diff --git a/my/core/common.py b/my/core/common.py
index 10599f5..0c7571e 100644
--- a/my/core/common.py
+++ b/my/core/common.py
@@ -130,6 +130,11 @@ def get_files(pp: Paths, glob: str=DEFAULT_GLOB, sort: bool=True) -> Tuple[Path,
     else:
         sources.extend(map(Path, pp))
 
+    def caller() -> str:
+        import traceback
+        # TODO ugh. very flaky... -3 because [<this function>, get_files(), <actual caller>]
+        return traceback.extract_stack()[-3].filename
+
     paths: List[Path] = []
     for src in sources:
         if src.parts[0] == '~':
@@ -141,7 +146,7 @@ def get_files(pp: Paths, glob: str=DEFAULT_GLOB, sort: bool=True) -> Tuple[Path,
             ss = str(src)
             if '*' in ss:
                 if glob != DEFAULT_GLOB:
-                    warnings.warn(f"Treating {ss} as glob path. Explicit glob={glob} argument is ignored!")
+                    warnings.warn(f"{caller()}: treating {ss} as glob path. Explicit glob={glob} argument is ignored!")
                 paths.extend(map(Path, do_glob(ss)))
             else:
                 if not src.is_file():
@@ -154,8 +159,10 @@ def get_files(pp: Paths, glob: str=DEFAULT_GLOB, sort: bool=True) -> Tuple[Path,
 
     if len(paths) == 0:
         # todo make it conditionally defensive based on some global settings
-        # todo stacktrace?
-        warnings.warn(f'No paths were matched against {paths}. This might result in missing data.')
+        # TODO not sure about using warnings module for this
+        import traceback
+        warnings.warn(f'{caller()}: no paths were matched against {paths}. This might result in missing data.')
+        traceback.print_stack()
 
     return tuple(paths)
 
@@ -274,13 +281,13 @@ from typing import Generic, Sized, Callable
 
 
 # X = TypeVar('X')
-def _warn_iterator(it):
+def _warn_iterator(it, f: Any=None):
     emitted = False
     for i in it:
         yield i
         emitted = True
     if not emitted:
-        warnings.warn(f"Function hasn't emitted any data, make sure your config paths are correct")
+        warnings.warn(f"Function {f} didn't emit any data, make sure your config paths are correct")
 
 
 # TODO ugh, so I want to express something like:
@@ -294,17 +301,17 @@ def _warn_iterator(it):
 from typing import overload
 X = TypeVar('X')
 @overload
-def _warn_iterable(it: List[X]    ) -> List[X]    : ...
+def _warn_iterable(it: List[X]    , f: Any=None) -> List[X]    : ...
 @overload
-def _warn_iterable(it: Iterable[X]) -> Iterable[X]: ...
-def _warn_iterable(it):
+def _warn_iterable(it: Iterable[X], f: Any=None) -> Iterable[X]: ...
+def _warn_iterable(it, f=None):
     if isinstance(it, Sized):
         sz = len(it)
         if sz == 0:
-            warnings.warn(f"Function is returning empty container, make sure your config paths are correct")
-        return it # type: ignore[return-value]
+            warnings.warn(f"Function {f} returned empty container, make sure your config paths are correct")
+        return it
     else:
-        return _warn_iterator(it)
+        return _warn_iterator(it, f=f)
 
 
 @overload
@@ -316,5 +323,5 @@ def warn_if_empty(f):
     @wraps(f)
     def wrapped(*args, **kwargs):
         res = f(*args, **kwargs)
-        return _warn_iterable(res)
+        return _warn_iterable(res, f=f)
     return wrapped
diff --git a/my/rss/all.py b/my/rss/all.py
index 90f5efa..61f9fab 100644
--- a/my/rss/all.py
+++ b/my/rss/all.py
@@ -1,11 +1,16 @@
 '''
 Unified RSS data, merged from different services I used historically
 '''
+# NOTE: you can comment out the sources you're not using
+from . import feedbin, feedly
+
 from typing import Iterable
 from .common import Subscription, compute_subscriptions
 
 
 def subscriptions() -> Iterable[Subscription]:
-    from . import feedbin, feedly
     # TODO google reader?
-    yield from compute_subscriptions(feedbin.states(), feedly.states())
+    yield from compute_subscriptions(
+        feedbin.states(),
+        feedly .states(),
+    )
diff --git a/my/rss/common.py b/my/rss/common.py
index 3dc761c..9aa5ed8 100644
--- a/my/rss/common.py
+++ b/my/rss/common.py
@@ -17,6 +17,8 @@ from typing import Iterable, Tuple, Sequence
 SubscriptionState = Tuple[datetime, Sequence[Subscription]]
 
 
+from ..core import warn_if_empty
+@warn_if_empty
 def compute_subscriptions(*sources: Iterable[SubscriptionState]) -> List[Subscription]:
     """
     Keeps track of everything I ever subscribed to.
@@ -34,6 +36,9 @@ def compute_subscriptions(*sources: Iterable[SubscriptionState]) -> List[Subscri
             if feed.url not in by_url:
                 by_url[feed.url] = feed
 
+    if len(states) == 0:
+        return []
+
     _, last_state = max(states, key=lambda x: x[0])
     last_urls = {f.url for f in last_state}
 
diff --git a/my/twitter/all.py b/my/twitter/all.py
index acb59a2..5c8103c 100644
--- a/my/twitter/all.py
+++ b/my/twitter/all.py
@@ -3,11 +3,9 @@ Unified Twitter data (merged from the archive and periodic updates)
 """
 
 # NOTE: you can comment out the sources you don't need
-
-
 from . import twint, archive
-from .common import merge_tweets
 
+from .common import merge_tweets
 
 def tweets():
     yield from merge_tweets(
@@ -15,6 +13,7 @@ def tweets():
         archive.tweets(),
     )
 
+from .common import merge_tweets
 
 def likes():
     yield from merge_tweets(
diff --git a/my/twitter/common.py b/my/twitter/common.py
index 1bf36f0..ecfaea3 100644
--- a/my/twitter/common.py
+++ b/my/twitter/common.py
@@ -2,7 +2,9 @@ from itertools import chain
 
 from more_itertools import unique_everseen
 
+from ..core import warn_if_empty
 
+@warn_if_empty
 def merge_tweets(*sources):
     yield from unique_everseen(
         chain(*sources),