Previewing Puppet ERB Files with JSON Datasource from Commandline

bosun.toml.erb

<%- if @hostname -%>Hostname = "<%= @hostname %>"
<%- end -%><%- if @httplisten -%>HTTPListen = "<%= @httplisten %>"
<%- end -%><%- if @httpslisten -%>HTTPSListen = "<%= @httpslisten %>"
<%- end -%><%- if @tlscertfile -%>TLSCertFile = "<%= @tlscertfile %>"
<%- end -%><%- if @tlskeyfile -%>TLSKeyFile = "<%= @tlskeyfile %>"
<%- end -%><%- if @timeanddate.any? -%>TimeAndDate = [<% @timeanddate.each_with_index do |v,i| -%><%- if i>0 -%>, <%- end -%><%= v %><% end -%>]
<%- end -%><%- if @shorturlkey -%>ShortURLKey = "<%= @shorturlkey %>"
<%- end -%><%- if @commandhookpath -%>CommandHookPath = "<%= @commandhookpath %>"
<%- end -%><%- if @rulefilepath -%>RuleFilePath = "<%= @rulefilepath %>"
<%- end -%><%- if @checkfrequency -%>CheckFrequency = "<%= @checkfrequency %>"
<%- end -%><%- if @defaultrunevery -%>DefaultRunEvery = <%= @defaultrunevery %>
<%- end -%>EnableSave = <%= @enablesave %>
EnableReload = true
Ping = <%= @ping %>
<%- if @opentsdb.any? -%>
[OpenTSDBConf]
    Host = "<%= @opentsdb['host'] %>"
    Version = <%= @opentsdb['version'] %>
    ResponseLimit = <%= @opentsdb['responselimit'] %>
<%- end -%><%- if @elastic.any? -%>
[ElasticConf]
    Hosts = [<% @elastic['hosts'].each_with_index do |v,i| -%><%- if i>0 -%>, <%- end -%>"<%= v %>"<% end -%>]
<%- end -%><%- if @db -%>
[DBConf]
    RedisHost = "<%= @db['redishost'] %>"
<% end -%><%- if @smtp.any? -%>
[SMTPConf]
    EmailFrom = "<%= @smtp['from'] %>"
    Host = "<%= @smtp['host'] %>"
<% end -%><%- if @annotate.any? -%>
[AnnotateConf]
    Hosts = [<% @annotate['hosts'].each_with_index do |v,i| -%><%- if i>0 -%>, <%- end -%>"<%= v %>"<% end -%>]
<% end -%><%- if @auth.any? -%>
[AuthConf]
    AuthDisabled = <%= @auth['disabled'] %>
    TokenSecret = "<%= @auth['tokensecret'] %>"
    CookieSecret = "<%= @auth['cookiesecret'] %>"
    [AuthConf.LDAP]
      Domain = "<%= @auth['domain'] %>"
      LdapArr = "<%= @auth['ldapaddr'] %>"
      DefaultPermission = "<%= @auth['defaultpermission'] %>"
      RootSearchPath = "<%= @auth['rootsearchpath'] %>"
      <%- @auth['ldapgroups'].each do |v| -%>
      [[ AuthConf.LDAP.Groups ]]
        Path = "<%= v['path'] %>"
        Role = "<%= v['role']%>" <% end -%>

<% end -%>

bosun.toml.sample_varts.rb

require 'json'

auth = %q(
{
    "disabled": false,
    "tokensecret": "shhhh",
    "cookiesecret": "alsoShhh",
    "domain": "STACKEXCHANGE",
    "ldapaddr": "ds.stackexchange.com:3269",
    "defaultpermission": "Reader",
    "rootsearchpath": "DC=ds,DC=stackexchange,DC=com",
    "ldapgroups": [
        {
            "path": "CN=Developers,OU=Security Groups,DC=ds,DC=stackexchange,DC=com",
            "role": "Writer"
        }
    ]
}
)

@auth = JSON.parse(auth)
@opentsdb = {}
@elastic = {}
@db = {}
@timeanddate = []
@smtp = {}
@annotate = {}

Overview

Based on the idea in this SO answer: http://stackoverflow.com/a/30037886/107156

1) Create a ruby file to contain the variables
2) when running erb, important that file as a library

Notes:
- The .rb file must have all variables that you call methods on (i.e. `any?`) or you will get a nilClass error.

- The switch to -r doesn't have the .rb extension on it, but the file does

The command is:
```
$ erb -r './bosun.toml.sample_vars' -T '-' bosun.toml.erb
EnableSave =
EnableReload = true
Ping =
[DBConf]
    RedisHost = ""
[AuthConf]
    AuthDisabled = false
    TokenSecret = "shhhh"
    CookieSecret = "alsoShhh"
    [AuthConf.LDAP]
      Domain = "STACKEXCHANGE"
      LdapArr = "ds.stackexchange.com:3269"
      DefaultPermission = "Reader"
      RootSearchPath = "DC=ds,DC=stackexchange,DC=com"
      [[ AuthConf.LDAP.Groups ]]
        Path = "CN=Developers,OU=Security Groups,DC=ds,DC=stackexchange,DC=com"
        Role = "Writer"
```