Empty header values are allowed & documented.

include/boost/beast/http/fields.hpp

@@ -421,6 +421,7 @@ public:
         If one or more fields with the same name already exist,
         the new field will be inserted after the last field with
         the matching name, in serialization order.
+        The value can be an empty string.
 
         @param name The field name.
 
@@ -439,6 +440,7 @@ public:
         If one or more fields with the same name already exist,
         the new field will be inserted after the last field with
         the matching name, in serialization order.
+        The value can be an empty string.
 
         @param name The field name.
 
@@ -457,6 +459,7 @@ public:
         If one or more fields with the same name already exist,
         the new field will be inserted after the last field with
         the matching name, in serialization order.
+        The value can be an empty string.
 
         @param name The field name.
 
@@ -477,13 +480,14 @@ public:
     /** Set a field value, removing any other instances of that field.
 
         First removes any values with matching field names, then
-        inserts the new field value.
+        inserts the new field value. The value may be an empty string.
 
         @param name The field name.
 
         @param value The value of the field, as a @ref boost::beast::string_view
 
         @return The field value.
+
     */
     void
     set(field name, string_view const& value);
@@ -494,7 +498,7 @@ public:
     /** Set a field value, removing any other instances of that field.
 
         First removes any values with matching field names, then
-        inserts the new field value.
+        inserts the new field value. The value can be an empty string.
 
         @param name The field name.
 

test/beast/http/fields.cpp

@@ -1072,6 +1072,20 @@ public:
         BOOST_STATIC_ASSERT(( insert_test<string_view, const char(&)[10]>::value));
     }
 
+    void
+    testEmpty()
+    {
+        beast::http::fields req;
+        req.insert("abc", "");
+        req.set("cba", "");
+        auto itr = req.find("abc");
+        BEAST_EXPECT(itr != req.end());
+        BEAST_EXPECT(itr->value().empty());
+        itr = req.find("cba");
+        BEAST_EXPECT(itr != req.end());
+        BEAST_EXPECT(itr->value().empty());
+    }
+
     void
     run() override
     {
@@ -1089,6 +1103,7 @@ public:
 
         testIssue1828();
         boost::ignore_unused(&fields_test::testIssue2085);
+        testEmpty();
     }
 };