[gentoo-dev] [PATCH] Check for USE_PYTHON <-> PYTHON_TARGETS sync.

[Michał Górny]

This is much more complex than the previous version.

If user doesn't have USE_PYTHON set, it tries to solve the issue using
eselect-python only, suggesting user to switch the active
implementation.

If eselect-python won't help or user has USE_PYTHON set, it nicely
suggests a new value, highlighting added and listing removed entries.

The basic issue here is that the package can only check PYTHON_TARGETS
values in IUSE, so only the implementations supported by the package. It
tries hard to help and not to do any damage, so user may need to modify
his USE_PYTHON more than once.

For example, consider the following:

- installed: 2.6, 2.7, 3.1, 3.2, pypy1.8
- active: 2.6, 3.2
- USE_PYTHON not set
- PYTHON_TARGETS: 2.7, 3.1, 3.2, pypy1.8

Package 1 supports Python 2 only. The eclass can't access Python 3
PYTHON_TARGETS, thus it can only suggest user to switch active Python
interpreter to Python 2.7. This solves the Python2 packages only.

Package 2 supports both Python 2 & 3. The eclass notices two Python 3
versions and suggests user to add USE_PYTHON='2.7 3.1 3.2'.

Package 3 supports PyPy additionally. The eclass notices that, and
suggests user to add '2.7-pypy-1.8' to USE_PYTHON.

Of course, that assumes building one-by-one. If more packages get pulled
into the dep tree, the results of checks may look even contradictory.
Hopefully, after a few changes and rebuilds user will finally get
the correct value.
---
 gx86/eclass/python-r1.eclass | 198 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 198 insertions(+)

diff --git a/gx86/eclass/python-r1.eclass b/gx86/eclass/python-r1.eclass
index 0d6ef4c..61edf94 100644
--- a/gx86/eclass/python-r1.eclass
+++ b/gx86/eclass/python-r1.eclass
@@ -363,6 +363,202 @@ python_copy_sources() {
 	done
 }
 
+# @FUNCTION: _python_check_USE_PYTHON
+# @INTERNAL
+# @DESCRIPTION:
+# Check whether USE_PYTHON and PYTHON_TARGETS are in sync. Output
+# warnings if they are not.
+_python_check_USE_PYTHON() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	if [[ ! ${_PYTHON_USE_PYTHON_CHECKED} ]]; then
+		_PYTHON_USE_PYTHON_CHECKED=1
+
+		# python-exec has profile-forced flags.
+		if [[ ${CATEGORY}/${PN} == dev-python/python-exec ]]; then
+			return
+		fi
+
+		_try_eselect() {
+			# The eselect solution will work only with one py2 & py3.
+
+			local impl py2 py3 dis_py2 dis_py3
+			for impl in "${PYTHON_COMPAT[@]}"; do
+				if use "python_targets_${impl}"; then
+					case "${impl}" in
+						python2_*)
+							if [[ ${py2+1} ]]; then
+								debug-print "${FUNCNAME}: -> more than one py2: ${py2} ${impl}"
+								return 1
+							fi
+							py2=${impl/_/.}
+							;;
+						python3_*)
+							if [[ ${py3+1} ]]; then
+								debug-print "${FUNCNAME}: -> more than one py3: ${py3} ${impl}"
+								return 1
+							fi
+							py3=${impl/_/.}
+							;;
+						*)
+							return 1
+							;;
+					esac
+				else
+					case "${impl}" in
+						python2_*)
+							dis_py2=1
+							;;
+						python3_*)
+							dis_py3=1
+							;;
+					esac
+				fi
+			done
+
+			# The eselect solution won't work if the disabled Python version
+			# is installed.
+			if [[ ! ${py2+1} && ${dis_py2} ]]; then
+				debug-print "${FUNCNAME}: -> all py2 versions disabled"
+				if has_version '=dev-lang/python-2*'; then
+					debug-print "${FUNCNAME}: ---> but =python-2* installed!"
+					return 1
+				fi
+			fi
+			if [[ ! ${py3+1} && ${dis_py3} ]]; then
+				debug-print "${FUNCNAME}: -> all py3 versions disabled"
+				if has_version '=dev-lang/python-3*'; then
+					debug-print "${FUNCNAME}: ---> but =python-3* installed!"
+					return 1
+				fi
+			fi
+
+			local warned
+
+			# Now check whether the correct implementations are active.
+			if [[ ${py2+1} ]]; then
+				local sel_py2=$(eselect python show --python2)
+
+				debug-print "${FUNCNAME}: -> py2 built: ${py2}, active: ${sel_py2}"
+				if [[ ${py2} != ${sel_py2} ]]; then
+					ewarn "Building package for ${py2} only while ${sel_py2} is active."
+					ewarn "Please consider switching the active Python 2 interpreter:"
+					ewarn
+					ewarn "	eselect python set --python2 ${py2}"
+					warned=1
+				fi
+			fi
+
+			if [[ ${py3+1} ]]; then
+				local sel_py3=$(eselect python show --python3)
+
+				debug-print "${FUNCNAME}: -> py3 built: ${py3}, active: ${sel_py3}"
+				if [[ ${py3} != ${sel_py3} ]]; then
+					[[ ${warned} ]] && ewarn
+					ewarn "Building package for ${py3} only while ${sel_py3} is active."
+					ewarn "Please consider switching the active Python 3 interpreter:"
+					ewarn
+					ewarn "	eselect python set --python3 ${py3}"
+					warned=1
+				fi
+			fi
+
+			if [[ ${warned} ]]; then
+				ewarn
+				ewarn "Please note that after switching the active Python interpreter,"
+				ewarn "you may need to run 'python-updater' to ensure the system integrity."
+				ewarn
+				ewarn "For more information on python.eclass compatibility, please see"
+				ewarn "the appropriate python-r1 User's Guide chapter [1]."
+				ewarn
+				ewarn "[1] http://www.gentoo.org/proj/en/Python/python-r1/user-guide.xml#doc_chap2"
+			fi
+		}
+
+		# If user has no USE_PYTHON, try to avoid it.
+		if [[ ! ${USE_PYTHON} ]]; then
+			debug-print "${FUNCNAME}: trying eselect solution ..."
+			_try_eselect && return
+		fi
+
+		debug-print "${FUNCNAME}: trying USE_PYTHON solution ..."
+		debug-print "${FUNCNAME}: -> USE_PYTHON=${USE_PYTHON}"
+
+		local impl old=${USE_PYTHON} new=() removed=()
+
+		for impl in "${PYTHON_COMPAT[@]}"; do
+			local abi
+			case "${impl}" in
+				python*)
+					abi=${impl#python}
+					;;
+				jython*)
+					abi=${impl#jython}-jython
+					;;
+				pypy*)
+					abi=2.7-pypy-${impl#pypy}
+					;;
+				*)
+					die "Unexpected Python implementation: ${impl}"
+					;;
+			esac
+			abi=${abi/_/.}
+
+			has "${abi}" ${USE_PYTHON}
+			local has_abi=${?}
+			use "python_targets_${impl}"
+			local has_impl=${?}
+
+			# 0 = has, 1 = does not have
+			if [[ ${has_abi} == 0 && ${has_impl} == 1 ]]; then
+				debug-print "${FUNCNAME}: ---> remove ${abi}"
+				# remove from USE_PYTHON
+				old=${old/${abi}/}
+				removed+=( ${abi} )
+			elif [[ ${has_abi} == 1 && ${has_impl} == 0 ]]; then
+				debug-print "${FUNCNAME}: ---> add ${abi}"
+				# add to USE_PYTHON
+				new+=( ${abi} )
+			fi
+		done
+
+		if [[ ${removed[@]} || ${new[@]} ]]; then
+			old=( ${old} )
+
+			debug-print "${FUNCNAME}: -> old: ${old[@]}"
+			debug-print "${FUNCNAME}: -> new: ${new[@]}"
+			debug-print "${FUNCNAME}: -> removed: ${removed[@]}"
+
+			if [[ ${USE_PYTHON} ]]; then
+				ewarn "It seems that your USE_PYTHON setting does list different Python"
+				ewarn "implementations than your PYTHON_TARGETS variable. Please consider"
+				ewarn "using the following value instead:"
+				ewarn
+				ewarn "	USE_PYTHON='\033[35m${old[@]}${new[@]+ \033[1m${new[@]}}\033[0m'"
+
+				if [[ ${removed[@]} ]]; then
+					ewarn
+					ewarn "(removed \033[31m${removed[@]}\033[0m)"
+				fi
+			else
+				ewarn "It seems that you need to set USE_PYTHON to make sure that legacy"
+				ewarn "packages will be built with respect to PYTHON_TARGETS correctly:"
+				ewarn
+				ewarn "	USE_PYTHON='\033[35;1m${new[@]}\033[0m'"
+			fi
+
+			ewarn
+			ewarn "Please note that after changing the USE_PYTHON variable, you may need"
+			ewarn "to run 'python-updater' to ensure the system integrity."
+			ewarn
+			ewarn "For more information on python.eclass compatibility, please see"
+			ewarn "the appropriate python-r1 User's Guide chapter [1]."
+			ewarn
+			ewarn "[1] http://www.gentoo.org/proj/en/Python/python-r1/user-guide.xml#doc_chap2"
+		fi
+	fi
+}
+
 # @FUNCTION: python_foreach_impl
 # @USAGE: <command> [<args>...]
 # @DESCRIPTION:
@@ -376,6 +572,8 @@ python_copy_sources() {
 python_foreach_impl() {
 	debug-print-function ${FUNCNAME} "${@}"
 
+	_python_check_USE_PYTHON
+
 	local impl
 	local bdir=${BUILD_DIR:-${S}}
 
-- 
1.8.0