Add TLCExt!PickSuccessor that, when set up as an action constraint,

lets users interactively explore the state graph.

This is based on a new TLC module override feature introduced with git
commit bb64cfd921c2e8846f47a5818d85cd0e8f2aa2c5
tlaplus/tlaplus@bb64cfd


Can't think of a test right now that fits the current (stateless)
framework. :-(

build.xml

@@ -27,7 +27,7 @@
 		<tstamp/>
 		<jar jarfile="${dist}/CommunityModules-${DSTAMP}${TSTAMP}.jar">
 			<fileset dir="${build}/"
-             includes="*.class"/>
+             includes="**/*.class"/>
 			<fileset dir="${src}/"
              includes="*.tla,*.java"/>
 			<fileset dir="."

modules/TLCExt.tla

@@ -18,4 +18,16 @@ AssertEq(a, b) ==
         /\ a = b
     ELSE a = b
 
+PickSuccessor(exp) ==
+  (******************************************************************************)
+  (* When set as an action constraint in the configuration file, interactively  *)
+  (* pick successor states during state exploration, iff the expression exp     *)
+  (* evaluates to FALSE.  To always pick successor states manually, use         *)
+  (* PickSuccessor(FALSE). To pick successor states when the current prefix of  *)
+  (* behaviors exceeds 22 states, use PickSuccessor(TLCGet("level") < 23).      *)
+  (******************************************************************************)
+  IF (exp)
+  THEN TRUE
+  ELSE CHOOSE bool \in BOOLEAN : TRUE 
+
 =============================================================================

modules/tlc2/overrides/TLCExt.java

@@ -0,0 +1,96 @@
+/*******************************************************************************
+ * Copyright (c) 2019 Microsoft Research. All rights reserved. 
+ *
+ * The MIT License (MIT)
+ * 
+ * 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.
+ *
+ * Contributors:
+ *   Markus Alexander Kuppe - initial API and implementation
+ ******************************************************************************/
+package tlc2.overrides;
+
+import java.util.Scanner;
+
+import tla2sany.semantic.ExprOrOpArgNode;
+import tlc2.output.EC;
+import tlc2.output.MP;
+import tlc2.tool.Action;
+import tlc2.tool.StateVec;
+import tlc2.tool.TLCState;
+import tlc2.tool.coverage.CostModel;
+import tlc2.tool.impl.Tool;
+import tlc2.util.Context;
+import tlc2.value.impl.BoolValue;
+import tlc2.value.impl.Value;
+import util.Assert;
+
+public class TLCExt {
+
+	private static final Scanner scanner = new Scanner(System.in);
+
+	// This is likely only useful with a single worker, but let's synchronize anyway.
+	@Evaluation(definition = "PickSuccessor", module = "TLCExt")
+	public synchronized static Value pickSuccessor(final Tool tool, final ExprOrOpArgNode[] args, final Context c, final TLCState s0,
+			final TLCState s1, final int control, final CostModel cm) {
+
+		// Eval expression and only let user interactively pick successor states when it evaluates to FALSE.
+		final Value guard = tool.eval(args[0], c, s0, s1, control, cm);
+		if (!(guard instanceof BoolValue)) {
+			Assert.fail("In evaluating TLCExt!PickSuccessor, a non-boolean expression (" + guard.getKindString()
+					+ ") was used as the condition " + "of an IF.\n" + args[0]);
+		}
+		if (((BoolValue) guard).val) {
+			return BoolValue.ValTrue;
+		}
+
+		// Find the (first) Action this pair of states belongs to. If more than one
+		// Action match, we pick the first one. 
+		// TODO: This is clumsy (we regenerate all next-states again) and incorrect if
+		// two actions generate the same successor states. It's good enough for now
+		// until the Action instance was passed down the call-stack.
+		Action action = null;
+		LOOP: for (Action act : tool.getActions()) {
+			StateVec nextStates = tool.getNextStates(act, s0);
+			if (nextStates.contains(s1)) {
+				action = act;
+				break LOOP;
+			}
+		}
+
+		while (true) {
+			// TODO Add more commands such as continue/resume to pick every successor,
+			// randomly pick next N successors, terminate to stop state space exploration, ...
+			MP.printMessage(EC.TLC_MODULE_OVERRIDE_STDOUT,
+					String.format("Extend behavior of length %s with a \"%s\" step [%s]? (Yes/no/states/diff):",
+							s0.getLevel(), action.getName(), action));
+
+			final String nextLine = scanner.nextLine();
+			if (nextLine.trim().isEmpty() || nextLine.toLowerCase().startsWith("y")) {
+				return BoolValue.ValTrue;
+			} else if (nextLine.charAt(0) == 's') {
+				MP.printMessage(EC.TLC_MODULE_OVERRIDE_STDOUT,
+						String.format("%s\n~>\n%s", s0.toString().trim(), s1.toString().trim()));
+			} else if (nextLine.charAt(0) == 'd') {
+				MP.printMessage(EC.TLC_MODULE_OVERRIDE_STDOUT, s1.toString(s0));
+			} else if (nextLine.charAt(0) == 'n') {
+				return BoolValue.ValFalse;
+			}
+		}
+	}
+}

modules/tlc2/overrides/TLCOverrides.java

@@ -0,0 +1,37 @@
+/*******************************************************************************
+ * Copyright (c) 2019 Microsoft Research. All rights reserved. 
+ *
+ * The MIT License (MIT)
+ * 
+ * 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.
+ *
+ * Contributors:
+ *   Markus Alexander Kuppe - initial API and implementation
+ ******************************************************************************/
+package tlc2.overrides;
+
+// tlc2.tool.impl.SpecProcessor's "api" only loads class
+// "tlc2.overrides.TLCOverrides".
+public class TLCOverrides implements ITLCOverrides {
+
+	@SuppressWarnings("rawtypes")
+	@Override
+	public Class[] get() {
+		return new Class[] {TLCExt.class};
+	}
+}