Introduce RealJenkinsRule.createSyntheticPlugin to allow synthetic …

…plugins to be installed dynamically and break compatibility for existing callers of `RealJenkinsRule.addSyntheticPlugin` (#920)

src/main/java/org/jvnet/hudson/test/RealJenkinsRule.java

@@ -293,13 +293,32 @@ public RealJenkinsRule addPlugins(String... plugins) {
      * (You will need to {@code .header("Plugin-Dependencies", "variant:0")} to use this API.)
      * Then use {@code @OptionalExtension} on all your test extensions.
      * These will then be loaded only in {@link RealJenkinsRule}-based tests requesting this plugin.
-     * @param pkg the Java package containing any classes and resources you want included
-     * @return a builder
+     * @param plugin the configured {@link SyntheticPlugin}
      */
-    public SyntheticPlugin addSyntheticPlugin(Package pkg) {
-        SyntheticPlugin p = new SyntheticPlugin(pkg.getName());
-        syntheticPlugins.add(p);
-        return p;
+    public RealJenkinsRule addSyntheticPlugin(SyntheticPlugin plugin) {
+        syntheticPlugins.add(plugin);
+        return this;
+    }
+
+    /**
+     * Creates a test-only plugin based on sources defined in this module, but does not install it.
+     * <p>See {@link #addSyntheticPlugin} for more details. Prefer that method if you simply want the
+     * plugin to be installed automatically.
+     * @see #addSyntheticPlugin
+     * @param plugin the configured {@link SyntheticPlugin}
+     * @return the JPI file for the plugin
+     */
+    @SuppressFBWarnings(value = "PATH_TRAVERSAL_IN", justification = "irrelevant, this is test code")
+    public File createSyntheticPlugin(SyntheticPlugin plugin) throws IOException, URISyntaxException {
+        File pluginJpi = new File(tmp.allocate("synthetic-plugin"), plugin.shortName + ".jpi");
+        if (war == null) {
+            throw new IllegalStateException("createSyntheticPlugin may only be invoked from within a test method");
+        }
+        try (JarFile jf = new JarFile(war)) {
+            String jenkinsVersion = jf.getManifest().getMainAttributes().getValue("Jenkins-Version");
+            plugin.writeTo(pluginJpi, jenkinsVersion);
+        }
+        return pluginJpi;
     }
 
     /**
@@ -1700,15 +1719,21 @@ private static class OutputPayload implements Serializable {
      * Alternative to {@link #addPlugins} or {@link TestExtension} that lets you build a test-only plugin on the fly.
      * ({@link ExtensionList#add(Object)} can also be used for certain cases, but not if you need to define new types.)
      */
-    public final class SyntheticPlugin {
+    public static final class SyntheticPlugin {
         private final String pkg;
         private String shortName;
         private String version = "1-SNAPSHOT";
         private Map<String, String> headers = new HashMap<>();
 
-        SyntheticPlugin(String pkg) {
-            this.pkg = pkg;
-            shortName = "synthetic-" + pkg.replace('.', '-');
+        /**
+         * Creates a new synthetic plugin builder.
+         * @see RealJenkinsRule#addSyntheticPlugin
+         * @see RealJenkinsRule#createSyntheticPlugin
+         * @param pkg the Java package containing any classes and resources you want included
+         */
+        public SyntheticPlugin(Package pkg) {
+            this.pkg = pkg.getName();
+            shortName = "synthetic-" + this.pkg.replace('.', '-');
         }
 
         /**
@@ -1744,13 +1769,6 @@ public SyntheticPlugin header(String key, String value) {
             return this;
         }
 
-        /**
-         * @return back to the rule builder
-         */
-        public RealJenkinsRule done() {
-            return RealJenkinsRule.this;
-        }
-
         void writeTo(File jpi, String defaultJenkinsVersion) throws IOException, URISyntaxException {
             var mani = new Manifest();
             var attr = mani.getMainAttributes();

src/test/java/org/jvnet/hudson/test/RealJenkinsRuleSyntheticPluginTest.java

@@ -32,6 +32,7 @@
 import static org.hamcrest.Matchers.is;
 import org.junit.Rule;
 import org.junit.Test;
+import org.jvnet.hudson.test.RealJenkinsRule.SyntheticPlugin;
 import org.jvnet.hudson.test.sample.plugin.CustomJobProperty;
 import org.jvnet.hudson.test.sample.plugin.Stuff;
 
@@ -40,7 +41,7 @@ public final class RealJenkinsRuleSyntheticPluginTest {
     @Rule public RealJenkinsRule rr = new RealJenkinsRule().prepareHomeLazily(true);
 
     @Test public void smokes() throws Throwable {
-        rr.addSyntheticPlugin(Stuff.class.getPackage()).done();
+        rr.addSyntheticPlugin(new SyntheticPlugin(Stuff.class.getPackage()));
         rr.then(RealJenkinsRuleSyntheticPluginTest::_smokes);
     }
 
@@ -50,12 +51,20 @@ private static void _smokes(JenkinsRule r) throws Throwable {
     }
 
     @Test public void classFilter() throws Throwable {
-        rr.addSyntheticPlugin(CustomJobProperty.class.getPackage()).done().withLogger(ClassFilterImpl.class, Level.FINE);
+        rr.addSyntheticPlugin(new SyntheticPlugin(CustomJobProperty.class.getPackage())).withLogger(ClassFilterImpl.class, Level.FINE);
         rr.then(r -> {
             var p = r.createFreeStyleProject();
             p.addProperty(new CustomJobProperty("expected in XML"));
             assertThat(p.getConfigFile().asString(), containsString("expected in XML"));
         });
     }
 
+    @Test public void dynamicLoad() throws Throwable {
+        var pluginJpi = rr.createSyntheticPlugin(new SyntheticPlugin(Stuff.class.getPackage()));
+        rr.then(r -> {
+            r.jenkins.pluginManager.dynamicLoad(pluginJpi);
+            assertThat(r.createWebClient().goTo("stuff", "text/plain").getWebResponse().getContentAsString(),
+                is(Jenkins.get().getLegacyInstanceId()));
+        });
+    }
 }