mikesimons / erbmash Goto Github PK

Guarding against nil is a bit of a PITA.
Consider:

@data['items'].each ...

If @data is empty or @data['items'] is not set you get template errors.
To make these optional you need to do...

((@data || {})['items'] || {})

... which is obviously horrendous.

In some cases the error may be desirable to protect output integrity but an optional --maybe-data flag or some way of accessing the data optionally could be handy.

Would be useful to be able to override / provide additional parameters that are merged in to @data from the command line.

e.g. data.yaml

item1:
  sub_item1: x
item2:
  sub_item2: y

templateer --data item1.sub_item2=z data.yml -

would yield @data:

item1:
  sub_item1: x
  sub_item2: z
item2:
  sub_item2: y

Need to consider the following scenarios:
--data some_bool=true should be Boolean, not the string true.
--data some_int=1 should be Numeric, not the string 1
--data some_array[]=append should append the string append to some_array
--data some_array=[1,2,3] should be an Array type containing Numeric types 1, 2 & 3

Where templateer is operating on a subset of a larger configuration file it may be handy to be able to change where in the tree @data is from.

Consider data.yaml

metadata:
  somestuff: hello

config:
  nested:
    subnest:
      useful_data1: 1
      useful_data2: 2

Where a template only operates on config -> nested -> subnest it would make sense for @data to only contain the contents of that.

A cli flag, --root of a dotted or slashed path type notation would make most sense I think.
Examples:
templateer --root config.nested.subnest data.yaml sometemplate.erb
or
templateer --root config/nested/subnest data.yaml sometemplate.erb

To support nicer inputs a truthy helper should be implemented (to be used at the discretion of template authors) that supports the following:

True
y, yes, numeric type != 0, true

False
n, no, 0, false, ""

Invocation forms could be truthy(val) or val.truthy?

Provide the ability to supply a director script as an argument that can massage input data and direct output data.

Example

# director.rb
template = load_template(ARGV[1])
@data['network']['interfaces'].each do |name, interface|
  File.write("/etc/sysconfig/network-scripts/ifcfg-#{name}", process(interface, template)
end

templateer --director director.rb some_data.yaml

Note that the director script controls template loading, processing order and output writing.
In this capacity templateer becomes far more general purpose but allows for higher level usage.