Added notion of synchronization between error handler

this is convenient to integrate two components using their own ERROR_HANDLER (not sharing the same object)

library/error/src/error_handler.e

@@ -21,7 +21,7 @@ feature {NONE} -- Initialization
 	make
 			-- Initialize `Current'.
 		do
-			create {ARRAYED_LIST [ERROR]} errors.make (3)
+			create {ARRAYED_LIST [like errors.item]} errors.make (3)
 			create error_added_actions
 		end
 
@@ -60,12 +60,139 @@ feature -- Events
 	error_added_actions: ACTION_SEQUENCE [TUPLE [ERROR]]
 			-- Actions triggered when a new error is added
 
+feature -- Synchronization
+
+	add_synchronized_handler (h: ERROR_HANDLER)
+			--| the same handler can be added more than once
+			--| it will be synchronized only once
+		require
+			no_cycle: not has_synchronized_handler_in_cycle (h)
+		local
+			lst: like synchronized_handlers
+		do
+			lst := synchronized_handlers
+			if lst = Void then
+				create {ARRAYED_LIST [like synchronized_handlers.item]} lst.make (0)
+				lst.compare_references
+				synchronized_handlers := lst
+			end
+			if lst.has (h) then
+				check attached h.synchronized_handlers as h_lst and then h_lst.has (Current) end
+			else
+				lst.extend (h)
+				h.add_synchronized_handler (Current)
+			end
+		end
+
+	has_synchronized_handler_in_cycle (h: ERROR_HANDLER): BOOLEAN
+		do
+			Result := False
+		end
+
+feature {ERROR_HANDLER} -- Synchronization implementation
+
+	synchronized_handlers: detachable LIST [ERROR_HANDLER]
+			-- Synchronized handlers
+
+	synchronize_error_from (e: ERROR; h_lst: LIST [ERROR_HANDLER])
+			-- Called by error_handler during synchronization process
+			-- if `synchronized_handlers' is Void, this means Current is synchronizing
+			-- this is to prevent infinite cycle iteration
+		require
+			not h_lst.has (Current)
+		do
+			h_lst.extend (Current)
+
+			if attached synchronized_handlers as lst then
+				synchronized_handlers := Void
+				add_error (e)
+				across
+					lst as c
+				loop
+					if not h_lst.has (c.item) then
+						c.item.synchronize_error_from (e, h_lst)
+					end
+				end
+				synchronized_handlers := lst
+			else
+				-- In synchronization
+			end
+		end
+
+	synchronize_reset_from (h_lst: LIST [ERROR_HANDLER])
+			-- Called by error_handler during synchronization process
+			-- if `synchronized_handlers' is Void, this means Current is synchronizing
+			-- this is to prevent infinite cycle iteration
+		require
+			not h_lst.has (Current)
+		do
+			h_lst.extend (Current)
+			if attached synchronized_handlers as lst then
+				synchronized_handlers := Void
+				reset
+				across
+					lst as c
+				loop
+					if not h_lst.has (c.item) then
+						c.item.synchronize_reset_from (h_lst)
+					end
+				end
+				synchronized_handlers := lst
+			else
+				-- In synchronization				
+			end
+		end
+
+	remove_synchronized_handler (h: ERROR_HANDLER)
+		do
+			if attached synchronized_handlers as lst then
+				lst.prune_all (h)
+				if lst.is_empty then
+					synchronized_handlers := Void
+				end
+			end
+		end
+
 feature {NONE} -- Event: implementation
 
 	on_error_added (e: ERROR)
 			-- Error `e' was just added
+		local
+			sync_list: LINKED_LIST [ERROR_HANDLER]
 		do
 			error_added_actions.call ([e])
+			if attached synchronized_handlers as lst then
+				synchronized_handlers := Void
+				create sync_list.make
+				sync_list.extend (Current)
+				across
+					lst as c
+				loop
+					if not sync_list.has (c.item) then
+						c.item.synchronize_error_from (e, sync_list)
+					end
+				end
+				synchronized_handlers := lst
+			end
+		end
+
+	on_reset
+		local
+			sync_list: LINKED_LIST [ERROR_HANDLER]
+		do
+			if attached synchronized_handlers as lst then
+				synchronized_handlers := Void
+				create sync_list.make
+				sync_list.extend (Current)
+				across
+					lst as c
+				loop
+					if not sync_list.has (c.item) then
+						c.item.synchronize_reset_from (sync_list)
+					end
+				end
+				synchronized_handlers := lst
+			end
 		end
 
 feature -- Basic operation
@@ -138,18 +265,30 @@ feature -- Element changes
 			-- Concatenate into a single error if any
 		do
 			if count > 1 and then attached as_single_error as e then
-				wipe_out
+				reset
-				errors.force (e)
+				add_error (e)
 			end
 		end
 
-	reset, wipe_out
+	reset
 		do
-			errors.wipe_out
+			if errors.count > 0 then
+				errors.wipe_out
+				on_reset
+			end
+		end
+
+	destroy
+		do
+			error_added_actions.wipe_out
+			if attached synchronized_handlers as lst then
+				lst.item.remove_synchronized_handler (Current)
+			end
+			synchronized_handlers := Void
 		end
 
 note
-	copyright: "Copyright (c) 1984-2011, Eiffel Software and others"
+	copyright: "2011-2012, Eiffel Software and others"
 	license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)"
 	source: "[
 			Eiffel Software

library/error/tests/test_error.e

@@ -0,0 +1,124 @@
+note
+	description: "[
+		Eiffel tests that can be executed by testing tool.
+	]"
+	author: "EiffelStudio test wizard"
+	date: "$Date$"
+	revision: "$Revision$"
+	testing: "type/manual"
+
+class
+	TEST_ERROR
+
+inherit
+	EQA_TEST_SET
+
+feature -- Test routines
+
+	test_error
+		note
+			testing:  "error"
+		local
+			h: ERROR_HANDLER
+			cl: CELL [INTEGER]
+		do
+			create h.make
+			h.add_custom_error (123, "abc", "abc error occurred")
+			h.add_custom_error (456, "abc", "abc error occurred")
+			assert ("has 2 errors", h.count = 2)
+			h.reset
+			assert ("reset then no error", h.count = 0)
+
+			-- error_added_actions
+			create cl.put (0)
+			h.error_added_actions.extend (agent (i_e: ERROR; i_cl: CELL [INTEGER]) do i_cl.replace (i_cl.item + 1)  end(?, cl))
+			h.add_custom_error (123, "abc", "abc error occurred")
+			h.add_custom_error (456, "abc", "abc error occurred")
+			assert ("has 2 errors, same as counted", h.count = 2 and h.count = cl.item)
+
+		end
+
+	test_sync_2
+		note
+			testing:  "error"
+		local
+			h1, h2: ERROR_HANDLER
+--			cl: CELL [INTEGER]
+		do
+			create h1.make
+			create h2.make
+			h1.add_synchronized_handler (h2)
+
+			h1.add_custom_error (123, "abc", "abc error occurred")
+			h1.add_custom_error (456, "abc", "abc error occurred")
+
+			assert ("has 2 errors", h1.count = 2 and h2.count = h1.count)
+
+			h1.reset
+			assert ("reset then no error", h1.count = 0 and h2.count = h1.count)
+
+		end
+
+	test_sync_3
+		note
+			testing:  "error"
+		local
+			h1, h2, h3: ERROR_HANDLER
+--			cl: CELL [INTEGER]
+		do
+			create h1.make
+			create h2.make
+			create h3.make
+
+			h1.add_synchronized_handler (h2)
+			h2.add_synchronized_handler (h3)
+
+			h1.add_custom_error (123, "abc", "abc error occurred")
+			h1.add_custom_error (456, "abc", "abc error occurred")
+
+			assert ("has 2 errors", h1.count = 2 and h2.count = h1.count and h3.count = h2.count)
+
+			h1.reset
+			assert ("reset then no error", h1.count = 0 and h2.count = h1.count and h3.count = h2.count)
+
+		end
+
+	test_sync_3_with_cycle
+		note
+			testing:  "error"
+		local
+			h1, h2, h3: ERROR_HANDLER
+--			cl: CELL [INTEGER]
+		do
+			create h1.make
+			create h2.make
+			create h3.make
+
+			h1.add_synchronized_handler (h2)
+			h2.add_synchronized_handler (h3)
+			h3.add_synchronized_handler (h1)
+
+			h1.add_custom_error (123, "abc", "abc error occurred")
+			h1.add_custom_error (456, "abc", "abc error occurred")
+
+			assert ("has 2 errors", h1.count = 2 and h2.count = h1.count and h3.count = h2.count)
+
+			h1.reset
+			assert ("reset then no error", h1.count = 0 and h2.count = h1.count and h3.count = h2.count)
+
+		end
+
+
+note
+	copyright: "Copyright (c) 1984-2011, Eiffel Software and others"
+	license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)"
+	source: "[
+			Eiffel Software
+			5949 Hollister Ave., Goleta, CA 93117 USA
+			Telephone 805-685-1006, Fax 805-685-6869
+			Website http://www.eiffel.com
+			Customer support http://support.eiffel.com
+		]"
+end
+
+

library/error/tests/tests-safe.ecf

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="ISO-8859-1"?>
+<system xmlns="http://www.eiffel.com/developers/xml/configuration-1-9-0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.eiffel.com/developers/xml/configuration-1-9-0 http://www.eiffel.com/developers/xml/configuration-1-9-0.xsd" name="error_tests" uuid="54F59BB2-AD49-42C7-ABAA-B60765F4F926">
+	<target name="error_tests">
+		<root class="ANY" feature="default_create"/>
+		<file_rule>
+			<exclude>/.git$</exclude>
+			<exclude>/EIFGENs$</exclude>
+			<exclude>/.svn$</exclude>
+		</file_rule>
+		<option warning="true" full_class_checking="true" is_attached_by_default="true" void_safety="all" syntax="transitional">
+			<assertions precondition="true"/>
+		</option>
+		<library name="base" location="$ISE_LIBRARY\library\base\base-safe.ecf"/>
+		<library name="error" location="..\error-safe.ecf" readonly="false"/>
+		<library name="testing" location="$ISE_LIBRARY\library\testing\testing-safe.ecf"/>
+		<tests name="tests" location=".\"/>
+	</target>
+</system>