Clear previous message fields in parser

fix #818

CHANGELOG.md

@@ -3,6 +3,7 @@ Version 123:
 * Use unit-test subtree
 * Fix spurious race in websocket close test
 * Check compiler feature in Jamfile
+* Clear previous message fields in parser
 
 --------------------------------------------------------------------------------
 

include/boost/beast/http/fields.hpp

@@ -373,17 +373,19 @@ public:
     //
     //--------------------------------------------------------------------------
 
-private:
-    // VFALCO But this leaves behind the method, target, and reason!
     /** Remove all fields from the container
 
         All references, pointers, or iterators referring to contained
         elements are invalidated. All past-the-end iterators are also
         invalidated.
+
+        @par Postconditions:
+        @code
+            std::distance(this->begin(), this->end()) == 0
+        @encode
     */
     void
     clear();
-public:
 
     /** Insert a field.
 

include/boost/beast/http/impl/parser.ipp

@@ -32,6 +32,7 @@ parser(Arg1&& arg1, ArgN&&... argn)
         std::forward<ArgN>(argn)...)
     , wr_(m_)
 {
+    m_.clear();
 }
 
 template<bool isRequest, class Body, class Allocator>

test/beast/http/parser.cpp

@@ -21,6 +21,7 @@
 #include <boost/beast/http/read.hpp>
 #include <boost/beast/http/string_body.hpp>
 #include <boost/system/system_error.hpp>
+#include <algorithm>
 
 namespace boost {
 namespace beast {
@@ -329,6 +330,19 @@ public:
         BEAST_EXPECT(used == 0);
     }
 
+    void
+    testIssue818()
+    {
+        // Make sure that the parser clears pre-existing fields
+        request<string_body> m;
+        m.set(field::accept, "html/text");
+        BEAST_EXPECT(std::distance(m.begin(), m.end()) == 1);
+        request_parser<string_body> p{std::move(m)};
+        BEAST_EXPECT(std::distance(m.begin(), m.end()) == 0);
+        auto& m1 = p.get();
+        BEAST_EXPECT(std::distance(m1.begin(), m1.end()) == 0);
+    }
+
     void
     run() override
     {
@@ -336,6 +350,7 @@ public:
         testNeedMore<flat_buffer>();
         testNeedMore<multi_buffer>();
         testGotSome();
+        testIssue818();
     }
 };