Raise new error if GS execution fails

lib/pdf_cover/converter.rb

@@ -1,10 +1,18 @@
+require "open3"
+
 module PdfCover
   class Converter
     # NOTE: Update the generate_jpegs.sh script when changing these values
     DEFAULT_FORMAT = "jpeg"
     DEFAULT_QUALITY = 85
     DEFAULT_RESOLUTION = 300
 
+    class CommandFailedError < StandardError
+      def initialize(stdout_str, stderr_str)
+        super("PDF conversion failed:\nSTDOUT: #{stdout_str}\nSTDERR: #{stderr_str}")
+      end
+    end
+
     class CommandNotFoundError < StandardError
       def initialize
         super("Could not run the `gs` command. Make sure that GhostScript is in your PATH.")
@@ -23,15 +31,19 @@ def initialize(file, options = {})
     end
 
     # @raises PdfCover::Converter::CommandNotFoundError if GhostScript is not found
+    # @raises PdfCover::Converter::CommandFailedError if GhostScript returns a non-zero status
     def converted_file
-      case convert_file
-        when :ok
-          destination_file
-        when :command_failed
-          @file
-        when :command_not_found
-          fail CommandNotFoundError
+      parameters = build_parameters(file_path, device)
+      stdout_str, stderr_str, status = execute_command("gs #{parameters}")
+
+      case status
+        when 0 then destination_file
+        when 127 then fail CommandNotFoundError
+        else fail CommandFailedError.new(stdout_str, stderr_str)
       end
+    rescue => e
+      destination_file.close
+      raise e
     end
 
     private
@@ -40,38 +52,31 @@ def basename
       @basename ||= File.basename(@file.path, File.extname(@file.path))
     end
 
-    def build_parameters(source, device, destination)
-      %W(-sOutputFile='#{destination}' -dNOPAUSE
+    def build_parameters(source, device)
+      %W(-sOutputFile='#{destination_path}' -dNOPAUSE
          -sDEVICE='#{device}' -dJPEGQ=#{@quality}
          -dFirstPage=1 -dLastPage=1
          -r#{@resolution} -q '#{source}'
          -c quit
       ).join(" ")
     end
 
-    def convert_file
-      parameters = build_parameters(file_path, device, File.expand_path(destination_file.path))
-      result = execute_command("gs #{parameters}")
-
-      if result
-        :ok
-      else
-        failed_result(result)
-      end
-    end
-
     def destination_file
       @destination_file ||= Tempfile.new([basename, ".#{@format}"]).tap do |file|
         file.binmode
       end
     end
 
+    def destination_path
+      File.expand_path(destination_file.path)
+    end
+
     def device
       @format.to_s == "jpg" ? "jpeg" : @format.to_s
     end
 
     def execute_command(command)
-      Kernel.system(command)
+      Open3.capture3(command)
     end
 
     def extract_options(options)
@@ -84,23 +89,8 @@ def extract_options(options)
       fail InvalidOption.new(:resolution, @resolution) unless @resolution > 1
     end
 
-    def failed_result(result)
-      destination_file.close
-
-      if result == false
-        logger.warn("GhostScript execution failed: #{$CHILD_STATUS}")
-        :command_failed
-      else
-        :command_not_found
-      end
-    end
-
     def file_path
       @file_path ||= File.expand_path(@file.path)
     end
-
-    def logger
-      @logger ||= defined?(Rails) ? Rails.logger : Logger.new(STDERR)
-    end
   end
 end

spec/xing/pdf_cover/converter_spec.rb

@@ -80,7 +80,7 @@
       end
 
       context "the conversion goes fine" do
-        let(:execution_result) { true }
+        let(:execution_result) { ["", "", 0] }
 
         it "returns the generated file" do
           expect(subject.converted_file).to eq(destination_file)
@@ -93,23 +93,16 @@
         end
 
         context "because the command execution failed" do
-          let(:execution_result) { false }
+          let(:execution_result) { ["", "", 1] }
           let(:logger) { double(Logger) }
 
-          const_set(:CHILD_STATUS, "something went wrong")
-
-          before do
-            expect(subject).to receive(:logger).and_return(logger)
-            expect(logger).to receive(:warn)
-          end
-
-          it "returns the original file" do
-            expect(subject.converted_file).to eq(source_file)
+          it "generates an error" do
+            expect { subject.converted_file }.to raise_error(PdfCover::Converter::CommandFailedError)
           end
         end
 
         context "because the GhostScript command is not found" do
-          let(:execution_result) { nil }
+          let(:execution_result) { ["", "", 127] }
 
           it "generates an error" do
             expect { subject.converted_file }.to raise_error(PdfCover::Converter::CommandNotFoundError)