Hold replayPairs to a whole replay of every read set rendering together

drawfence_test.go

@@ -146,3 +146,117 @@ func renderRecordRoot(s *session, t *template, columns []Column) {
 	}
 	renderRecord(s, t, columns, sc)
 }
+
+func TestReplayPairsFindsWhatAWholeReplayFinds(t *testing.T) {
+	corpus := fenceCorpus(t)
+	roots, _ := fenceRoots(t, corpus)
+	shipped, err := New()
+	if err != nil {
+		t.Fatalf("New() = %v", err)
+	}
+	_ = walkNodes(shipped.categories, func(path string, n node) error {
+		if tm, ok := n.(*template); ok {
+			roots = append(roots, fenceRoot{path, tm})
+		}
+		return nil
+	})
+	for _, root := range roots {
+		wantPairsFindAll(t, root.label, renderDraws(root.t).reads)
+		if root.t.isRecord && len(root.t.fields) > 0 {
+			wantPairsFindAll(t, root.label+" as a record", columnDraws(root.t, sortedNames(root.t.fields)).reads)
+		}
+	}
+}
+
+func TestReplayPairsFindsWhatAWholeReplayOfSelectedRowsFinds(t *testing.T) {
+	f, err := New(WithDataPath(writeFiles(t, siblings())))
+	if err != nil {
+		t.Fatalf("New = %v", err)
+	}
+	var reads []pathRead
+	_ = walkNodes(f.categories, func(_ string, n node) error {
+		tb, isTable := n.(*table)
+		if !isTable || tb.keyIndex < 0 || tb.familyRoot().path != "region" {
+			return nil
+		}
+		for r := 0; r < tb.rowCount(); r++ {
+			inline, err := f.NewTemplate(`"{/` + tb.selectorSpelling(r) + `}"`)
+			if err != nil {
+				t.Fatalf("NewTemplate(%s) = %v", tb.selectorSpelling(r), err)
+			}
+			root, isTemplate := inline.n.(*template)
+			if !isTemplate {
+				t.Fatalf("NewTemplate(%s) compiled to %T", tb.selectorSpelling(r), inline.n)
+			}
+			reads = append(reads, renderDraws(root).reads...)
+		}
+		return nil
+	})
+	conflicts := 0
+	for _, a := range reads {
+		for _, b := range reads {
+			for _, c := range reads {
+				triple := []pathRead{a, b, c}
+				wantPairsFindAll(t, a.a.spelling+", "+b.a.spelling+", "+c.a.spelling, triple)
+				if replayPairs(triple) != nil {
+					conflicts++
+				}
+			}
+		}
+	}
+	if conflicts == 0 {
+		t.Error("no triple of selected rows conflicts, so the comparison proved nothing")
+	}
+}
+
+func wantPairsFindAll(t *testing.T, label string, reads []pathRead) {
+	t.Helper()
+	var tabled []pathRead
+	for _, r := range reads {
+		if r.tr != nil {
+			tabled = append(tabled, r)
+		}
+	}
+	pairs := replayPairs(reads)
+	var whole error
+	eachRenderSet(tabled, func(set []pathRead) {
+		var d pinSet
+		for _, r := range set {
+			if err := r.tr.replay(&d); err != nil && whole == nil {
+				whole = err
+			}
+		}
+	})
+	if (pairs == nil) != (whole == nil) {
+		t.Errorf("%s: replayPairs = %v, a whole replay of every read set rendering together = %v", label, pairs, whole)
+	}
+}
+
+// eachRenderSet calls fn with every maximal set of reads that render together, by Bron–Kerbosch.
+func eachRenderSet(reads []pathRead, fn func([]pathRead)) {
+	together := func(a, b pathRead) bool { return a.at.group == b.at.group && !alternatives(a.at, b.at) }
+	var grow func(set, candidates, excluded []pathRead)
+	grow = func(set, candidates, excluded []pathRead) {
+		if len(candidates) == 0 && len(excluded) == 0 {
+			fn(set)
+			return
+		}
+		for len(candidates) > 0 {
+			r := candidates[0]
+			var nextC, nextX []pathRead
+			for _, c := range candidates[1:] {
+				if together(r, c) {
+					nextC = append(nextC, c)
+				}
+			}
+			for _, x := range excluded {
+				if together(r, x) {
+					nextX = append(nextX, x)
+				}
+			}
+			grow(append(set[:len(set):len(set)], r), nextC, nextX)
+			candidates, excluded = candidates[1:], append(excluded, r)
+		}
+	}
+	grow(nil, reads, nil)
+}

todo.md

@@ -23,9 +23,6 @@ Shape 5.8, Self-sufficiency 5.7), every seat capped by Locality, all nine naming
 
 This round, in order:
 
-- Hold `replayPairs`' claim that pairs find every conflict a full replay would to a
-  test replaying every read set whole, over the fixtures and the shipped data: six
-  seats could only take the comment's proof on trust.
 - Key `drawWalk`'s visits by the pins, not `rowsKey`'s `%p` strings, and make leaving
   `wholeTable` out of the key fail loudly where `checkOwnFamily` has not run: the walk is
   sound only because another fence ran first, and nothing at the walk enforces it.