rubocop-yard: Add support for symbol and string literals in TypesExplainer

lib/yard/code_objects/base.rb

@@ -63,6 +63,9 @@ def push(value)
     # Regular expression to match a fully qualified method def (self.foo, Class.foo).
     METHODMATCH = /(?:(?:#{NAMESPACEMATCH}|[a-z]\w*)\s*(?:#{CSEPQ}|#{NSEPQ})\s*)?#{METHODNAMEMATCH}/
 
+    # Regular expression to match symbol and string literals
+    LITERALMATCH = /:\w+|'[^']*'|"[^"]*"/
+
     # All builtin Ruby exception classes for inheritance tree.
     BUILTIN_EXCEPTIONS = ["ArgumentError", "ClosedQueueError", "EncodingError",
       "EOFError", "Exception", "FiberError", "FloatDomainError", "IndexError",

lib/yard/tags/types_explainer.rb

@@ -31,16 +31,14 @@ def initialize(name)
         end
 
         def to_s(singular = true)
-          if name[0, 1] == "#"
-            singular ? "an object that responds to #{name}" : "objects that respond to #{name}"
-          elsif name[0, 1] =~ /[A-Z]/
+          if name[0, 1] =~ /[A-Z]/
             singular ? "a#{name[0, 1] =~ /[aeiou]/i ? 'n' : ''} " + name : "#{name}#{name[-1, 1] =~ /[A-Z]/ ? "'" : ''}s"
           else
             name
           end
         end
 
-        private
+        protected
 
         def list_join(list)
           index = 0
@@ -54,6 +52,20 @@ def list_join(list)
         end
       end
 
+      # @private
+      class LiteralType < Type
+        def to_s(_singular = true)
+          "a literal value #{name}"
+        end
+      end
+
+      # @private
+      class DuckType < Type
+        def to_s(singular = true)
+          singular ? "an object that responds to #{name}" : "objects that respond to #{name}"
+        end
+      end
+
       # @private
       class CollectionType < Type
         attr_accessor :types
@@ -101,7 +113,7 @@ class Parser
           :collection_end => />/,
           :fixed_collection_start => /\(/,
           :fixed_collection_end => /\)/,
-          :type_name => /#{ISEP}#{METHODNAMEMATCH}|#{NAMESPACEMATCH}|\w+/,
+          :type_name => /#{ISEP}#{METHODNAMEMATCH}|#{NAMESPACEMATCH}|#{LITERALMATCH}|\w+/,
           :type_next => /[,;]/,
           :whitespace => /\s+/,
           :hash_collection_start => /\{/,
@@ -135,7 +147,7 @@ def parse
                 name = token
               when :type_next
                 raise SyntaxError, "expecting name, got '#{token}' at #{@scanner.pos}" if name.nil?
-                type = Type.new(name) unless type
+                type = create_type(name) unless type
                 types << type
                 type = nil
                 name = nil
@@ -148,14 +160,26 @@ def parse
                 type = HashCollectionType.new(name, parse, parse)
               when :hash_collection_next, :hash_collection_end, :fixed_collection_end, :collection_end, :parse_end
                 raise SyntaxError, "expecting name, got '#{token}'" if name.nil?
-                type = Type.new(name) unless type
+                type = create_type(name) unless type
                 types << type
                 return types
               end
             end
             raise SyntaxError, "invalid character at #{@scanner.peek(1)}" unless found
           end
         end
+
+        private
+
+        def create_type(name)
+          if name[0, 1] == ":" || (name[0, 1] =~ /['"]/ && name[-1, 1] =~ /['"]/)
+            LiteralType.new(name)
+          elsif name[0, 1] == "#"
+            DuckType.new(name)
+          else
+            Type.new(name)
+          end
+        end
       end
     end
   end

spec/code_objects/constants_spec.rb

@@ -56,6 +56,26 @@ def silence_warnings
     end
   end
 
+  describe :LITERALMATCH do
+    it "matches symbol literals" do
+      expect(":symbol"[CodeObjects::LITERALMATCH]).to eq ":symbol"
+      expect(":some_symbol"[CodeObjects::LITERALMATCH]).to eq ":some_symbol"
+      expect("not_a_symbol"[CodeObjects::LITERALMATCH]).to be nil
+    end
+
+    it "matches single-quoted string literals" do
+      expect("'string'"[CodeObjects::LITERALMATCH]).to eq "'string'"
+      expect("'some string with spaces'"[CodeObjects::LITERALMATCH]).to eq "'some string with spaces'"
+      expect("not_quoted"[CodeObjects::LITERALMATCH]).to be nil
+    end
+
+    it "matches double-quoted string literals" do
+      expect('"string"'[CodeObjects::LITERALMATCH]).to eq '"string"'
+      expect('"some string with spaces"'[CodeObjects::LITERALMATCH]).to eq '"some string with spaces"'
+      expect("not_quoted"[CodeObjects::LITERALMATCH]).to be nil
+    end
+  end
+
   describe :BUILTIN_EXCEPTIONS do
     it "includes all base exceptions" do
       bad_names = []

spec/tags/types_explainer_spec.rb

@@ -2,6 +2,8 @@
 
 RSpec.describe YARD::Tags::TypesExplainer do
   Type = YARD::Tags::TypesExplainer::Type
+  LiteralType = YARD::Tags::TypesExplainer::LiteralType
+  DuckType = YARD::Tags::TypesExplainer::DuckType
   CollectionType = YARD::Tags::TypesExplainer::CollectionType
   FixedCollectionType = YARD::Tags::TypesExplainer::FixedCollectionType
   HashCollectionType = YARD::Tags::TypesExplainer::HashCollectionType
@@ -32,12 +34,6 @@ def parse_fail(types)
       expect(@t.to_s(false)).to eq "Arrays"
     end
 
-    it "works for a method (ducktype)" do
-      @t.name = "#mymethod"
-      expect(@t.to_s).to eq "an object that responds to #mymethod"
-      expect(@t.to_s(false)).to eq "objects that respond to #mymethod"
-    end
-
     it "works for a constant value" do
       ['false', 'true', 'nil', '4'].each do |name|
         @t.name = name
@@ -47,6 +43,24 @@ def parse_fail(types)
     end
   end
 
+  describe DuckType, '#to_s' do
+    it "works for a method (ducktype)" do
+      duck_type = DuckType.new("#mymethod")
+      expect(duck_type.to_s).to eq "an object that responds to #mymethod"
+      expect(duck_type.to_s(false)).to eq "objects that respond to #mymethod"
+    end
+  end
+
+  describe LiteralType, '#to_s' do
+    it "works for literal values" do
+      [':symbol', "'5'"].each do |name|
+        literal_type = LiteralType.new(name)
+        expect(literal_type.to_s).to eq "a literal value #{name}"
+        expect(literal_type.to_s(false)).to eq "a literal value #{name}"
+      end
+    end
+  end
+
   describe CollectionType, '#to_s' do
     before { @t = CollectionType.new("Array", nil) }
 
@@ -85,7 +99,7 @@ def parse_fail(types)
     end
   end
 
-  describe FixedCollectionType, '#to_s' do
+  describe HashCollectionType, '#to_s' do
     before { @t = HashCollectionType.new("Hash", nil, nil) }
 
     it "can contain a single key type and value type" do
@@ -131,6 +145,17 @@ def parse_fail(types)
       expect(type[3].name).to eq "E"
     end
 
+    it 'parses a list of literal values' do
+      type = parse("true, false, nil, 4, :symbol, '5'")
+      expect(type.size).to eq 6
+      expect(type[0].name).to eq "true"
+      expect(type[1].name).to eq "false"
+      expect(type[2].name).to eq "nil"
+      expect(type[3].name).to eq "4"
+      expect(type[4].name).to eq ":symbol"
+      expect(type[5].name).to eq "'5'"
+    end
+
     it "parses a collection type" do
       type = parse("MyList<String>")
       expect(type.first).to be_a(CollectionType)
@@ -192,7 +217,8 @@ def parse_fail(types)
           a Hash with keys made of (Foos or Bars) and values of (Symbols or Numbers)",
         "#weird_method?, #<=>, #!=" => "an object that responds to #weird_method?;
           an object that responds to #<=>;
-          an object that responds to #!="
+          an object that responds to #!=",
+        ":symbol, 'string'" => "a literal value :symbol; a literal value 'string'"
       }
       expect.each do |input, expected|
         explain = YARD::Tags::TypesExplainer.explain(input)