Tolerate HttpResponse thrown from Descriptor.newInstance

[jglick]

Downstream of jenkinsci/stapler#571. Appears to solve the problem described in jenkinsci/workflow-cps-plugin#907 (comment): allows you to throw Descriptor.FormException from a @DataBoundConstructor and have it be rendered properly.

Testing done

diff --git plugin/src/main/java/org/jenkinsci/plugins/workflow/cps/CpsFlowDefinition.java plugin/src/main/java/org/jenkinsci/plugins/workflow/cps/CpsFlowDefinition.java
index eea31e59..2d04e223 100644
--- plugin/src/main/java/org/jenkinsci/plugins/workflow/cps/CpsFlowDefinition.java
+++ plugin/src/main/java/org/jenkinsci/plugins/workflow/cps/CpsFlowDefinition.java
@@ -27,6 +27,7 @@ package org.jenkinsci.plugins.workflow.cps;
 import edu.umd.cs.findbugs.annotations.NonNull;
 import hudson.Extension;
 import hudson.model.Action;
+import hudson.model.Descriptor;
 import hudson.model.Item;
 import hudson.model.Job;
 import hudson.model.Queue;
@@ -75,15 +76,18 @@ public class CpsFlowDefinition extends FlowDefinition {
      * @deprecated use {@link #CpsFlowDefinition(String, boolean)} instead
      */
     @Deprecated
-    public CpsFlowDefinition(String script) {
+    public CpsFlowDefinition(String script) throws Descriptor.FormException {
         this(script, false);
     }
 
     @DataBoundConstructor
-    public CpsFlowDefinition(String script, boolean sandbox) {
+    public CpsFlowDefinition(String script, boolean sandbox) throws Descriptor.FormException {
         StaplerRequest req = Stapler.getCurrentRequest();
         this.script = sandbox ? script : ScriptApproval.get().configuring(script, GroovyLanguage.get(),
                 ApprovalContext.create().withCurrentUser().withItemAsKey(req != null ? req.findAncestorObject(Item.class) : null), req == null);
+        if (!sandbox) {
+            throw new Descriptor.FormException("Sandbox is mandatory", "sandbox");
+        }
         this.sandbox = sandbox;
     }
 

displays a polite page with the message when you Save a form with the sandbox field unchecked, rather than an “angry Jenkins” / UUID as before. Also if you Apply then the error is shown nicely in the bottom bar.

Proposed changelog entries

• Developer: HttpResponse exceptions such as Descriptor.FormException are now rendered properly from @DataBoundConstructors.

Proposed upgrade guidelines

N/A

Submitter checklist

Beta Give feedback

1. The Jira issue, if it exists, is well-described.
2. The changelog entries and upgrade guidelines are appropriate for the audience affected by the change (users or developers, depending on the change) and are in the imperative mood (see examples). Fill in the Proposed upgrade guidelines section only if there are breaking changes or changes that may require extra steps from users during upgrade.

Desired reviewers

@amuniz

Before the changes are marked as ready-for-merge:

Maintainer checklist

Beta Give feedback

1. There are at least two (2) approvals for the pull request and no outstanding requests for change.
2. Conversations in the pull request are over, or it is explicit that a reviewer is not blocking the change.
3. Changelog entries in the pull request title and/or Proposed changelog entries are accurate, human-readable, and in the imperative mood.
4. Proper changelog labels are set so that the changelog can be generated automatically.
5. If the change needs additional upgrade steps from users, the upgrade-guide-needed label is set and there is a Proposed upgrade guidelines section in the pull request title (see example).
6. If it would make sense to backport the change to LTS, a Jira issue must exist, be a Bug or Improvement, and be labeled as lts-candidate to be considered (see query).

[amuniz]

Verified that it works as expected in jenkinsci/workflow-cps-plugin#907

[MarkEWaite]

This PR is now ready for merge. We will merge it after approximately 24 hours if there is no negative feedback.

/label ready-for-merge