option to check duplicate object keys

include/boost/json/detail/handler.hpp

@@ -35,6 +35,7 @@ struct handler
         max_string_size = string::max_size();
 
     value_stack st;
+    bool ignore_duplicate_keys = true;
 
     template<class... Args>
     explicit

include/boost/json/detail/impl/handler.ipp

@@ -51,8 +51,13 @@ bool
 handler::
 on_object_end(
     std::size_t n,
-    error_code&)
+    error_code& ec)
 {
+    if( !ignore_duplicate_keys )
+        ec = st.check_duplicates(n);
+    if( ec.failed() )
+        return false;
+
     st.push_object(n);
     return true;
 }

include/boost/json/error.hpp

@@ -66,6 +66,9 @@ enum class error
     /// error occured when trying to read input
     input_error,
 
+    /// duplicate object key
+    duplicate_key,
+
     //
     // generic errors
     //

include/boost/json/impl/error.ipp

@@ -45,6 +45,7 @@ case error::array_too_large: return "array too large";
 case error::key_too_large: return "key too large";
 case error::string_too_large: return "string too large";
 case error::input_error: return "input error";
+case error::duplicate_key: return "duplicate key";
 
 case error::exception: return "got exception";
 case error::test_failure: return "test failure";
@@ -93,6 +94,7 @@ case error::array_too_large:
 case error::key_too_large:
 case error::string_too_large:
 case error::input_error:
+case error::duplicate_key:
     return condition::parse_error;
 
 case error::missing_slash:

include/boost/json/impl/parser.ipp

@@ -32,20 +32,19 @@ parser(
         size)
 {
     reset();
+    p_.handler().ignore_duplicate_keys = opt.ignore_duplicate_keys;
 }
 
 parser::
 parser(
     storage_ptr sp,
     parse_options const& opt) noexcept
-    : p_(
-        opt,
+    : parser(
         std::move(sp),
-        nullptr,
+        opt,
+        static_cast<unsigned char*>(nullptr),
         0)
-{
-    reset();
-}
+{ }
 
 void
 parser::

include/boost/json/impl/stream_parser.ipp

@@ -32,20 +32,19 @@ stream_parser(
         size)
 {
     reset();
+    p_.handler().ignore_duplicate_keys = opt.ignore_duplicate_keys;
 }
 
 stream_parser::
 stream_parser(
     storage_ptr sp,
     parse_options const& opt) noexcept
-    : p_(
-        opt,
+    : stream_parser(
         std::move(sp),
-        nullptr,
+        opt,
+        static_cast<unsigned char*>(nullptr),
         0)
-{
-    reset();
-}
+{ }
 
 void
 stream_parser::

include/boost/json/impl/value_stack.ipp

@@ -82,6 +82,35 @@ has_chars()
     return chars_ != 0;
 }
 
+error_code
+value_stack::
+stack::
+check_duplicates(std::size_t n)
+{
+    error_code ec;
+
+    for( value* first = top_ - 2 * n; first != top_; first += 2 )
+    {
+        value* other = first + 2;
+        while( true )
+        {
+            if( first->as_string() == other->as_string() )
+            {
+                BOOST_JSON_FAIL( ec, error::duplicate_key );
+                goto before_return;
+            }
+
+            if( other == top_ )
+                break;
+
+            other += 2;
+        }
+    }
+
+before_return:
+    return ec;
+}
+
 //--------------------------------------
 
 // destroy the values but
@@ -467,6 +496,13 @@ push_null()
     st_.push(nullptr, sp_);
 }
 
+error_code
+value_stack::
+check_duplicates(std::size_t n)
+{
+    return st_.check_duplicates(n);
+}
+
 BOOST_JSON_NS_END
 
 #endif

include/boost/json/parse_options.hpp

@@ -76,6 +76,20 @@ struct parse_options
             @ref stream_parser.
     */
     bool allow_invalid_utf8 = false;
+
+
+    /** Unique keys restriction setting
+
+        Forbid duplicate keys to appear in objects.
+
+        @note Since @ref basic_parser doesn't store parsed elements directly,
+        this option has to be taken account by implementers of handlers.
+
+        @see
+            @ref basic_parser,
+            @ref stream_parser.
+    */
+    bool ignore_duplicate_keys = true;
 };
 
 BOOST_JSON_NS_END

include/boost/json/value_stack.hpp

@@ -140,6 +140,7 @@ class value_stack
         inline void run_dtors(bool b) noexcept;
         inline std::size_t size() const noexcept;
         inline bool has_chars();
+        inline error_code check_duplicates(std::size_t n);
 
         inline void clear() noexcept;
         inline void maybe_grow();
@@ -501,6 +502,10 @@ class value_stack
     BOOST_JSON_DECL
     void
     push_null();
+
+    BOOST_JSON_DECL
+    error_code
+    check_duplicates(std::size_t n);
 };
 
 BOOST_JSON_NS_END

test/error.cpp

@@ -61,6 +61,7 @@ class error_test
         check(condition::parse_error, error::key_too_large);
         check(condition::parse_error, error::string_too_large);
         check(condition::parse_error, error::input_error);
+        check(condition::parse_error, error::duplicate_key);
 
         check(condition::pointer_parse_error, error::missing_slash);
         check(condition::pointer_parse_error, error::invalid_escape);

test/parse.cpp

@@ -203,13 +203,28 @@ class parse_test
         BOOST_TEST_THROWS( parse(ss), system_error );
     }
 
+    void
+    testDuplicates()
+    {
+        value jv = parse( R"( {"a": 1, "a": 2} )" );
+        BOOST_TEST( jv.as_object().size() == 1 );
+
+        parse_options opt;
+
+        error_code ec;
+        opt.ignore_duplicate_keys = false;
+        jv = parse( R"( {"a": 1, "a": 2} )", ec, {}, opt );
+        BOOST_TEST( ec == error::duplicate_key );
+    }
+
     void
     run()
     {
         testParse();
         testMemoryUsage();
         testIssue726();
         testIstream();
+        testDuplicates();
     }
 };