allow Configurator to define a custom documentation/schema

src/main/java/org/jenkinsci/plugins/casc/HeteroDescribableConfigurator.java

@@ -30,6 +30,7 @@ public class HeteroDescribableConfigurator extends Configurator<Describable> {
         final List<Descriptor> candidates = Jenkins.getInstance().getDescriptorList(target);
         return candidates.stream()
                 .map(d -> Configurator.lookup(d.getKlass().toJavaClass()))
+                .filter(c -> c != null)
                 .collect(Collectors.toList());
     }
 

src/main/resources/org/jenkinsci/plugins/casc/ConfigurationAsCode/index.jelly

@@ -19,37 +19,7 @@
 
   <div class='sect3'>
   <j:forEach items="${it.configurators}" var="c">
-    <h4 id="${c.extensionPoint.simpleName}-${c.name}">${c.name}</h4>
-    <j:if test="${c.extensionPoint != c.target}">
-      Implementation of <a href="https://jenkins.io/doc/developer/extensions/${c.extensionSource}/#${c.extensionPoint.simpleName.toLowerCase()}">${c.extensionPoint.simpleName}</a>
-    </j:if>
-    <div class='paragraph'>${c.displayName}</div>
-    <div class='dlist'><dl>
-    <j:forEach items="${c.attributes}" var="a">
-      <dt class='hdlist1'>${a.name}</dt>
-
-      <dd>
-      <j:out value="${c.getHtmlHelp(a.name)}"/>
-      <!-- FIXME .html is not a standard facet, stapler only looks for groovy/jelly
-      <st:include page="help-${a.name}.html" class="${c.target}" optional="true"/>
-      -->
-      </dd>
-      
-      <j:if test="${a.multiple}">
-        list of
-      </j:if>
-      ${a.type.simpleName}
-      <j:if test="${not a.possibleValues().isEmpty()}">
-        <ul>
-          <j:forEach items="${a.possibleValues()}" var="v">
-            <li><a href="#${a.type.simpleName}-${v}">${v}</a></li>
-          </j:forEach>
-        </ul>
-
-      </j:if>
-    </j:forEach>
-    </dl>
-    </div>
+    <st:include page="documentation.jelly" it="${c}" optional="true"/>
   </j:forEach>
   </div>
   </div>

src/main/resources/org/jenkinsci/plugins/casc/ConfigurationAsCode/schema.jelly

@@ -16,21 +16,7 @@
   },
   "definitions": {
 <j:forEach items="${it.configurators}" var="c" varStatus="cst">
-    "${c.target.name}": {
-      "type": "object",
-      "properties": {
-<j:forEach items="${c.attributes}" var="a" varStatus="ast">
-        "${a.name}": {
-<j:if test="${a.multiple}">
-          "type": "array",
-          "items": {
-</j:if>
-<st:include page="schema.jelly" it="${a}"/>
-<j:if test="${a.multiple}">}</j:if>
-        } <j:if test="${!ast.last}">,</j:if>
-</j:forEach>
-      }
-    }<j:if test="${!cst.last}">,</j:if>
+<st:include page="schema.jelly" it="${c}"/><j:if test="${!cst.last}">,</j:if>
 </j:forEach>
   }
 }

src/main/resources/org/jenkinsci/plugins/casc/Configurator/documentation.jelly

@@ -0,0 +1,37 @@
+<?jelly escape-by-default='true'?>
+<j:jelly xmlns:j="jelly:core" xmlns:st="jelly:stapler" xmlns:l="/lib/layout">
+
+  <div class='section'>
+    <h4 id="${it.extensionPoint.simpleName}-${it.name}">${it.name}</h4>
+    <j:if test="${it.extensionPoint != c.target}">
+      Implementation of <a href="https://jenkins.io/doc/developer/extensions/${it.extensionSource}/#${it.extensionPoint.simpleName.toLowerCase()}">${it.extensionPoint.simpleName}</a>
+    </j:if>
+    <div class='paragraph'>${it.displayName}</div>
+    <div class='dlist'><dl>
+    <j:forEach items="${it.attributes}" var="a">
+      <dt class='hdlist1'>${a.name}</dt>
+
+      <dd>
+      <j:out value="${it.getHtmlHelp(a.name)}"/>
+      <!-- FIXME .html is not a standard facet, stapler only looks for groovy/jelly
+      <st:include page="help-${a.name}.html" class="${it.target}" optional="true"/>
+      -->
+      </dd>
+
+      <j:if test="${a.multiple}">
+        list of
+      </j:if>
+      ${a.type.simpleName}
+      <j:if test="${not a.possibleValues().isEmpty()}">
+        <ul>
+          <j:forEach items="${a.possibleValues()}" var="v">
+            <li><a href="#${a.type.simpleName}-${v}">${v}</a></li>
+          </j:forEach>
+        </ul>
+
+      </j:if>
+    </j:forEach>
+    </dl></div>
+  </div>
+
+</j:jelly>

src/main/resources/org/jenkinsci/plugins/casc/Configurator/schema.jelly

@@ -0,0 +1,18 @@
+<?jelly escape-by-default='true'?>
+<j:jelly xmlns:j="jelly:core" xmlns:st="jelly:stapler" xmlns:l="/lib/layout">
+    "${it.target.name}": {
+      "type": "object",
+      "properties": {
+<j:forEach items="${it.attributes}" var="a" varStatus="ast">
+        "${a.name}": {
+<j:if test="${a.multiple}">
+          "type": "array",
+          "items": {
+</j:if>
+<st:include page="schema.jelly" it="${a}"/>
+<j:if test="${a.multiple}">}</j:if>
+        } <j:if test="${!ast.last}">,</j:if>
+</j:forEach>
+      }
+    }
+</j:jelly>