strop-engine 0.28.0

strop editor engine: documents, grammar dispatch, services, sessions — no terminal
Documentation
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
//! Picker modal-field and navigation behavior (the input box is a
//! real modal field: Esc/i, jk on results, arrows move the caret).

#[cfg(test)]
mod picker_tests {
    use super::super::*;
    use strop_core::Buffer;

    #[test]
    fn picker_field_is_modal() {
        // rootle's input boxes: Esc enters normal mode on the field,
        // keys edit the query, i returns to insert, Esc closes
        let mut e = Editor::new(Buffer::from_text("x\n"));
        e.open_picker(Kind::Files);
        e.feed_text("main");
        e.feed(crate::editor::Key::Esc);
        assert!(e.picker_open(), "esc once: picker stays open");
        e.feed_text("0x"); // to 0, delete 'm'
        assert_eq!(e.picker.as_ref().unwrap().picker.input.text, "ain");
        e.feed(crate::editor::Key::Esc);
        assert!(!e.picker_open(), "esc twice closes");
    }

    #[test]
    fn picker_normal_mode_jk_walk_results() {
        // Esc into the field's normal mode; j/k move the selection,
        // not the text caret (user report: only Tab/arrows navigated)
        let dir = tempfile::tempdir().unwrap();
        let mut e = Editor::new(Buffer::from_text("x\n"));
        for f in ["a.txt", "b.txt", "c.txt", "d.txt"] {
            std::fs::write(dir.path().join(f), "x\n").unwrap();
            e.open_fixture(&dir.path().join(f)).unwrap();
        }
        e.open_picker(Kind::Buffers);
        e.wait_picker();
        let sel = |e: &Editor| e.picker.as_ref().unwrap().picker.selected;
        assert_eq!(sel(&e), 0);
        e.feed(crate::editor::Key::Esc); // normal mode on the field
        e.feed_text("jj");
        assert_eq!(sel(&e), 2, "j moved the selection down twice");
        e.feed_text("k");
        assert_eq!(sel(&e), 1);
        e.feed_text("i"); // back to insert
        e.feed_text("j"); // types into the query instead
        assert_eq!(
            e.picker.as_ref().unwrap().picker.input.text,
            "j",
            "insert mode: j filters"
        );
    }

    #[test]
    fn picker_arrows_navigate_and_move_caret() {
        // user report: physical arrows did nothing in pickers — the
        // translation layer dropped KeyCode::Up/Down entirely
        let dir = tempfile::tempdir().unwrap();
        let mut e = Editor::new(Buffer::from_text("x\n"));
        for f in ["aa.txt", "ab.txt", "ac.txt"] {
            std::fs::write(dir.path().join(f), "x\n").unwrap();
            e.open_fixture(&dir.path().join(f)).unwrap();
        }
        e.open_picker(Kind::Buffers);
        e.feed_text("a");
        e.wait_picker();
        e.feed(crate::editor::Key::Down);
        assert_eq!(
            e.picker.as_ref().unwrap().picker.selected,
            1,
            "Down walks results"
        );
        e.feed(crate::editor::Key::Up);
        assert_eq!(e.picker.as_ref().unwrap().picker.selected, 0);
        e.feed(crate::editor::Key::Left);
        assert_eq!(
            e.picker.as_ref().unwrap().picker.input.cursor,
            0,
            "Left moves the caret"
        );
        e.feed(crate::editor::Key::Right);
        assert_eq!(e.picker.as_ref().unwrap().picker.input.cursor, 1);
    }

    #[test]
    fn paste_into_picker_edits_the_field_not_the_document() {
        // user report: bracketed paste in a picker or the connect-to-
        // remote field was silently dropped (or worse, could land in
        // the buffer behind the card)
        let mut e = Editor::new(Buffer::from_text("x\n"));
        e.open_picker(Kind::Files);
        e.paste_bracketed("main");
        assert_eq!(e.picker.as_ref().unwrap().picker.input.text, "main");
        assert_eq!(e.buf().text(), "x\n", "the document is untouched");
        // caret placement is honored
        e.feed(crate::editor::Key::Left);
        e.feed(crate::editor::Key::Left);
        e.paste_bracketed("__");
        assert_eq!(e.picker.as_ref().unwrap().picker.input.text, "ma__in");
        // paste works in the field's normal mode too (the ex line's
        // pending reducer pastes the same way)
        e.feed(crate::editor::Key::Esc);
        e.feed_text("0");
        e.paste_bracketed("#");
        assert_eq!(e.picker.as_ref().unwrap().picker.input.text, "#ma__in");
    }

    #[test]
    fn paste_newline_into_picker_is_rejected_with_a_message() {
        let mut e = Editor::new(Buffer::from_text("x\n"));
        e.open_picker(Kind::Files);
        e.paste_bracketed("a\nb");
        assert_eq!(
            e.message, "picker input cannot contain a newline",
            "a refused paste says so — silence reads as a broken terminal"
        );
        assert_eq!(e.picker.as_ref().unwrap().picker.input.text, "");
    }

    #[test]
    fn jumps_picker_walks_history_and_ctrl_o_returns() {
        // 0047 §2: the jumplist as a menu — past newest-first, the
        // current position marked, accepting an entry lands there and
        // records the spot so ctrl-o returns.
        let mut e = Editor::new(Buffer::from_text("one\ntwo\nthree\nfour\n"));
        e.feed_text("G"); // jump to line 4
        e.feed_text("gg"); // jump back to line 1
        e.open_picker(Kind::Jumps);
        e.wait_picker();
        let glue = e.picker.as_ref().unwrap();
        let texts: Vec<&str> = glue.picker.items.iter().map(|i| i.text.as_str()).collect();
        assert_eq!(texts.len(), 3, "two jumps + the current row: {texts:?}");
        assert!(
            texts[0].contains(":4") && texts[0].contains("four"),
            "newest past entry first: {texts:?}"
        );
        assert!(
            texts[2].starts_with("> "),
            "the current row is marked: {texts:?}"
        );
        e.feed(crate::editor::Key::Enter);
        assert!(!e.picker_open(), "accept closes the picker");
        assert_eq!(e.buf().line_of(e.head()), 3, "landed on the accepted entry");
        e.feed(crate::editor::Key::CtrlO);
        assert_eq!(
            e.buf().line_of(e.head()),
            0,
            "ctrl-o returns to where the picker was opened"
        );
    }

    #[test]
    fn jumps_picker_filters_dead_documents() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("other.txt");
        std::fs::write(&path, "x\n").unwrap();
        let mut e = Editor::new(Buffer::from_text("one\ntwo\n"));
        e.open_fixture(&path).unwrap();
        e.feed_text("G"); // a jump inside other.txt
        let dead = e.current();
        e.close_buffer(true);
        assert!(e.docs.get(dead).is_none(), "the document is gone");
        e.open_picker(Kind::Jumps);
        e.wait_picker();
        let glue = e.picker.as_ref().unwrap();
        assert!(
            glue.picker
                .items
                .iter()
                .all(|i| !i.text.contains("other.txt")),
            "dead-document entries are absent: {:?}",
            glue.picker
                .items
                .iter()
                .map(|i| i.text.as_str())
                .collect::<Vec<_>>()
        );
    }

    #[test]
    fn remote_hosts_enter_carries_unmatched_text_into_the_address_box() {
        // 0.21.0 field report: a typed hostname that matched no listed
        // destination made Enter a no-op. Now the pinned "Add a host…"
        // row survives filtering and Enter carries the text into the
        // address box as a draft — never a blind connect to a host
        // literally named like the filter text.
        let mut e = Editor::new(Buffer::from_text("x\n"));
        let mut picker = Picker::new(
            Kind::RemoteHosts,
            vec![Item {
                badge: None,
                text: "Add a host\u{2026}".into(),
                payload: Payload::RemoteConnect,
            }],
            false,
        );
        picker.pinned_tail = 1;
        e.set_picker(PickerGlue::diagnostics(picker));
        e.feed_text("ewosd-tt-925");
        let filter = e.picker.as_ref().unwrap().picker.filter_request();
        let ranking = strop_picker::rank::rank(&filter, || false).unwrap();
        e.picker.as_mut().unwrap().picker.install_ranking(ranking);
        assert_eq!(
            e.picker
                .as_ref()
                .unwrap()
                .picker
                .current()
                .map(|i| i.text.as_str()),
            Some("Add a host\u{2026}"),
            "the pinned row survives a dead query"
        );
        e.accept_current_picker();
        let glue = e.picker.as_ref().expect("the address box opens");
        assert_eq!(glue.picker.kind, Kind::RemoteAddress);
        assert_eq!(
            glue.picker.input.text, "ewosd-tt-925",
            "the typed destination arrives as the address draft"
        );
    }

    #[test]
    fn remote_hosts_empty_enter_opens_the_address_box() {
        let mut e = Editor::new(Buffer::from_text("x\n"));
        let mut picker = Picker::new(
            Kind::RemoteHosts,
            vec![Item {
                badge: None,
                text: "Add a host\u{2026}".into(),
                payload: Payload::RemoteConnect,
            }],
            false,
        );
        picker.pinned_tail = 1;
        e.set_picker(PickerGlue::diagnostics(picker));
        let filter = e.picker.as_ref().unwrap().picker.filter_request();
        let ranking = strop_picker::rank::rank(&filter, || false).unwrap();
        e.picker.as_mut().unwrap().picker.install_ranking(ranking);
        e.accept_current_picker();
        assert_eq!(
            e.picker.as_ref().map(|glue| glue.picker.kind),
            Some(Kind::RemoteAddress),
            "empty input on the pinned row still opens the address box"
        );
    }

    #[test]
    fn paste_into_remote_address_field_is_accepted_verbatim() {
        // the connect-to-remote case: an ssh://user@host:port/path URL
        let mut e = Editor::new(Buffer::from_text("x\n"));
        e.open_picker(Kind::RemoteAddress);
        e.paste_bracketed("ssh://user@example.com:2222/tmp/dir");
        assert_eq!(
            e.picker.as_ref().unwrap().picker.input.text,
            "ssh://user@example.com:2222/tmp/dir"
        );
    }
}

// Worker lifecycle: injected terminal events (deterministic — no real
// rg, no sleeps, no HOME assumptions; the supervisor's own decisions
// are unit-tested in strop-picker).
#[cfg(test)]
mod worker_lifecycle_tests {
    use super::super::preview::read_preview;
    use super::super::*;
    use std::path::PathBuf;
    use strop_core::worker::{CancelReason, Completion, FailureKind, Load, Outcome, Ticket};
    use strop_core::Buffer;
    use strop_picker::{Item, Payload, PickerMsg};

    fn editor() -> Editor {
        Editor::new(Buffer::from_text("x\n"))
    }

    fn item(text: &str) -> Item {
        Item {
            badge: None,
            text: text.into(),
            payload: Payload::File(PathBuf::from(text)),
        }
    }

    fn rank_fixture(e: &mut Editor) {
        let picker = &mut e.picker.as_mut().unwrap().picker;
        let ranking = strop_picker::rank::rank(&picker.filter_request(), || false).unwrap();
        assert!(picker.install_ranking(ranking));
    }

    /// Register a grep-stream request without launching rg: the glue
    /// only needs the ticket; events are injected by hand.
    fn register_stream(e: &mut Editor) -> Ticket<PickerKey> {
        e.open_picker(Kind::Grep);
        let picker = e.picker.as_ref().map(|g| g.id).unwrap();
        let request = e.worker_ids.allocate().unwrap();
        let ticket = Ticket {
            request,
            key: PickerKey {
                picker,
                cwd: e.cwd.clone(),
            },
        };
        let glue = e.picker.as_mut().unwrap();
        glue.active = Some(ticket.clone());
        glue.picker.streaming = true;
        ticket
    }

    /// Register a preview request without launching a read thread.
    fn register_preview(e: &mut Editor, rel: &str) -> (Ticket<PreviewKey>, PathBuf) {
        let path = e.cwd.join(rel);
        let picker = e.picker.as_ref().map(|g| g.id).unwrap();
        let request = e.worker_ids.allocate().unwrap();
        let ticket = Ticket {
            request,
            key: PreviewKey {
                picker,
                path: path.clone(),
            },
        };
        e.preview_loads
            .insert(path.clone(), Load::Running(ticket.clone()));
        (ticket, path)
    }

    #[test]
    fn files_request_registers_before_launch_and_cancels_on_close() {
        let mut e = editor();
        e.open_picker(Kind::Files);
        let glue = e.picker.as_ref().unwrap();
        assert!(glue.picker.streaming, "the walk streams");
        assert!(
            glue.active.is_some(),
            "the request owns the stream before launch"
        );
        assert!(matches!(glue.worker, Some(PickerWorker::Files(_))));
        e.close_picker();
        assert!(!e.picker_open(), "close settles the picker");
        // a terminal event from the cancelled walk cannot resurrect it
        e.handle_picker_event(PickerEvent {
            ticket: Ticket {
                request: strop_core::worker::WorkerId::new(1),
                key: PickerKey {
                    picker: PickerId(strop_core::worker::WorkerId::new(2)),
                    cwd: e.cwd.clone(),
                },
            },
            msg: PickerMsg::Finished(Outcome::Success(())),
        });
        assert!(!e.picker_open());
    }

    #[test]
    fn streamed_items_survive_a_terminal_failure_and_error_is_sticky() {
        let mut e = editor();
        let ticket = register_stream(&mut e);
        e.handle_picker_event(PickerEvent {
            ticket: ticket.clone(),
            msg: PickerMsg::Items(vec![item("a.rs"), item("b.rs")].into()),
        });
        e.handle_picker_event(PickerEvent {
            ticket: ticket.clone(),
            msg: PickerMsg::Finished(Outcome::failed(FailureKind::Spawn, "rg: not found")),
        });
        e.wait_picker();
        let glue = e.picker.as_ref().unwrap();
        assert!(!glue.picker.streaming, "terminal failure settles streaming");
        assert_eq!(glue.picker.rows.len(), 2, "useful partial results survive");
        assert_eq!(
            glue.picker.error.as_deref(),
            Some("rg: not found"),
            "error is sticky"
        );
        assert!(glue.active.is_none(), "the request is released");
        // duplicate terminals and post-terminal items are rejected
        e.handle_picker_event(PickerEvent {
            ticket: ticket.clone(),
            msg: PickerMsg::Finished(Outcome::Success(())),
        });
        e.handle_picker_event(PickerEvent {
            ticket: ticket.clone(),
            msg: PickerMsg::Items(vec![item("late.rs")].into()),
        });
        let glue = e.picker.as_ref().unwrap();
        assert_eq!(glue.picker.rows.len(), 2, "settled state is immutable");
        assert!(!glue.picker.streaming);
    }

    #[test]
    fn empty_success_settles_the_stream_without_error() {
        // exit-1/no-matches and empty queries land as Success: an
        // empty picker, not a failure and not perpetual loading
        let mut e = editor();
        let ticket = register_stream(&mut e);
        e.handle_picker_event(PickerEvent {
            ticket,
            msg: PickerMsg::Finished(Outcome::Success(())),
        });
        let glue = e.picker.as_ref().unwrap();
        assert!(!glue.picker.streaming);
        assert!(glue.picker.error.is_none(), "no fabricated failure");
        assert!(glue.picker.rows.is_empty());
    }

    #[test]
    fn superseded_requests_cannot_touch_the_new_owner() {
        let mut e = editor();
        let old = register_stream(&mut e);
        // the next query's registration (no rg: emulated by hand)
        let fresh = {
            let picker = e.picker.as_ref().unwrap().id;
            let request = e.worker_ids.allocate().unwrap();
            let ticket = Ticket {
                request,
                key: PickerKey {
                    picker,
                    cwd: e.cwd.clone(),
                },
            };
            e.picker.as_mut().unwrap().active = Some(ticket.clone());
            ticket
        };
        // A's late messages in every shape are rejected wholesale
        for msg in [
            PickerMsg::Items(vec![item("stale.rs")].into()),
            PickerMsg::Warning("stale".into()),
            PickerMsg::Finished(Outcome::Success(())),
            PickerMsg::Finished(Outcome::failed(FailureKind::Io, "stale pipe")),
            PickerMsg::Finished(Outcome::Cancelled(CancelReason::Superseded)),
        ] {
            e.handle_picker_event(PickerEvent {
                ticket: old.clone(),
                msg,
            });
        }
        let glue = e.picker.as_ref().unwrap();
        assert!(
            glue.picker.rows.is_empty(),
            "stale streams never touch the model"
        );
        assert!(glue.picker.error.is_none(), "stale failures never surface");
        assert!(glue.picker.streaming, "B keeps streaming");
        assert_eq!(glue.active.as_ref(), Some(&fresh), "B keeps ownership");
        // B then settles normally
        e.handle_picker_event(PickerEvent {
            ticket: fresh,
            msg: PickerMsg::Finished(Outcome::Success(())),
        });
        assert!(!e.picker.as_ref().unwrap().picker.streaming);
    }

    #[test]
    fn preview_failure_is_visible_and_retryable_after_reopen() {
        let mut e = editor();
        e.open_picker(Kind::Grep);
        e.picker
            .as_mut()
            .unwrap()
            .picker
            .append(vec![item("a.txt")]);
        rank_fixture(&mut e);
        let (ticket, path) = register_preview(&mut e, "a.txt");
        e.handle_preview(Completion {
            ticket: ticket.clone(),
            outcome: Outcome::failed(FailureKind::Io, "no such file"),
        });
        assert!(
            matches!(e.preview_loads.get(&path), Some(Load::Failed { .. })),
            "the failure is owned, not a forever-empty success"
        );
        assert!(
            !e.previews.contains_key(&path),
            "a failure is not an empty file"
        );
        assert!(matches!(
            e.picker_preview().unwrap().2,
            PreviewSource::Failed(_)
        ));
        // Later frames preserve the terminal error instead of retrying.
        assert!(
            matches!(e.preview_loads.get(&path), Some(Load::Failed { .. })),
            "no silent per-frame retry"
        );
        // closing forgets the negative cache…
        e.close_picker();
        assert!(!e.previews.contains_key(&path), "negative cache forgotten");
        assert!(!e.preview_loads.contains_key(&path));
        // …so an explicit reopen can retry with a fresh request
        e.open_picker(Kind::Grep);
        e.picker
            .as_mut()
            .unwrap()
            .picker
            .append(vec![item("a.txt")]);
        rank_fixture(&mut e);
        let (fresh, path) = register_preview(&mut e, "a.txt");
        assert_ne!(
            fresh.request, ticket.request,
            "a reopen allocates a new request"
        );
        // the old ticket's late success cannot touch the fresh request
        e.handle_preview(Completion {
            ticket: ticket.clone(),
            outcome: Outcome::Success(String::from("late").into()),
        });
        assert!(
            matches!(e.preview_loads.get(&path), Some(Load::Running(t)) if *t == fresh),
            "stale preview results are rejected"
        );
        // the fresh one succeeds and its cache survives the next close
        e.handle_preview(Completion {
            ticket: fresh,
            outcome: Outcome::Success(String::from("body").into()),
        });
        let entry = e.previews.get(&path).unwrap();
        assert_eq!(entry.rope.to_string(), "body");
        // (highlighter presence is strop-syntax's language call, not
        // this lifecycle contract)
        e.close_picker();
        assert!(
            e.previews.contains_key(&path),
            "positive caches survive reopen"
        );
        assert!(matches!(e.preview_loads.get(&path), Some(Load::Ready(_))));
    }

    #[test]
    fn preview_empty_success_is_ready_and_cancel_does_not_resubmit() {
        let mut e = editor();
        e.open_picker(Kind::Grep);
        e.picker
            .as_mut()
            .unwrap()
            .picker
            .append(vec![item("empty.txt")]);
        rank_fixture(&mut e);
        let (ticket, path) = register_preview(&mut e, "empty.txt");
        // an empty file is a real success: cached Ready
        e.handle_preview(Completion {
            ticket,
            outcome: Outcome::Success(String::new().into()),
        });
        assert!(matches!(e.preview_loads.get(&path), Some(Load::Ready(_))));
        assert!(e.previews[&path].rope.to_string().is_empty());

        // an explicit cancellation settles the load and frames do not
        // silently retry it
        let (ticket, path) = register_preview(&mut e, "cancelled.txt");
        e.handle_preview(Completion {
            ticket,
            outcome: Outcome::Cancelled(CancelReason::Dismissed),
        });
        assert!(
            matches!(e.preview_loads.get(&path), Some(Load::Cancelled { .. })),
            "cancelled settles terminal"
        );
        e.picker
            .as_mut()
            .unwrap()
            .picker
            .append(vec![item("cancelled.txt")]);
        rank_fixture(&mut e);
        e.picker.as_mut().unwrap().picker.move_by(1);
        let preview = e.picker_preview().unwrap();
        assert!(
            matches!(preview.2, PreviewSource::Cancelled(CancelReason::Dismissed)),
            "cancelled previews are terminal, not perpetually loading"
        );
        assert!(
            matches!(e.preview_loads.get(&path), Some(Load::Cancelled { .. })),
            "no new request was enqueued"
        );
    }

    #[test]
    fn read_preview_types_every_miss() {
        let dir = tempfile::tempdir().unwrap();
        std::fs::write(dir.path().join("ok.txt"), "body\n").unwrap();
        match read_preview(&dir.path().join("ok.txt")) {
            Outcome::Success(text) => assert_eq!(text.rope, "body\n"),
            outcome => panic!("readable file must succeed: {outcome:?}"),
        }
        // empty file: a real success, not a failure
        std::fs::write(dir.path().join("empty.txt"), "").unwrap();
        let empty = read_preview(&dir.path().join("empty.txt"));
        assert!(matches!(&empty, Outcome::Success(t) if t.rope.len_bytes() == 0));
        // over the 512 KiB cap
        std::fs::write(dir.path().join("big.txt"), vec![b'x'; 512 * 1024 + 1]).unwrap();
        let big = read_preview(&dir.path().join("big.txt"));
        assert!(
            matches!(&big, Outcome::Failed { failure, .. } if failure.kind == FailureKind::Unavailable)
        );
        // a directory is not a preview target
        let dir_result = read_preview(dir.path());
        assert!(
            matches!(&dir_result, Outcome::Failed { failure, .. } if failure.kind == FailureKind::Unavailable)
        );
        // missing path
        let missing = read_preview(&dir.path().join("missing.txt"));
        assert!(
            matches!(&missing, Outcome::Failed { failure, .. } if failure.kind == FailureKind::Io)
        );
        // invalid UTF-8
        std::fs::write(dir.path().join("bin.bin"), [0xff, 0xfe, 0xfd]).unwrap();
        let bin = read_preview(&dir.path().join("bin.bin"));
        assert!(matches!(&bin, Outcome::Failed { failure, .. } if failure.kind == FailureKind::Io));
    }
}