fix(vt): enforce history snapshot invariants

commit: 4dede25fcc17e81ffd5f7a7f9e60017a1c895995
author: brice · 3mo ago · 2026-07-21 18:55 UTC
parent: 1fa07cc
signature: GPG VerifiedCD88F9E564E0102646FB6077A1A07C7C7C3E349D · arch-gpg Verified for the committer email

5 files · +52 -3

M pkg/vt/history.go +10 -0


@@ -108,6 +108,16 @@ func (h *History) sealTail() {
108	108		h.tail = nil
109	109		}
110	110
	111	+	// normalizeTail seals complete chunks so the mutable tail remains shorter than
	112	+	// chunkRows. Restored snapshots may have been written with a different chunk
	113	+	// size than the current history configuration.
	114	+	func (h *History) normalizeTail() {
	115	+	for h.chunkRows > 0 && len(h.tail) >= h.chunkRows {
	116	+	h.chunks = append(h.chunks, &HistoryChunk{rows: h.tail[:h.chunkRows]})
	117	+	h.tail = h.tail[h.chunkRows:]
	118	+	}
	119	+	}
	120	+
111	121		func (h *History) evict() {
112	122		h.evictUntil(0, 0)
113	123		}


@@ -108,6 +108,16 @@ func (h *History) sealTail() {
108	h.tail = nil	108		h.tail = nil
109	}	109		}
110		110
		111	+	// normalizeTail seals complete chunks so the mutable tail remains shorter than
		112	+	// chunkRows. Restored snapshots may have been written with a different chunk
		113	+	// size than the current history configuration.
		114	+	func (h *History) normalizeTail() {
		115	+	for h.chunkRows > 0 && len(h.tail) >= h.chunkRows {
		116	+	h.chunks = append(h.chunks, &HistoryChunk{rows: h.tail[:h.chunkRows]})
		117	+	h.tail = h.tail[h.chunkRows:]
		118	+	}
		119	+	}
		120	+
111	func (h *History) evict() {	121		func (h *History) evict() {
112	h.evictUntil(0, 0)	122		h.evictUntil(0, 0)
113	}	123		}

M pkg/vt/history_codec_test.go +3 -3


@@ -137,9 +137,9 @@ func TestChunkCodecRejectsDimensionsBeyondSupportedLimits(t *testing.T) {
137	137		data: historyPayloadWithDimensions(supportedRows+1, 0),
138	138		},
139	139		{
140		-	name: "too many aggregate cells",
141		-	view: historyViewWithDimensions(maxHistoryCells+1, 0),
142		-	data: historyPayloadWithDimensions(maxHistoryRows+1, 0),
	140	+	name: "too many aggregate cells within row budget",
	141	+	view: historyViewWithDimensions(maxHistoryRows, maxHistoryRowCells+1),
	142	+	data: historyPayloadWithDimensions(maxHistoryRows, maxHistoryRowCells+1),
143	143		},
144	144		}
145	145


@@ -137,9 +137,9 @@ func TestChunkCodecRejectsDimensionsBeyondSupportedLimits(t *testing.T) {
137		data: historyPayloadWithDimensions(supportedRows+1, 0),	137		data: historyPayloadWithDimensions(supportedRows+1, 0),
138		},	138		},
139		{	139		{
140	-	name: "too many aggregate cells",	140	+	name: "too many aggregate cells within row budget",
141	-	view: historyViewWithDimensions(maxHistoryCells+1, 0),	141	+	view: historyViewWithDimensions(maxHistoryRows, maxHistoryRowCells+1),
142	-	data: historyPayloadWithDimensions(maxHistoryRows+1, 0),	142	+	data: historyPayloadWithDimensions(maxHistoryRows, maxHistoryRowCells+1),
143		},	143		},
144		}	144		}
145			145

M pkg/vt/history_test.go +21 -0


@@ -217,6 +217,27 @@ func TestHistoryBoundsRowsAndCellsWithExactRowEviction(t *testing.T) {
217	217		}
218	218		}
219	219
	220	+	func TestHistoryAppendIsNoOpForNilAndZeroValue(t *testing.T) {
	221	+	tests := []struct {
	222	+	name string
	223	+	history *History
	224	+	}{
	225	+	{name: "nil history"},
	226	+	{name: "zero-value history", history: &History{}},
	227	+	}
	228	+
	229	+	for _, tt := range tests {
	230	+	t.Run(tt.name, func(t *testing.T) {
	231	+	if err := tt.history.Append(historyRow("row")); err != nil {
	232	+	t.Fatalf("append error = %v, want nil", err)
	233	+	}
	234	+	if got := tt.history.Len(); got != 0 {
	235	+	t.Fatalf("retained rows = %d, want 0", got)
	236	+	}
	237	+	})
	238	+	}
	239	+	}
	240	+
220	241		func TestHistoryRejectsRowWiderThanCellBudgetWithoutMutation(t *testing.T) {
221	242		history := NewHistory(HistoryConfig{MaxRows: 2, MaxCells: 2, ChunkRows: 2})
222	243		if err := history.Append(historyRow("ok")); err != nil {


@@ -217,6 +217,27 @@ func TestHistoryBoundsRowsAndCellsWithExactRowEviction(t *testing.T) {
217	}	217		}
218	}	218		}
219		219
		220	+	func TestHistoryAppendIsNoOpForNilAndZeroValue(t *testing.T) {
		221	+	tests := []struct {
		222	+	name string
		223	+	history *History
		224	+	}{
		225	+	{name: "nil history"},
		226	+	{name: "zero-value history", history: &History{}},
		227	+	}
		228	+
		229	+	for _, tt := range tests {
		230	+	t.Run(tt.name, func(t *testing.T) {
		231	+	if err := tt.history.Append(historyRow("row")); err != nil {
		232	+	t.Fatalf("append error = %v, want nil", err)
		233	+	}
		234	+	if got := tt.history.Len(); got != 0 {
		235	+	t.Fatalf("retained rows = %d, want 0", got)
		236	+	}
		237	+	})
		238	+	}
		239	+	}
		240	+
220	func TestHistoryRejectsRowWiderThanCellBudgetWithoutMutation(t *testing.T) {	241		func TestHistoryRejectsRowWiderThanCellBudgetWithoutMutation(t *testing.T) {
221	history := NewHistory(HistoryConfig{MaxRows: 2, MaxCells: 2, ChunkRows: 2})	242		history := NewHistory(HistoryConfig{MaxRows: 2, MaxCells: 2, ChunkRows: 2})
222	if err := history.Append(historyRow("ok")); err != nil {	243		if err := history.Append(historyRow("ok")); err != nil {

M pkg/vt/snapshot.go +1 -0


@@ -106,6 +106,7 @@ func HistoryFromBlobs(config HistoryConfig, sealed [][]byte, tail []byte) (*Hist
106	106		h.cells += view.Cells()
107	107		}
108	108		h.evict()
	109	+	h.normalizeTail()
109	110		return h, nil
110	111		}
111	112


@@ -106,6 +106,7 @@ func HistoryFromBlobs(config HistoryConfig, sealed [][]byte, tail []byte) (*Hist
106	h.cells += view.Cells()	106		h.cells += view.Cells()
107	}	107		}
108	h.evict()	108		h.evict()
		109	+	h.normalizeTail()
109	return h, nil	110		return h, nil
110	}	111		}
111		112

M pkg/vt/snapshot_test.go +17 -0


@@ -4,6 +4,7 @@ import (
4	4		"strings"
5	5		"testing"
6	6
	7	+	"github.com/bnema/vev/pkg/renderer"
7	8		"github.com/stretchr/testify/require"
8	9		)
9	10

@@ -48,6 +49,22 @@ func TestHistorySnapshotViewDoesNotSealTailAndCopiesIt(t *testing.T) {
48	49		require.Equal(t, []string{"CCCC"}, historyViewTexts(decoded))
49	50		}
50	51
	52	+	func TestHistoryFromBlobsNormalizesFullTailBeforeAppend(t *testing.T) {
	53	+	fullTail, err := MarshalHistory(HistoryView{
	54	+	chunks: []*HistoryChunk{{rows: [][]renderer.Cell{historyRow("AAAA"), historyRow("BBBB")}}},
	55	+	rows: 2,
	56	+	})
	57	+	require.NoError(t, err)
	58	+
	59	+	restored, err := HistoryFromBlobs(HistoryConfig{MaxRows: 4, ChunkRows: 2}, nil, fullTail)
	60	+	require.NoError(t, err)
	61	+	require.NoError(t, restored.Append(historyRow("CCCC")))
	62	+
	63	+	require.Equal(t, []string{"AAAA", "BBBB", "CCCC"}, historyViewTexts(restored.View()))
	64	+	require.Len(t, restored.chunks, 1, "a full restored tail must become sealed")
	65	+	require.Len(t, restored.tail, 1, "the appended row must be the mutable tail")
	66	+	}
	67	+
51	68		func TestHistoryFromBlobsRestoresCellAccountingAndEvictsToBothBudgets(t *testing.T) {
52	69		history := NewHistory(HistoryConfig{MaxRows: 4, MaxCells: 10, ChunkRows: 2})
53	70		for _, text := range []string{"a", "b", "cc"} {


@@ -4,6 +4,7 @@ import (
4	"strings"	4		"strings"
5	"testing"	5		"testing"
6		6
		7	+	"github.com/bnema/vev/pkg/renderer"
7	"github.com/stretchr/testify/require"	8		"github.com/stretchr/testify/require"
8	)	9		)
9		10

@@ -48,6 +49,22 @@ func TestHistorySnapshotViewDoesNotSealTailAndCopiesIt(t *testing.T) {
48	require.Equal(t, []string{"CCCC"}, historyViewTexts(decoded))	49		require.Equal(t, []string{"CCCC"}, historyViewTexts(decoded))
49	}	50		}
50		51
		52	+	func TestHistoryFromBlobsNormalizesFullTailBeforeAppend(t *testing.T) {
		53	+	fullTail, err := MarshalHistory(HistoryView{
		54	+	chunks: []*HistoryChunk{{rows: [][]renderer.Cell{historyRow("AAAA"), historyRow("BBBB")}}},
		55	+	rows: 2,
		56	+	})
		57	+	require.NoError(t, err)
		58	+
		59	+	restored, err := HistoryFromBlobs(HistoryConfig{MaxRows: 4, ChunkRows: 2}, nil, fullTail)
		60	+	require.NoError(t, err)
		61	+	require.NoError(t, restored.Append(historyRow("CCCC")))
		62	+
		63	+	require.Equal(t, []string{"AAAA", "BBBB", "CCCC"}, historyViewTexts(restored.View()))
		64	+	require.Len(t, restored.chunks, 1, "a full restored tail must become sealed")
		65	+	require.Len(t, restored.tail, 1, "the appended row must be the mutable tail")
		66	+	}
		67	+
51	func TestHistoryFromBlobsRestoresCellAccountingAndEvictsToBothBudgets(t *testing.T) {	68		func TestHistoryFromBlobsRestoresCellAccountingAndEvictsToBothBudgets(t *testing.T) {
52	history := NewHistory(HistoryConfig{MaxRows: 4, MaxCells: 10, ChunkRows: 2})	69		history := NewHistory(HistoryConfig{MaxRows: 4, MaxCells: 10, ChunkRows: 2})
53	for _, text := range []string{"a", "b", "cc"} {	70		for _, text := range []string{"a", "b", "cc"} {