Sequence broken in 2.5-rc10

[salanki]

Checklist:

• I've included the version.
• I've included reproduction steps.
• I've included the workflow YAML.
• I've included the logs.

What happened:

Running the standard loop-sequence example: https://github.com/argoproj/argo/blob/master/examples/loops-sequence.yaml leads to only 0s being printed.

argo logs -w -f loops-sequence-whtdr
sequence-start-end(4:0):	0
sequence-count(1:0):	0
sequence-count(3:0):	0
sequence-count(0:0):	0
sequence-start-end(3:0):	0
sequence-negative(2:0):	0
sequence-count(2:0):	0
sequence-start-end(2:0):	0
sequence-start-end(1:0):	0
sequence-param(1:0):	0
sequence-start-end(0:0):	0
sequence-negative(0:0):	0
sequence-count(4:0):	0
sequence-negative(1:0):	0
sequence-negative(3:0):	0
sequence-format(3:0):	0
sequence-negative(5:0):	0
sequence-param(2:0):	0
sequence-param(0:0):	0
sequence-format(4:0):	0
sequence-negative(4:0):	0
sequence-start-end(5:0):	0
sequence-format(1:0):	0
sequence-format(0:0):	0
sequence-format(2:0):	0

What you expected to happen:

A sequence of numbers should be printed. None of them should be 0.

How to reproduce it (as minimally and precisely as possible):

wget https://github.com/argoproj/argo/blob/7864ad36788dc78d035d59ddb27ecd979f7216f4/examples/loops-sequence.yaml
argo submit loops-sequence.yaml

Anything else we need to know?:
One of the commits touching item is: CodecLondon@14c004f. Could possibly be a culprit?

It is weird that no tests have caught this. Perhaps no test actually covers the full path to what is rendered as item.

Environment:
Argo version: 2.5.0-rc10

• Kubernetes version :

Client Version: version.Info{Major:"1", Minor:"16", GitVersion:"v1.16.1", GitCommit:"d647ddbd755faf07169599a625faf302ffc34458", GitTreeState:"clean", BuildDate:"2019-10-02T23:49:20Z", GoVersion:"go1.12.9", Compiler:"gc", Platform:"darwin/amd64"}
Server Version: version.Info{Major:"1", Minor:"16", GitVersion:"v1.16.2", GitCommit:"c97fe5036ef3df2967d086711e6c0c405941e14b", GitTreeState:"clean", BuildDate:"2019-10-15T19:09:08Z", GoVersion:"go1.12.10", Compiler:"gc", Platform:"linux/amd64"}

Other debugging information (if applicable):

• workflow result:

argo get <workflowname>

• executor logs:

kubectl logs <failedpodname> -c init
kubectl logs <failedpodname> -c wait

• workflow-controller logs:

kubectl logs -n argo $(kubectl get pods -l app=workflow-controller -n argo -o name)

Logs

argo get <workflowname>
kubectl logs <failedpodname> -c init
kubectl logs <failedpodname> -c wait
kubectl logs -n argo $(kubectl get pods -l app=workflow-controller -n argo -o name)

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Message from the maintainers:

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[alexec]

@mark9white investigating.