New CSV reading fails when there are no draws

[WardBrian]

For some testing, @bob-carpenter is running Stan with iter_sampling=0 and save_warmup=false, meaning the only input he reads is comments.

This is a bit esoteric, but it did work in previous versions, and is broken following #799

There are two places it breaks:

• in stancsv.csv_bytes_list_to_numpy, we throw an error if the size is 0
• the assignment to self._draws[:, chain, :] in assemble_draws fails if the output is size 0

cc @amas0

[amas0]

Thanks for flagging -- I'll add a test for this edge case and submit a bugfix.

…

On Wed, Aug 6, 2025 at 12:41 PM Brian Ward ***@***.***> wrote: *WardBrian* created an issue (stan-dev/cmdstanpy#800) <#800> For some testing, @bob-carpenter <https://github.com/bob-carpenter> is running Stan with iter_sampling=0 and save_warmup=false, meaning the only input he reads is comments. This is a bit esoteric, but it did work in previous versions, and is broken following #799 <#799> There are two places it breaks: - in stancsv.csv_bytes_list_to_numpy, we throw an error if the size is 0 - the assignment to self._draws[:, chain, :] in assemble_draws fails if the output is size 0 cc @amas0 <https://github.com/amas0> — Reply to this email directly, view it on GitHub <#800>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AB3SOHZDP7Z5NGM2NVZYJN33MIV3BAVCNFSM6AAAAACDIQ25YOVHI2DSMVQWIX3LMV43ASLTON2WKOZTGI4TOMZVHE3DCMI> . You are receiving this because you were mentioned.Message ID: ***@***.***>