feat: reset_device() wait_for_output option — poll for boot output instead of returning immediately

[zackees]

Summary

SerialMonitor.reset_device() currently sends POST /api/reset and returns immediately. Add a wait_for_output option that watches for serial output after reset and returns as soon as the device starts producing data (= rebooted and running).

Current behavior

mon.reset_device(board="esp32s3")  # Returns True immediately after DTR toggle
time.sleep(3.0)  # Caller has to guess how long to wait

Proposed behavior

mon.reset_device(board="esp32s3", wait_for_output=True, timeout=5.0)
# Returns True as soon as any serial output is detected (device rebooted)
# Returns False if timeout expires with no output
# Typical ESP32-S3 USB-CDC: returns in <500ms instead of fixed 3s

Implementation

In crates/fbuild-python/src/lib.rs, after the HTTP reset call succeeds:

1. If wait_for_output is false (default): return immediately (current behavior)
2. If wait_for_output is true:
   • Attach a serial monitor to the port
   • Poll read_lines() in a tight loop (100ms intervals)
   • Return true as soon as any line is received
   • Return false if timeout expires

This is generic — no application-specific signatures needed. Any serial output = device booted.

API

#[pyo3(signature = (board=None, wait_for_output=false, timeout=5.0))]
fn reset_device(
    &self,
    board: Option<String>,
    wait_for_output: bool,
    timeout: f64,
) -> PyResult<bool>

Parent issue

FastLED/FastLED#2265 — replace sleep-based reset waits with spin-poll validation

[zackees]

Looks like this is already implemented in the current tree. The SerialMonitor.reset_device method at crates/fbuild-python/src/lib.rs already carries the exact signature and semantics proposed:

• #[pyo3(signature = (board=None, wait_for_output=false, timeout=5.0))]
• WebSocket fast path: when __enter__ has been called, polls read_lines_inner(0.2s) in a tight loop (reset_device lines 524–535) and returns true on the first non-empty batch.
• HTTP fallback: when no WebSocket session exists, polls /api/serial/output?port=...&limit=1 at 100ms intervals (reset_device lines 537–559).
• Honors timeout as a deadline and returns false if no output arrives in time.
• 300ms pause for USB re-enumeration after the DTR toggle (line 520), matching the proposed flow.

Closing.