ValueError: No objects to concatenate

[staff0rd]

After running nostalgia I can successfully get a result from;

from nostalgia.sources.reddit_posts import RedditPosts
posts = RedditPosts.load()

However, running timeline and browsing fails with this;

nostalgia_timeline | Traceback (most recent call last):
nostalgia_timeline |   File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 2463, in __call__
nostalgia_timeline |     return self.wsgi_app(environ, start_response)
nostalgia_timeline |   File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 2449, in wsgi_app
nostalgia_timeline |     response = self.handle_exception(e)
nostalgia_timeline |   File "/usr/local/lib/python3.8/site-packages/flask_cors/extension.py", line 161, in wrapped_function
nostalgia_timeline |     return cors_after_request(app.make_response(f(*args, **kwargs)))
nostalgia_timeline |   File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 1866, in handle_exception
nostalgia_timeline |     reraise(exc_type, exc_value, tb)
nostalgia_timeline |   File "/usr/local/lib/python3.8/site-packages/flask/_compat.py", line 39, in reraise
nostalgia_timeline |     raise value
nostalgia_timeline |   File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 2446, in wsgi_app
nostalgia_timeline |     response = self.full_dispatch_request()
nostalgia_timeline |   File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 1951, in full_dispatch_request
nostalgia_timeline |     rv = self.handle_user_exception(e)
nostalgia_timeline |   File "/usr/local/lib/python3.8/site-packages/flask_cors/extension.py", line 161, in wrapped_function
nostalgia_timeline |     return cors_after_request(app.make_response(f(*args, **kwargs)))
nostalgia_timeline |   File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 1820, in handle_user_exception
nostalgia_timeline |     reraise(exc_type, exc_value, tb)
nostalgia_timeline |   File "/usr/local/lib/python3.8/site-packages/flask/_compat.py", line 39, in reraise
nostalgia_timeline |     raise value
nostalgia_timeline |   File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 1949, in full_dispatch_request
nostalgia_timeline |     rv = self.dispatch_request()
nostalgia_timeline |   File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 1935, in dispatch_request
nostalgia_timeline |     return self.view_functions[rule.endpoint](**req.view_args)
nostalgia_timeline |   File "/nostalgia_timeline/timeline.py", line 59, in root
nostalgia_timeline |     res = Results.merge(*[v for k, v in registry.items() if v.df_name != "results"])
nostalgia_timeline |   File "/usr/local/lib/python3.8/site-packages/nostalgia/ndf.py", line 736, in merge
nostalgia_timeline |     data = pd.concat([x.as_simple(max_n) for x in dfs])
nostalgia_timeline |   File "/usr/local/lib/python3.8/site-packages/pandas/core/reshape/concat.py", line 271, in concat
nostalgia_timeline |     op = _Concatenator(
nostalgia_timeline |   File "/usr/local/lib/python3.8/site-packages/pandas/core/reshape/concat.py", line 329, in __init__
nostalgia_timeline |     raise ValueError("No objects to concatenate")
nostalgia_timeline | ValueError: No objects to concatenate

My nostalgia_entry.py

# File contents of ~/nostalgia_data/nostalgia_entry.py below
from nostalgia.sources.reddit_posts import RedditPosts
reddit_posts = RedditPosts.register()

[staff0rd]

This is due to empty nostalgia_entry.py and no data.

[kootenpv]

As per your own suggestion, we should probably throw a

ValueError("No data found in nostalgia_entry, have you ingested sources?") in core

then catch it here and display it.