Implement emitting utf8 charset when seen in output

output_compressed.cpp

@@ -10,14 +10,23 @@
 namespace Sass {
   using namespace std;
 
-  Output_Compressed::Output_Compressed(Context* ctx) : buffer(""), rendered_imports(""), ctx(ctx) { }
+  Output_Compressed::Output_Compressed(Context* ctx) : buffer(""), rendered_imports(""), ctx(ctx), seen_utf8(false) { }
   Output_Compressed::~Output_Compressed() { }
 
   inline void Output_Compressed::fallback_impl(AST_Node* n)
   {
     Inspect i(ctx);
     n->perform(&i);
-    buffer += i.get_buffer();
+    const string& text = i.get_buffer();
+    for(const char& chr : text) {
+      // abort clause
+      if (seen_utf8) break;
+      // skip all normal ascii chars
+      if (Util::isAscii(chr)) continue;
+      // singleton
+      seen_utf8 = true;
+    }
+    buffer += text;
   }
 
   void Output_Compressed::operator()(Import* imp)
@@ -205,7 +214,16 @@ namespace Sass {
     else {
       Inspect i(ctx);
       c->perform(&i);
-      buffer += i.get_buffer();
+      const string& text = i.get_buffer();
+      for(const char& chr : text) {
+        // abort clause
+        if (seen_utf8) break;
+        // skip all normal ascii chars
+        if (Util::isAscii(chr)) continue;
+        // singleton
+        seen_utf8 = true;
+      }
+      buffer += text;
     }
   }
 
@@ -364,6 +382,14 @@ namespace Sass {
   void Output_Compressed::append_singleline_part_to_buffer(const string& text)
   {
     buffer += text;
+    for(const char& chr : text) {
+      // abort clause
+      if (seen_utf8) break;
+      // skip all normal ascii chars
+      if (Util::isAscii(chr)) continue;
+      // singleton
+      seen_utf8 = true;
+    }
     if (ctx && !ctx->_skip_source_map_update)
       ctx->source_map.update_column(text);
   }

output_compressed.hpp

@@ -16,6 +16,7 @@ namespace Sass {
     string buffer;
     string rendered_imports;
     Context* ctx;
+    bool seen_utf8;
 
     void fallback_impl(AST_Node* n);
 
@@ -25,7 +26,10 @@ namespace Sass {
     Output_Compressed(Context* ctx = 0);
     virtual ~Output_Compressed();
 
-    string get_buffer() { return rendered_imports + buffer; }
+    string get_buffer() {
+      return (seen_utf8 ? "@charset \"UTF-8\";\n" : "")
+             + rendered_imports + buffer;
+    }
 
     // statements
     virtual void operator()(Block*);

output_nested.cpp

@@ -12,15 +12,24 @@ namespace Sass {
   using namespace std;
 
   Output_Nested::Output_Nested(bool source_comments, Context* ctx)
-  : buffer(""), rendered_imports(""), indentation(0), source_comments(source_comments), ctx(ctx)
+  : buffer(""), rendered_imports(""), indentation(0), source_comments(source_comments), ctx(ctx), seen_utf8(false)
   { }
   Output_Nested::~Output_Nested() { }
 
   inline void Output_Nested::fallback_impl(AST_Node* n)
   {
     Inspect i(ctx);
     n->perform(&i);
-    buffer += i.get_buffer();
+    const string& text = i.get_buffer();
+    for(const char& chr : text) {
+      // abort clause
+      if (seen_utf8) break;
+      // skip all normal ascii chars
+      if (Util::isAscii(chr)) continue;
+      // singleton
+      seen_utf8 = true;
+    }
+    buffer += text;
   }
 
   void Output_Nested::operator()(Import* imp)
@@ -338,6 +347,14 @@ namespace Sass {
   void Output_Nested::append_to_buffer(const string& text)
   {
     buffer += text;
+    for(const char& chr : text) {
+      // abort clause
+      if (seen_utf8) break;
+      // skip all normal ascii chars
+      if (Util::isAscii(chr)) continue;
+      // singleton
+      seen_utf8 = true;
+    }
     if (ctx && !ctx->_skip_source_map_update)
       ctx->source_map.update_column(text);
   }

output_nested.hpp

@@ -21,6 +21,7 @@ namespace Sass {
     size_t indentation;
     bool source_comments;
     Context* ctx;
+    bool seen_utf8;
     void indent();
 
     void fallback_impl(AST_Node* n);
@@ -33,10 +34,11 @@ namespace Sass {
     virtual ~Output_Nested();
 
     string get_buffer() {
-        if (!rendered_imports.empty() && !buffer.empty()) {
-            rendered_imports += "\n";
-        }
-        return rendered_imports + buffer;
+      if (!rendered_imports.empty() && !buffer.empty()) {
+        rendered_imports += "\n";
+      }
+      return (seen_utf8 ? "@charset \"UTF-8\";\n" : "")
+             + rendered_imports + buffer;
     }
 
     // statements