Handle custom errors in Alchemy::Picture#url

Currently we raise custom errors in the Alchemy::Picture#url
method without rescueing them later. This causes pages and the image library
to fail completely if one the images could not be rendered because the image file
is missing or the image format could not be used.

This is bad user experience. We should not display the broken image and not break the whole page.

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Change Log
 
+## 3.6.2 (unreleased)
+
+* Handle custom errors in `Alchemy::Picture#url` [#1305](https://github.com/AlchemyCMS/alchemy_cms/pull/1305) by [tvdeyen](https://github.com/tvdeyen)
+
 ## 3.6.1 (2017-08-16)
 
 * Do not ask `systempage?` everytime we load the page definition [#1239](https://github.com/AlchemyCMS/alchemy_cms/pull/1283) by [tvdeyen](https://github.com/tvdeyen)

app/models/alchemy/picture/url.rb

@@ -1,5 +1,7 @@
 module Alchemy
   module Picture::Url
+    include Alchemy::Logger
+
     TRANSFORMATION_OPTIONS = [
       :crop,
       :crop_from,
@@ -28,6 +30,9 @@ def url(options = {})
       image = encoded_image(image, options)
 
       image.url(options.except(*TRANSFORMATION_OPTIONS).merge(name: name))
+    rescue MissingImageFileError, WrongImageFormatError => e
+      log_warning e.message
+      nil
     end
 
     private
@@ -53,7 +58,10 @@ def processed_image(image, options = {})
     #
     def encoded_image(image, options = {})
       target_format = options[:format] || default_render_format
-      raise WrongImageFormatError if !target_format.in?(Alchemy::Picture.allowed_filetypes)
+
+      unless target_format.in?(Alchemy::Picture.allowed_filetypes)
+        raise WrongImageFormatError.new(self, target_format)
+      end
 
       options = {
         flatten: target_format != 'gif' && image_file_format == 'gif'

lib/alchemy/errors.rb

@@ -55,9 +55,14 @@ class MissingImageFileError < StandardError; end
 
   # Raised if calling +image_file+ on a Picture object returns nil.
   class WrongImageFormatError < StandardError
+    def initialize(image, requested_format)
+      @image = image
+      @requested_format = requested_format
+    end
+
     def message
       allowed_filetypes = Alchemy::Picture.allowed_filetypes.map(&:upcase).to_sentence
-      "Requested image format is not one of allowed filetypes (#{allowed_filetypes})."
+      "Requested image format (#{@requested_format.inspect}) for #{@image.inspect} is not one of allowed filetypes (#{allowed_filetypes})."
     end
   end
 

spec/models/alchemy/picture_url_spec.rb

@@ -35,8 +35,13 @@ def decode_dragon_fly_job(url)
           expect(picture).to receive(:image_file) { nil }
         end
 
-        it 'raises error' do
-          expect { url }.to raise_error(Alchemy::MissingImageFileError)
+        it 'returns nil' do
+          expect(url).to be_nil
+        end
+
+        it "logs warning" do
+          expect(Alchemy::Logger).to receive(:warn)
+          url
         end
       end
 
@@ -171,8 +176,13 @@ def decode_dragon_fly_job(url)
           {format: 'zip'}
         end
 
-        it "raises error" do
-          expect { url }.to raise_error(Alchemy::WrongImageFormatError)
+        it "returns nil" do
+          expect(url).to be_nil
+        end
+
+        it "logs warning" do
+          expect(Alchemy::Logger).to receive(:warn)
+          url
         end
       end