Warnings on unused sync hints (closing #151)

README.md

@@ -48,6 +48,7 @@ a link to this page somewhere in the documentation/system about section.
 
 * :sparkles: :sparkles: :tada: :sparkles: :tada: :sparkles: :rainbow: :sparkles: :sparkles: :sparkles: BPjs now uses Rhino's native continuation equality and hash code ([#116](https://github.com/bThink-BGU/BPjs/issues/116). Also, :tada: :rainbow: :sparkles:.
 * :arrow_up: Scope and context creations across BPjs have been consolidated to utility methods in a new class called `BPjs`.
+* :arrow_up: Event selection strategies that ignore the synchronization statement data field, issue a warning when b-threads put data there ([#151](https://github.com/bThink-BGU/BPjs/issues/151)).
 * :bug: Fixed an issue that caused `toString` for JavaScript objects to crash at certain cases ([#145](https://github.com/bThink-BGU/BPjs/issues/145)).
 
 

src/main/java/il/ac/bgu/cs/bp/bpjs/model/SyncStatement.java

@@ -47,7 +47,7 @@ public class SyncStatement implements java.io.Serializable {
     private final boolean hot;
 
     /**
-     * Optional data a BThread can pass to the event selector. This may serve as
+     * Optional data a b-thread can pass to the event selector. This may serve as
      * a "danger level", or any other hint for a specific event selection policy.
      */
     private final Object data;

src/main/java/il/ac/bgu/cs/bp/bpjs/model/eventselection/AbstractEventSelectionStrategy.java

@@ -98,4 +98,21 @@ protected Set<BEvent> getRequestedAndNotBlocked(SyncStatement stmt, EventSet blo
         }
     }
 
+    private boolean warningIssued = false;
+
+    /**
+     * Log a warning when b-threads send synchronization statement data. This 
+     * is useful for strategies that ignore these data, as users might be sending
+     * them and not understand why they are ignored.
+     * 
+     * @param bpss the state the b-program is at.
+     */
+    protected void warnOnHints( BProgramSyncSnapshot bpss ){
+        if ( warningIssued ) return; // warn only once
+        if ( bpss.getStatements().stream().anyMatch( s->s.getData()!=null ) ) {
+            System.out.println("[WARNING] Sync statements contain data. Current strategy ("+getClass().getCanonicalName()+") ignores this field.");
+            warningIssued = true;
+        }
+    }
+
 }

src/main/java/il/ac/bgu/cs/bp/bpjs/model/eventselection/OrderedEventSelectionStrategy.java

@@ -52,6 +52,7 @@ public class OrderedEventSelectionStrategy extends AbstractEventSelectionStrateg
 
     @Override
     public Set<BEvent> selectableEvents(BProgramSyncSnapshot bpss) {
+        warnOnHints(bpss);
         Set<SyncStatement> statements = bpss.getStatements();
         List<BEvent> externalEvents = bpss.getExternalEvents();
 

src/main/java/il/ac/bgu/cs/bp/bpjs/model/eventselection/PrioritizedBThreadsEventSelectionStrategy.java

@@ -47,6 +47,7 @@ public PrioritizedBThreadsEventSelectionStrategy() {
 
     @Override
     public Set<BEvent> selectableEvents(BProgramSyncSnapshot bpss) {
+        warnOnHints(bpss);
         Set<SyncStatement> statements = bpss.getStatements();
         List<BEvent> externalEvents = bpss.getExternalEvents();
 

src/main/java/il/ac/bgu/cs/bp/bpjs/model/eventselection/SimpleEventSelectionStrategy.java

@@ -38,6 +38,7 @@ public SimpleEventSelectionStrategy() {}
 
     @Override
     public Set<BEvent> selectableEvents(BProgramSyncSnapshot bpss) {
+        warnOnHints(bpss);
         Set<SyncStatement> statements = bpss.getStatements();
         List<BEvent> externalEvents = bpss.getExternalEvents();
         if ( statements.isEmpty() ) {

src/test/java/il/ac/bgu/cs/bp/bpjs/model/eventselection/SimpleEventSelectionStrategyTest.java

@@ -7,6 +7,10 @@
 import il.ac.bgu.cs.bp.bpjs.model.BThreadSyncSnapshot;
 import il.ac.bgu.cs.bp.bpjs.model.SyncStatement;
 import il.ac.bgu.cs.bp.bpjs.model.eventsets.ExplicitEventSet;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.PrintStream;
+import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -164,4 +168,55 @@ public void testSeed() {
 
         assertEquals( selectedBySut, selectedBySameSeed );
     }
+
+    @Test
+    public void testWarnOnHints() throws IOException {
+
+        PrintStream origStdout = System.out;
+        String output;
+        try (ByteArrayOutputStream baos = new ByteArrayOutputStream();
+                    PrintStream testStream = new PrintStream(baos)) {
+            System.setOut(testStream);
+            BProgramSyncSnapshot bpss = TestUtils.makeBPSS(
+                new MockBThreadSyncSnapshot(SyncStatement.make(null).waitFor(eventOne).data("I will create a warning"))
+            );  sut.selectableEvents(bpss);
+            sut.selectableEvents(bpss);
+            sut.selectableEvents(bpss);
+            testStream.flush();
+            baos.flush();
+            output = baos.toString(StandardCharsets.UTF_8);
+        }
+        assertTrue( "SimpleSelectionStrategy should warn about using hints", output.contains("WARNING") );
+        output = output.replaceFirst("WARNING", "");
+        assertFalse( "SimpleSelectionStrategy should warn about using hints only once", output.contains("WARNING") );
+
+        System.setOut(origStdout);
+    }
+
+       @Test
+    public void testNoWarnOnNoHints() throws IOException {
+
+        PrintStream origStdout = System.out;
+        String output;
+        try (ByteArrayOutputStream baos = new ByteArrayOutputStream();
+                    PrintStream testStream = new PrintStream(baos) ) {
+            System.setOut(testStream);
+
+            BProgramSyncSnapshot bpss = TestUtils.makeBPSS(
+                new MockBThreadSyncSnapshot(SyncStatement.make(null).waitFor(eventOne))
+            );
+
+            sut.selectableEvents(bpss);
+            sut.selectableEvents(bpss);
+            sut.selectableEvents(bpss);
+
+            testStream.flush();
+            baos.flush();
+            output = baos.toString(StandardCharsets.UTF_8);
+        }
+        assertFalse( "SimpleSelectionStrategy should not warn when there are no hints", output.contains("WARNING") );
+
+        System.setOut(origStdout);
+    }
+
 }