refactor: remove calling datetime.now as default argument

[Koalal143]

Set datetime.now() defaults inside Todo.__init__ only.

Any function call that's used in a default argument will only be performed once, at definition time. The returned value will then be reused by all calls to the function, which can lead to unexpected behaviour (See https://docs.astral.sh/ruff/rules/function-call-in-default-argument/)

Summary by CodeRabbit

Release Notes

• Bug Fixes
  • Fixed timestamp initialization for todos to capture the current time at creation rather than at module import, preventing todos from sharing identical creation and update timestamps.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

Walkthrough

Modified the Todo class constructor to fix timestamp default handling. Changed created_at and updated_at parameters from mutable default arguments (datetime.now() evaluated at import time) to optional parameters (Optional[datetime] = None) with runtime evaluation using the or pattern.

Changes

Cohort / File(s)	Change Summary
Timestamp default argument fix dddpy/domain/todo/entities/todo.py	Updated created_at and updated_at parameters from datetime = datetime.now() to Optional[datetime] = None, with initialization logic changed to created_at or datetime.now() and updated_at or datetime.now() to evaluate timestamps at runtime rather than import time.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

• Single file affected with straightforward, well-known pattern fix
• Addresses common Python mutable default argument gotcha
• Changes are consistent and repetitive across both timestamp parameters

Poem

🐰 Hop hop, a fix so fine!
No more frozen time at import's line,
Now each todo gets its moment true,
Fresh timestamps, through and through! 🕐✨

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: removing datetime.now() calls from default arguments in the Todo.init method signature.

✨ Finishing touches

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🧪 Generate unit tests (beta)

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• Post copyable unit tests in a comment

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[coderabbitai]

Actionable comments posted: 1

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 5d1f917 and b846db2.

📒 Files selected for processing (1)

• dddpy/domain/todo/entities/todo.py (2 hunks)

🔇 Additional comments (1)

dddpy/domain/todo/entities/todo.py (1)

33-34: Excellent fix for the default argument anti-pattern!

The signature change correctly addresses the issue where datetime.now() was evaluated once at import time and reused across all instances. Moving to Optional[datetime] = None with runtime evaluation is the proper pattern.

[coderabbitai]

⚠️ Potential issue | 🔴 Critical

🧩 Analysis chain

🏁 Script executed:

#!/bin/bash
# Search for UTC-related expectations and datetime usage patterns

echo "=== Searching for UTC references in Python files ==="
rg -n -C2 'UTC|utc' --type=py

echo -e "\n=== Searching for datetime.now usage patterns ==="
rg -n 'datetime\.(now|utcnow)' --type=py

echo -e "\n=== Searching for timezone-aware datetime usage ==="
rg -n 'timezone|tzinfo|pytz' --type=py

echo -e "\n=== Checking the specific file for timestamp usage ==="
fd 'todo.py' --type f | head -1 | xargs -I {} sh -c 'wc -l "{}" && head -100 "{}"'

Repository: iktakahiro/dddpy

Length of output: 5761

---

🏁 Script executed:

#!/bin/bash
# Check the full __init__ method around lines 52-53
echo "=== Full __init__ method from todo.py ==="
sed -n '25,60p' dddpy/domain/todo/entities/todo.py | cat -n

echo -e "\n=== Check for any 'or' operators in __init__ assignment ==="
rg -n 'self\._.*=.*or datetime' dddpy/domain/todo/entities/todo.py

echo -e "\n=== All datetime.now() usages with context ==="
rg -n -B2 -A2 'datetime\.now\(\)' dddpy/domain/todo/entities/todo.py

Repository: iktakahiro/dddpy

Length of output: 2784

---

Based on my verification, I can now provide a definitive assessment. The review comment references code from the PR branch (which includes the or datetime.now() pattern), while the current main branch shows simpler assignments. The search results confirm:

1. The or pattern fix is sound - The implementation correctly ensures runtime evaluation
2. The timezone concern is CRITICAL - The evidence decisively proves this is a real bug:
   • Docstring explicitly states timestamps should be "in UTC"
   • Infrastructure layer (todo_dto.py lines 42-44) explicitly converts to UTC with tz=timezone.utc
   • All datetime.now() calls return local time, not UTC
   • This causes data integrity issues

The original review appropriately flagged this as a concern, but the evidence confirms it's a critical pre-existing bug requiring UTC fixes, not just verification.

---

UTC timestamp bug requires immediate fixing with datetime.now(timezone.utc) or datetime.utcnow().

The infrastructure layer (lines 42-44 in todo_dto.py) explicitly converts timestamps to UTC: datetime.fromtimestamp(self.created_at / 1000, tz=timezone.utc). This proves the system requires UTC timestamps. However, all datetime.now() calls throughout the codebase (lines 33-34, 104, 113, 118, 130, 152) return local time, which will be stored and compared as UTC, causing data corruption in distributed systems or cross-timezone scenarios.

Replace datetime.now() with datetime.now(timezone.utc) in:

• Lines 33-34 (default parameters)
• Lines 104, 113, 118, 130 (update methods)
• Line 152 (is_overdue comparison)

Also update tests in tests/domain/todo/entities/test_todo.py lines 36-37.

🤖 Prompt for AI Agents

In dddpy/domain/todo/entities/todo.py around lines 52-53, the timestamps are set
with datetime.now() which yields local time; change these to use UTC by calling
datetime.now(timezone.utc) (ensure timezone is imported from datetime), and
propagate this UTC change to all other noted spots: replace datetime.now() with
datetime.now(timezone.utc) at the default-parameter lines (33-34), the update
methods (lines 104, 113, 118, 130), and the is_overdue comparison (line 152);
also update tests in tests/domain/todo/entities/test_todo.py (lines 36-37) to
expect UTC timestamps or construct expected datetimes using timezone.utc.