Project: A Persistent Task Tracker

import argparsefrom dataclasses import asdict, dataclassimport jsonfrom pathlib import Pathimport sysimport tempfileclass StoreError(ValueError):    pass@dataclassclass Task:    id: int    title: str    done: bool = False    def __post_init__(self):        if type(self.id) is not int or self.id <= 0:            raise ValueError("task id must be a positive integer")        if not isinstance(self.title, str) or not self.title.strip():            raise ValueError("task title must be nonblank text")        if type(self.done) is not bool:            raise ValueError("task done must be a boolean")        self.title = self.title.strip()def load_tasks(path):    try:        text = path.read_text(encoding="utf-8")    except FileNotFoundError:        return []    except (OSError, UnicodeError) as exc:        raise StoreError(f"cannot read data: {exc}") from exc    try:        payload = json.loads(text)    except json.JSONDecodeError as exc:        raise StoreError("data file is not valid JSON") from exc    if not isinstance(payload, dict):        raise StoreError("data root must be an object")    if type(payload.get("schema_version")) is not int or payload["schema_version"] != 1:        raise StoreError("unsupported schema version")    rows = payload.get("tasks")    if not isinstance(rows, list):        raise StoreError("tasks must be a list")    tasks = []    seen = set()    for number, row in enumerate(rows, start=1):        if not isinstance(row, dict) or set(row) != {"id", "title", "done"}:            raise StoreError(f"task row {number} has unexpected fields")        try:            task = Task(row["id"], row["title"], row["done"])        except ValueError as exc:            raise StoreError(f"task row {number}: {exc}") from exc        if task.id in seen:            raise StoreError(f"duplicate task id: {task.id}")        seen.add(task.id)        tasks.append(task)    return tasksdef save_tasks(path, tasks):    payload = {"schema_version": 1, "tasks": [asdict(task) for task in tasks]}    text = json.dumps(payload, ensure_ascii=False, indent=2) + "\n"    temporary = None    try:        with tempfile.NamedTemporaryFile(            mode="w", encoding="utf-8", dir=path.parent,            prefix=path.name + ".", suffix=".tmp", delete=False        ) as handle:            temporary = Path(handle.name)            handle.write(text)        temporary.replace(path)    except OSError as exc:        raise StoreError(f"cannot save data: {exc}") from exc    finally:        if temporary is not None:            temporary.unlink(missing_ok=True)def make_parser():    parser = argparse.ArgumentParser(description="Track local study tasks")    parser.add_argument("--file", type=Path, required=True, help="JSON data path")    commands = parser.add_subparsers(dest="command", required=True)    add = commands.add_parser("add", help="add a task")    add.add_argument("title")    commands.add_parser("list", help="list all tasks")    done = commands.add_parser("done", help="complete a task")    done.add_argument("id", type=int)    return parserdef main(argv=None):    args = make_parser().parse_args(argv)    try:        tasks = load_tasks(args.file)        if args.command == "add":            next_id = max((task.id for task in tasks), default=0) + 1            task = Task(next_id, args.title)            tasks.append(task)            save_tasks(args.file, tasks)            print(f"Added {task.id}: {task.title}")        elif args.command == "list":            if not tasks:                print("No tasks")            for task in tasks:                marker = "x" if task.done else " "                print(f"{task.id} [{marker}] {task.title}")        elif args.command == "done":            task = next((task for task in tasks if task.id == args.id), None)            if task is None:                raise ValueError(f"unknown task id: {args.id}")            task.done = True            save_tasks(args.file, tasks)            print(f"Completed {task.id}")    except (StoreError, ValueError) as exc:        print(f"Error: {exc}", file=sys.stderr)        return 2    return 0if __name__ == "__main__":    raise SystemExit(main())

from contextlib import redirect_stderr, redirect_stdoutimport iofrom pathlib import Pathfrom tempfile import TemporaryDirectoryfrom tracker import load_tasks, mainwith TemporaryDirectory() as folder:    path = Path(folder) / "tasks.json"    base = ["--file", str(path)]    output = io.StringIO()    errors = io.StringIO()    with redirect_stdout(output), redirect_stderr(errors):        assert main(base + ["list"]) == 0        assert main(base + ["add", "Learn files"]) == 0        assert main(base + ["add", "Write tests"]) == 0        assert main(base + ["done", "1"]) == 0        assert main(base + ["list"]) == 0        before = path.read_text(encoding="utf-8")        assert main(base + ["add", " "]) == 2        assert main(base + ["done", "999"]) == 2        assert path.read_text(encoding="utf-8") == before    tasks = load_tasks(path)    assert [(task.id, task.done) for task in tasks] == [(1, True), (2, False)]    assert "1 [x] Learn files" in output.getvalue()    assert "unknown task id" in errors.getvalue()print("All acceptance checks passed")