Fix bug in UnnecessaryInterpolation

The UnnecessaryInterpolation linter would incorrectly report a lint for
tags with content that contained interpolation at the beginning, e.g.

  %tag #{interpolation} -- #{more_interpolation}

This was due to the really naive way we were checking if a string only
contained interpolation (only check if the first two characters were
`#{`).

Solve this by using the `extract_interpolated_values` helper originally
defined in the `ScriptExtractor`, but is now pulled out into the
`HamlLint::Utils` module.

Change-Id: I6eb1b2c06b4df0a3f6dc896e089636c853464bb1
Reviewed-on: http://gerrit.causes.com/42566
Tested-by: jenkins <[email protected]>
Reviewed-by: Shane da Silva <[email protected]>

lib/haml_lint/linter/unnecessary_interpolation.rb

@@ -10,20 +10,20 @@ class Linter::UnnecessaryInterpolation < Linter
     include LinterRegistry
 
     def visit_tag(node)
-      inline_content = node.script
-      return if inline_content.empty?
+      return if node.script.empty?
 
-      if contains_interpolation?(inline_content) &&
-         only_interpolation?(inline_content)
+      count = 0
+      chars = 2 # Include surrounding quote chars
+      HamlLint::Utils.extract_interpolated_values(node.script) do |interpolated_code|
+        count += 1
+        return if count > 1
+        chars += interpolated_code.length + 3
+      end
+
+      if chars == node.script.length
         add_lint(node, '`%... \#{expression}` can be written without ' \
                        'interpolation as `%...= expression`')
       end
     end
-
-    private
-
-    def only_interpolation?(content)
-      content.lstrip.start_with?('"#{')
-    end
   end
 end

lib/haml_lint/script_extractor.rb

@@ -90,7 +90,7 @@ def visit_filter(node)
           add_line(line, node.line + index + 1)
         end
       else
-        extract_interpolated_values(node.text) do |interpolated_code|
+        HamlLint::Utils.extract_interpolated_values(node.text) do |interpolated_code|
           add_line(interpolated_code, node)
         end
       end
@@ -150,19 +150,5 @@ def block_keyword(text)
       return unless keyword = text.scan(Haml::Parser::BLOCK_KEYWORD_REGEX)[0]
       keyword[0] || keyword[1]
     end
-
-    # Yields interpolated values within a block of filter text.
-    def extract_interpolated_values(filter_text)
-      Haml::Util.handle_interpolation(filter_text.dump) do |scan|
-        escape_count = (scan[2].size - 1) / 2
-        scan.matched[0...-3 - escape_count]
-        if escape_count.even?
-          dumped_interpolated_str = Haml::Util.balance(scan, '{', '}', 1)[0][0...-1]
-
-          # Hacky way to turn a dumped string back into a regular string
-          yield eval('"' + dumped_interpolated_str + '"') # rubocop:disable Eval
-        end
-      end
-    end
   end
 end

lib/haml_lint/utils.rb

@@ -24,6 +24,20 @@ def extract_files_from(list)
       files.uniq
     end
 
+    # Yields interpolated values within a block of filter text.
+    def extract_interpolated_values(filter_text)
+      Haml::Util.handle_interpolation(filter_text.dump) do |scan|
+        escape_count = (scan[2].size - 1) / 2
+        scan.matched[0...-3 - escape_count]
+        if escape_count.even?
+          dumped_interpolated_str = Haml::Util.balance(scan, '{', '}', 1)[0][0...-1]
+
+          # Hacky way to turn a dumped string back into a regular string
+          yield eval('"' + dumped_interpolated_str + '"') # rubocop:disable Eval
+        end
+      end
+    end
+
     # Converts a string containing underscores/hyphens/spaces into CamelCase.
     def camel_case(str)
       str.split(/_|-| /).map { |part| part.sub(/^\w/) { |c| c.upcase } }.join

spec/haml_lint/linter/unnecessary_interpolation_spec.rb

@@ -13,6 +13,11 @@
     it { should_not report_lint }
   end
 
+  context 'when tag contains inline text with interpolation at the start' do
+    let(:haml) { '%tag #{interpolation} -- #{more_interpolation}' }
+    it { should_not report_lint }
+  end
+
   context 'when tag contains inline text with only interpolation' do
     let(:haml) { '%tag #{only_interpolation}' }
     it { should report_lint }