New rule: trailing whitespace

spec/ameba/rules/trailing_whitespace_spec.cr

@@ -0,0 +1,27 @@
+require "../../spec_helper"
+
+module Ameba::Rules
+  subject = TrailingWhitespace.new
+
+  describe TrailingWhitespace do
+    it "passes if all lines do not have trailing whitespace" do
+      source = Source.new "", "no-whispace"
+      subject.catch(source).valid?.should be_true
+    end
+
+    it "fails if there is a line with trailing whitespace" do
+      source = Source.new "", "whitespace at the end "
+      subject.catch(source).valid?.should be_false
+    end
+
+    it "reports rule, pos and message" do
+      source = Source.new "", "a = 1\n b = 2 "
+      subject.catch(source).valid?.should be_false
+
+      error = source.errors.first
+      error.rule.should_not be_nil
+      error.pos.should eq 2
+      error.message.should eq "Trailing whitespace detected"
+    end
+  end
+end

src/ameba/rule.cr

@@ -1,6 +1,7 @@
 module Ameba
   RULES = [
     Rules::LineLength,
+    Rules::TrailingWhitespace,
   ]
 
   abstract struct Rule

src/ameba/rules/line_length.cr

@@ -6,9 +6,8 @@ module Ameba::Rules
   struct LineLength < Rule
     def test(source)
       source.lines.each_with_index do |line, index|
-        if line.size > 79
-          source.error self, index + 1, "Line too long (#{line.size} symbols)"
-        end
+        next unless line.size > 79
+        source.error self, index + 1, "Line too long (#{line.size} symbols)"
       end
     end
   end

src/ameba/rules/trailing_whitespace.cr

@@ -0,0 +1,11 @@
+module Ameba::Rules
+  # A rule that disallows trailing whitespace at the end of a line.
+  struct TrailingWhitespace < Rule
+    def test(source)
+      source.lines.each_with_index do |line, index|
+        next unless line =~ /\s$/
+        source.error self, index + 1, "Trailing whitespace detected"
+      end
+    end
+  end
+end