Fix parsing errors (#19)

* Fix incorrect parsing of PURLs beginning with pkg:/

* Fix escaping of subpaths

* Relax Rubocop configuration

* Fix linting errors

Author: mattt

.rubocop.yml

@@ -19,6 +19,6 @@ Metrics/MethodLength:
 Metrics/ParameterLists:
   Max: 7
 Metrics/PerceivedComplexity:
-  Max: 20
+  Max: 30
 Style/ConditionalAssignment:
   Enabled: false

lib/package_url.rb

@@ -93,9 +93,14 @@ def self.parse(string)
     # - This is the subpath
     case string.rpartition('#')
     in String => remainder, separator, String => subpath unless separator.empty?
-      components[:subpath] = subpath.split('/').select do |segment|
-        !segment.empty? && segment != '.' && segment != '..'
-      end.compact.join('/')
+      subpath_components = []
+      subpath.split('/').each do |segment|
+        next if segment.empty? || segment == '.' || segment == '..'
+
+        subpath_components << URI.decode_www_form_component(segment)
+      end
+
+      components[:subpath] = subpath_components.compact.join('/')
 
       string = remainder
     else
@@ -152,10 +157,11 @@ def self.parse(string)
     end
 
     # Strip the remainder from leading and trailing '/'
+    # Use gsub to remove ALL leading slashes instead of just one
+    string = string.gsub(%r{^/+}, '').delete_suffix('/')
     # - Split this once from left on '/'
     # - The left side lowercased is the type
     # - The right side is the remainder
-    string = string.delete_suffix('/')
     case string.partition('/')
     in String => type, separator, remainder unless separator.empty?
       components[:type] = type
@@ -343,7 +349,13 @@ def to_s
       subpath.delete_prefix('/').delete_suffix('/').split('/').each do |segment|
         next if segment.empty? || segment == '.' || segment == '..'
 
-        segments << URI.encode_www_form_component(segment)
+        # Custom encoding for URL fragment segments:
+        # 1. Explicitly encode % as %25 to prevent double-encoding issues
+        # 2. Percent-encode special characters according to URL fragment rules
+        # 3. This ensures proper round-trip encoding/decoding with the parse method
+        segments << segment.gsub(/%|[^A-Za-z0-9\-\._~]/) do |m|
+          m == '%' ? '%25' : format('%%%02X', m.ord)
+        end
       end
 
       unless segments.empty?

spec/package_url_spec.rb

@@ -187,6 +187,89 @@
 
       it { should have_description 'pkg:rpm/fedora/[email protected]?arch=i386&distro=fedora-25' }
     end
+
+    context 'with escaped subpath characters', url: 'pkg:type/name#path/with/%25/percent' do
+      it {
+        should have_attributes type: 'type',
+                               namespace: nil,
+                               name: 'name',
+                               version: nil,
+                               qualifiers: nil,
+                               subpath: 'path/with/%/percent'
+      }
+
+      it 'should properly round-trip the URL' do
+        expect(subject.to_s).to eq('pkg:type/name#path/with/%25/percent')
+      end
+    end
+
+    context 'with multiple escaped subpath characters', url: 'pkg:type/name#path/%20space/%3Fquery/%25percent' do
+      it {
+        should have_attributes type: 'type',
+                               namespace: nil,
+                               name: 'name',
+                               version: nil,
+                               qualifiers: nil,
+                               subpath: 'path/ space/?query/%percent'
+      }
+
+      it 'should properly round-trip the URL' do
+        expect(subject.to_s).to eq('pkg:type/name#path/%20space/%3Fquery/%25percent')
+      end
+    end
+
+    context 'with the specific issue case', url: 'pkg:t/n#%25' do
+      it {
+        should have_attributes type: 't',
+                               namespace: nil,
+                               name: 'n',
+                               version: nil,
+                               qualifiers: nil,
+                               subpath: '%'
+      }
+
+      it 'should properly round-trip the URL' do
+        expect(subject.to_s).to eq('pkg:t/n#%25')
+      end
+    end
+
+    context 'with URLs containing extra slashes after scheme' do
+      it 'should parse pkg:/type/namespace/name correctly' do
+        purl = PackageURL.parse('pkg:/maven/org.apache.commons/io')
+        expect(purl).to have_attributes(
+          type: 'maven',
+          namespace: 'org.apache.commons',
+          name: 'io',
+          version: nil,
+          qualifiers: nil,
+          subpath: nil
+        )
+      end
+
+      it 'should parse pkg://type/namespace/name correctly' do
+        purl = PackageURL.parse('pkg://maven/org.apache.commons/io')
+        expect(purl).to have_attributes(
+          type: 'maven',
+          namespace: 'org.apache.commons',
+          name: 'io',
+          version: nil,
+          qualifiers: nil,
+          subpath: nil
+        )
+      end
+
+      it 'should parse pkg:///type/namespace/name correctly' do
+        purl = PackageURL.parse('pkg:///maven/org.apache.commons/io')
+        expect(purl).to have_attributes(
+          type: 'maven',
+          namespace: 'org.apache.commons',
+          name: 'io',
+          version: nil,
+          qualifiers: nil,
+          subpath: nil
+        )
+      end
+    end
   end
 
   describe 'pattern matching' do