make peekLastUpdate alway return lastVersion when available

services/track-changes/app/coffee/MongoManager.coffee

@@ -18,7 +18,7 @@ module.exports = MongoManager =
 
 	peekLastCompressedUpdate: (doc_id, callback = (error, update, version) ->) ->
 		# under normal use we pass back the last update as
-		# callback(null,update).
+		# callback(null,update,version).
 		#
 		# when we have an existing last update but want to force a new one
 		# to start, we pass it back as callback(null,null,version), just
@@ -26,17 +26,18 @@ module.exports = MongoManager =
 		MongoManager.getLastCompressedUpdate doc_id, (error, update) ->
 			return callback(error) if error?
 			if update?
-				if update.inS3?
-					# we want to force a new update, but ensure that it is
-					# consistent with the version of the existing one in S3
-					return callback null, null, update.v
-				else if update.broken
+				if update.broken
 					# the update is marked as broken so we will force a new op
 					return callback null, null
+				else if update.pack?
+					return callback null, update, update.pack[0]?.v
 				else
-					return callback null, update
+					return callback null, update, update.v
 			else
-				callback null, null
+				MongoManager.getArchivedDocStatus doc_id, (error, status) ->
+					return callback(error) if error?
+					return callback(null, null, status.lastVersion) if status?.inS3? and status?.lastVersion?
+					callback null, null
 
 	insertCompressedUpdates: (project_id, doc_id, updates, temporary, callback = (error) ->) ->
 		jobs = []
@@ -152,6 +153,9 @@ module.exports = MongoManager =
 		db.docHistoryStats.ensureIndex { doc_id: 1 }, { background: true }
 		db.docHistoryStats.ensureIndex { updates: -1, doc_id: 1 }, { background: true }
 
+	getArchivedDocStatus: (doc_id, callback)->
+		db.docHistoryStats.findOne {doc_id: ObjectId(doc_id.toString()), inS3: {$exists:true}}, {inS3: true, lastVersion: true}, callback
+
 	getDocChangesCount: (doc_id, callback)->
 		db.docHistory.count { doc_id : ObjectId(doc_id.toString()), inS3 : { $exists : false }}, callback
 

services/track-changes/app/coffee/UpdatesManager.coffee

@@ -17,17 +17,13 @@ module.exports = UpdatesManager =
 			return callback()
 
 		MongoManager.peekLastCompressedUpdate doc_id, (error, lastCompressedUpdate, lastVersion) ->
-			# lastCompressedUpdate is the most recent update in Mongo.
+			# lastCompressedUpdate is the most recent update in Mongo, and
+			# lastVersion is its sharejs version number.
 			#
-			# The peekLastCompressedUpdate method may pass it back as 'null'
-			# to force the start of a new compressed update, even when there
-			# was a previous compressed update in Mongo.  In this case it
-			# passes back the lastVersion from the update to check
-			# consistency.
-
-			# when lastVersion is not provided, default to lastCompressedUpdate.v
-			lastVersion ?= lastCompressedUpdate?.v
-
+			# The peekLastCompressedUpdate method may pass the update back
+			# as 'null' (for example if the previous compressed update has
+			# been archived).  In this case it can still pass back the
+			# lastVersion from the update to allow us to check consistency.
 			return callback(error) if error?
 
 			# Ensure that raw updates start where lastVersion left off

services/track-changes/test/unit/coffee/MongoManager/MongoManagerTests.coffee

@@ -57,6 +57,8 @@ describe "MongoManager", ->
 	describe "peekLastCompressedUpdate", ->
 		describe "when there is no last update", ->
 			beforeEach ->
+				@db.docHistoryStats = {}
+				@db.docHistoryStats.findOne = sinon.stub().callsArgWith(2, null, null)
 				@MongoManager.getLastCompressedUpdate = sinon.stub().callsArgWith(1, null, null)
 				@MongoManager.peekLastCompressedUpdate @doc_id, @callback
 
@@ -84,8 +86,10 @@ describe "MongoManager", ->
 
 		describe "when there is a last update in S3", ->
 			beforeEach ->
-				@update = { _id: Object(), v: 12345, inS3: true }
-				@MongoManager.getLastCompressedUpdate = sinon.stub().callsArgWith(1, null, @update)
+				@update = { _id: Object(), v: 12345}
+				@db.docHistoryStats = {}
+				@db.docHistoryStats.findOne = sinon.stub().callsArgWith(2, null, {inS3:true, lastVersion: @update.v})
+				@MongoManager.getLastCompressedUpdate = sinon.stub().callsArgWith(1, null)
 				@MongoManager.peekLastCompressedUpdate @doc_id, @callback
 
 			it "should get the last update", ->

services/track-changes/test/unit/coffee/UpdatesManager/UpdatesManagerTests.coffee

@@ -69,7 +69,7 @@ describe "UpdatesManager", ->
 				@lastCompressedUpdate = { v: 11, op: "compressed-op-11" }
 				@compressedUpdates = [ { v: 12, op: "compressed-op-11+12" }, { v: 13, op: "compressed-op-12" } ]
 
-				@MongoManager.peekLastCompressedUpdate = sinon.stub().callsArgWith(1, null, @lastCompressedUpdate)
+				@MongoManager.peekLastCompressedUpdate = sinon.stub().callsArgWith(1, null, @lastCompressedUpdate, @lastCompressedUpdate.v)
 				@MongoManager.modifyCompressedUpdate = sinon.stub().callsArg(2)
 				@MongoManager.insertCompressedUpdates = sinon.stub().callsArg(4)
 				@UpdateCompressor.compressRawUpdates = sinon.stub().returns(@compressedUpdates)