build-sys: Add --enable-code-generator

This flag is only used for git builds, and can usually safely be
disabled.
When it's enabled, configure.ac will check that python-six and pyparsing
are available, and will use these together with the codegen python
scripts in order to automatically regenerate enums.h when the .proto
files change.

autogen.sh

@@ -11,7 +11,7 @@ test -z "$srcdir" && srcdir=.
     autoreconf --verbose --force --install
 )
 
-CONFIGURE_ARGS="--enable-maintainer-mode"
+CONFIGURE_ARGS="--enable-maintainer-mode --enable-code-generator"
 
 if [ -z "$NOCONFIGURE" ]; then
     echo "Running configure with $CONFIGURE_ARGS $@"

configure.ac

@@ -14,6 +14,22 @@ AM_MAINTAINER_MODE
 
 m4_ifdef([AM_SILENT_RULES],[AM_SILENT_RULES([yes])])
 
+dnl Enable generation of enums.h, mainly useful when building from git,
+dnl should not be needed for tarball users
+AC_ARG_ENABLE([code-generator],
+    AS_HELP_STRING([--enable-code-generator=@<:@yes/no/auto@:>@],
+                       [Enable checks needed to use the Python code generator @<:@default=auto@:>@]),
+                       [],
+                       [enable_code_generator="auto"])
+if test "x$enable_code_generator" != "xno"; then
+    AS_IF([test "x$enable_code_generator" = "xyes"], modules_required=[1], modules_required=[])
+    AX_PYTHON_MODULE([six], $modules_required)
+    AX_PYTHON_MODULE([pyparsing], $modules_required)
+    AS_IF([test "x${HAVE_PYMOD_SIX}" = "xno"], enable_code_generator="no")
+    AS_IF([test "x${HAVE_PYMOD_PYPARSING}" = "xno"], enable_code_generator="no")
+fi
+AM_CONDITIONAL([ENABLE_CODEGEN], [test "x$enable_code_generator" != "xno"])
+
 AC_OUTPUT([
 Makefile
 spice-protocol.pc

spice/Makefile.am

@@ -21,4 +21,28 @@ spice_protocol_include_HEADERS =		\
 	vdi_dev.h				\
 	$(NULL)
 
+# Using the python code generator requires some python modules
+# which might not be installed on the user computer. Given that
+# enums.h is stored in git, and should be up-to-date anyway,
+# we can make this part optional
+if ENABLE_CODEGEN
+MARSHALLERS_DEPS =					\
+	$(top_srcdir)/python_modules/__init__.py	\
+	$(top_srcdir)/python_modules/codegen.py		\
+	$(top_srcdir)/python_modules/demarshal.py	\
+	$(top_srcdir)/python_modules/marshal.py		\
+	$(top_srcdir)/python_modules/ptypes.py		\
+	$(top_srcdir)/python_modules/spice_parser.py	\
+	$(top_srcdir)/spice_codegen.py			\
+	$(NULL)
+
+BUILT_SOURCES = enums.h
+
+# this is going to upset automake distcheck, since we try to write to
+# readonly srcdir. To limit the fail chances, rebuild automatically
+# enums.h only if the spice.proto has changed.
+enums.h: $(top_srcdir)/spice.proto # $(MARSHALLERS_DEPS)
+	$(AM_V_GEN)$(PYTHON) $(top_srcdir)/spice_codegen.py --generate-enums $< $@ >/dev/null
+endif
+
 -include $(top_srcdir)/git.mk