Previously the `quotesEscape` function was escaping only double quotes.
This wasn't enough, since the input string could contain other special chars,
which must be escaped when put inside JSON string. For example, carriage return and line feed chars (\n\r),
backslash char, etc. This led to the following issues, which were improperly fixed:
- https://github.com/VictoriaMetrics/VictoriaMetrics/issues/890 - this issue
was "fixed" by introducing the `crlfEscape` function, which led to unnecessary
complications in user templates, while not fixing various corner cases
such as backslash chars in the input string.
See 1de15ad490
- https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3139 - this issue
was "fixed" by urlencoding the whole string passed to -external.alert.source
command-line flag. This led to invalid urls, which couldn't be parsed by Grafana.
See 00c838353d
and 4bd0244599
This commit properly encodes the input string passed to `quotesEscape`, so it can be safely embedded inside JSON strings.
This commit deprecates crlfEscape template function and adds the following new template functions:
- strvalue and stripDomain - these functions are supported by Prometheus, so they were added
for compatibility purposes.
- jsonEscape and htmlEscape for converting the input string to valid quoted JSON string
and for html-escaping the input string, so it could be safely embedded as a plaintext
into html.
This commit also documents all supported template functions at https://docs.victoriametrics.com/vmalert.html#template-functions
The deprecated crlfEscape function isn't documented on purpose, since its usefulness is negative in general case.
