Fix passing empty string to #image_cache= causes existing ones deleted.

Fixes #2412

Refs. 8f18a95

lib/carrierwave/mounter.rb

@@ -72,9 +72,10 @@ def cache_names
     end
 
     def cache_names=(cache_names)
+      cache_names = cache_names.reject(&:blank?)
       return if cache_names.blank?
       clear_unstaged
-      cache_names.map do |cache_name|
+      cache_names.each do |cache_name|
         begin
           uploader = blank_uploader
           uploader.retrieve_from_cache!(cache_name)
@@ -91,7 +92,7 @@ def remote_urls=(urls)
       @remote_urls = urls
 
       clear_unstaged
-      urls.zip(remote_request_headers || []).map do |url, header|
+      urls.zip(remote_request_headers || []).each do |url, header|
         handle_error do
           uploader = blank_uploader
           uploader.download!(url, header || {})

spec/mount_multiple_spec.rb

@@ -487,6 +487,18 @@ def monkey
           expect(instance.images.map(&:cache_name)).to eq(['1369894322-123-0123-1234/test.jpg'])
         end
       end
+
+      context "when an empty string is assigned" do
+        before do
+          instance.images = [test_file_stub]
+          instance.store_images!
+          instance.images_cache = [''].to_json
+        end
+
+        it "does not write over a previously stored file" do
+          expect(instance.images[0].current_path).to match(/test.jpg$/)
+        end
+      end
     end
 
     describe "#remote_images_urls" do
@@ -565,6 +577,22 @@ def monkey
         it { is_expected.to match(/portrait.jpg$/) }
       end
 
+      context "when an empty string is assigned" do
+        subject { images[0].current_path }
+
+        let(:remote_images_url) { [""] }
+
+        before do
+          instance.images = [stub_file("portrait.jpg")]
+          instance.store_images!
+          instance.remote_images_urls = remote_images_url
+        end
+
+        it "does not write over a previously stored file" do
+          is_expected.to match(/portrait.jpg$/)
+        end
+      end
+
       context "if a file fails to be downloaded" do
         let(:remote_images_url) { ["http://www.example.com/test.txt", "http://www.example.com/test.jpg"] }
 

spec/mount_single_spec.rb

@@ -288,6 +288,13 @@ def default_url
         @instance.image_cache = '1369894322-123-0123-1234/monkey.jpg'
         expect(@instance.image.current_path).to match(/test.jpg$/)
       end
+
+      it "should not clear a previously stored file when an empty string is assigned" do
+        @instance.image = stub_file('test.jpg')
+        @instance.image.store!
+        @instance.image_cache = ''
+        expect(@instance.image.current_path).to match(/test.jpg$/)
+      end
     end
 
     describe "#remote_image_url" do
@@ -354,6 +361,13 @@ def default_url
 
         expect(@instance.image.current_path).to match(/portrait.jpg$/)
       end
+
+      it "does not clear a previously stored file when an empty string is assigned" do
+        @instance.remote_image_url = "http://www.example.com/test.jpg"
+        @instance.image.store!
+        @instance.remote_image_url = ""
+        expect(@instance.image.current_path).to match(/test.jpg$/)
+      end
     end
 
     describe '#store_image!' do