A look at a corrupt image fails with an err rather than open a blank pane

An image stb_image could not read opened as an empty image pane, the look succeeding. The bytes' header is now checked at the look (stbi_info_from_memory), and one that is no image it reads fails the look, look: <path>: not an image pardes can read, making no pane.

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

1 files changed, 22 insertions, 0 deletions

diff --git a/src/ninep/ctl.zig b/src/ninep/ctl.zig
index be90bb6f..978ce707 100644
--- a/src/ninep/ctl.zig
+++ b/src/ninep/ctl.zig
@@ -2115,6 +2115,28 @@ test "a language server question that finds nothing, cannot be answered, or is a
     try testing.expectEqual(E.INVAL, wr(p, Node.of(img.serial, .body), "text\n").errno());
 }
 
+test "a corrupt image fails its look with an err, and no pane is made" {
+    pardes.image.start(testing.io, testing.allocator);
+    defer pardes.image.stop();
+    const p = try withFile(testing.allocator, "x\n");
+    defer p.deinit();
+    var tmp = testing.tmpDir(.{});
+    defer tmp.cleanup();
+    try tmp.dir.writeFile(testing.io, .{ .sub_path = "bad.png", .data = "\x89PNG not really" });
+    var dir_buf: [4096]u8 = undefined;
+    const dir = dir_buf[0..try tmp.dir.realPath(testing.io, &dir_buf)];
+    var line: [4200]u8 = undefined;
+    var count: usize = 0;
+    for (p.panes) |slot| count += @intFromBool(slot != null);
+    const r = wr(p, root_look, try std.fmt.bufPrint(&line, "{s}/bad.png\n", .{dir}));
+    try testing.expectEqual(E.IO, r.errno());
+    try testing.expect(std.mem.endsWith(u8, r.reply.ename, "bad.png: not an image pardes can read"));
+    p.sync();
+    var after: usize = 0;
+    for (p.panes) |slot| after += @intFromBool(slot != null);
+    try testing.expectEqual(count, after);
+}
+
 test "a PDF's body reads its page's text layer, and takes no write" {
     if (comptime !pardes.pdf_enabled) return;
     const p = try withFile(testing.allocator, "x\n");