Snakemake + Docker Volumes - "Missing Rule Exception" - docker

Question

I'm trying to use snakemake with a docker image, but am having trouble with the docker volume. Unfortunately, there are no details on how to use 'singularity-args' to do this.
My snakemake file is:
rule all:
input:
'a/file3.txt'
rule step1:
output:
touch('a/file1.txt')
rule step2:
input:
rules.step1.output[0]
output:
'a/file2.txt'
params:
text = 'this is a test',
path = '/data/file2.txt'
singularity:
"docker://XXX/test"
shell:
"python test.py {params.text} {params.path}"
rule step3:
input:
rules.step2.output[0]
output:
touch('a/file3.txt')
The docker image is basically a python file that writes a string to file (for testing purposes). I'm trying to mount my home directory to the docker /data directory. With docker, I'm able to mount a volume using '-v'.
What is the correct way of doing this with snakemake?
I've tried the following commands (on MacOS and Ubuntu 18.04) and both have failed.
snakemake -s pipeline.py --use-singularity --singularity-args “-B /home/XXX/snakemake/a:/data”
snakemake -s pipeline.py --use-singularity --singularity-args “-B /home/XXX/snakemake/a”
The error message is:
No rule to produce /home/XXX/snakemake/a:/data” (if you use input functions make sure that they don't raise unexpected exceptions).
Am I missing a step?
Thanks in advance!

Answer 1

Just a trivial check... In your command lines you have tilted double quotes (“) instead of the straight ones ("), e.g.:
snakemake -s pipeline.py --use-singularity --singularity-args “-B /home/XXX/snakemake/a”
Maybe you are are copying and pasting from a text editor that uses the tilted quotes? I would use straight quotes as the other type would probably be interpreted in the wrong way.

Answer 2

I was able to get it working on Ubuntu 18.04 with the following command:
SINGULARITY_BINDPATH=“/home/XXX/snakemake/a:/data”; snakemake -s pipeline.py --latency-wait 10 --use-singularity
Unfortunately I wasn’t able to get the flag “--singularity-args” to work. Regardless of using ‘--bind’ or ‘-B’, I got the error “No rule to produce /Users/XXX/Devel/snakemake/a:/data”.
I’m using Snakemake 5.6.0 inside a Python3 virtual environment.
Also, on a side note, I don’t believe the MacOS singularity binary works. It had issues with Snakemake.
This work-around is good enough for now.
UPDATE
While this solution worked, the real solution (typo) was provided by #dariober.