An a, c or i text with no . line fails the Edit, as an open { does

sam takes the end of input as a text block's end, so a block cut short (a
write that lost its tail, an open closed early) inserted half of itself.
An Edit whose a, c or i text never meets its . line now fails with "a, c
or i text not ended by a . line" and changes nothing, as an unclosed {
does; at a close, logged as an err.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 5 insertions, 0 deletions

diff --git a/src/sam_edit.zig b/src/sam_edit.zig
index 604e2b31..cd2998ef 100644
--- a/src/sam_edit.zig
+++ b/src/sam_edit.zig
@@ -75,6 +75,11 @@ pub fn run(arena: std.mem.Allocator, text: []const u8, dot: Range, name: []const
         if (last) |l| l.next = c else first = c;
         last = c;
     }
+    // An a, c or i text that never met its `.` line is refused, as an
+    // unclosed `{` is: sam takes the end of input for one, but a block that
+    // reaches Edit unfinished was cut short (a write, an open closed), and
+    // half of it inserted is worse than none.
+    if (ps.open_text) return fail(why, "a, c or i text not ended by a . line", .{});
     const cmds = first orelse return .{ .ops = &.{}, .dot = dot, .printed = "" };
     // acme's u runs at once (ecmd.c:532), outside the edit log; here it is
     // an Edit of its own.