Added capability to automatically load addon library script files.

Adds code in libinit.sh to check for a property 'sys.addon.code.load', which
can be defined by an addon in its 'project.properties' file. The introduced
property defines a path to a script file, relative to the addon's source tree
root, which should be automatically loaded by the init system into the global
namespace. The loading must occur before any user-specific properties are
loaded in order to avoid redefinitions.

libinit.sh

@@ -1035,6 +1035,40 @@ function _load_version_addons() {
   return $ret_val;
 }
 
+# Loads the specified addon library script file.
+#
+# The specified script path must be valid and the file
+# to be loaded must exist. If any condition is not satisfied, then
+# this function will exit the program by means of the failure() function.
+#
+# Args:
+# $1 - The name of the file to load, relative to the source tree root
+#      of the active addon. This is a mandatory argument.
+#
+function _load_addon_declared_libs() {
+  local addon_libs="$1";
+  if _is_absolute_path "$addon_libs"; then
+    logE "Addon code path is invalid.";
+    logE "Invalid property with key 'sys.addon.code.load': '${addon_libs}'";
+    logE "File path must be relative to addon directory.";
+    _show_helptext "E" "Addons#loading-common-code";
+    failure "An addon configuration has errors";
+  fi
+  if [[ "${addon_libs}" == *"../"* ]]; then
+    logE "Addon code path is invalid.";
+    failure "An addon configuration has errors";
+  fi
+  addon_libs="${PROJECT_INIT_ADDONS_DIR}/${addon_libs}";
+  if ! [ -r "${addon_libs}" ]; then
+    logE "Addon code file not found:";
+    logE "at: '${addon_libs}'";
+    logE "Invalid property with key 'sys.addon.code.load'";
+    _show_helptext "E" "Addons#loading-common-code";
+    failure "An addon configuration has errors";
+  fi
+  source "$addon_libs";
+}
+
 # Loads the quickstart function definitions.
 #
 # The path to the directory containing the quickstart script
@@ -2118,6 +2152,21 @@ function _fill_files_list_from() {
   fi
 }
 
+# Handler function for when the addon-specific configuration file was loaded.
+#
+# This function can be used to perform checks for the addon-specific
+# 'project.properties' configuration file after the base variant was loaded
+# but before the user variant is loaded. It is only called if
+# the addon-specific file was loaded.
+#
+function _after_addons_properties_loaded() {
+  get_property "sys.addon.code.load";
+  local addon_libs="$PROPERTY_VALUE";
+  if [ -n "$addon_libs" ]; then
+    _load_addon_declared_libs "$addon_libs";
+  fi
+}
+
 # Loads the base system configuration files and stores the
 # data in the corresponding global variables.
 #
@@ -2144,6 +2193,7 @@ function _load_configuration() {
   if [ -n "$PROJECT_INIT_ADDONS_DIR" ]; then
     if [ -f "$PROJECT_INIT_ADDONS_DIR/project.properties" ]; then
       _read_properties "$PROJECT_INIT_ADDONS_DIR/project.properties";
+      _after_addons_properties_loaded;
     fi
   fi
 

project.properties

@@ -129,6 +129,15 @@ sys.starttext.show=true
 # to be shown, the notify-send command must be available.
 sys.notification.success.show=true
 
+# A script file to source after an addon is loaded. This property must only be
+# defined in a 'project.properties' file of an addon. It is a path to a
+# script, relative to the addon's source tree, which gets automatically
+# sourced after the addon has been successfully loaded. This can be used to
+# put common code used throughout an addon into a separate file which acts like
+# a library, and instruct Project Init to automatically load it once the addon
+# is loaded. The code in the file is loaded into the global namespace.
+# sys.addon.code.load=mylibs.sh
+
 # ------------------------- Language-specific Settings ---------------------- #
 
 # ##### C settings