Variables defined in environment cannot have trailing spaces

[ColemanTom]

Describe the bug

If you define a variable like follows, the result in the job script is _="". I would expect it to be _=" ".

[environment]
    _ = " "

I posted this in the Cylc discourse

NOTE: Depending on what you are doing, you could work around it by defining _ = " \0", but that isn't ok in all situations (it was in mine).

Release version(s) and/or repository branch(es) affected?

7.8.4

Steps to reproduce the bug

Create a suite and add _ = " " to the environment section for any task.

Expected behavior

Resultant job script to have _=" "

Screenshots

N/A

Additional context

Not a common need, but it should be allowed.

[oliver-sanders]

This whitespace stripping is a parsec feature (the configuration file parser Cylc uses), I believe it is applied to all settings.

I don't think we can change this as a large number of workflows are relying on this behaviour to strip arbitrary whitespace from environment variables.

This is also used to allow environment variable definitions (which may be sub-shells including line breaks) to be written over multiple lines e.g:

[environment]
    FOO = """
        bar
    """

[ColemanTom]

It would only be if the variable is enclosed in quotes, like in my example that I think it would make sense. In my view, if you have trailing spaces and have intentionally put double or single quotes around it, it must be intentional.

[hjoliver]

I don't think we can change this as a large number of workflows are relying on this behaviour to strip arbitrary whitespace from environment variables.

Presumably you mean this sort of thing (using "_" to mean whitespace):

DRINK =___beer________

where the value should end up as beer (no spaces).

I think it's not so difficult because we can distinguish quoted/unquoted single-line values, and multi-line (triple-quoted) values. The space inside quoted values is actually not stripped until the final validation stage. I'll put up a small PR for consideration...

I'll post a small PR for consideration.

[oliver-sanders]

TLDR; The current pattern of stripping leading/trailing whitespace from env vars goes back a long way, we now have a substantial body of workflows which have grown into this pattern, for several of them, changing tack now would result in breaking changes.

https://github.com/cylc/cylc-flow/pull/5085#issuecomment-1637809624

Removing the bug label as this is an intentional design choice (will try do do a better job of documenting this).

The workarounds are:

• Use escape characters where possible.
• Refactor script logic.
• Set the environment variable within a *script setting.

Leaving this issue open for now, should close going forward unless there is further demand for this functionality.