[JENKINS-44892] DescribableModel customization

plugin/src/main/java/org/jenkinsci/plugins/structs/describable/CustomDescribableModel.java

@@ -0,0 +1,93 @@
+/*
+ * The MIT License
+ *
+ * Copyright 2019 CloudBees, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package org.jenkinsci.plugins.structs.describable;
+
+import hudson.model.Describable;
+import hudson.model.Descriptor;
+import java.util.Map;
+import javax.annotation.CheckForNull;
+import javax.annotation.Nonnull;
+import jenkins.model.Jenkins;
+import org.kohsuke.accmod.Restricted;
+import org.kohsuke.accmod.restrictions.Beta;
+import org.kohsuke.stapler.DataBoundConstructor;
+import org.kohsuke.stapler.DataBoundSetter;
+
+/**
+ * Allows the usage of {@link DescribableModel} to be fine-tuned to cover special cases such as backwards compatibility.
+ * Implement this interface on a {@link Descriptor}.
+ * <p>Normally introspection of a struct class with {@link DataBoundConstructor} and {@link DataBoundSetter} suffices for databinding.
+ * This facility allows the definer of the struct to accept variant inputs to {@link DescribableModel#instantiate(Map)},
+ * or recommend variant outputs for {@link DescribableModel#uninstantiate2(Object)}.
+ * This is somewhat analogous to implementing a {@code readResolve} method to customize XStream serialization behavior.
+ * <p>These are relatively high-level (syntactic) transformations,
+ * including details such as {@link UninstantiatedDescribable#ANONYMOUS_KEY} vs. {@link DescribableModel#CLAZZ}.
+ * On the one hand, that allows implementations precise control over behavior.
+ * On the other hand, it means that implementations must sometimes take care
+ * to handle several surface variants of the same underlying data model.
+ * <p>Only those methods explicitly indicated are customized by this interface,
+ * so for example {@link DescribableModel#getSoleRequiredParameter} will continue to be determined
+ * entirely by Java reflection.
+ * Furthermore, only those use cases (such as Pipeline and some modes of Job DSL)
+ * which run inside the Jenkins master and use the indicated methods will honor customizations made in this way;
+ * in particular, the Configuration as Code plugin currently will not,
+ * and anything that relies on inspection of bytecode from an external process cannot.
+ * Therefore it is best to limit usage of this API to preserving compatibility
+ * or otherwise adjusting behavior in ways that cannot be done otherwise.
+ * <p>Arguments passed to customization methods are immutable.
+ * If you wish to make changes, create and return a copy of the argument.
+ */
+@Restricted(Beta.class)
+public interface CustomDescribableModel /* extends Descriptor */ {
+
+    /**
+     * Permits customization of the behavior of {@link DescribableModel#instantiate(Map)}.
+     */
+    default @Nonnull Map<String, Object> customInstantiate(@Nonnull Map<String, Object> arguments) {
+        return arguments;
+    }
+
+    /**
+     * Permits customization of the behavior of {@link DescribableModel#uninstantiate2(Object)}.
+     * @see UninstantiatedDescribable#withArguments
+     */
+    default @Nonnull UninstantiatedDescribable customUninstantiate(@Nonnull UninstantiatedDescribable ud) {
+        return ud;
+    }
+
+    static @CheckForNull CustomDescribableModel of(Class<?> type) {
+        if (Describable.class.isAssignableFrom(type)) {
+            Jenkins j = Jenkins.getInstanceOrNull();
+            if (j != null) {
+                Descriptor<?> d = j.getDescriptor(type.asSubclass(Describable.class));
+                if (d instanceof CustomDescribableModel) {
+                    return (CustomDescribableModel) d;
+                }
+            }
+        }
+        return null;
+    }
+
+}

plugin/src/main/java/org/jenkinsci/plugins/structs/describable/DescribableModel.java

@@ -268,6 +268,12 @@ public String getDisplayName() {
      * and only one subtype is registered (as a {@link Descriptor}) with that simple name.
      */
     public T instantiate(Map<String,?> arguments) throws Exception {
+        CustomDescribableModel cdm = CustomDescribableModel.of(type);
+        if (cdm != null) {
+            Map<String, Object> input = deeplyImmutable(arguments);
+            arguments = cdm.customInstantiate(input);
+            LOGGER.log(Level.FINE, "{0} translated {1} to {2}", new Object[] {cdm.getClass(), input, arguments});
+        }
         if (arguments.containsKey(ANONYMOUS_KEY)) {
             if (arguments.size()!=1)
                 throw new IllegalArgumentException("All arguments have to be named but it has "+ANONYMOUS_KEY);
@@ -288,6 +294,25 @@ public T instantiate(Map<String,?> arguments) throws Exception {
         }
     }
 
+    @SuppressWarnings("unchecked")
+    private static Map<String, Object> deeplyImmutable(Map<String, ?> m) {
+        Map<String, Object> r = new HashMap<>();
+        for (Map.Entry<String, ?> e : m.entrySet()) {
+            Object v = e.getValue();
+            if (v instanceof UninstantiatedDescribable) {
+                v = deeplyImmutable((UninstantiatedDescribable) v);
+            } else if (v instanceof Map) {
+                v = deeplyImmutable((Map) v);
+            }
+            r.put(e.getKey(), v);
+        }
+        return Collections.unmodifiableMap(r);
+    }
+
+    private static UninstantiatedDescribable deeplyImmutable(UninstantiatedDescribable ud) {
+        return ud.withArguments(deeplyImmutable(ud.getArguments()));
+    }
+
         // adapted from RequestImpl
     @SuppressWarnings("unchecked")
     private Constructor<T> findConstructor(int length) {
@@ -644,6 +669,12 @@ public UninstantiatedDescribable uninstantiate2(T o) throws UnsupportedOperation
         }
         UninstantiatedDescribable ud = new UninstantiatedDescribable(symbolOf(o), null, r);
         ud.setModel(this);
+        CustomDescribableModel cdm = CustomDescribableModel.of(type);
+        if (cdm != null) {
+            UninstantiatedDescribable input = deeplyImmutable(ud);
+            ud = cdm.customUninstantiate(input);
+            LOGGER.log(Level.FINE, "{0} translated {1} to {2}", new Object[] {cdm.getClass(), input, ud});
+        }
         return ud;
     }
 

plugin/src/main/java/org/jenkinsci/plugins/structs/describable/UninstantiatedDescribable.java

@@ -34,6 +34,17 @@ public UninstantiatedDescribable(Map<String, ?> arguments) {
         this(null,null,arguments);
     }
 
+    /**
+     * Makes a copy of this struct with an alternate argument map.
+     * @param arguments a replacement for {@link #getArguments}
+     * @return a new object with the same {@link #getSymbol}, {@link #getKlass}, and {@link #getModel}
+     */
+    public UninstantiatedDescribable withArguments(Map<String, ?> arguments) {
+        UninstantiatedDescribable copy = new UninstantiatedDescribable(symbol, klass, arguments);
+        copy.model = model;
+        return copy;
+    }
+
     /**
      * If this nested describable has a suitable {@linkplain Symbol symbol name},
      * this method returns one.