python-tools.sh, py-mod.mk: Use --symbol-filter

Letting python-tools.sh rewrite symbols is more robust than rewriting an entire __init__.py with PY_INIT_FILTER in the including Makefile. The latter can break in non-obvious ways if python-tools.sh changes __init__.py's format.
Make python-tools.sh support --symbol-filter to remedy that. The option takes an sed script which should expect a string of two non-whitespace tokens: The module from which the symbol is imported, and the name of the symbol in that module. It's output will then be used as the symbol to be exported from __init__.py.
Also, support the PY_SYMBOL_FILTER variable in py-mod.mk. If it's defined, it is used for --symbol-filter.
Signed-off-by: Jan Lindemann <jan@janware.com>

scripts/python-tools.sh

@@ -34,6 +34,12 @@ module_path()
 
 cmd_create_init()
 {
+	__add_seen() {
+		local type="$1"
+		[[ -n "${seen[$type]+x}" ]] && fatal "Duplicate symbol: $type"
+		seen["$type"]=1
+	}
+
 	local import_submodules=0
 	local files="$*"
 	local del="-------------------------- generated by $myname"
@@ -42,26 +48,38 @@ cmd_create_init()
 	echo "from pkgutil import extend_path"
 	echo ""
 	echo "__path__ = extend_path(__path__, __name__)"
+	echo
 	local f
 	local -A seen=()
+	local dst_type
 	for f in $files; do
 		test -d $f && continue
 		local base=${f##*/}
 		base=${base%.py}
-		if [ "$sed_extract_command" ]; then
-			local type types=`sed "$sed_extract_command" $f`
-			for type in $types; do
-				echo "from `module_path $base` import $type as $type"
-				[[ -n "${seen[$type]+x}" ]] && fatal "Duplicate symbol: $type"
-				seen["$type"]=1
+		if [ "$sed_extract_cmd" ]; then
+			local src_type types=$(sed "$sed_extract_cmd" $f)
+			for src_type in $types; do
+				[ "$sed_symbol_filter_cmd" ] && dst_type=$(echo $base $src_type | sed "$sed_symbol_filter_cmd")
+				echo "from `module_path $base` import $src_type as $dst_type"
+				__add_seen $dst_type
 			done
 		fi
 	done
 	if [ "$import_submodules" = 1 ]; then
 		for f in $files; do
-			[ -f $f/__init__.py ] && echo "import `module_path $f` as $f"
+			[ -f $f/__init__.py ] || continue
+			echo "import `module_path $f` as $f"
+			__add_seen $f
 		done
 	fi
+
+	echo
+	echo "__all__ = ["
+	for dst_type in ${!seen[@]}; do
+		echo "    \"$dst_type\","
+	done
+	echo "]"
+
 	echo "# << $del <<"
 }
 
@@ -69,11 +87,15 @@ cmd_create_init()
 
 myname=`basename $0`
 
-eval set -- `getopt -o 'he:m:' "$@"`
+eval set -- `getopt -l 'symbol-filter:' -o 'he:m:' "$@"`
 while [ "$1" != -- ]; do
 case $1 in
 	-e)
-		sed_extract_command="$2"
+		sed_extract_cmd="$2"
+		shift
+		;;
+	--symbol-filter)
+		sed_symbol_filter_cmd="$2"
 		shift
 		;;
 	-m)