added an extension point to contribute environment variables

core/src/main/java/hudson/model/EnvironmentContributor.java

+/*
+ * The MIT License
+ *
+ * Copyright (c) 2010, 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 hudson.model;
+
+import hudson.EnvVars;
+import hudson.ExtensionList;
+import hudson.ExtensionPoint;
+
+import java.io.IOException;
+
+/**
+ * Contributes environment variables to builds.
+ *
+ * <p>
+ * This extension point can be used to externally add environment variables. Aside from adding environment variables
+ * of the fixed name, a typical strategy is to look for specific {@link JobProperty}s and other similar configurations
+ * of {@link Job}s to compute values.
+ *
+ * @author Kohsuke Kawaguchi
+ * @since 1.392
+ */
+public abstract class EnvironmentContributor implements ExtensionPoint {
+    /**
+     * Contributes environment variables used for a build.
+     *
+     * <p>
+     * This method can be called repeatedly for the same {@link Run}, thus
+     * the computation of this method needs to be efficient. If you have a time-consuming
+     * computation, one strategy is to take the hit once and then add the result as {@link InvisibleAction}
+     * to {@link Run}, then reuse those values later on.
+     *
+     * <p>
+     * This method gets invoked concurrently for multiple {@link Run}s that are being built at the same time,
+     * so it must be concurrent-safe.
+     *
+     * @param r
+     *      Build that's being performed. Never null.
+     * @param envs
+     *      Partially built environment variable map. Implementation of this method is expected to
+     *      add additional variables here. Never null.
+     * @param listener
+     *      Connected to the build console. Can be used to report errors. Never null.
+     */
+    public abstract void buildEnvironmentFor(Run r, EnvVars envs, TaskListener listener) throws IOException, InterruptedException;
+
+    /**
+     * Returns all the registered {@link EnvironmentContributor}s.
+     */
+    public static ExtensionList<EnvironmentContributor> all() {
+        return Hudson.getInstance().getExtensionList(EnvironmentContributor.class);
+    }
+}

core/src/main/java/hudson/model/Run.java

@@ -1785,6 +1785,9 @@ public abstract class Run <JobT extends Job<JobT,RunT>,RunT extends Run<JobT,Run
                 env.put("NODE_LABELS",Util.join(n.getAssignedLabels()," "));
         }
 
+        for (EnvironmentContributor ec : EnvironmentContributor.all())
+            ec.buildEnvironmentFor(this,env,log);
+
         return env;
     }