build: fix errors when building with gtk-doc 1.32

gtkdoc-scan 1.32 performs stricter checks on structures definitions
and so it complains on:

 /build/networkmanager/src/NetworkManager/libnm/./nm-vpn-plugin-old.h:0: warning: partial declaration (struct) : typedef struct {
 	NM_DEPRECATED_IN_1_2
 	GObject parent;
 } NMVpnPluginOld NM_DEPRECATED_IN_1_2;

because of the unrecognized token 'NM_DEPRECATED_IN_1_2'.

Pass all allowed macros to gtkdoc-scan through the --ignore-decorators
argument.

https://gitlab.gnome.org/GNOME/gtk-doc/issues/98
https://gitlab.freedesktop.org/NetworkManager/NetworkManager/issues/238

docs/libnm/Makefile.am

@@ -18,8 +18,10 @@ DOC_SOURCE_DIR= \
 	$(top_srcdir)/libnm \
 	$(top_builddir)/libnm
 
+decorators := $(shell $(top_srcdir)/tools/decorators.sh $(top_srcdir)/libnm-core/nm-version.h)
+
 # Extra options to supply to gtkdoc-scan.
-SCAN_OPTIONS=--rebuild-types --rebuild-sections
+SCAN_OPTIONS=--rebuild-types --rebuild-sections --ignore-decorators "$(decorators)"
 
 # Extra options to supply to gtkdoc-mkdb.
 MKDB_OPTIONS=--sgml-mode --output-format=xml

docs/libnm/meson.build

@@ -32,6 +32,9 @@ configure_file(
   configuration: version_conf,
 )
 
+result = run_command(join_paths(meson.source_root(), 'tools', 'decorators.sh'),
+                     join_paths(meson.source_root(), 'libnm-core', 'nm-version.h'))
+
 gnome.gtkdoc(
   doc_module,
   main_xml: doc_module + '-docs.xml',
@@ -43,6 +46,7 @@ gnome.gtkdoc(
   scan_args: [
     '--rebuild-types',
     '--rebuild-sections',
+    '--ignore-decorators=' + result.stdout().strip(),
     '--ignore-headers=' + ' '.join(private_headers),
   ],
   scanobjs_args: '--type-init-func="g_type_init();"',

tools/decorators.sh

@@ -0,0 +1,7 @@
+#!/bin/sh
+
+# Extract NM_DEPRECATED_IN_* and NM_AVAILABLE_IN_* macros from a
+# header file and output them in a way suitable to be passed to
+# 'gtkdoc-scan --ignore-decorators'
+
+grep -o "NM_DEPRECATED_IN_[0-9]_[0-9]\+$\|NM_AVAILABLE_IN_[0-9]_[0-9]\+$" "$1" | sed ':a;N;$!ba;s/\n/|/g'