyhd8ed1ab_0        conda-forge
  hatch                       1.14.1               pyhd8ed1ab_0        conda-forge
  hatchling                   1.27.0               pypyhd8ed1ab_0      conda-forge
  hpack                       4.1.0                pyhd8ed1ab_0        conda-forge
  httpcore                    1.0.7                pyh29332c3_1        conda-forge
  httpx                       0.28.1               pyhd8ed1ab_0        conda-forge
  hyperframe                  6.1.0                pyhd8ed1ab_0        conda-forge
  hyperlink                   21.0.0               pyh29332c3_1        conda-forge
  idna                        3.10                 pyhd8ed1ab_1        conda-forge
  importlib-metadata          8.6.1                pyha770c72_0        conda-forge
  importlib_resources         6.5.2                pyhd8ed1ab_0        conda-forge
  isodate                     0.7.2                pyhd8ed1ab_1        conda-forge
  jaraco.classes              3.4.0                pyhd8ed1ab_2        conda-forge
  jaraco.context              6.0.1                pyhd8ed1ab_0        conda-forge
  jaraco.functools            4.1.0                pyhd8ed1ab_0        conda-forge
  jinja2                      3.1.6                pyhd8ed1ab_0        conda-forge
  jsonpatch                   1.33                 pyhd8ed1ab_1        conda-forge
  jsonpointer                 3.0.0                py312h81bd7bf_1     conda-forge
  jsonschema                  4.23.0               pyhd8ed1ab_1        conda-forge
  jsonschema-specifications   2025.4.1             pyh29332c3_0        conda-forge
  keyring                     25.6.0               pyh534df25_0        conda-forge
  krb5                        1.21.3               h237132a_0          conda-forge
  ld64                        951.9                h4c6efb1_6          conda-forge
  ld64_osx-arm64              951.9                hb6b49e2_6          conda-forge
  libarchive                  3.7.7                h3b16cec_3          conda-forge
  libcurl                     8.13.0               h73640d1_0          conda-forge
  libcxx                      20.1.3               ha82da77_0          conda-forge
  libedit                     3.1.20250104         pl5321hafb1f1b_0    conda-forge
  libev                       4.33                 h93a5062_2          conda-forge
  libexpat                    2.7.0                h286801f_0          conda-forge
  libffi                      3.4.6                h1da3d7d_1          conda-forge
  libgit2                     1.9.0                h211146d_0          conda-forge
  libiconv                    1.18                 hfe07756_1          conda-forge
  libintl                     0.23.1               h493aca8_0          conda-forge
  liblief                     0.16.4               h286801f_0          conda-forge
  libllvm18                   18.1.8               default_hb458b26_5  conda-forge
  liblzma                     5.8.1                h39f12f2_0          conda-forge
  libmamba                    2.1.0                h7c3736b_0          conda-forge
  libmambapy                  2.1.0                py312h9b24f82_0     conda-forge
  libnghttp2                  1.64.0               h6d7220d_0          conda-forge
  libsodium                   1.0.20               h99b78c6_0          conda-forge
  libsolv                     0.7.30               h6c9b7f8_0          conda-forge
  libsqlite                   3.49.1               h3f77e49_2          conda-forge
  libssh2                     1.11.1               h9cc3647_0          conda-forge
  libxml2                     2.14.2               h3e1e5eb_0          conda-forge
  libzlib                     1.3.1                h8359307_2          conda-forge
  license-expression          30.4.1               pyhd8ed1ab_0        conda-forge
  llvm-tools                  18.1.8               default_hb458b26_5  conda-forge
  llvm-tools-18               18.1.8               default_hb458b26_5  conda-forge
  lz4-c                       1.10.0               h286801f_1          conda-forge
  lzo                         2.10                 h93a5062_1001       conda-forge
  markdown-it-py              3.0.0                pyhd8ed1ab_1        conda-forge
  markupsafe                  3.0.2                py312h998013c_1     conda-forge
  mbedtls                     3.5.1                h286801f_1          conda-forge
  mdurl                       0.1.2                pyhd8ed1ab_1        conda-forge
  menuinst                    2.2.0                py312h81bd7bf_0     conda-forge
  more-itertools              10.7.0               pyhd8ed1ab_0        conda-forge
  msgpack-python              1.1.0                py312h6142ec9_0     conda-forge
  msrest                      0.6.21               pyh44b312d_0        conda-forge
  ncurses                     6.5                  h5e97a16_3          conda-forge
  nlohmann_json               3.11.3               h00cdb27_1          conda-forge
  oauthlib                    3.2.2                pyhd8ed1ab_1        conda-forge
  openssl                     3.5.0                h81ee809_0          conda-forge
  packaging                   25.0                 pyh29332c3_1        conda-forge
  patch                       2.7.6                h27ca646_1002       conda-forge
  pathspec                    0.12.1               pyhd8ed1ab_1        conda-forge
  pcre2                       10.44                h297a79d_2          conda-forge
  perl                        5.32.1               7_h4614cfb_perl5    conda-forge
  pexpect                     4.9.0                pyhd8ed1ab_1        conda-forge
  pip                         25.0.1               pyh8b19718_0        conda-forge
  pkginfo                     1.12.1.2             pyhd8ed1ab_0        conda-forge
  pkgutil-resolve-name        1.3.10               pyhd8ed1ab_2        conda-forge
  platformdirs                4.3.7                pyh29332c3_0        conda-forge
  pluggy                      1.5.0                pyhd8ed1ab_1        conda-forge
  psutil                      7.0.0                py312hea69d52_0     conda-forge
  ptyprocess                  0.7.0                pyhd8ed1ab_1        conda-forge
  py-lief                     0.16.4               py312hd8f9ff3_0     conda-forge
  pybind11-abi                4                    hd8ed1ab_3          conda-forge
  pycosat                     0.6.6                py312hea69d52_2     conda-forge
  pycparser                   2.22                 pyh29332c3_1        conda-forge
  pycryptodome                3.22.0               py312ha135e06_0     conda-forge
  pygit2                      1.17.0               py312hd525726_0     conda-forge
  pygithub                    2.6.1                pyhd8ed1ab_0        conda-forge
  pygments                    2.19.1               pyhd8ed1ab_0        conda-forge
  pyjwt                       2.10.1               pyhd8ed1ab_0        conda-forge
  pynacl                      1.5.0                py312h024a12e_4     conda-forge
  pysocks                     1.7.1                pyha55dd90_7        conda-forge
  python                      3.12.10              hc22306f_0_cpython  conda-forge
  python-dateutil             2.9.0.post0          pyhff2d567_1        conda-forge
  python-libarchive-c         5.2                  pyh29332c3_0        conda-forge
  python_abi                  3.12                 7_cp312             conda-forge
  pytz                        2025.2               pyhd8ed1ab_0        conda-forge
  pyyaml                      6.0.2                py312h998013c_2     conda-forge
  rattler-build               0.40.0               h8dba533_0          conda-forge
  rattler-build-conda-compat  1.4.3                pyhd8ed1ab_0        conda-forge
  readline                    8.2                  h1d1bf99_2          conda-forge
  referencing                 0.36.2               pyh29332c3_0        conda-forge
  reproc                      14.2.5.post0         h5505292_0          conda-forge
  reproc-cpp                  14.2.5.post0         h286801f_0          conda-forge
  requests                    2.32.3               pyhd8ed1ab_1        conda-forge
  requests-oauthlib           2.0.0                pyhd8ed1ab_1        conda-forge
  rich                        14.0.0               pyh29332c3_0        conda-forge
  ripgrep                     14.1.1               h0ef69ab_0          conda-forge
  rpds-py                     0.24.0               py312hd60eec9_0     conda-forge
  ruamel.yaml                 0.18.10              py312hea69d52_0     conda-forge
  ruamel.yaml.clib            0.2.8                py312h0bf5046_1     conda-forge
  scrypt                      0.8.27               py312ha571a58_0     conda-forge
  setuptools                  79.0.0               pyhff2d567_0        conda-forge
  shellingham                 1.5.4                pyhd8ed1ab_1        conda-forge
  sigtool                     0.1.3                h44b9a77_0          conda-forge
  simdjson                    3.12.3               ha393de7_0          conda-forge
  six                         1.17.0               pyhd8ed1ab_0        conda-forge
  smmap                       5.0.2                pyhd8ed1ab_0        conda-forge
  sniffio                     1.3.1                pyhd8ed1ab_1        conda-forge
  soupsieve                   2.5                  pyhd8ed1ab_1        conda-forge
  spdlog                      1.15.2               h008cadb_0          conda-forge
  tapi                        1300.6.5             h03f4b80_0          conda-forge
  tk                          8.6.13               h5083fa2_1          conda-forge
  tomli                       2.2.1                pyhd8ed1ab_1        conda-forge
  tomli-w                     1.2.0                pyhd8ed1ab_0        conda-forge
  tomlkit                     0.13.2               pyha770c72_1        conda-forge
  toolz                       1.0.0                pyhd8ed1ab_1        conda-forge
  tqdm                        4.67.1               pyhd8ed1ab_1        conda-forge
  trove-classifiers           2025.4.11.15         pyhd8ed1ab_0        conda-forge
  truststore                  0.10.1               pyh29332c3_0        conda-forge
  typer                       0.15.2               pyhff008b6_0        conda-forge
  typer-slim                  0.15.2               pyh29332c3_0        conda-forge
  typer-slim-standard         0.15.2               h801b22e_0          conda-forge
  typing-extensions           4.13.2               h0e9735f_0          conda-forge
  typing_extensions           4.13.2               pyh29332c3_0        conda-forge
  tzdata                      2025b                h78e105d_0          conda-forge
  urllib3                     2.4.0                pyhd8ed1ab_0        conda-forge
  userpath                    1.9.2                pyhd8ed1ab_0        conda-forge
  uv                          0.6.16               h668ec48_0          conda-forge
  virtualenv                  20.30.0              pyhd8ed1ab_0        conda-forge
  vsts-python-api             0.1.25               pyhd8ed1ab_2        conda-forge
  wheel                       0.45.1               pyhd8ed1ab_1        conda-forge
  wrapt                       1.17.2               py312hea69d52_0     conda-forge
  yaml                        0.2.5                h3422bc3_2          conda-forge
  yaml-cpp                    0.8.0                h13dd4ca_0          conda-forge
  zipp                        3.21.0               pyhd8ed1ab_1        conda-forge
  zstandard                   0.23.0               py312hea69d52_1     conda-forge
  zstd                        1.5.7                h6491c7d_2          conda-forge

Additional Context

No response

[ndevenish]

An extra note that although 74dc428 warns explicitly against using jinja in the output list, the same problem happened even when I completely stripped out the jinja parts of the output names.