Add GDScript lexer (#1036)

This commit adds a lexer for GDScript.

lib/rouge/demos/gdscript

@@ -0,0 +1,18 @@
+extends Node
+
+# Variables & Built-in Types
+
+var a = 5
+var b = true
+var s = "Hello"
+var arr = [1, 2, 3]
+
+# Constants & Enums
+
+const ANSWER = 42
+enum { UNIT_NEUTRAL, UNIT_ENEMY, UNIT_ALLY }
+
+# Functions
+
+func _ready():
+    print("Hello, World")

lib/rouge/lexers/gdscript.rb

@@ -0,0 +1,171 @@
+# -*- coding: utf-8 -*- #
+# frozen_string_literal: true
+
+module Rouge
+  module Lexers
+    class GDScript < RegexLexer
+      title "GDScript"
+      desc "The Godot Engine programming language (https://godotengine.org/)"
+      tag 'gdscript'
+      aliases 'gd', 'gdscript'
+      filenames '*.gd'
+      mimetypes 'text/x-gdscript', 'application/x-gdscript'
+
+      def self.keywords
+        @keywords = %w(
+          and in not or as breakpoint class class_name extends is func setget
+          signal tool const enum export onready static var break continue
+          if elif else for pass return match while remote master puppet
+          remotesync mastersync puppetsync
+        ).join('|')
+      end
+
+      # Reserved for future implementation
+      def self.keywords_reserved
+        @keywords_reserved = %w(
+          do switch case
+        ).join('|')
+      end
+
+      def self.builtins
+        builtins = %w(
+          Color8 ColorN abs acos asin assert atan atan2 bytes2var ceil char
+          clamp convert cos cosh db2linear decimals dectime deg2rad dict2inst
+          ease exp floor fmod fposmod funcref hash inst2dict instance_from_id
+          is_inf is_nan lerp linear2db load log max min nearest_po2 pow
+          preload print print_stack printerr printraw prints printt rad2deg
+          rand_range rand_seed randf randi randomize range round seed sign
+          sin sinh sqrt stepify str str2var tan tan tanh type_exist typeof
+          var2bytes var2str weakref yield
+        ).join('|')
+      end
+
+      def self.builtins_type
+        @builtins_type = %w(
+          bool int float String Vector2 Rect2 Transform2D Vector3 AABB
+          Plane Quat Basis Transform Color RID Object NodePath Dictionary
+          Array PoolByteArray PoolIntArray PoolRealArray PoolStringArray
+          PoolVector2Array PoolVector3Array PoolColorArray null
+        ).join('|')
+      end
+
+      state :root do
+        rule %r/\n/, Text
+        rule %r/[^\S\n]+/, Text
+        rule %r/#.*/, Comment::Single
+        rule %r/[\[\]{}:(),;]/, Punctuation
+        rule %r/\\\n/, Text
+        rule %r/(in|and|or|not)\b/, Operator::Word
+        rule %r/!=|==|<<|>>|&&|\+=|-=|\*=|\/=|%=|&=|\|=|\|\||[-~+\/*%=<>&^.!|$]/, Operator
+        rule %r/(func)((?:\s|\\)+)/ do
+          groups Keyword, Text
+          push :funcname
+        end
+        rule %r/(class)((?:\s|\\)+)/ do
+          groups Keyword, Text
+          push :classname
+        end
+        mixin :keywords
+        mixin :builtins
+        rule %r/"""/, Str::Double, :escape_tdqs
+        rule %r/'''/, Str::Double, :escape_tsqs
+        rule %r/"/, Str::Double, :escape_dqs
+        rule %r/'/, Str::Double, :escape_sqs
+        mixin :name
+        mixin :numbers
+      end
+
+      state :keywords do
+        rule %r/\b(#{GDScript.keywords})\b/, Keyword
+        rule %r/\b(#{GDScript.keywords_reserved})\b/, Keyword::Reserved
+      end
+
+      state :builtins do
+        rule %r/\b(#{GDScript.builtins})\b/, Name::Builtin
+        rule %r/\b((self|false|true)|(PI|TAU|NAN|INF))\b/, Name::Builtin::Pseudo
+        rule %r/\b(#{GDScript.builtins_type})\b/, Keyword::Type
+      end
+
+      state :numbers do
+        rule %r/(\d+\.\d*|\d*\.\d+)([eE][+-]?[0-9]+)?j?/, Num::Float
+        rule %r/\d+[eE][+-]?[0-9]+j?/, Num::Float
+        rule %r/0[xX][a-fA-F0-9]+/, Num::Hex
+        rule %r/\d+j?/, Num::Integer
+      end
+
+      state :name do
+        rule %r/[a-zA-Z_]\w*/, Name
+      end
+
+      state :funcname do
+        rule %r/[a-zA-Z_]\w*/, Name::Function, :pop!
+      end
+
+      state :classname do
+        rule %r/[a-zA-Z_]\w*/, Name::Class, :pop!
+      end
+
+      state :string_escape do
+        rule %r/\\([\\abfnrtv"\']|\n|N\{.*?\}|u[a-fA-F0-9]{4}|U[a-fA-F0-9]{8}|x[a-fA-F0-9]{2}|[0-7]{1,3})/, Str::Escape
+      end
+
+      state :strings_single do
+        rule %r/%(\(\w+\))?[-#0 +]*([0-9]+|[*])?(\.([0-9]+|[*]))?[hlL]?[E-GXc-giorsux%]/, Str::Interpol
+        rule %r/[^\\'%\n]+/, Str::Single
+        rule %r/["\\]/, Str::Single
+        rule %r/%/, Str::Single
+      end
+
+      state :strings_double do
+        rule %r/%(\(\w+\))?[-#0 +]*([0-9]+|[*])?(\.([0-9]+|[*]))?[hlL]?[E-GXc-giorsux%]/, Str::Interpol
+        rule %r/[^\\"%\n]+/, Str::Double
+        rule %r/['\\]/, Str::Double
+        rule %r/%/, Str::Double
+      end
+
+      state :dqs do
+        rule %r/"/, Str::Double, :pop!
+        rule %r/\\\\|\\"|\\\n/, Str::Escape
+        mixin :strings_double
+      end
+
+      state :escape_dqs do
+        mixin :string_escape
+        mixin :dqs
+      end
+
+      state :sqs do
+        rule %r/'/, Str::Single, :pop!
+        rule %r/\\\\|\\'|\\\n/, Str::Escape
+        mixin :strings_single
+      end
+
+      state :escape_sqs do
+        mixin :string_escape
+        mixin :sqs
+      end
+
+      state :tdqs do
+        rule %r/"""/, Str::Double, :pop!
+        mixin :strings_double
+        rule %r/\n/, Str::Double
+      end
+
+      state :escape_tdqs do
+        mixin :string_escape
+        mixin :tdqs
+      end
+
+      state :tsqs do
+        rule %r/'''/, Str::Single, :pop!
+        mixin :strings_single
+        rule %r/\n/, Str::Single
+      end
+
+      state :escape_tsqs do
+        mixin :string_escape
+        mixin :tsqs
+      end
+    end
+  end
+end

spec/lexers/gdscript_spec.rb

@@ -0,0 +1,19 @@
+# -*- coding: utf-8 -*- #
+# frozen_string_literal: true
+
+describe Rouge::Lexers::GDScript do
+  let(:subject) { Rouge::Lexers::GDScript.new }
+
+  describe 'guessing' do
+    include Support::Guessing
+
+    it 'guesses by filename' do
+      assert_guess :filename => 'foo.gd'
+    end
+
+    it 'guesses by mimetype' do
+      assert_guess :mimetype => 'text/x-gdscript'
+      assert_guess :mimetype => 'application/x-gdscript'
+    end
+  end
+end

spec/visual/samples/gdscript

@@ -0,0 +1,44 @@
+""" Everything on these lines is considered
+a comment. """
+
+tool
+extends BaseClass
+class_name ScriptName, "res://path/to/optional/icon.svg"
+
+# Variables & Built-in Types
+
+var i = 5
+var f = 1.23
+var h = 0xDEADC0DE
+var b = true
+var s = "Hello"
+var arr = [1, 2, 3]
+var dict = {"key": "value", 2: 3}
+var v = Vector2(1, 2)
+var t = "Hello, " \
+        + "very long " \
+        + "text"
+
+# Constants & Enums
+
+const ANSWER = 42
+enum { UNIT_NEUTRAL, UNIT_ENEMY, UNIT_ALLY }
+
+# Functions
+
+signal some_signal
+
+func some_function(param1: int, param2: float) -> int:
+    var local_var = 5
+    var format_string_1 = "We're waiting for %s." % "Godot"
+    var format_string_2 = "We're waiting for {str}"
+    var actual_string = format_string_2.format({"str": "Godot"})
+    print(param1, param2, local_var)
+    return local_var
+
+# Inner Classes
+class InnerClass extends BaseClass:
+    var local_var
+
+    func _init():
+        print(local_var)