Alert rule validation does not accept valid templates II

[kfindeisen]

Chronograf version: 1.7.15
Installation method: built from source
Related issues: #5090, #5137
Related PRs: #5228

This is a re-opening of #5137, which was reported fixed in 1.7.13 through #5228.

As of Chronograf 1.7.15 I still see the old behavior: the alert builder GUI rejects messages with valid Go templates such as:

CI ID = {{ with (index .Tags "ci_id") }}{{ . }}{{ else }}Unknown{{ end }}

CI ID = {{ if (index .Tags "ci_id") }}{{ index .Tags "ci_id" }}{{ else -}} Unknown {{ end }}

# of Tags = {{ len .Tags }}

The messages pass validation if one removes {{ . }}, -, and len, respectively. The validator's aversion to {{- and -}} is a bit harder to reproduce than the other two; - tends to be accepted in simple expressions but rejected in complex ones.

In none of the above examples do I see the parse error added in #5228; all triggering strings return "Please correct templates in alert message." I do see the parse error if I reproduce the demo from #5228 (i.e., closing with } instead of }}), confirming that I'm using the new code at least some of the time.

[russorat]

@kfindeisen thanks for opening. we will take a look. this code seems to keep causing us issues, so many we should just remove the template validation altogether.