Support custom error handlers

.gitignore

@@ -5,7 +5,7 @@
 /doc/
 /pkg/
 /spec/reports/
-/spec/support/rendered/*.yml
+/spec/support/rendered/*
 /tmp/
 
 # rspec failure tracking

lib/consult.rb

@@ -19,6 +19,7 @@ module Consult
 
   class << self
     attr_reader :config, :templates
+    attr_writer :exception_handler
 
     def load(config_dir: nil)
       root directory: config_dir
@@ -78,6 +79,10 @@ def render!
       active_templates.each(&:render)
     end
 
+    def exception_handler
+      @exception_handler ||= ->(e) { puts e.message }
+    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/template.rb

@@ -15,20 +15,31 @@ def initialize(name, config)
     end
 
     def render(save: true)
-      renderer = ERB.new(File.read(path, encoding: 'utf-8'), nil, '-')
+      # Attempt to render
+      renderer = ERB.new(contents, nil, '-')
       result = renderer.result(binding)
 
       File.open(dest, 'w') { |f| f << result } if save
       result
     rescue StandardError => e
-      puts "Error rendering template: #{name}"
-      raise e
+      Consult.exception_handler.call(e)
+      nil
     end
 
     def path
+      return unless @config.key?(:path)
       resolve @config.fetch(:path)
     end
 
+    def paths
+      return [] unless @config.key?(:paths)
+      @config.fetch(:paths).map { |path| resolve(path) }
+    end
+
+    def vars
+      @config[:vars]
+    end
+
     def dest
       resolve @config.fetch(:dest)
     end
@@ -42,5 +53,26 @@ def expired?
       return true if !config.key?(:ttl) || !dest.exist?
       dest.mtime < (Time.now - @config[:ttl].to_i)
     end
+
+    private
+
+    # Concatenate all the source templates together, in the order provided
+    # Disk contents go first
+    def contents
+      disk_contents + consul_contents
+    end
+
+    def consul_contents
+      [@config[:consul_key], @config[:consul_keys]].compact.flatten.map do |key|
+        Diplomat::Kv.get(key, options: nil, not_found: :return, found: :return)
+      end.join
+    end
+
+    # Concatenate all the source templates together, in the order provided
+    def disk_contents
+      [path, paths].compact.flatten.map do |file_path|
+        File.read file_path, encoding: 'utf-8'
+      end.join
+    end
   end
 end

spec/consult_spec.rb

@@ -21,5 +21,10 @@
 
   it 'renders without error' do
     expect { Consult.render! }.to_not raise_exception
+
+    # Verify text templates rendered correctly
+    %w[elements.txt more_elements.txt consul_elements.txt more_consul_elements.txt multi_pass.txt].each do |template|
+      expect(FileUtils.compare_file("spec/support/expected/#{template}", "spec/support/rendered/#{template}")).to be true
+    end
   end
 end

spec/lib/template_spec.rb

@@ -1,5 +1,14 @@
 # frozen_string_literal: true
 
+class Handler
+  class << self
+    attr_reader :error
+    def call(error)
+      @error = error
+    end
+  end
+end
+
 RSpec.describe Consult::Template do
   let(:name) { 'database.yml' }
   let(:config) do
@@ -11,6 +20,14 @@
   end
   let(:template) { Consult::Template.new(name, config) }
 
+  let(:error_template) { 'Corbin Dallas' }
+  let(:error_config) do
+    {
+      consul_key: 'templates/error_test',
+      dest:       'rendered/error_test.txt'
+    }
+  end
+
   before :all do
     Consult.load config_dir: 'spec/support'
   end
@@ -75,4 +92,19 @@
       expect(template.indent(colon_separated, 1, ':')).to eq ' hello: world'
     end
   end
+
+  context 'error handling' do
+    it 'allows custom error handlers' do
+      Consult.exception_handler = Handler
+      Diplomat::Kv.put('templates/error_test', error_template)
+      template = Consult::Template.new('error_template', error_config)
+      expect(template.render).to eq error_template
+
+      Diplomat::Kv.delete('templates/error_test')
+      expect(template.render).to be nil
+      expect(Handler.error).to be_instance_of Diplomat::KeyNotFound
+
+      expect(File.read(template.dest)).to eq error_template
+    end
+  end
 end

spec/support/config/consult.yml

@@ -14,6 +14,70 @@ shared:
       dest: rendered/database.yml
       ttl: 10 # seconds
 
+    elements:
+      paths:
+        - templates/elements/air.txt
+        - templates/elements/fire.txt
+      dest: rendered/elements.txt
+      vars:
+        air: 1
+        fire: 2
+
+    more_elements:
+      path: templates/elements/air.txt
+      paths:
+        - templates/elements/fire.txt
+        - templates/elements/water.txt
+      dest: rendered/more_elements.txt
+      vars:
+        air: 1
+        fire: 2
+        water: 3
+
+    consul_elements:
+      consul_keys:
+        - templates/elements/earth
+        - templates/elements/love
+      dest: rendered/consul_elements.txt
+      vars:
+        earth: 4
+        love: 5
+
+    more_consul_elements:
+      consul_key: templates/elements/earth
+      consul_keys:
+        - templates/elements/love
+        - templates/elements/aziz
+      dest: rendered/more_consul_elements.txt
+      vars:
+        earth: 4
+        love: 5
+        aziz: 'Light!'
+
+    multi_pass:
+      path: templates/elements/air.txt
+      paths:
+        - templates/elements/fire.txt
+        - templates/elements/water.txt
+      consul_key: templates/elements/earth
+      consul_keys:
+        - templates/elements/love
+        - templates/elements/aziz
+      dest: rendered/multi_pass.txt
+      vars:
+        air: 1
+        fire: 2
+        water: 3
+        earth: 4
+        love: 5
+        aziz: 'Light!'
+
+    dest_fail:
+      consul_key: templates/elements/aziz
+      dest: rendered/nope/dest_fail.keep
+      vars:
+        aziz: 'Light!'
+
 test:
   templates:
     secrets:

spec/support/expected/consul_elements.txt

@@ -0,0 +1,2 @@
+Earth is the 4th element
+Love is the 5th element!

spec/support/expected/elements.txt

@@ -0,0 +1,2 @@
+Air is the 1st element
+Fire is the 2nd element

spec/support/expected/more_consul_elements.txt

@@ -0,0 +1,3 @@
+Earth is the 4th element
+Love is the 5th element!
+Aziz! Light!

spec/support/expected/more_elements.txt

@@ -0,0 +1,3 @@
+Air is the 1st element
+Fire is the 2nd element
+Water is the 3rd element

spec/support/expected/multi_pass.txt

@@ -0,0 +1,6 @@
+Air is the 1st element
+Fire is the 2nd element
+Water is the 3rd element
+Earth is the 4th element
+Love is the 5th element!
+Aziz! Light!

spec/support/populate_consul.sh

@@ -13,3 +13,18 @@ curl \
     --request PUT \
     --data 'db1.local.net' \
     http://0.0.0.0:8500/v1/kv/infrastructure/db1/dns
+
+curl \
+    --request PUT \
+    --data $'Earth is the <%= vars[:earth] %>th element\n' \
+    http://0.0.0.0:8500/v1/kv/templates/elements/earth
+
+curl \
+    --request PUT \
+    --data $'Love is the <%= vars[:love] %>th element!\n' \
+    http://0.0.0.0:8500/v1/kv/templates/elements/love
+
+curl \
+    --request PUT \
+    --data $'Aziz! <%= vars[:aziz] %>\n' \
+    http://0.0.0.0:8500/v1/kv/templates/elements/aziz

spec/support/templates/elements/air.txt

@@ -0,0 +1 @@
+Air is the <%= vars[:air] %>st element

spec/support/templates/elements/fire.txt

@@ -0,0 +1 @@
+Fire is the <%= vars[:fire] %>nd element

spec/support/templates/elements/water.txt

@@ -0,0 +1 @@
+Water is the <%= vars[:water] %>rd element