ib: more detailed comments on wait-for-quote-task todo

piker/brokers/ib/feed.py

@@ -816,7 +816,10 @@ async def stream_quotes(
     proxy: MethodProxy
     mkt: MktPair
     details: ibis.ContractDetails
-    async with open_data_client() as proxy:
+    async with (
+        open_data_client() as proxy,
+        trio.open_nursery() as tn,
+    ):
         mkt, details = await get_mkt_info(
             sym,
             proxy=proxy,  # passed to avoid implicit client load
@@ -844,18 +847,32 @@ async def stream_quotes(
                 f'{pformat(first_quote)}'
             )
 
-        # TODO: we should instead spawn a task that waits on a feed to start
-        # and let it wait indefinitely..instead of this hard coded stuff.
+        # TODO: we should instead spawn a task that waits on a feed
+        # to start and let it wait indefinitely..instead of this
+        # hard coded stuff.
+        # async def wait_for_first_quote():
+        #     with trio.CancelScope() as cs:
+
         with trio.move_on_after(1):
             first_ticker = await proxy.get_quote(
                 contract=con,
                 raise_on_timeout=True,
             )
 
-        # it might be outside regular trading hours so see if we can at
-        # least grab history.
+        # NOTE: it might be outside regular trading hours for
+        # assets with "standard venue operating hours" so we
+        # only "pretend the feed is live" when the dst asset
+        # type is NOT within the NON-NORMAL-venue set: aka not
+        # commodities, forex or crypto currencies which CAN
+        # always return a NaN on a snap quote request during
+        # normal venue hours. In the case of a closed venue
+        # (equitiies, futes, bonds etc.) we at least try to
+        # grab the OHLC history.
         if (
-            isnan(first_ticker.last)  # last quote price value is nan
+            isnan(first_ticker.last)
+            # SO, if the last quote price value is NaN we ONLY
+            # "pretend to do" `feed_is_live.set()` if it's a known
+            # dst asset venue with a lot of closed operating hours.
             and mkt.dst.atype not in {
                 'commodity',
                 'fiat',
@@ -895,7 +912,7 @@ async def stream_quotes(
 
                     # only on first entry at feed boot up
                     if startup:
-                        startup = False
+                        startup: bool = False
                         task_status.started((
                             init_msgs,
                             first_quote,
@@ -923,7 +940,7 @@ async def stream_quotes(
 
                             # generally speaking these feeds don't
                             # include vlm data.
-                            atype = mkt.dst.atype
+                            atype: str = mkt.dst.atype
                             log.info(
                                 f'No-vlm {mkt.fqme}@{atype}, skipping quote poll'
                             )
@@ -959,7 +976,8 @@ async def stream_quotes(
                             quote = normalize(ticker)
                             log.debug(f"First ticker received {quote}")
 
-                        # tell caller quotes are now coming in live
+                        # tell data-layer spawner-caller that live
+                        # quotes are now streaming.
                         feed_is_live.set()
 
                         # last = time.time()