shareAI-lab/learn-claude-code · error · ValueError

Task subject cannot be empty

Error message

Task subject cannot be empty

What it means

create_task() strips the subject and raises ValueError when the result is empty. A task must have a non-empty human-readable subject; this is the earliest of create_task's three validation gates (subject, dependency existence, ID allocation).

Source

Thrown at s13_agent_teams/code.py:137

    blockedBy: list[str]
    worktree: str | None = None


def _task_path(task_id: str) -> Path:
    if not isinstance(task_id, str) or not TASK_ID_PATTERN.fullmatch(task_id):
        raise ValueError(f"Invalid task ID: {task_id!r}")
    path = (TASKS_DIR / f"{task_id}.json").resolve()
    if (not TASKS_ROOT.is_relative_to(WORKDIR.resolve())
            or not path.is_relative_to(TASKS_ROOT)):
        raise ValueError(f"Invalid task ID: {task_id!r}")
    return path


def create_task(subject: str, description: str = "",
                blockedBy: list[str] | None = None) -> Task:
    subject = subject.strip()
    if not subject:
        raise ValueError("Task subject cannot be empty")
    dependencies = list(dict.fromkeys(blockedBy or []))
    with task_store_lock():
        for dependency in dependencies:
            if not _task_path(dependency).is_file():
                raise ValueError(f"Dependency not found: {dependency}")
        for _ in range(100):
            task = Task(
                id=f"task_{secrets.token_hex(4)}",
                subject=subject,
                description=description,
                status="pending",
                owner=None,
                blockedBy=dependencies,
            )
            try:
                with _task_path(task.id).open("x", encoding="utf-8") as handle:
                    json.dump(asdict(task), handle, indent=2)
                return task

View on GitHub (pinned to 985456f4ad)

Solutions

1. Check subject.strip() before calling create_task and supply a real title.
2. If generating tasks in a loop, skip/log entries whose subject is blank instead of calling.
3. Default missing subjects to a generated name like f'Task {date}' rather than ''.

Example fix

// before
task = create_task(subject or '')  // ValueError

// after
if not (subject or '').strip():
    raise ValueError('subject required')
task = create_task(subject)

def valid_subject(subject: str) -> bool:
    return isinstance(subject, str) and bool(subject.strip())

from typing import TypeGuard

def is_nonempty_subject(value: object) -> TypeGuard[str]:
    return isinstance(value, str) and len(value.strip()) > 0

When it happens

Trigger: create_task(''), create_task(' ') (whitespace-only — it is stripped first), or passing a subject that is None-adjacent glue like f"{missing_var}" producing ''.

Common situations: Building subjects from optional template variables that are empty, forwarding unvalidated form input, or programmatic task generation where a list field was empty.

Related errors

• Invalid task ID: {task_id!r}
• Dependency not found: {dependency}
• Invalid task ID: {task_id!r}
• Task subject cannot be empty
• Max 20 todos allowed

AI-assisted analysis of shareAI-lab/learn-claude-code@985456f4ad (2026-08-14). Data as JSON: /api/errors/ec322e9ff1eab0c7. Report an issue: GitHub.