[JENKINS-43507] This stuff is seeming reasonably solid

src/main/java/jenkins/scm/api/SCMHeadObserver.java

@@ -1,7 +1,7 @@
 /*
  * The MIT License
  *
- * Copyright (c) 2011-2013, CloudBees, Inc., Stephen Connolly.
+ * Copyright (c) 2011-2017, CloudBees, Inc., Stephen Connolly.
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -158,6 +158,17 @@ public static Any any() {
         return new Any();
     }
 
+    /**
+     * Creates an observer that selects the first revision it finds. Also useful for quick checks of non-empty.
+     *
+     * @return an observer that selects the first revision of a any head.
+     * @since 2.2.0
+     */
+    @NonNull
+    public static None none() {
+        return None.INSTANCE;
+    }
+
     /**
      * An observer that wraps multiple observers and keeps observing as long as one of the wrapped observers wants to.
      */
@@ -545,6 +556,39 @@ public boolean isObserving() {
 
     }
 
+    /**
+     * An observer that is already finished.
+     *
+     * @since 2.2.0
+     */
+    public static final class None extends SCMHeadObserver {
+        /**
+         * Singleton.
+         */
+        public static final None INSTANCE = new None();
+
+        /**
+         * Constructor.
+         */
+        private None() {
+        }
+
+        /**
+         * {@inheritDoc}
+         */
+        @Override
+        public void observe(@NonNull SCMHead head, @NonNull SCMRevision revision) {
+        }
+
+        /**
+         * {@inheritDoc}
+         */
+        @Override
+        public boolean isObserving() {
+            return false;
+        }
+    }
+
     /**
      * Base class for an {@link SCMHeadObserver} that wraps another {@link SCMHeadObserver} while allowing access to the
      * original observer via {@link #unwrap()}.

src/main/java/jenkins/scm/api/trait/SCMHeadAuthority.java

@@ -0,0 +1,53 @@
+/*
+ * The MIT License
+ *
+ * Copyright (c) 2017, 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 jenkins.scm.api.trait;
+
+import edu.umd.cs.findbugs.annotations.NonNull;
+import hudson.model.AbstractDescribableImpl;
+import jenkins.scm.api.SCMHead;
+import jenkins.scm.api.mixin.SCMHeadMixin;
+
+public abstract class SCMHeadAuthority<S extends SCMSourceRequest, H extends SCMHeadMixin>
+        extends AbstractDescribableImpl<SCMHeadAuthority<?, ?>> {
+
+    public final boolean isApplicableTo(@NonNull SCMHead head) {
+        return getDescriptor().isApplicableToHead(head);
+    }
+
+    public final boolean isApplicableTo(@NonNull SCMSourceRequest request) {
+        return getDescriptor().isApplicableToRequest(request);
+    }
+
+    @SuppressWarnings("unchecked")
+    public final boolean isTrusted(@NonNull SCMSourceRequest request, @NonNull SCMHead head) {
+        return isApplicableTo(request) && isApplicableTo(head) && checkTrusted((S) request, (H) head);
+    }
+
+    protected abstract boolean checkTrusted(@NonNull S request, @NonNull H head);
+
+    @Override
+    public SCMHeadAuthorityDescriptor getDescriptor() {
+        return (SCMHeadAuthorityDescriptor) super.getDescriptor();
+    }
+}

src/main/java/jenkins/scm/api/trait/SCMHeadAuthorityDescriptor.java

@@ -0,0 +1,87 @@
+/*
+ * The MIT License
+ *
+ * Copyright (c) 2017, 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 jenkins.scm.api.trait;
+
+import hudson.model.Descriptor;
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+import jenkins.scm.api.SCMHead;
+import jenkins.scm.api.SCMSource;
+import jenkins.scm.api.mixin.SCMHeadMixin;
+import org.jvnet.tiger_types.Types;
+
+public abstract class SCMHeadAuthorityDescriptor extends Descriptor<SCMHeadAuthority<?, ?>> {
+
+    private final Class<? extends SCMSourceRequest> requestClass;
+    private final Class<? extends SCMHeadMixin> headClass;
+
+    protected SCMHeadAuthorityDescriptor(Class<? extends SCMHeadAuthority<?, ?>> clazz,
+                                         Class<? extends SCMSourceRequest> requestClass,
+                                         Class<? extends SCMHeadMixin> headClass) {
+        super(clazz);
+        this.requestClass = requestClass;
+        this.headClass = headClass;
+    }
+
+    protected SCMHeadAuthorityDescriptor() {
+        Type bt = Types.getBaseClass(clazz, SCMHeadAuthority.class);
+        if (bt instanceof ParameterizedType) {
+            ParameterizedType pt = (ParameterizedType) bt;
+            // this 'headClass' is the closest approximation of T of SCMHeadAuthority<T>.
+            requestClass = Types.erasure(pt.getActualTypeArguments()[0]);
+            headClass = Types.erasure(pt.getActualTypeArguments()[1]);
+            if (!SCMSource.class.isAssignableFrom(requestClass)) {
+                throw new AssertionError(
+                        "Failed to correctly detect SCMSourceRequest specialization. Use the constructor that takes "
+                                + "the "
+                                + "Class objects explicitly");
+            }
+            if (!SCMHeadMixin.class.isAssignableFrom(headClass)) {
+                throw new AssertionError(
+                        "Failed to correctly detect SCMHead specialization. Use the constructor that takes the Class "
+                                + "objects explicitly");
+            }
+        } else {
+            throw new AssertionError(
+                    "Failed to correctly detect specialization. Use the constructor that takes the Class objects "
+                            + "explicitly");
+        }
+    }
+
+    public boolean isApplicableToHead(SCMHead head) {
+        return isApplicableToHead(head.getClass());
+    }
+
+    public boolean isApplicableToHead(Class<? extends SCMHead> headClass) {
+        return this.headClass.isAssignableFrom(headClass);
+    }
+
+    public boolean isApplicableToRequest(SCMSourceRequest request) {
+        return requestClass.isInstance(request);
+    }
+
+    public boolean isApplicableToRequest(Class<? extends SCMSourceRequest> requestClass) {
+        return this.requestClass.isAssignableFrom(requestClass);
+    }
+}

src/main/java/jenkins/scm/api/trait/SCMHeadFilter.java

@@ -1,3 +1,26 @@
+/*
+ * The MIT License
+ *
+ * Copyright (c) 2017, 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 jenkins.scm.api.trait;
 
 import edu.umd.cs.findbugs.annotations.NonNull;

src/main/java/jenkins/scm/api/trait/SCMHeadPrefilter.java

@@ -0,0 +1,34 @@
+/*
+ * The MIT License
+ *
+ * Copyright (c) 2017, 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 jenkins.scm.api.trait;
+
+import edu.umd.cs.findbugs.annotations.NonNull;
+import jenkins.scm.api.SCMHead;
+import jenkins.scm.api.SCMSource;
+
+public abstract class SCMHeadPrefilter {
+
+    public abstract boolean isExcluded(@NonNull SCMSource source, @NonNull SCMHead head);
+
+}