CASSANDRA-20828: property testing now has a withOnlySeed which is short hand for withSeed + withExample(1). Updated gitignore to exclude build artifacts for other IDEs. Updated gradle wrapper to have a longer timeout to make CI more stable

.gitignore

@@ -4,3 +4,10 @@ build/
 accord-core/build/
 accord-maelstrom/build/
 .rat-excludes.txt
+
+# Coding tools like NeoVim and Visual Studio Code will store their metadata at the following paths
+accord-core/bin/
+accord-maelstrom/bin/
+.project
+.settings
+.classpath

accord-core/src/main/java/accord/utils/RandomSource.java

@@ -292,24 +292,32 @@ default long pickLong(long[] array, int offset, int length)
 
     default <T> T pickOrderedSet(SortedSet<T> set)
     {
+        Invariants.require(!set.isEmpty(), "can not pick from an empty collection");
+        if (set.size() == 1) return Iterables.getFirst(set, null);
         int offset = nextInt(0, set.size());
         return Iterables.get(set, offset);
     }
 
     default <T> T pickOrderedSet(LinkedHashSet<T> set)
     {
+        Invariants.require(!set.isEmpty(), "can not pick from an empty collection");
+        if (set.size() == 1) return Iterables.getFirst(set, null);
         int offset = nextInt(0, set.size());
         return Iterables.get(set, offset);
     }
 
     default <T extends Enum<T>> T pickOrderedSet(EnumSet<T> set)
     {
+        Invariants.require(!set.isEmpty(), "can not pick from an empty collection");
+        if (set.size() == 1) return Iterables.getFirst(set, null);
         int offset = nextInt(0, set.size());
         return Iterables.get(set, offset);
     }
 
     default <T extends Comparable<? super T>> T pickUnorderedSet(Set<T> set)
     {
+        Invariants.require(!set.isEmpty(), "can not pick from an empty collection");
+        if (set.size() == 1) return Iterables.getFirst(set, null);
         if (set instanceof SortedSet)
             return pickOrderedSet((SortedSet<T>) set);
         List<T> values = new ArrayList<>(set);

accord-core/src/test/java/accord/utils/Gens.java

@@ -862,6 +862,9 @@ public static <T> Gen<Gen<T>> mixedDistribution(T... list)
      */
     public static <T> Gen<Gen<T>> mixedDistribution(List<T> list)
     {
+        Invariants.require(!list.isEmpty(), "can not pick from an empty collection");
+        if (list.size() == 1)
+            return i -> constant(list.get(0));
         return rs -> {
             switch (rs.nextInt(0, 4))
             {

accord-core/src/test/java/accord/utils/Property.java

@@ -72,6 +72,11 @@ public T withSeed(long seed)
         }
 
         @SuppressWarnings("unchecked")
+        public T withOnlySeed(long seed)
+        {
+            return withSeed(seed).withExamples(1);
+        }
+
         public T withExamples(int examples)
         {
             if (examples <= 0)
@@ -104,7 +109,7 @@ protected void checkWithTimeout(Runnable fn)
             }
             catch (ExecutionException e)
             {
-                throw new PropertyError(propertyError(this, e.getCause()));
+                throw new PropertyError(propertyError(this, e.getCause()), e.getCause());
             }
             catch (InterruptedException e)
             {
@@ -213,10 +218,11 @@ private static String propertyError(Common<?> input, Throwable cause, Object...
         return sb.toString();
     }
 
-    private static String statefulPropertyError(StatefulBuilder input, Throwable cause, Object state, List<String> history)
+    private static String statefulPropertyError(StatefulBuilder input, Throwable cause, Object state, int failingStep, List<String> history)
     {
         StringBuilder sb = propertyErrorCommon(input, cause);
         sb.append("Steps: ").append(input.steps).append('\n');
+        sb.append("Failing Step: ").append(failingStep).append('\n');
         sb.append("Values:\n");
         String stateStr = state == null ? null : state.toString().replace("\n", "\n\t\t");
         sb.append("\tState: ").append(stateStr).append(": ").append(state == null ? "unknown type" : state.getClass().getCanonicalName()).append('\n');
@@ -493,6 +499,7 @@ public <State, SystemUnderTest> void check(Commands<State, SystemUnderTest> comm
             {
                 State state = null;
                 List<String> history = new ArrayList<>(steps);
+                int seenCommands = 0;
                 LongArrayList historyTiming = stepTimeout == null ? null : new LongArrayList();
                 try
                 {
@@ -506,7 +513,7 @@ public <State, SystemUnderTest> void check(Commands<State, SystemUnderTest> comm
                         for (int j = 0; j < steps; j++)
                         {
                             Gen<Command<State, SystemUnderTest, ?>> cmdGen = commands.commands(state);
-                            Command cmd = cmdGen.next(rs);
+                            Command<State, SystemUnderTest, ?> cmd = cmdGen.next(rs);
                             for (int a = 0; cmd.checkPreconditions(state) != PreCheckResult.Ok && a < 42; a++)
                             {
                                 if (a == 41)
@@ -517,14 +524,16 @@ public <State, SystemUnderTest> void check(Commands<State, SystemUnderTest> comm
                             {
                                 for (Command<State, SystemUnderTest, ?> sub : ((MultistepCommand<State, SystemUnderTest>) cmd))
                                 {
+                                    seenCommands++;
                                     history.add(sub.detailed(state));
-                                    process(sub, state, sut, history.size(), historyTiming);
+                                    process(sub, state, sut, seenCommands, historyTiming);
                                 }
                             }
                             else
                             {
+                                seenCommands++;
                                 history.add(cmd.detailed(state));
-                                process(cmd, state, sut, history.size(), historyTiming);
+                                process(cmd, state, sut, seenCommands, historyTiming);
                             }
                         }
                         commands.destroySut(sut, null);
@@ -542,7 +551,7 @@ public <State, SystemUnderTest> void check(Commands<State, SystemUnderTest> comm
                 }
                 catch (Throwable t)
                 {
-                    throw new PropertyError(statefulPropertyError(this, t, state, maybeRewriteHistory(history, historyTiming)), t);
+                    throw new PropertyError(statefulPropertyError(this, t, state, seenCommands, maybeRewriteHistory(history, historyTiming)), t);
                 }
                 if (pure)
                 {
@@ -577,8 +586,7 @@ private static List<String> maybeRewriteHistory(List<String> history, @Nullable
             return newHistory;
         }
 
-        @SuppressWarnings({ "rawtypes", "unchecked" })
-        private <State, SystemUnderTest> void process(Command cmd, State state, SystemUnderTest sut, int id, @Nullable LongArrayList stepTiming) throws Throwable
+        private <State, SystemUnderTest> void process(Command<State, SystemUnderTest, ?> cmd, State state, SystemUnderTest sut, int id, @Nullable LongArrayList stepTiming) throws Throwable
         {
             if (stepTimeout == null)
             {
@@ -609,8 +617,10 @@ default void checkPostconditions(State state, Result expected,
         default String detailed(State state) {return this.toString();}
         default void process(State state, SystemUnderTest sut) throws Throwable
         {
-            checkPostconditions(state, apply(state),
-                                sut, run(sut));
+            Result apply = apply(state);
+            Result run = run(sut);
+            checkPostconditions(state, apply,
+                                sut, run);
         }
     }
 
@@ -851,6 +861,7 @@ default void onFailure(State state, SystemUnderTest sut, List<String> history, T
         default void destroyState(State state, @Nullable Throwable cause) throws Throwable {}
         default void destroySut(SystemUnderTest sut, @Nullable Throwable cause) throws Throwable {}
         Gen<Command<State, SystemUnderTest, ?>> commands(State state) throws Throwable;
+
     }
 
     public static <State, SystemUnderTest> CommandsBuilder<State, SystemUnderTest> commands(Supplier<Gen<State>> stateGen, Function<State, SystemUnderTest> sutFactory)
@@ -907,6 +918,7 @@ public CommandsBuilder(Supplier<Gen<State>> stateGen, Function<State, SystemUnde
             this.sutFactory = sutFactory;
         }
 
+
         public CommandsBuilder<State, SystemUnderTest> preCommands(FailingConsumer<State> preCommands)
         {
             this.preCommands = preCommands;
@@ -1126,7 +1138,7 @@ public Setup<State, SystemUnderTest> next(RandomSource rs)
                                 for (Setup<State, SystemUnderTest> s : unknownWeights)
                                     weights.put(s, unknownWeightGen.nextInt(rs));
                             }
-                            nonConditional = Gens.pick(weights);
+                            nonConditional = weights.isEmpty() ? null : Gens.pick(weights);
                             if (conditionalCommands != null)
                             {
                                 conditionalWeights = new LinkedHashMap<>();
@@ -1233,6 +1245,7 @@ public void onFailure(State state, SystemUnderTest sut, List<String> history, Th
                     for (var fn : onFailures)
                         fn.onFailure(state, sut, history, cause);
                 }
+
             };
         }
 
@@ -1251,4 +1264,5 @@ public interface FailingBiConsumer<A, B>
             void accept(A a, B b) throws Throwable;
         }
     }
+
 }

gradle.properties

@@ -17,3 +17,7 @@
 accord_group=accord
 accord_artifactId=accord
 accord_version=1.0-SNAPSHOT
+
+# Some times there are ephemeral issues with fetching dependencies (namely Rat) in CI, so this bumps the timeout to 120s to try to make it more stable
+systemProp.org.gradle.internal.http.connectionTimeout=120000
+systemProp.org.gradle.internal.http.socketTimeout=120000

gradle/wrapper/gradle-wrapper.properties

@@ -17,6 +17,7 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 distributionUrl=https\://services.gradle.org/distributions/gradle-8.5-bin.zip
-networkTimeout=10000
+# Some CI environments have ephemeral issues fetching the gradle runtime, so increased the timeout from the default 10s to 60s to make it more stable
+networkTimeout=60000
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists