Hi. I've been asked to look into an issue of making JSON notifications (for instance to POST JSON to PD on an incident ack, etc.). My understanding is that composing JSON using a text template engine is inherently incorrect: it is clumsy and error-prone.

From this pull request #2135 and @kylebrandt's comment I see that there is an effort to improve the situation. There are three helpers makeSlice, makeMap and | json that could be used to assemble and serialise a data structure and avoid dealing with JSON encoding issues. Yet they don't seem to quite cut it.

One issue in particular is related to a complex data structure provided to, say, actionBodyAck and limited capabilites of Go's text/template package: how to traverse multi-dimensional data? .States is an array, so I presume multiple accidents may be acknowledged at once. Here is where I fail to come up with an appropriate way to get IDs across all .States items.

I can think of two potential enhancements.

1. Keep composing JSON by hand as text, but provide with a JSON escaping helper that would be a middle ground between built-in js and Bosun's json. It would encode given values (both scalar and structures) in such a way that it can be always safely used in place of an object field value:

jsonBody = `{
  "key": {{ V "$key" | json_val }},
  "accident_nr": {{ len .States | json_val }},
  "accident_ids": [ {{ range .States }}{{ .Id }},{{ end }} ],
  "summary": {{ .Subject | json_val }}
}
`

2. Provide templates with another helper that could help querying data, return it in a structured way which then can be serialised with json. Something alike jq. For example:

jsonBody = `
  {{- $accident_nr := len .States -}}
  {{- makeMap "key" (V "$key") "accident_nr" $accident_nr "summary" .Subject "accident_ids" (jq "[.States[].Id]") | json -}}
`

I would be glad to hear what's your vision on improving support for JSON notifications? Thanks.