From 7d3d0902e5e66f4f2da36736f26d9998965873f5 Mon Sep 17 00:00:00 2001
From: Vitalii Elenhaupt <velenhaupt@gmail.com>
Date: Mon, 30 Oct 2017 22:35:11 +0200
Subject: [PATCH] New rule: trailing whitespace

---
 spec/ameba/rules/trailing_whitespace_spec.cr | 27 ++++++++++++++++++++
 src/ameba/rule.cr                            |  1 +
 src/ameba/rules/line_length.cr               |  5 ++--
 src/ameba/rules/trailing_whitespace.cr       | 11 ++++++++
 4 files changed, 41 insertions(+), 3 deletions(-)
 create mode 100644 spec/ameba/rules/trailing_whitespace_spec.cr
 create mode 100644 src/ameba/rules/trailing_whitespace.cr

diff --git a/spec/ameba/rules/trailing_whitespace_spec.cr b/spec/ameba/rules/trailing_whitespace_spec.cr
new file mode 100644
index 00000000..6c799563
--- /dev/null
+++ b/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
diff --git a/src/ameba/rule.cr b/src/ameba/rule.cr
index 72fa994c..25664c84 100644
--- a/src/ameba/rule.cr
+++ b/src/ameba/rule.cr
@@ -1,6 +1,7 @@
 module Ameba
   RULES = [
     Rules::LineLength,
+    Rules::TrailingWhitespace,
   ]
 
   abstract struct Rule
diff --git a/src/ameba/rules/line_length.cr b/src/ameba/rules/line_length.cr
index 87c573a6..520ef46e 100644
--- a/src/ameba/rules/line_length.cr
+++ b/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
diff --git a/src/ameba/rules/trailing_whitespace.cr b/src/ameba/rules/trailing_whitespace.cr
new file mode 100644
index 00000000..93ec84c7
--- /dev/null
+++ b/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