fix: _KeyRotator index bounds check

[fan-67]

[Bug] _KeyRotator IndexError when key list shrinks

What

_KeyRotator.get() in astrbot/core/tools/web_search_tools.py raises IndexError when the configured key list has fewer entries than the internal index counter expects.

Same bug affects all four rotators: _TAVILY_KEY_ROTATOR, _BOCHA_KEY_ROTATOR, _BRAVE_KEY_ROTATOR, _FIRECRAWL_KEY_ROTATOR.

Why

_KeyRotator is a module-level singleton. self.index persists across calls but only resets on bot restart. If someone configures 2 keys (index advances to 1), then later removes one (1 key left), the if not keys guard passes but keys[self.index] still blows up.

Fix

One-line bounds check before accessing keys[self.index]:

async with self.lock:
    if self.index >= len(keys):
        self.index = 0
    key = keys[self.index]
    ...

Tested

• index=1, keys=["a"] → was IndexError, now returns "a" and resets index to 0
• Normal rotation with 2 keys still works correctly
• Single key with index=0 unchanged

Closes #9039

Summary by Sourcery

Bug Fixes:

• Prevent IndexError in key rotator when the internal index exceeds the current number of configured keys.

[gemini-code-assist]

Code Review

This pull request introduces a bounds check on self.index before accessing the keys list to prevent potential out-of-bounds errors. The reviewer pointed out that the async with self.lock: block is redundant because the synchronous code within it executes atomically in a single-threaded asyncio event loop, and suggested removing the lock to simplify the code and avoid unnecessary overhead.

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[gemini-code-assist]

In a single-threaded asyncio event loop, synchronous code blocks (those without any await statements) are executed atomically and will not be interrupted by other coroutines. Therefore, the async with self.lock: block is redundant and can be safely removed to simplify the code and avoid unnecessary locking overhead.

        if self.index >= len(keys):
            self.index = 0
        key = keys[self.index]
        self.index = (self.index + 1) % len(keys)
        return key

References

1. In a single-threaded asyncio event loop, synchronous functions (code blocks without 'await') are executed atomically and will not be interrupted by other coroutines. Therefore, they are safe from race conditions when modifying shared state within that block.

[sourcery-ai]

Hey - I've reviewed your changes and they look great!

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