don't raise an error if consul is completely unconfigured

just pretend it's empty. the caller should be responsible for dealing
with missing consul data as appropriate

Change-Id: I2c37d33481b55776b14c6c17e109005a75dd600b
Reviewed-on: https://gerrit.instructure.com/125567
Reviewed-by: Tyler Pickett <tpickett@instructure.com>
Reviewed-by: Simon Williams <simon@instructure.com>
Tested-by: Jenkins
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>

lib/authentication_methods.rb

@@ -70,8 +70,7 @@ module AuthenticationMethods
       @authenticated_with_jwt = true
     rescue JSON::JWT::InvalidFormat,             # definitely not a JWT
            Canvas::Security::TokenExpired,       # it could be a JWT, but it's expired if so
-           Canvas::Security::InvalidToken,       # Looks like garbage
-           Canvas::DynamicSettings::NoFallbackError  # no config present for talking to consul
+           Canvas::Security::InvalidToken       # Looks like garbage
       # these will happen for some configurations (no consul)
       # and for some normal use cases (old token, access token),
       # so we can return and move on

lib/canvas/dynamic_settings.rb

@@ -25,7 +25,6 @@ module Canvas
 
     class Error < StandardError; end
     class ConsulError < Error; end
-    class NoFallbackError < Error; end
 
     CONSUL_READ_OPTIONS = %i{recurse stale}.freeze
     KV_NAMESPACE = "config/canvas".freeze
@@ -94,8 +93,7 @@ module Canvas
         elsif @fallback_data.present?
           DynamicSettings::FallbackProxy.new(@fallback_data[prefix])
         else
-          raise NoFallbackError, 'DynamicSettings.fallback_data is not set and'\
-            ' consul is not configured, unable to supply configuration values.'
+          DynamicSettings::FallbackProxy.new({})
         end
       end
 

lib/math_man.rb

@@ -54,18 +54,13 @@ module MathMan
     def with_plugin_settings
       dynamic_settings = Canvas::DynamicSettings.find('math-man')
       plugin_settings = Canvas::Plugin.find(:mathman).settings
+      raise "math-man not properly configured in consul" if !dynamic_settings[:base_url] && Rails.env.production?
       settings = {
         base_url: dynamic_settings[:base_url],
         use_for_mml: plugin_settings[:use_for_mml],
         use_for_svg: plugin_settings[:use_for_svg]
       }
       yield settings
-    rescue Canvas::DynamicSettings::NoFallbackError
-      if Rails.env.production?
-        raise
-      else
-        yield({})
-      end
     end
   end
 end

spec/lib/canvas/dynamic_settings_spec.rb

@@ -113,13 +113,11 @@ module Canvas
         expect(proxy).to be_a(DynamicSettings::PrefixProxy)
       end
 
-      it 'must raise an error when neither consul or fallback data have been configured' do
+      it 'must return a FallbackProxy when neither consul or fallback data have been configured' do
         allow(DynamicSettings).to receive(:kv_client).and_return(nil)
         DynamicSettings.fallback_data = nil
-        expect { DynamicSettings.find('foo') }.to raise_error(
-          DynamicSettings::NoFallbackError,
-          /fallback_data is not set/
-        )
+        expect(DynamicSettings.find('foo')).to be_a(DynamicSettings::FallbackProxy)
+        expect(DynamicSettings.find('foo')['bar']).to eq nil
       end
 
       it 'must return a FallbackProxy when consul is not configured' do