Merge pull request rubocop#1205 from jonas054/835_percent_q_case_cop

Add cop PercentQLiterals

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Change log
 
+### New features
+
+* [#835](https://github.com/bbatsov/rubocop/issues/835): New cop `PercentQLiterals` checks if use of `%Q` and `%q` matches configuration. ([@jonas054][])
+
 ## master (unreleased)
 
 ### Bugs fixed

config/default.yml

@@ -325,6 +325,12 @@ Style/PercentLiteralDelimiters:
     '%W': ()
     '%x': ()
 
+Style/PercentQLiterals:
+  EnforcedStyle: lower_case_q
+  SupportedStyles:
+    - lower_case_q # Use %q when possible, %Q when necessary
+    - upper_case_q # Always use %Q
+
 Style/PredicateName:
   NamePrefixBlacklist:
     - is_

config/enabled.yml

@@ -371,6 +371,10 @@ Style/PercentLiteralDelimiters:
   Description: 'Use `%`-literal delimiters consistently'
   Enabled: true
 
+Style/PercentQLiterals:
+  Description: 'Checks if uses of %Q/%q match the configured preference.'
+  Enabled: true
+
 Style/PerlBackrefs:
   Description: 'Avoid Perl-style regex back references.'
   Enabled: true

lib/rubocop.rb

@@ -186,6 +186,7 @@
 require 'rubocop/cop/style/parameter_lists'
 require 'rubocop/cop/style/parentheses_around_condition'
 require 'rubocop/cop/style/percent_literal_delimiters'
+require 'rubocop/cop/style/percent_q_literals'
 require 'rubocop/cop/style/perl_backrefs'
 require 'rubocop/cop/style/predicate_name'
 require 'rubocop/cop/style/proc'

lib/rubocop/cop/mixin/percent_literal.rb

@@ -10,7 +10,8 @@ def percent_literal?(node)
       end
 
       def process(node, *types)
-        on_percent_literal(node, types) if percent_literal?(node)
+        return unless percent_literal?(node) && types.include?(type(node))
+        on_percent_literal(node)
       end
 
       def begin_source(node)

lib/rubocop/cop/style/percent_literal_delimiters.rb

@@ -59,11 +59,10 @@ def autocorrect(node)
           end
         end
 
-        def on_percent_literal(node, types)
+        def on_percent_literal(node)
           type = type(node)
-          return unless types.include?(type) &&
-            !uses_preferred_delimiter?(node, type) &&
-            !contains_preferred_delimiter?(node, type)
+          return if uses_preferred_delimiter?(node, type) ||
+            contains_preferred_delimiter?(node, type)
 
           add_offense(node, :expression)
         end

lib/rubocop/cop/style/percent_q_literals.rb

@@ -0,0 +1,53 @@
+# encoding: utf-8
+
+module RuboCop
+  module Cop
+    module Style
+      # This cop checks for usage of the %Q() syntax when %q() would do.
+      class PercentQLiterals < Cop
+        include PercentLiteral
+        include ConfigurableEnforcedStyle
+
+        def on_str(node)
+          process(node, '%Q', '%q')
+        end
+
+        private
+
+        def on_percent_literal(node)
+          if style == :lower_case_q
+            if type(node) == '%Q'
+              check(node,
+                    'Do not use `%Q` unless interpolation is needed.  ' \
+                    'Use `%q`.')
+            end
+          elsif type(node) == '%q'
+            check(node, 'Use `%Q` instead of `%q`.')
+          end
+        end
+
+        def check(node, msg)
+          src = node.loc.expression.source
+          # Report offense only if changing case doesn't change semantics,
+          # i.e., if the string would become dynamic or has special characters.
+          return if node.children !=
+            ProcessedSource.new(corrected(src)).ast.children
+
+          add_offense(node, :begin, msg)
+        end
+
+        def autocorrect(node)
+          src = node.loc.expression.source
+
+          @corrections << lambda do |corrector|
+            corrector.replace(node.loc.expression, corrected(src))
+          end
+        end
+
+        def corrected(src)
+          src.sub(src[1], src[1].swapcase)
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/style/unneeded_capital_w.rb

@@ -16,10 +16,8 @@ def on_array(node)
 
         private
 
-        def on_percent_literal(node, types)
-          type = type(node)
-          return unless types.include?(type) &&
-            node.children.none? { |x| x.type == :dstr }
+        def on_percent_literal(node)
+          return unless node.children.none? { |x| x.type == :dstr }
 
           add_offense(node, :expression)
         end

spec/rubocop/cop/style/percent_q_literals_spec.rb

@@ -0,0 +1,122 @@
+# encoding: utf-8
+
+require 'spec_helper'
+
+describe RuboCop::Cop::Style::PercentQLiterals, :config do
+  subject(:cop) { described_class.new(config) }
+
+  shared_examples 'accepts quote characters' do
+    it 'accepts single quotes' do
+      inspect_source(cop, ["'hi'"])
+      expect(cop.offenses).to be_empty
+    end
+
+    it 'accepts double quotes' do
+      inspect_source(cop, ['"hi"'])
+      expect(cop.offenses).to be_empty
+    end
+  end
+
+  shared_examples 'accepts any q string with backslash t' do
+    context 'with special characters' do
+      it 'accepts %q' do
+        inspect_source(cop, ['%q(\t)'])
+        expect(cop.offenses).to be_empty
+      end
+
+      it 'accepts %Q' do
+        inspect_source(cop, ['%Q(\t)'])
+        expect(cop.offenses).to be_empty
+      end
+    end
+  end
+
+  context 'when EnforcedStyle is lower_case_q' do
+    let(:cop_config) { { 'EnforcedStyle' => 'lower_case_q' } }
+
+    context 'without interpolation' do
+      it 'accepts %q' do
+        inspect_source(cop, ['%q(hi)'])
+        expect(cop.offenses).to be_empty
+      end
+
+      it 'registers offense for %Q' do
+        inspect_source(cop, ['%Q(hi)'])
+        expect(cop.messages)
+          .to eq(['Do not use `%Q` unless interpolation is needed.  Use `%q`.'])
+        expect(cop.highlights).to eq(['%Q('])
+      end
+
+      it 'auto-corrects' do
+        new_source = autocorrect_source(cop, '%Q(hi)')
+        expect(new_source).to eq('%q(hi)')
+      end
+
+      include_examples 'accepts quote characters'
+      include_examples 'accepts any q string with backslash t'
+    end
+
+    context 'with interpolation' do
+      it 'accepts %Q' do
+        inspect_source(cop, ['%Q(#{1 + 2})'])
+        expect(cop.offenses).to be_empty
+      end
+
+      it 'accepts %q' do
+        # This is most probably a mistake, but not this cop's responisibility.
+        inspect_source(cop, ['%q(#{1 + 2})'])
+        expect(cop.offenses).to be_empty
+      end
+
+      include_examples 'accepts quote characters'
+    end
+  end
+
+  context 'when EnforcedStyle is upper_case_q' do
+    let(:cop_config) { { 'EnforcedStyle' => 'upper_case_q' } }
+
+    context 'without interpolation' do
+      it 'registers offense for %q' do
+        inspect_source(cop, ['%q(hi)'])
+        expect(cop.messages).to eq(['Use `%Q` instead of `%q`.'])
+        expect(cop.highlights).to eq(['%q('])
+      end
+
+      it 'accepts %Q' do
+        inspect_source(cop, ['%Q(hi)'])
+        expect(cop.offenses).to be_empty
+      end
+
+      it 'auto-corrects' do
+        new_source = autocorrect_source(cop, '%q[hi]')
+        expect(new_source).to eq('%Q[hi]')
+      end
+
+      include_examples 'accepts quote characters'
+      include_examples 'accepts any q string with backslash t'
+    end
+
+    context 'with interpolation' do
+      it 'accepts %Q' do
+        inspect_source(cop, ['%Q(#{1 + 2})'])
+        expect(cop.offenses).to be_empty
+      end
+
+      it 'accepts %q' do
+        # It's strange if interpolation syntax appears inside a static string,
+        # but we can't be sure if it's a mistake or not. Changing it to %Q
+        # would alter semantics, so we leave it as it is.
+        inspect_source(cop, ['%q(#{1 + 2})'])
+        expect(cop.offenses).to be_empty
+      end
+
+      it 'does not auto-correct' do
+        source = '%q(#{1 + 2})'
+        new_source = autocorrect_source(cop, source)
+        expect(new_source).to eq(source)
+      end
+
+      include_examples 'accepts quote characters'
+    end
+  end
+end

spec/rubocop/cop/style/unneeded_percent_q_spec.rb

@@ -18,7 +18,7 @@
     end
 
     it 'accepts a string with single quotes and double quotes' do
-      inspect_source(cop, %Q(%q('"hi"')))
+      inspect_source(cop, %q(%q('"hi"')))
       expect(cop.offenses).to be_empty
     end
 
@@ -43,7 +43,7 @@
     end
 
     it 'accepts a string with single quotes and double quotes' do
-      inspect_source(cop, %Q(%Q('"hi"')))
+      inspect_source(cop, %q(%Q('"hi"')))
       expect(cop.offenses).to be_empty
     end