Raising useful exceptions

Rakefile

@@ -26,7 +26,7 @@ require 'rake/rdoctask'
 
 gemspec = Gem::Specification.new do |s|
   s.name     = 'jsmin'
-  s.version  = '1.0.1'
+  s.version  = '1.0.2'
   s.author   = 'Ryan Grove'
   s.email    = 'ryan@wonko.com'
   s.homepage = 'http://github.com/rgrove/jsmin/'

lib/jsmin.rb

@@ -55,22 +55,30 @@ module JSMin
   CHR_QUOTE      = '"'.freeze
   CHR_SPACE      = ' '.freeze
 
-  if RUBY_VERSION >= '1.9'
-    ORD_LF    = "\n".freeze
-    ORD_SPACE = ' '.freeze
-    ORD_TILDE = '~'.freeze
-  else
-    ORD_LF    = "\n"[0].freeze
-    ORD_SPACE = ' '[0].freeze
-    ORD_TILDE = '~'[0].freeze
+  ORD_LF    = "\n"[0].freeze
+  ORD_SPACE = ' '[0].freeze
+  ORD_TILDE = '~'[0].freeze
+
+  class ParseError < RuntimeError
+    attr_accessor :source, :line
+    def initialize(err, source, line)
+      @source = source,
+      @line = line
+      super "JSMin Parse Error: #{err} at line #{line} of #{source}"
+    end
   end
 
   class << self
+    def raise(err)
+      super ParseError.new(err, @source, @line)
+    end
 
     # Reads JavaScript from _input_ (which can be a String or an IO object) and
     # returns a String containing minified JS.
     def minify(input)
       @js = StringScanner.new(input.is_a?(IO) ? input.read : input.to_s)
+      @source = input.is_a?(IO) ? input.inspect : input.to_s[0..100]
+      @line = 1
 
       @a         = "\n"
       @b         = nil
@@ -147,15 +155,15 @@ def action_copy
           break if @a == @b
 
           if @a[0] <= ORD_LF
-            raise "JSMin parse error: unterminated string literal: #{@a}"
+            raise "unterminated string literal: #{@a.inspect}"
           end
 
           if @a == CHR_BACKSLASH
             @output << @a
             @a = get
 
             if @a[0] <= ORD_LF
-              raise "JSMin parse error: unterminated string literal: #{@a}"
+              raise "unterminated string literal: #{@a.inspect}"
             end
           end
         end
@@ -181,8 +189,7 @@ def action_get
             @output << @a
             @a = get
           elsif @a[0] <= ORD_LF
-            raise "JSMin parse error: unterminated regular expression " +
-                "literal: #{@a}"
+            raise "unterminated regular expression : #{@a.inspect}"
           end
 
           @output << @a
@@ -201,12 +208,18 @@ def alphanum?(c)
     # Returns the next character from the input. If the character is a control
     # character, it will be translated to a space or linefeed.
     def get
-      c = @lookahead.nil? ? @js.getch : @lookahead
-      @lookahead = nil
-
-      return c if c.nil? || c == CHR_LF || c[0] >= ORD_SPACE
-      return "\n" if c == CHR_CR
-      return ' '
+      if @lookahead
+        c = @lookahead
+        @lookahead = nil
+      else
+        c = @js.getch
+        if c == CHR_LF || c == CHR_CR
+          @line += 1
+          return CHR_LF
+        end
+        return ' ' unless c.nil? || c[0] >= ORD_SPACE
+      end
+      c
     end
 
     # Gets the next character, excluding comments.
@@ -232,7 +245,7 @@ def nextchar
             end
 
           when nil
-            raise 'JSMin parse error: unterminated comment'
+            raise 'unterminated comment'
           end
         end
 

test/js/error.js

@@ -0,0 +1,4 @@
+// This javascript is bad
+var whatever;
+whatever = "hello
+function (

test/test_exception.rb

@@ -0,0 +1,14 @@
+require File.expand_path(File.dirname(__FILE__) + "/../lib/jsmin")
+require 'test/unit'
+
+class ExceptionTest < Test::Unit::TestCase
+  def test_exception
+    File.open("js/error.js") do |i|
+      JSMin.minify(i)
+    end
+    assert_raise {}
+  rescue JSMin::ParseError => e
+    assert_equal %q{JSMin Parse Error: unterminated string literal: "\n" at line 4 of #<File:js/error.js>},
+                  e.to_s
+  end
+end