Error using a period within Cylc cyling task names

[jwarner8]

Describe the bug

Many recipes involving looping over variables or model levels to produce numerous plots. If we are iterating over values that include periods, etc. model half levels [0.5,1.5,2.5], parsing these values and creating a unique tasks in the Cylc workflow causes an error and the workflow fails to validate. This is because tasks would be named, for example, plot_[var]_[modellev] would become plot_airtempertaure_0.5.

A possible solution for floats would be to parse '.' as 'p', etc. 0.5 -> 0p5. I can't think of any cases where variable names would involve periods,

How to reproduce

Steps to reproduce the behaviour:

Expected behaviour

Environment

• Version: [e.g. from cset --version]
• Browser (if UI issue): [e.g. Chrome, Firefox]

[jwarner8]

Testing solution which uses jinja2 parsing, etc.
{% set level = 1.2 %}
{% set formatted_level = level|string|replace('.', 'p') %}

[jfrost-mo]

One of my questions for the cylc surgery this afternoon is what characters are allowed in task names. After that, replacing invalid characters sounds like a sensible plan.

[jfrost-mo]

The allowed task names are documented here: https://cylc.github.io/cylc-doc/stable/html/user-guide/writing-workflows/runtime.html#cylc.flow.unicode_rules.TaskNameValidator