Lua scanner for CodeRay. Meta-commit.

This commit is a super-commit containing all the subcommits for
implementing the Lua scanner.

1 files changed, 267 insertions, 0 deletions

diff --git a/lib/coderay/scanners/lua.rb b/lib/coderay/scanners/lua.rb
new file mode 100644
index 0000000..e7706fc
--- /dev/null
+++ b/lib/coderay/scanners/lua.rb
@@ -0,0 +1,267 @@
+# -*- coding: utf-8 -*-
+
+# Scanner for the Lua[http://lua.org] programming lanuage.
+#
+# The language’s complete syntax is defined in
+# {the Lua manual}[http://www.lua.org/manual/5.2/manual.html],
+# which is what this scanner tries to conform to.
+class CodeRay::Scanners::Lua < CodeRay::Scanners::Scanner
+
+  register_for :lua
+  file_extension "lua"
+  title "Lua"
+
+  # Keywords used in Lua.
+  KEYWORDS = %w[and break do else elseif end
+  for function goto if in
+  local not or repeat return
+  then until while
+  ]
+
+  # Constants set by the Lua core.
+  PREDEFINED_CONSTANTS = %w[false true nil]
+
+  # The expressions contained in this array are parts of Lua’s `basic'
+  # library. Although it’s not entirely necessary to load that library,
+  # it is highly recommended and one would have to provide own implementations
+  # of some of these expressions if one does not do so. They however aren’t
+  # keywords, neither are they constants, but nearly predefined, so they
+  # get tagged as `predefined' rather than anything else.
+  #
+  # This list excludes values of form `_UPPERCASE' because the Lua manual
+  # requires such identifiers to be reserved by Lua anyway and they are
+  # highlighted directly accordingly, without the need for specific
+  # identifiers to be listed here.
+  PREDEFINED_EXPRESSIONS = %w[
+  assert collectgarbage dofile error getmetatable
+  ipairs load loadfile next pairs pcall print
+  rawequal rawget rawlen rawset select setmetatable
+  tonumber tostring type xpcall
+  ]
+
+  # Automatic token kind selection for normal words.
+  IDENT_KIND = CodeRay::WordList.new(:ident)
+    .add(KEYWORDS, :keyword)
+    .add(PREDEFINED_CONSTANTS, :predefined_constant)
+    .add(PREDEFINED_EXPRESSIONS, :predefined)
+
+  protected
+
+  # Scanner initialization.
+  def setup
+    @state       = :initial
+    @brace_depth = 0
+  end
+
+  # CodeRay entry hook. Starts parsing.
+  def scan_tokens(encoder, options)
+    @encoder = encoder
+    @options = options
+
+    send(:"handle_state_#@state") until eos?
+
+    @encoder
+  end
+
+  def handle_state_initial
+    if match = scan(/\-\-\[\=*\[/)   #--[[ long (possibly multiline) comment ]]
+      @num_equals = match.count("=") # Number must match for comment end
+      @encoder.begin_group(:comment)
+      @encoder.text_token(match, :delimiter)
+      @state = :long_comment
+
+    elsif match = scan(/--.*?$/) # --Lua comment
+      @encoder.text_token(match, :comment)
+
+    elsif match = scan(/\[=*\[/)     # [[ long (possibly multiline) string ]]
+      @num_equals = match.count("=") # Number must match for comment end
+      @encoder.begin_group(:string)
+      @encoder.text_token(match, :delimiter)
+      @state = :long_string
+
+    elsif match = scan(/::\s*[a-zA-Z_][a-zA-Z0-9_]+\s*::/) # ::goto_label::
+      @encoder.text_token(match, :label)
+
+    elsif match = scan(/_[A-Z]+/) # _UPPERCASE are names reserved for Lua
+      @encoder.text_token(match, :predefined)
+
+    elsif match = scan(/[a-zA-Z_][a-zA-Z0-9_]*/) # Normal letters (or letters followed by digits)
+      kind = IDENT_KIND[match]
+
+      # Extra highlighting for entities following certain keywords
+      if kind == :keyword and match == "function"
+        @state = :function_expected
+      elsif kind == :keyword and match == "goto"
+        @state = :goto_label_expected
+      elsif kind == :keyword and match == "local"
+        @state = :local_var_expected
+      end
+
+      @encoder.text_token(match, kind)
+
+    elsif match = scan(/{/) # Opening table brace {
+      @encoder.begin_group(:table)
+      @encoder.text_token(match, @brace_depth >= 1 ? :inline_delimiter : :delimiter)
+      @brace_depth += 1
+      @state        = :table
+
+    elsif match = scan(/}/) # Closing table brace }
+      if @brace_depth == 1
+        @brace_depth = 0
+        @encoder.text_token(match, :delimiter)
+      elsif @brace_depth == 0 # Mismatched brace
+        @encoder.text_token(match, :error)
+      else
+        @brace_depth -= 1
+        @encoder.text_token(match, :inline_delimiter)
+        @state = :table
+      end
+      @encoder.end_group(:table)
+
+    elsif match = scan(/["']/) # String delimiters " and '
+      @encoder.begin_group(:string)
+      @encoder.text_token(match, :delimiter)
+      @start_delim = match
+      @state       = :string
+
+                      # ↓Prefix                hex number ←|→ decimal number
+    elsif match = scan(/-? (?:0x\h* \. \h+ (?:p[+\-]?\d+)? | \d*\.\d+ (?:e[+\-]?\d+)?)/ix) # hexadecimal constants have no E power, decimal ones no P power
+      @encoder.text_token(match, :float)
+
+                      # ↓Prefix         hex number ←|→ decimal number
+    elsif match = scan(/-? (?:0x\h+ (?:p[+\-]?\d+)? | \d+ (?:e[+\-]?\d+)?)/ix) # hexadecimal constants have no E power, decimal ones no P power
+      @encoder.text_token(match, :integer)
+
+    elsif match = scan(/[\+\-\*\/%^\#=~<>\(\)\[\]:;,] | \.(?!\d)/x) # Operators
+      @encoder.text_token(match, :operator)
+
+    elsif match = scan(/\s+/) # Space
+      @encoder.text_token(match, :space)
+
+    else # Invalid stuff. Note that Lua doesn’t accept multibyte chars outside of strings, hence these are also errors.
+      @encoder.text_token(getch, :error)
+    end
+
+    # It may be that we’re scanning a full-blown subexpression of a table
+    # (tables can contain full expressions in parts).
+    # If this is the case, return to :table scanning state.
+    @state = :table if @state == :initial && @brace_depth >= 1
+  end
+
+  def handle_state_function_expected
+    if match = scan(/\(.*?\)/m) # x = function() # "Anonymous" function without explicit name
+      @encoder.text_token(match, :operator)
+      @state = :initial
+    elsif match = scan(/[a-zA-Z_] (?:[a-zA-Z0-9_\.] (?!\.\d))* [\.\:]/x) # function tbl.subtbl.foo() | function tbl:foo() # Colon only allowed as last separator
+      @encoder.text_token(match, :ident)
+    elsif match = scan(/[a-zA-Z_][a-zA-Z0-9_]*/) # function foo()
+      @encoder.text_token(match, :function)
+      @state = :initial
+    elsif match = scan(/\s+/) # Between the `function' keyword and the ident may be any amount of whitespace
+      @encoder.text_token(match, :space)
+    else
+      @encoder.text_token(getch, :error)
+      @state = :initial
+    end
+  end
+
+  def handle_state_goto_label_expected
+    if match = scan(/[a-zA-Z_][a-zA-Z0-9_]*/)
+      @encoder.text_token(match, :label)
+      @state = :initial
+    elsif match = scan(/\s+/) # Between the `goto' keyword and the label may be any amount of whitespace
+      @encoder.text_token(match, :space)
+    else
+      @encoder.text_token(getch, :error)
+    end
+  end
+
+  def handle_state_local_var_expected
+    if match = scan(/function/) # local function ...
+      @encoder.text_token(match, :keyword)
+      @state = :function_expected
+    elsif match = scan(/[a-zA-Z_][a-zA-Z0-9_]*/)
+      @encoder.text_token(match, :local_variable)
+    elsif match = scan(/,/)
+      @encoder.text_token(match, :operator)
+    elsif match = scan(/=/)
+      @encoder.text_token(match, :operator)
+      # After encountering the equal sign, arbitrary expressions are
+      # allowed again, so just return to the main state for further
+      # parsing.
+      @state = :initial
+    elsif match = scan(/\n/)
+      @encoder.text_token(match, :space)
+      @state = :initial
+    elsif match = scan(/\s+/)
+      @encoder.text_token(match, :space)
+    else
+      @encoder.text_token(getch, :error)
+    end
+  end
+
+  def handle_state_long_comment
+    if match = scan(/.*?(?=\]={#@num_equals}\])/m)
+      @encoder.text_token(match, :content)
+
+      delim = scan(/\]={#@num_equals}\]/)
+      @encoder.text_token(delim, :delimiter)
+    else # No terminator found till EOF
+      @encoder.text_token(rest, :error)
+      terminate
+    end
+    @encoder.end_group(:comment)
+    @state = :initial
+  end
+
+  def handle_state_long_string
+    if match = scan(/.*?(?=\]={#@num_equals}\])/m) # Long strings do not interpret any escape sequences
+      @encoder.text_token(match, :content)
+
+      delim = scan(/\]={#@num_equals}\]/)
+      @encoder.text_token(delim, :delimiter)
+    else # No terminator found till EOF
+      @encoder.text_token(rest, :error)
+      terminate
+    end
+    @encoder.end_group(:string)
+    @state = :initial
+  end
+
+  def handle_state_string
+    if match = scan(/[^\\#@start_delim\n]+/) # Everything except \ and the start delimiter character is string content (newlines are only allowed if preceeded by \ or \z)
+      @encoder.text_token(match, :content)
+    elsif match = scan(/\\(?:['"abfnrtv\\]|z\s*|x\h\h|\d{1,3}|\n)/m)
+      @encoder.text_token(match, :char)
+    elsif match = scan(Regexp.compile(@start_delim))
+      @encoder.text_token(match, :delimiter)
+      @encoder.end_group(:string)
+      @state = :initial
+    elsif match = scan(/\n/) # Lua forbids unescaped newlines in normal non-long strings
+      @encoder.text_token("\\n\n", :error) # Visually appealing error indicator--otherwise users may wonder whether the highlighter cannot highlight multine strings
+      @encoder.end_group(:string)
+      @state = :initial
+    else
+      @encoder.text_token(getch, :error)
+    end
+  end
+
+  def handle_state_table
+    if match = scan(/[,;]/)
+      @encoder.text_token(match, :operator)
+    elsif match = scan(/[a-zA-Z_][a-zA-Z0-9_]* (?=\s*=)/x)
+      @encoder.text_token(match, :key)
+      @encoder.text_token(scan(/\s+/), :space) if check(/\s+/)
+      @encoder.text_token(scan(/=/), :operator)
+      @state = :initial
+    elsif match = scan(/\s+/m)
+      @encoder.text_token(match, :space)
+    else
+      # Note this clause doesn’t advance the scan pointer, it’s a kind of
+      # "retry with other options" (the :initial state then of course
+      # advances the pointer).
+      @state = :initial
+    end
+  end
+
+end