tune prawn-gmagick recommendation (PR #2222)

5 files changed, 34 insertions, 5 deletions

diff --git a/CHANGELOG.adoc b/CHANGELOG.adoc
index 1690933c..7b4dec88 100644
--- a/CHANGELOG.adoc
+++ b/CHANGELOG.adoc
@@ -5,6 +5,13 @@
 This document provides a high-level view of the changes to the {project-name} by release.
 For a detailed view of what has changed, refer to the {url-repo}/commits/main[commit history] on GitHub.
 
+== Unreleased
+
+Improvements::
+
+* don't recommend prawn-gmagick if PNG or JPG is corrupt or incomplete
+* add helper method to determine when to recommend the prawn-gmagick gem
+
 == 2.0.6 (2022-05-30) - @mojavelinux
 
 Bug Fixes::
diff --git a/lib/asciidoctor/pdf/converter.rb b/lib/asciidoctor/pdf/converter.rb
index 79cc0c87..5c5ef13e 100644
--- a/lib/asciidoctor/pdf/converter.rb
+++ b/lib/asciidoctor/pdf/converter.rb
@@ -1811,7 +1811,7 @@ module Asciidoctor
           end
         rescue => e
           raise if ::StopIteration === e
-          on_image_error :exception, node, target, (opts.merge align: alignment, message: %(could not embed image: #{image_path}; #{e.message}#{::Prawn::Errors::UnsupportedImageType === e && !(defined? ::GMagick::Image) ? '; install prawn-gmagick gem to add support' : ''}))
+          on_image_error :exception, node, target, (opts.merge align: alignment, message: %(could not embed image: #{image_path}; #{e.message}#{(recommend_prawn_gmagick? e, image_format) ? %(; install prawn-gmagick gem to add support for #{image_format&.upcase || 'unknown'} image format) : ''}))
         end
       end
 
diff --git a/lib/asciidoctor/pdf/ext/prawn/images.rb b/lib/asciidoctor/pdf/ext/prawn/images.rb
index 8bae4cdb..23dffde2 100644
--- a/lib/asciidoctor/pdf/ext/prawn/images.rb
+++ b/lib/asciidoctor/pdf/ext/prawn/images.rb
@@ -53,6 +53,10 @@ module Asciidoctor
         # NOTE: image cannot be read, so it won't be used anyway
         { width: 0, height: 0 }
       end
+
+      def recommend_prawn_gmagick? err, image_format
+        ::Prawn::Errors::UnsupportedImageType === err && !(defined? ::GMagick::Image) && ((err.message.include? 'PNG') || (%w(jpg png).none? image_format))
+      end
     end
 
     ::Prawn::Document.extensions << Images
diff --git a/lib/asciidoctor/pdf/formatted_text/inline_image_arranger.rb b/lib/asciidoctor/pdf/formatted_text/inline_image_arranger.rb
index e563a43a..dc5512e4 100644
--- a/lib/asciidoctor/pdf/formatted_text/inline_image_arranger.rb
+++ b/lib/asciidoctor/pdf/formatted_text/inline_image_arranger.rb
@@ -62,7 +62,7 @@ module Asciidoctor::PDF::FormattedText
         max_image_h = fragment[:image_fit] == 'line' ? [available_h, doc.font.height].min : available_h
 
         # TODO: make helper method to calculate width and height of image
-        if fragment[:image_format] == 'svg'
+        if (image_format = fragment[:image_format]) == 'svg'
           svg_obj = ::Prawn::SVG::Interface.new ::File.read(image_path, mode: 'r:UTF-8'), doc,
             at: doc.bounds.top_left,
             width: image_w,
@@ -117,7 +117,7 @@ module Asciidoctor::PDF::FormattedText
         fragment[:image_width] = fragment[:width] = image_w
         fragment[:image_height] = image_h
       rescue
-        logger.warn %(could not embed image: #{image_path}; #{$!.message}#{::Prawn::Errors::UnsupportedImageType === $! && !(defined? ::GMagick::Image) ? '; install prawn-gmagick gem to add support' : ''}) unless scratch
+        logger.warn %(could not embed image: #{image_path}; #{$!.message}#{(doc.recommend_prawn_gmagick? $!, image_format) ? %(; install prawn-gmagick gem to add support for #{image_format&.upcase || 'unknown'} image format) : ''}) unless scratch
         drop = true # delegate to cleanup logic in ensure block
       ensure
         # NOTE: skip rendering image in scratch document or if image can't be loaded
diff --git a/spec/image_spec.rb b/spec/image_spec.rb
index 90113db4..c0973900 100644
--- a/spec/image_spec.rb
+++ b/spec/image_spec.rb
@@ -917,6 +917,24 @@ describe 'Asciidoctor::PDF::Converter - Image' do
       (expect pdf.images[0][:width]).to eql reference_width
     end
 
+    it 'should fail to embed incomplete PNG with warning' do
+      Tempfile.create %w(incomplete- .png), output_dir do |tmp_file|
+        tmp_file.binmode
+        tmp_file.write [137, 80, 78, 71, 10].pack 'C*' # make a PNG with incomplete data
+        tmp_file.close
+        image_path = tmp_file.path
+        { '::' => %([Incomplete PNG] | #{image_path}), ':' => '[Incomplete PNG]' }.each do |macro_delim, alt_text|
+          (expect do
+            input = <<~EOS
+            image#{macro_delim}#{image_path}[Incomplete PNG]
+            EOS
+            pdf = to_pdf input, analyze: true
+            (expect pdf.lines).to eql [alt_text]
+          end).to log_message severity: :WARN, message: %(could not embed image: #{image_path}; image file is an unrecognised format)
+        end
+      end
+    end
+
     it 'should fail to embed interlaced PNG image with warning', unless: (defined? GMagick::Image) do
       { '::' => '[Interlaced PNG] | interlaced.png', ':' => '[Interlaced PNG]' }.each do |macro_delim, alt_text|
         (expect do
@@ -928,7 +946,7 @@ describe 'Asciidoctor::PDF::Converter - Image' do
           EOS
           pdf = to_pdf input, analyze: true
           (expect pdf.lines).to eql [alt_text]
-        end).to log_message severity: :WARN, message: %(could not embed image: #{fixture_file 'interlaced.png'}; PNG uses unsupported interlace method; install prawn-gmagick gem to add support)
+        end).to log_message severity: :WARN, message: %(could not embed image: #{fixture_file 'interlaced.png'}; PNG uses unsupported interlace method; install prawn-gmagick gem to add support for PNG image format)
       end
     end
 
@@ -1051,7 +1069,7 @@ describe 'Asciidoctor::PDF::Converter - Image' do
         (expect do
           pdf = to_pdf 'image:waterfall.bmp[waterfall,16] is not agile.', analyze: true
           (expect pdf.lines).to eql ['[waterfall] is not agile.']
-        end).to log_message severity: :WARN, message: '~image file is an unrecognised format; install prawn-gmagick gem to add support'
+        end).to log_message severity: :WARN, message: '~image file is an unrecognised format; install prawn-gmagick gem to add support for BMP image format'
       ensure
         GMagick.const_set :Image, old_gmagick_image
         Gmagick.singleton_class.remove_method :can_render?