Scheduler crashes with TypeError

[victorlin]

Snakemake version

Version 6.15.3 (latest available on bioconda)

Describe the bug

A specific workflow crashes with a TypeError stemming from the scheduler and its usage of pulp.lpSum.

• Running the workflow again picking up from where it left off, it will complete an additional step then fail with the same error.
• If I delete target files and start from scratch, it deterministically crashes at the same step.

Logs

[Tue Feb  8 20:19:42 2022]
Finished job 5.
16 of 32 steps (50%) done
Select jobs to execute...
Traceback (most recent call last):
  File "/opt/homebrew/Caskroom/miniconda/base/envs/conda-env-name/lib/python3.7/site-packages/snakemake/__init__.py", line 785, in snakemake
    keepmetadata=keep_metadata,
  File "/opt/homebrew/Caskroom/miniconda/base/envs/conda-env-name/lib/python3.7/site-packages/snakemake/workflow.py", line 1077, in execute
    success = self.scheduler.schedule()
  File "/opt/homebrew/Caskroom/miniconda/base/envs/conda-env-name/lib/python3.7/site-packages/snakemake/scheduler.py", line 491, in schedule
    run = self.job_selector(needrun)
  File "/opt/homebrew/Caskroom/miniconda/base/envs/conda-env-name/lib/python3.7/site-packages/snakemake/scheduler.py", line 740, in job_selector_ilp
    for job in jobs
  File "/opt/homebrew/Caskroom/miniconda/base/envs/conda-env-name/lib/python3.7/site-packages/pulp/pulp.py", line 2281, in lpSum
    return LpAffineExpression().addInPlace(vector)
  File "/opt/homebrew/Caskroom/miniconda/base/envs/conda-env-name/lib/python3.7/site-packages/pulp/pulp.py", line 897, in addInPlace
    self.addInPlace(e)
  File "/opt/homebrew/Caskroom/miniconda/base/envs/conda-env-name/lib/python3.7/site-packages/pulp/pulp.py", line 889, in addInPlace
    self.constant += other.constant
TypeError: unsupported operand type(s) for +=: 'int' and 'str'

Looks like something here is mixing int and str:

snakemake/snakemake/scheduler.py

Lines 737 to 742 in 41a5071

	lpSum(
	[
	scheduled_jobs[job] * job.resources.get(name, 0)
	for job in jobs
	]
	)

Minimal example

Unfortunately, I am only able to reproduce this with a private workflow. However, see additional context below.

Additional context

The same workflow runs successfully with Snakemake versions 5.x.

I spot-checked several versions of Snakemake, and determined that the bug was introduced somewhere between 6.4.1 (runs fine) and 6.5.3 (crashes). I am unable to run this workflow on 6.5.0-6.5.2 due to #1069 which was fixed in 6.5.3. Could this be related?

Here's the diff between 6.4.1 and 6.5.3, in case it's handy: v6.4.1...v6.5.3

[johanneskoester]

Good catch. A part of the fixed has been done in #1552. The other part comes in #1556.

[johanneskoester]

Thanks for reporting!