Poetry: select olddeps using `poetry` (#12407)

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

1 files changed, 66 insertions, 5 deletions

diff --git a/.ci/scripts/test_old_deps.sh b/.ci/scripts/test_old_deps.sh

index b2859f7522..769ca4517e 100755
--- a/.ci/scripts/test_old_deps.sh
+++ b/.ci/scripts/test_old_deps.sh
@@ -1,6 +1,9 @@
 #!/usr/bin/env bash
-# this script is run by GitHub Actions in a plain `focal` container; it installs the
-# minimal requirements for tox and hands over to the py3-old tox environment.
+# this script is run by GitHub Actions in a plain `focal` container; it
+# - installs the minimal system requirements, and poetry;
+# - patches the project definition file to refer to old versions only;
+# - creates a venv with these old versions using poetry; and finally
+# - invokes `trial` to run the tests with old deps.
 
 # Prevent tzdata from asking for user input
 export DEBIAN_FRONTEND=noninteractive
@@ -9,12 +12,70 @@ set -ex
 
 apt-get update
 apt-get install -y \
-        python3 python3-dev python3-pip python3-venv \
-        libxml2-dev libxslt-dev xmlsec1 zlib1g-dev tox libjpeg-dev libwebp-dev
+        python3 python3-dev python3-pip python3-venv pipx \
+        libxml2-dev libxslt-dev xmlsec1 zlib1g-dev libjpeg-dev libwebp-dev
 
 export LANG="C.UTF-8"
 
 # Prevent virtualenv from auto-updating pip to an incompatible version
 export VIRTUALENV_NO_DOWNLOAD=1
 
-exec tox -e py3-old
+# TODO: in the future, we could use an implementation of
+#   https://github.com/python-poetry/poetry/issues/3527
+#   https://github.com/pypa/pip/issues/8085
+# to select the lowest possible versions, rather than resorting to this sed script.
+
+# Patch the project definitions in-place:
+# - Replace all lower and tilde bounds with exact bounds
+# - Make the pyopenssl 17.0, which is the oldest version that works with
+#   a `cryptography` compiled against OpenSSL 1.1.
+# - Delete all lines referring to psycopg2 --- so no testing of postgres support.
+# - Omit systemd: we're not logging to journal here.
+
+# TODO: also replace caret bounds, see https://python-poetry.org/docs/dependency-specification/#version-constraints
+# We don't use these yet, but IIRC they are the default bound used when you `poetry add`.
+# The sed expression 's/\^/==/g' ought to do the trick. But it would also change
+# `python = "^3.7"` to `python = "==3.7", which would mean we fail because olddeps
+# runs on 3.8 (#12343).
+
+sed -i \
+   -e "s/[~>]=/==/g" \
+   -e "/psycopg2/d" \
+   -e 's/pyOpenSSL = "==16.0.0"/pyOpenSSL = "==17.0.0"/' \
+   -e '/systemd/d' \
+   pyproject.toml
+
+# Use poetry to do the installation. This ensures that the versions are all mutually
+# compatible (as far the package metadata declares, anyway); pip's package resolver
+# is more lax.
+#
+# Rather than `poetry install --no-dev`, we drop all dev dependencies from the
+# toml file. This means we don't have to ensure compatibility between old deps and
+# dev tools.
+
+pip install --user toml
+
+REMOVE_DEV_DEPENDENCIES="
+import toml
+with open('pyproject.toml', 'r') as f:
+    data = toml.loads(f.read())
+
+del data['tool']['poetry']['dev-dependencies']
+
+with open('pyproject.toml', 'w') as f:
+    toml.dump(data, f)
+"
+python3 -c "$REMOVE_DEV_DEPENDENCIES"
+
+pipx install poetry==1.1.12
+~/.local/bin/poetry lock
+
+echo "::group::Patched pyproject.toml"
+cat pyproject.toml
+echo "::endgroup::"
+echo "::group::Lockfile after patch"
+cat poetry.lock
+echo "::endgroup::"
+
+~/.local/bin/poetry install -E "all test"
+~/.local/bin/poetry run trial --jobs=2 tests