Template validation

bin/consult

@@ -1,6 +1,7 @@
 #!/usr/bin/env ruby
 
-require_relative '../lib/consult/cli'
+require 'bundler/setup'
+require 'consult/cli'
 
 cli = Consult::CLI.instance
 cli.parse

consult.gemspec

@@ -26,6 +26,7 @@ Gem::Specification.new do |spec|
 
   spec.add_dependency 'diplomat', '~> 2.6'
   spec.add_dependency 'vault', '>= 0.10.0', '< 1.0.0'
+  spec.add_dependency 'dry-validation', '<= 1.9.0'
 
   spec.add_development_dependency 'bundler'
   spec.add_development_dependency 'guard'

lib/consult.rb

@@ -100,6 +100,13 @@ def render!
       active_templates.each(&:render)
     end
 
+    def validate_templates
+      active_templates do |t|
+        t.validate
+        puts "#{t.name}: #{t.validation.errors}"
+      end
+    end
+
     # Map more conventional `token` parameter to Diplomat's `acl_token` configuration.
     # Additionally, we support ~/.consul-token, similar to Vault's support for ~/.vault-token
     def consul_token

lib/consult/cli.rb

@@ -19,6 +19,7 @@ def parse(args = ARGV)
     end
 
     def render
+      Consult.validate_templates
       Consult.render!
     end
 

lib/consult/template.rb

@@ -2,6 +2,7 @@
 
 require 'fileutils'
 require_relative 'template_functions'
+require_relative 'template_schema'
 require_relative '../support/hash_extensions'
 
 module Consult
@@ -24,7 +25,11 @@ def render(save: true)
       end
 
       # Attempt to render
-      renderer = ERB.new(contents, nil, '-')
+      renderer = if legacy_erb_args?
+        ERB.new(contents, nil, '-')
+      else
+        ERB.new(contents, trim_mode: '-')
+      end
       result = renderer.result(binding)
 
       puts "Consult: Rendering #{name}" + (save ? " to #{dest}" : "...") if verbose?
@@ -76,8 +81,19 @@ def ordered_locations
       @config.keys & LOCATIONS
     end
 
+    def validate
+      @validation = TemplateSchema.new.call(@config)
+    end
+
     private
 
+    def legacy_erb_args?
+      # prior to 2.2.2 ERB.version was a string rather than a Gem::Version-compatible version number, so this will raise an exception
+      Gem::Version.new(ERB.version) < Gem::Version.new('2.2.0')
+    rescue
+      true
+    end
+
     # Concatenate all the source templates together, in the order provided
     def contents
       @_contents ||= ordered_locations.map do |location|

lib/consult/template_schema.rb

@@ -0,0 +1,30 @@
+# frozen_string-literal: true
+
+require 'dry-validation'
+
+class TemplateSchema < Dry::Validation::Contract
+  schema do
+    # Output destination is required
+    required(:dest).value(:string)
+
+    # At least one of path/paths/consul_key/consul_keys is required
+    optional(:path).value(:string)
+    optional(:paths).value(:array)
+    optional(:consul_key).value(:string)
+    optional(:consul_keys).value(:array)
+
+    # Other configuration
+    optional(:ttl).value(:integer)
+    optional(:vars).value(:hash)
+  end
+
+  rule(:path, :paths, :consul_key, :consul_keys) do
+    unless key?(:path) || key?(:paths) || key?(:consul_key) || key?(:consul_keys)
+      base.failure("A template source must be specified. Please provide one or more of: path, paths, consul_key, consul_keys")
+    end
+  end
+
+  rule(:ttl) do
+    key.failure "A TTL is strongly recommended to avoid rendering templates too often, especially in multi-process environments." if value.to_i == 0
+  end
+end

spec/support/config/consult.yml

@@ -87,6 +87,9 @@ shared:
       path: x/y/z.txt
       dest: rendered/nope/skip_missing_template
 
+    missing_source:
+      dest: rendered/nowhere.txt
+
 test:
   vars:
     test_env_override: some value