make the PostgreSQL client optional

README.rst

@@ -17,11 +17,14 @@ You need:
 - a C++20 compliant compiler (e.g. gcc or clang)
 - `libfmt <https://fmt.dev/>`__
 - `LuaJIT <http://luajit.org/>`__
-- `libpq <https://www.postgresql.org/>`__ for PostgreSQL support in
-  Lua code
 - `systemd <https://www.freedesktop.org/wiki/Software/systemd/>`__
 - `Meson 0.56 <http://mesonbuild.com/>`__ and `Ninja <https://ninja-build.org/>`__
 
+Optional dependencies:
+
+- `libpq <https://www.postgresql.org/>`__ for PostgreSQL support in
+  Lua code
+
 Get the source code::
 
  git clone --recursive https://github.com/CM4all/qrelay.git

debian/changelog

@@ -1,6 +1,6 @@
 cm4all-qrelay (0.27) unstable; urgency=low
 
-  * 
+  * make the PostgreSQL client optional
 
  --   
 

meson.build

@@ -10,6 +10,8 @@ debug = get_option('b_ndebug') != 'true'
 
 compiler = meson.get_compiler('cpp')
 
+conf = configuration_data()
+
 common_flags = [
   '-D_GNU_SOURCE',
 ]
@@ -120,9 +122,17 @@ subdir('libcommon/src/event/systemd')
 subdir('libcommon/src/lua/event')
 subdir('libcommon/src/stock')
 subdir('libcommon/src/time')
-subdir('libcommon/src/pg')
 subdir('libcommon/src/lua/io')
-subdir('libcommon/src/lua/pg')
+
+libcommon_require_pg = get_option('pg')
+subdir('libcommon/src/pg')
+if pg_dep.found()
+  subdir('libcommon/src/lua/pg')
+  pg_dep = lua_pg_dep
+endif
+
+conf.set('HAVE_PG', pg_dep.found())
+configure_file(output: 'config.h', configuration: conf)
 
 executable('cm4all-qrelay',
   'src/CommandLine.cxx',
@@ -146,7 +156,7 @@ executable('cm4all-qrelay',
     lua_io_dep,
     lua_net_dep,
     lua_event_dep,
-    lua_pg_dep,
+    pg_dep,
     event_net_dep,
     event_net_djb_dep,
     event_systemd_dep,

meson_options.txt

@@ -1,2 +1,4 @@
+option('pg', type: 'feature', description: 'PostgreSQL client for Lua')
+
 option('documentation', type: 'feature',
   description: 'Build documentation')

src/Main.cxx

@@ -18,10 +18,13 @@
 #include "lua/io/CgroupInfo.hxx"
 #include "lua/net/SocketAddress.hxx"
 #include "lua/event/Init.hxx"
-#include "lua/pg/Init.hxx"
 #include "util/PrintException.hxx"
 #include "util/ScopeExit.hxx"
 
+#ifdef HAVE_PG
+#include "lua/pg/Init.hxx"
+#endif
+
 extern "C" {
 #include <lauxlib.h>
 #include <lualib.h>
@@ -100,7 +103,10 @@ SetupConfigState(lua_State *L, Instance &instance)
 	luaL_openlibs(L);
 
 	Lua::InitEvent(L, instance.GetEventLoop());
+
+#ifdef HAVE_PG
 	Lua::InitPg(L, instance.GetEventLoop());
+#endif
 
 	Lua::InitSocketAddress(L);
 	RegisterLuaResolver(L);