python-utils-r1.eclass: Add EPYTEST_PLUGIN_LOAD_VIA_ENV

Add an `EPYTEST_PLUGIN_LOAD_VIA_ENV` option to explicitly load plugins
via `PYTEST_PLUGINS` environment variable rather than `-p` options.
This is useful for testing pytest plugins.

While the use case is not very common and therefore may not deserve
explicit eclass support, the value of `PYTEST_PLUGINS` consists
of Python import names that are not trivial to find and have
historically changed across package versions.

Signed-off-by: Michał Górny <mgorny@gentoo.org>
Part-of: https://github.com/gentoo/gentoo/pull/42876
Signed-off-by: Michał Górny <mgorny@gentoo.org>

1 files changed, 45 insertions, 17 deletions

diff --git a/eclass/python-utils-r1.eclass b/eclass/python-utils-r1.eclass
index bbb57901f281..68faa9e2adf9 100644
--- a/eclass/python-utils-r1.eclass
+++ b/eclass/python-utils-r1.eclass
@@ -1312,6 +1312,15 @@ _python_check_occluded_packages() {
 # The recommended way to disable it in EAPI 8 or earlier is to set
 # EPYTEST_PLUGINS (possibly to an empty array).
 
+# @ECLASS_VARIABLE: EPYTEST_PLUGIN_LOAD_VIA_ENV
+# @DEFAULT_UNSET
+# @DESCRIPTION:
+# If set to a non-empty value, plugins will be loaded via PYTEST_PLUGINS
+# environment variable rather than explicit "-p" options.  This ensures
+# that plugins are passed down to subprocess, which may be necessary
+# when testing pytest plugins.  However, this is also more likely
+# to cause duplicate plugin errors.
+
 # @FUNCTION: _set_epytest_plugins
 # @INTERNAL
 # @DESCRIPTION:
@@ -1442,23 +1451,39 @@ epytest() {
 
 	if [[ ${PYTEST_DISABLE_PLUGIN_AUTOLOAD} ]]; then
 		if [[ ${EPYTEST_PLUGINS[@]} ]]; then
-			local plugin_args=()
-			readarray -t -d '' plugin_args < <(
-				"${EPYTHON}" - "${EPYTEST_PLUGINS[@]}" <<-EOF || die
-					import os
-					import sys
-					from importlib.metadata import distribution, entry_points
-
-					env_plugins = os.environ.get("PYTEST_PLUGINS", "").split(",")
-					packages = {distribution(x).name for x in sys.argv[1:]}
-					eps = {
-						f"-p{x.name}" for x in entry_points(group="pytest11")
-						if x.dist.name in packages and x.value not in env_plugins
-					}
-					sys.stdout.write("\\0".join(sorted(eps)))
-				EOF
-			)
-			args+=( "${plugin_args[@]}" )
+			if [[ ${EPYTEST_PLUGIN_LOAD_VIA_ENV} ]]; then
+				local -x PYTEST_PLUGINS=$(
+					"${EPYTHON}" - "${EPYTEST_PLUGINS[@]}" <<-EOF || die
+						import sys
+						from importlib.metadata import distribution, entry_points
+
+						packages = {distribution(x).name for x in sys.argv[1:]}
+						plugins = {
+							x.value for x in entry_points(group="pytest11")
+							if x.dist.name in packages
+						}
+						sys.stdout.write(",".join(sorted(plugins)))
+					EOF
+				)
+			else
+				local plugin_args=()
+				readarray -t -d '' plugin_args < <(
+					"${EPYTHON}" - "${EPYTEST_PLUGINS[@]}" <<-EOF || die
+						import os
+						import sys
+						from importlib.metadata import distribution, entry_points
+
+						env_plugins = os.environ.get("PYTEST_PLUGINS", "").split(",")
+						packages = {distribution(x).name for x in sys.argv[1:]}
+						eps = {
+							f"-p{x.name}" for x in entry_points(group="pytest11")
+							if x.dist.name in packages and x.value not in env_plugins
+						}
+						sys.stdout.write("\\0".join(sorted(eps)))
+					EOF
+				)
+				args+=( "${plugin_args[@]}" )
+			fi
 		fi
 	else
 		args+=(
@@ -1541,6 +1566,9 @@ epytest() {
 	done
 	set -- "${EPYTHON}" -m pytest "${args[@]}" "${@}" ${EPYTEST_FLAGS}
 
+	if [[ ${PYTEST_PLUGINS} ]]; then
+		einfo "PYTEST_PLUGINS=${PYTEST_PLUGINS}"
+	fi
 	echo "${@}" >&2
 	"${@}"
 	local ret=${?}