Merge pull request #182 from ruby-docx/fix-127-nil-guards

Guard against nil crashes on malformed documents (#127)

Author: satoryu

lib/docx/containers/paragraph.rb

@@ -140,7 +140,7 @@ def font_size
 
         def font_color
           color_tag = @node.xpath('w:r//w:rPr//w:color').first
-          color_tag ? color_tag.attributes['val'].value : nil
+          color_tag ? color_tag.attributes['val']&.value : nil
         end
 
         def style

lib/docx/document.rb

@@ -104,7 +104,11 @@ def font_size
     # Hyperlink targets are extracted from the document.xml.rels file
     def hyperlinks
       hyperlink_relationships.each_with_object({}) do |rel, hash|
-        hash[rel.attributes['Id'].value] = rel.attributes['Target'].value
+        id = rel.attributes['Id']
+        target = rel.attributes['Target']
+        next unless id && target
+
+        hash[id.value] = target.value
       end
     end
 
@@ -184,7 +188,7 @@ def replace_entry(entry_path, file_contents)
     end
 
     def default_paragraph_style
-      @styles.at_xpath("w:styles/w:style[@w:type='paragraph' and @w:default='1']/w:name/@w:val").value
+      @styles&.at_xpath("w:styles/w:style[@w:type='paragraph' and @w:default='1']/w:name/@w:val")&.value
     end
 
     def style_name_of(style_id)

spec/docx/document_spec.rb

@@ -680,6 +680,34 @@
     end
   end
 
+  # Regression tests for #127: malformed documents should not crash with
+  # internal "undefined method 'value' for nil" errors.
+  describe 'robustness against malformed documents' do
+    it 'ignores hyperlink relationships missing an Id or Target' do
+      doc = Docx::Document.open(@fixtures_path + '/malformed_hyperlink_rels.docx')
+      expect { doc.hyperlinks }.to_not raise_error
+      # the well-formed relationships are still returned; the malformed one is skipped
+      expect(doc.hyperlinks).to be_a(Hash)
+    end
+
+    it 'returns nil for default_paragraph_style when there is no default paragraph style' do
+      doc = Docx::Document.open(@fixtures_path + '/no_default_paragraph_style.docx')
+      expect { doc.default_paragraph_style }.to_not raise_error
+      expect(doc.default_paragraph_style).to be_nil
+    end
+
+    it 'returns nil for a paragraph font_color when the color tag has no value' do
+      node = Nokogiri::XML(<<~XML).root
+        <w:p xmlns:w="http://schemas.openxmlformats.org/wordprocessingml/2006/main">
+          <w:r><w:rPr><w:color/></w:rPr><w:t>x</w:t></w:r>
+        </w:p>
+      XML
+      paragraph = Docx::Elements::Containers::Paragraph.new(node)
+      expect { paragraph.font_color }.to_not raise_error
+      expect(paragraph.font_color).to be_nil
+    end
+  end
+
   describe 'replacing contents' do
     let(:replacement_file_path) { @fixtures_path + '/replacement.png' }
     let(:temp_file_path) { Tempfile.new(['docx_gem', '.docx']).path }