PFC storm stop on arista fanout: use if else semantics to prevent command trailing

[wendani]

The conditional jinja2 template causes the next command in the next line to be piggy-backed at the end of the preceding command, causing a syntax error to run the command

sudo pkill -f "sudo python pfc_gen.py -p 16 -t 65535 -n 100000000 -i et16 -r 10.3.147.195" exit

Signed-off-by: Wenda Ni [email protected]

Description of PR

Summary:
Fixes # (issue)

Type of change

• [*] Bug fix
• [] Testbed and Framework(new/improvement)
• [] Test case(new/improvement)

Approach

How did you do it?

How did you verify/test it?

Any platform specific information?

Supported testbed topology if it's a new test case?

Documentation

[qiluo-msft]

Seems a Jinja2 syntax error, why change behavior. Did you try raw or other escaping method?

[jleveque]

It seems like Jinja2 is not adding the newline after the conditional. Have you tried forcing the trailing newline to be added by adding a plus sign to the final endif: {% endif +%}?

Nevermind. The plus sign can only be added to the leading percent sign, and will disable 'lstrip_blocks'. It doesn't affect whitespace like the minus sign does :(

[jleveque]

Here's someone with a similar issue: ansible/ansible#32220

The suggested solution may not apply here because in one case we want to add the &, otherwise we don't want to add anything. There must be a way to do that...

[jleveque]

@wendani: Did you try a solution similar to the example I linked above? Maybe something like the following will work?

{{ '&' if pfc_storm_stop_defer_time is defined else '' }}