Check if v1 project was exported if not found

This prevents a redirect loop for projects which were exported but then
deleted on v2. v2 would not find the project, redirect to v1, which
would find that it was exported and redirect back to v2.

services/web/app/coffee/Features/TokenAccess/TokenAccessController.coffee

@@ -1,6 +1,7 @@
 ProjectController = require "../Project/ProjectController"
 AuthenticationController = require '../Authentication/AuthenticationController'
 TokenAccessHandler = require './TokenAccessHandler'
+V1Api = require '../V1/V1Api'
 Errors = require '../Errors/Errors'
 logger = require 'logger-sharelatex'
 settings = require 'settings-sharelatex'
@@ -36,9 +37,12 @@ module.exports = TokenAccessController =
 				return next(err)
 			if !projectExists and settings.overleaf
 				logger.log {token, userId},
-						"[TokenAccess] no project found for this token"
-				return res.redirect(302, "/sign_in_to_v1?return_to=/#{token}")
-			if !project?
+					"[TokenAccess] no project found for this token"
+				TokenAccessHandler.checkV1ProjectExported token, (err, exported) ->
+					return next err if err?
+					return next(new Errors.NotFoundError()) if exported
+					return res.redirect(302, "/sign_in_to_v1?return_to=/#{token}")
+			else if !project?
 				logger.log {token, userId},
 					"[TokenAccess] no token-based project found for readAndWrite token"
 				if !userId?

services/web/app/coffee/Features/TokenAccess/TokenAccessHandler.coffee

@@ -116,3 +116,9 @@ module.exports = TokenAccessHandler =
 			return callback err if err?
 			callback null, false, body.published_path if body.allow == false
 			callback null, true
+
+	checkV1ProjectExported: (token, callback = (err, exists) ->) ->
+		return callback(null, false) unless Settings.apis?.v1?
+		V1Api.request { url: "/api/v1/sharelatex/docs/#{token}/exported_to_v2" }, (err, response, body) ->
+			return callback err if err?
+			callback null, body.exported

services/web/test/acceptance/coffee/helpers/MockV1Api.coffee

@@ -85,4 +85,7 @@ module.exports = MockV1Api =
 		app.get '/api/v1/sharelatex/docs/:token/is_published', (req, res, next) =>
 			res.json { allow: true }
 
+		app.get '/api/v1/sharelatex/docs/:token/exported_to_v2', (req, res, next) =>
+			res.json { exported: false }
+
 MockV1Api.run()

services/web/test/unit/coffee/TokenAccess/TokenAccessControllerTests.coffee

@@ -248,18 +248,30 @@ describe "TokenAccessController", ->
 						@req.params['read_and_write_token'] = '123abc'
 						@TokenAccessHandler.findProjectWithReadAndWriteToken = sinon.stub()
 							.callsArgWith(1, null, null, false)
-						@TokenAccessHandler.findProjectWithHigherAccess =
-							sinon.stub()
-							.callsArgWith(2, null, @project)
-						@TokenAccessController.readAndWriteToken @req, @res, @next
 
-					it 'should redirect to v1', (done) ->
-						expect(@res.redirect.callCount).to.equal 1
-						expect(@res.redirect.calledWith(
-							302,
-							'/sign_in_to_v1?return_to=/123abc'
-						)).to.equal true
-						done()
+					describe 'when project was not exported from v1', ->
+						beforeEach ->
+							@TokenAccessHandler.checkV1ProjectExported = sinon.stub()
+								.callsArgWith(1, null, false)
+							@TokenAccessController.readAndWriteToken @req, @res, @next
+
+						it 'should redirect to v1', (done) ->
+							expect(@res.redirect.callCount).to.equal 1
+							expect(@res.redirect.calledWith(
+								302,
+								'/sign_in_to_v1?return_to=/123abc'
+							)).to.equal true
+							done()
+
+					describe 'when project was exported from v1', ->
+						beforeEach ->
+							@TokenAccessHandler.checkV1ProjectExported = sinon.stub()
+								.callsArgWith(1, null, false)
+							@TokenAccessController.readAndWriteToken @req, @res, @next
+
+						it 'should call next with a not-found error', (done) ->
+							expect(@next.callCount).to.equal 0
+							done()
 
 				describe 'when token access is off, but user has higher access anyway', ->
 					beforeEach ->