Let --context expand any selection past its range, drawing from the whole file

tests/test_range.py

@@ -2,13 +2,17 @@
 
 import asyncio
 import json
+from datetime import UTC, datetime
 
 from kanta.serialization import JsonSerializer
+from kanta.structs import META_FORMAT, ChangeRecord, Snapshot
 from tests.support import Data, make_kanta
 
 # The CLI reads files with its own JSON Kanta instance unless -k is given.
 JSON = ("json", JsonSerializer)
 
+T0 = datetime(2026, 1, 1, tzinfo=UTC)
+
 
 def _run_cli(path, *args):
     from kanta.__main__ import main
@@ -148,7 +152,7 @@ def test_unit_and_plain_combine(tmp_path, capsys):
 
 
 def test_context_expands_after_grep(tmp_path, capsys):
-    """Context records come from the in-window pool, free of --grep."""
+    """Context records come from the whole file, free of --grep."""
     path = tmp_path / "data.kantadb"
     _build(path, increments=5)
     capsys.readouterr()
@@ -168,7 +172,7 @@ def test_context_expands_after_grep(tmp_path, capsys):
     assert "inc1" not in err
     assert "inc2" in err
 
-    # Context is clamped at the start of the range.
+    # Context is clamped at the start of the file.
     assert _run_cli(path, "--grep", "bootstrap", "--context", "2") == 0
     err = capsys.readouterr().err
     assert "bootstrap" in err
@@ -177,6 +181,62 @@ def test_context_expands_after_grep(tmp_path, capsys):
     assert "inc2" not in err
 
 
+def test_context_expands_past_unit_window(tmp_path, capsys):
+    """Context expands whatever a unit selection would show, past the window."""
+    path = tmp_path / "data.kantadb"
+    _build(path)
+    capsys.readouterr()
+
+    # -r r2 alone shows only inc0 (the record producing state 2); context 1
+    # expands past the window to bootstrap and inc1, and the dump follows
+    # the last printed record.
+    assert _run_cli(path, "-r", "r2", "--context", "1", "-o", "-") == 0
+    out = capsys.readouterr()
+    assert "bootstrap" in out.err
+    assert "inc0" in out.err
+    assert "inc1" in out.err
+    assert "inc2" not in out.err
+    assert json.loads(out.out) == {"users": {}, "counter": 2}
+
+
+def test_context_expands_snapshot_selection(tmp_path, capsys):
+    """-r sN --context N shows the snapshot plus its neighbors."""
+    path = tmp_path / "data.kantadb"
+    serializer = JsonSerializer()
+    framer = serializer.framer_cls()
+    out_bytes = bytearray()
+    out_bytes += framer.frame_change(
+        serializer.encode(ChangeRecord(ts=T0, a="inc0", v=0, diff={"counter": 1})),
+        record_offset=len(out_bytes),
+    )
+    snap = Snapshot(ts=T0, v=0, state={"counter": 1}, r=1, k=META_FORMAT)
+    out_bytes += framer.frame_snapshot(
+        serializer.encode(snap), record_offset=len(out_bytes)
+    )
+    out_bytes += framer.frame_change(
+        serializer.encode(ChangeRecord(ts=T0, a="inc1", v=0, diff={"counter": 2})),
+        record_offset=len(out_bytes),
+    )
+    path.write_bytes(bytes(out_bytes))
+    capsys.readouterr()
+
+    # Without context, s1 (the file starts with a change, so s0 is l0)
+    # shows just the snapshot and its state.
+    assert _run_cli(path, "-r", "s1", "-o", "-") == 0
+    out = capsys.readouterr()
+    assert "snapshot s1" in out.err
+    assert "inc0" not in out.err
+    assert json.loads(out.out) == {"counter": 1}
+
+    # With context, the selection expands past the snapshot line.
+    assert _run_cli(path, "-r", "s1", "--context", "1", "-o", "-") == 0
+    out = capsys.readouterr()
+    assert "inc0" in out.err
+    assert "snapshot s1" in out.err
+    assert "inc1" in out.err
+    assert json.loads(out.out) == {"counter": 2}
+
+
 def test_context_merges_overlaps(tmp_path, capsys):
     """Nearby matches share context instead of duplicating records."""
     path = tmp_path / "data.kantadb"