add test showing bug in incr. interpreter: single-source reachability

core/incremental/ddTests.ts

@@ -33,6 +33,7 @@ export function incrTests(writeResults: boolean): Suite {
     ["contracts", evalTest],
     ["transitiveClosure", evalTest],
     ["transitiveClosureMultiSupport", evalTest],
+    ["singleSourceReach", evalTest],
     ["sccs", evalTest],
     ["parse", evalTest],
     ["aggregation", evalTest],

core/incremental/operators/distinct.ts

@@ -15,3 +15,13 @@ export function processDistinct(
   desc.state.update(data.bindings.bindings, payload.multiplicity);
   return [{ ...payload, multiplicity: multDiff }];
 }
+
+function getMultDiff(curMult: number, newMult: number): number {
+  if (curMult < 1 && newMult >= 1) {
+    return 1;
+  }
+  if (curMult >= 1 && newMult < 1) {
+    return -1;
+  }
+  return 0;
+}

core/incremental/testdata/singleSourceReach.dd.txt

@@ -0,0 +1,129 @@
+.table edge
+----
+application/datalog
+
+.table start
+----
+application/datalog
+
+start{node: "x"}.
+----
+incremental-datalog/trace
+start: [start{node: "x"}+1]
+
+reach{node: B} :-
+  start{node: B} |
+  reach{node: A} &
+  edge{from: A, to: B}.
+----
+application/datalog
+
+reach{}?
+----
+application/datalog
+reach{node: "x"}.
+
+.ruleGraph
+----
+application/graphviz
+digraph G {
+  "edge" [fillcolor="darksalmon" fontname="Courier" label="edge:  []" shape="box" style="filled"];
+  "start" [fillcolor="darksalmon" fontname="Courier" label="start:  []" shape="box" style="filled"];
+  "0" [fillcolor="moccasin" fontname="Courier" label="0: Union []" shape="box" style="filled"];
+  "1" [fillcolor="darkseagreen2" fontname="Courier" label="1: Match(start{node: B}) []" shape="box" style="filled"];
+  "2" [fillcolor="darkseagreen2" fontname="Courier" label="2: Match(reach{node: A}) [A]" shape="box" style="filled"];
+  "3" [fillcolor="darkseagreen2" fontname="Courier" label="3: Match(edge{from: A, to: B}) [A]" shape="box" style="filled"];
+  "4" [fillcolor="thistle" fontname="Courier" label="4: Join(A) []" shape="box" style="filled"];
+  "5" [fillcolor="" fontname="Courier" label="5: Distinct []" shape="box" style="filled"];
+  "reach" [fillcolor="lightblue" fontname="Courier" label="reach: Subst(reach{node: B}) []" shape="box" style="filled"];
+  "start" -> "1" [];
+  "1" -> "0" [];
+  "reach" -> "2" [];
+  "edge" -> "3" [];
+  "3" -> "4" [];
+  "2" -> "4" [];
+  "4" -> "0" [];
+  "0" -> "5" [];
+  "5" -> "reach" [];
+}
+
+reach{}?
+----
+application/datalog
+reach{node: "x"}.
+
+edge{from: "x", to: "a"}.
+----
+incremental-datalog/trace
+edge: [edge{from: "x", to: "a"}+1]
+3: [{A: "x", B: "a"}+1]
+4: [{A: "x", B: "a"}+1]
+0: [{A: "x", B: "a"}+1]
+5: [{A: "x", B: "a"}+1]
+reach: [reach{node: "a"}+1]
+2: [{A: "a"}+1]
+4: []
+
+edge{from: "a", to: "b"}.
+----
+incremental-datalog/trace
+edge: [edge{from: "a", to: "b"}+1]
+3: [{A: "a", B: "b"}+1]
+4: [{A: "a", B: "b"}+1]
+0: [{A: "a", B: "b"}+1]
+5: [{A: "a", B: "b"}+1]
+reach: [reach{node: "b"}+1]
+2: [{A: "b"}+1]
+4: []
+
+edge{from: "b", to: "c"}.
+----
+incremental-datalog/trace
+edge: [edge{from: "b", to: "c"}+1]
+3: [{A: "b", B: "c"}+1]
+4: [{A: "b", B: "c"}+1]
+0: [{A: "b", B: "c"}+1]
+5: [{A: "b", B: "c"}+1]
+reach: [reach{node: "c"}+1]
+2: [{A: "c"}+1]
+4: []
+
+edge{from: "c", to: "b"}.
+----
+incremental-datalog/trace
+edge: [edge{from: "c", to: "b"}+1]
+3: [{A: "c", B: "b"}+1]
+4: [{A: "c", B: "b"}+1]
+0: [{A: "c", B: "b"}+1]
+5: [{A: "c", B: "b"}+1]
+reach: [reach{node: "b"}+1]
+2: [{A: "b"}+1]
+4: [{A: "b", B: "c"}+1]
+0: [{A: "b", B: "c"}+1]
+5: []
+
+-edge{from: "x", to: "a"}.
+----
+incremental-datalog/trace
+edge: [edge{from: "x", to: "a"}-1]
+3: [{A: "x", B: "a"}-1]
+4: [{A: "x", B: "a"}-1]
+0: [{A: "x", B: "a"}-1]
+5: [{A: "x", B: "a"}-1]
+reach: [reach{node: "a"}-1]
+2: [{A: "a"}-1]
+4: [{A: "a", B: "b"}-1]
+0: [{A: "a", B: "b"}-1]
+5: [{A: "a", B: "b"}-1]
+reach: [reach{node: "b"}-1]
+2: [{A: "b"}-1]
+4: [{A: "b", B: "c"}-1]
+0: [{A: "b", B: "c"}-1]
+5: []
+
+reach{}?
+----
+application/datalog
+reach{node: "b"}.
+reach{node: "c"}.
+reach{node: "x"}.