Updating Parent Link via REST API fails

Summary

Updating Parent field on an issue with no Parent Link via REST API works fine. But when clearing the Parent Link value or updating the value, the REST API fails with Internal server error.

Environment

• JIRA Portfolio 2.3.0 is installed.

Steps to Reproduce

1. Sample REST API call:

   <Base URL>/rest/api/2/issue/<Issue key>
   

   Body:

   {
       "update" : {
           "customfield_<custom field ID>" : [{"set" : "<parent link issue key>"}]
       }
   }
   

Expected Results

1. Parent field should be able to set to null to clear the value.
2. Parent field should be able to be updated to a different parent issue.

Actual Results

1. Issues with no Parent link is able to be updated with the REST API.
2. Updating an issue with a new Parent issue, the Parent link fails with the following error in atlassian-jira.log:

   2017-09-07 15:19:07,091 http-nio-8740-exec-13 ERROR admin 919x19417x1 1istpb8 10.60.3.49 /rest/api/2/issue/MOK-17 [c.a.j.rest.exception.ExceptionInterceptor] Returning internal server error in response
   java.lang.reflect.InvocationTargetException
           at sun.reflect.GeneratedMethodAccessor4746.invoke(Unknown Source)
           at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
           at java.lang.reflect.Method.invoke(Method.java:498)
           at com.atlassian.plugins.rest.common.interceptor.impl.DispatchProviderHelper$ResponseOutInvoker$1.invoke(DispatchProviderHelper.java:192)
           at com.atlassian.plugins.rest.common.interceptor.impl.DispatchProviderHelper$1.intercept(DispatchProviderHelper.java:83)
           ... 3 filtered
           at com.atlassian.jira.rest.exception.ExceptionInterceptor.intercept(ExceptionInterceptor.java:55)
           ... 1 filtered
           at com.atlassian.jira.rest.v2.issue.scope.RequestScopeInterceptor.intercept(RequestScopeInterceptor.java:39)
           ... 15 filtered
           at com.atlassian.plugins.rest.module.RestDelegatingServletFilter$JerseyOsgiServletContainer.doFilter(RestDelegatingServletFilter.java:154)
           ... 1 filtered
           at com.atlassian.plugins.rest.module.RestDelegatingServletFilter.doFilter(RestDelegatingServletFilter.java:68)
           ... 32 filtered
           at com.atlassian.servicedesk.internal.web.ExternalCustomerLockoutFilter.doFilter(ExternalCustomerLockoutFilter.java:56)
           ... 13 filtered
           at com.atlassian.web.servlet.plugin.request.RedirectInterceptingFilter.doFilter(RedirectInterceptingFilter.java:21)
           ... 53 filtered
           at com.atlassian.jira.security.JiraSecurityFilter.lambda$doFilter$0(JiraSecurityFilter.java:66)
           ... 1 filtered
           at com.atlassian.jira.security.JiraSecurityFilter.doFilter(JiraSecurityFilter.java:64)
           ... 16 filtered
           at com.atlassian.plugins.rest.module.servlet.RestSeraphFilter.doFilter(RestSeraphFilter.java:37)
           ... 19 filtered
           at com.atlassian.jira.servermetrics.CorrelationIdPopulatorFilter.doFilter(CorrelationIdPopulatorFilter.java:30)
           ... 5 filtered
           at com.atlassian.servicedesk.internal.web.CustomerContextSettingFilter.lambda$invokeFilterChain$0(CustomerContextSettingFilter.java:181)
           at com.atlassian.servicedesk.internal.utils.context.ReentrantThreadLocalBasedCodeContext.rteInvoke(ReentrantThreadLocalBasedCodeContext.java:134)
           at com.atlassian.servicedesk.internal.utils.context.ReentrantThreadLocalBasedCodeContext.runOutOfContext(ReentrantThreadLocalBasedCodeContext.java:87)
           at com.atlassian.servicedesk.internal.utils.context.CustomerContextServiceImpl.runOutOfCustomerContext(CustomerContextServiceImpl.java:64)
           at com.atlassian.servicedesk.internal.web.CustomerContextSettingFilter.outOfCustomerContext(CustomerContextSettingFilter.java:174)
           at com.atlassian.servicedesk.internal.web.CustomerContextSettingFilter.doFilterImpl(CustomerContextSettingFilter.java:130)
           at com.atlassian.servicedesk.internal.web.CustomerContextSettingFilter.doFilter(CustomerContextSettingFilter.java:121)
           ... 4 filtered
           at com.atlassian.jwt.internal.servlet.JwtAuthFilter.doFilter(JwtAuthFilter.java:32)
           ... 8 filtered
           at com.atlassian.web.servlet.plugin.request.RedirectInterceptingFilter.doFilter(RedirectInterceptingFilter.java:21)
           ... 4 filtered
           at com.atlassian.web.servlet.plugin.LocationCleanerFilter.doFilter(LocationCleanerFilter.java:36)
           ... 26 filtered
           at com.atlassian.jira.servermetrics.MetricsCollectorFilter.doFilter(MetricsCollectorFilter.java:25)
           ... 23 filtered
           at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
           at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
           at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
           at java.lang.Thread.run(Thread.java:745)
   Caused by: java.lang.ClassCastException: com.atlassian.rm.jpo.env.issues.JiraIssueService$3 cannot be cast to java.lang.String
           at com.atlassian.jira.issue.customfields.impl.rest.TextCustomFieldOperationsHandler.getInitialValue(TextCustomFieldOperationsHandler.java:43)
           at com.atlassian.jira.issue.customfields.impl.rest.TextCustomFieldOperationsHandler.getInitialValue(TextCustomFieldOperationsHandler.java:17)
           at com.atlassian.jira.issue.customfields.impl.rest.AbstractCustomFieldOperationsHandler.updateIssueInputParameters(AbstractCustomFieldOperationsHandler.java:75)
           at com.atlassian.jira.rest.v2.issue.IssueInputParametersAssembler$IssueInputParametersBuilder.finalizeIssueInputParams(IssueInputParametersAssembler.java:428)
           at com.atlassian.jira.rest.v2.issue.IssueInputParametersAssembler$IssueInputParametersBuilder.buildForEdit(IssueInputParametersAssembler.java:230)
           at com.atlassian.jira.rest.v2.issue.UpdateIssueResource.editIssue(UpdateIssueResource.java:58)
           at com.atlassian.jira.rest.v2.issue.IssueResource.editIssue(IssueResource.java:752)
           ... 254 more
   

Workaround

1. Update the Parent field via UI instead of using REST API.