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Share the diagnostic-position setter of the DOM SAX parsers

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json_sax_dom_parser and json_sax_dom_callback_parser each had a private
copy of handle_diagnostic_positions_for_json_value(), identical except
for comments. Move the body into one static member function,
detail::diagnostic_positions::set_from_lexer(value, lexer), which both
classes call with their lexer pointer. basic_json befriends the new
struct (only when JSON_DIAGNOSTIC_POSITIONS is enabled), as the position
members are private.

The discarded case is reached through the callback parser, so the
LCOV_EXCL markers that only the dom parser's copy had are gone. The
NOLINT on the unreachable default case loses the stray
"-warnings-as-errors", which is not a check name.

The start-position setup in start_object()/start_array() is left alone,
as #5706 is editing the callback parser's versions.

Behavior, the public API and the ABI are unchanged.

Part of #5712

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann
2026-09-30 09:44:47 +02:00
parent 633de8e44b
commit c620c01063
3 changed files with 182 additions and 284 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/nlohmann/detail/input/json_sax.hpp
+88 -142
View File
@@ -175,6 +175,88 @@ template<typename ArrayType>
inline void reserve_array(ArrayType& /*arr*/, std::size_t /*len*/, priority_tag<0> /*unused*/)
{}
#if JSON_DIAGNOSTIC_POSITIONS
/*!
@brief set the diagnostic positions of a value the DOM SAX parsers just stored
Shared by json_sax_dom_parser and json_sax_dom_callback_parser. basic_json
befriends this struct, as the position members are private.
*/
struct diagnostic_positions
{
/*!
@param[in,out] v the value that was just parsed
@param[in] lexer the lexer that read it, or nullptr to leave @a v alone
*/
template<typename BasicJsonType, typename LexerType>
static void set_from_lexer(BasicJsonType& v, LexerType* lexer)
{
if (lexer)
{
// Lexer has read past the current field value, so set the end position to the current position.
// The start position will be set below based on the length of the string representation
// of the value.
v.end_position = lexer->get_position();
switch (v.type())
{
case value_t::boolean:
{
// 4 and 5 are the string length of "true" and "false"
v.start_position = v.end_position - (v.m_data.m_value.boolean ? 4 : 5);
break;
}
case value_t::null:
{
// 4 is the string length of "null"
v.start_position = v.end_position - 4;
break;
}
case value_t::string:
{
// escape sequences make the token longer than the value it
// parses to, so the start position cannot be derived from
// the value; use the offset the lexer recorded instead
v.start_position = lexer->get_token_start_position();
break;
}
case value_t::discarded:
{
// an object or array the callback of
// json_sax_dom_callback_parser rejected has no position
v.end_position = std::string::npos;
v.start_position = v.end_position;
break;
}
case value_t::binary:
case value_t::number_integer:
case value_t::number_unsigned:
case value_t::number_float:
{
v.start_position = v.end_position - lexer->get_string().size();
break;
}
case value_t::object:
case value_t::array:
{
// object and array are handled in start_object() and start_array() handlers
// skip setting the values here.
break;
}
default: // LCOV_EXCL_LINE
// Handle all possible types discretely, default handler should never be reached.
JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert) LCOV_EXCL_LINE
}
}
}
};
#endif
/*!
@brief SAX implementation to create a JSON value from SAX events
@@ -376,76 +458,6 @@ class json_sax_dom_parser
private:
#if JSON_DIAGNOSTIC_POSITIONS
void handle_diagnostic_positions_for_json_value(BasicJsonType& v)
{
if (m_lexer_ref)
{
// Lexer has read past the current field value, so set the end position to the current position.
// The start position will be set below based on the length of the string representation
// of the value.
v.end_position = m_lexer_ref->get_position();
switch (v.type())
{
case value_t::boolean:
{
// 4 and 5 are the string length of "true" and "false"
v.start_position = v.end_position - (v.m_data.m_value.boolean ? 4 : 5);
break;
}
case value_t::null:
{
// 4 is the string length of "null"
v.start_position = v.end_position - 4;
break;
}
case value_t::string:
{
// escape sequences make the token longer than the value it
// parses to, so the start position cannot be derived from
// the value; use the offset the lexer recorded instead
v.start_position = m_lexer_ref->get_token_start_position();
break;
}
// As we handle the start and end positions for values created during parsing,
// we do not expect the following value type to be called. Regardless, set the positions
// in case this is created manually or through a different constructor. Exclude from lcov
// since the exact condition of this switch is esoteric.
// LCOV_EXCL_START
case value_t::discarded:
{
v.end_position = std::string::npos;
v.start_position = v.end_position;
break;
}
// LCOV_EXCL_STOP
case value_t::binary:
case value_t::number_integer:
case value_t::number_unsigned:
case value_t::number_float:
{
v.start_position = v.end_position - m_lexer_ref->get_string().size();
break;
}
case value_t::object:
case value_t::array:
{
// object and array are handled in start_object() and start_array() handlers
// skip setting the values here.
break;
}
default: // LCOV_EXCL_LINE
// Handle all possible types discretely, default handler should never be reached.
JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert,-warnings-as-errors) LCOV_EXCL_LINE
}
}
}
#endif
/*!
@invariant If the ref stack is empty, then the passed value will be the new
root.
@@ -461,7 +473,7 @@ class json_sax_dom_parser
root = BasicJsonType(std::forward<Value>(v));
#if JSON_DIAGNOSTIC_POSITIONS
handle_diagnostic_positions_for_json_value(root);
diagnostic_positions::set_from_lexer(root, m_lexer_ref);
#endif
return &root;
@@ -474,7 +486,7 @@ class json_sax_dom_parser
ref_stack.back()->m_data.m_value.array->emplace_back(std::forward<Value>(v));
#if JSON_DIAGNOSTIC_POSITIONS
handle_diagnostic_positions_for_json_value(ref_stack.back()->m_data.m_value.array->back());
diagnostic_positions::set_from_lexer(ref_stack.back()->m_data.m_value.array->back(), m_lexer_ref);
#endif
return &(ref_stack.back()->m_data.m_value.array->back());
@@ -485,7 +497,7 @@ class json_sax_dom_parser
*object_element = BasicJsonType(std::forward<Value>(v));
#if JSON_DIAGNOSTIC_POSITIONS
handle_diagnostic_positions_for_json_value(*object_element);
diagnostic_positions::set_from_lexer(*object_element, m_lexer_ref);
#endif
return object_element;
@@ -662,7 +674,7 @@ class json_sax_dom_callback_parser
#if JSON_DIAGNOSTIC_POSITIONS
// Set start/end positions for discarded object.
handle_diagnostic_positions_for_json_value(*ref_stack.back());
diagnostic_positions::set_from_lexer(*ref_stack.back(), m_lexer_ref);
#endif
}
}
@@ -778,7 +790,7 @@ class json_sax_dom_callback_parser
#if JSON_DIAGNOSTIC_POSITIONS
// Set start/end positions for discarded array.
handle_diagnostic_positions_for_json_value(*ref_stack.back());
diagnostic_positions::set_from_lexer(*ref_stack.back(), m_lexer_ref);
#endif
}
}
@@ -831,72 +843,6 @@ class json_sax_dom_callback_parser
private:
#if JSON_DIAGNOSTIC_POSITIONS
void handle_diagnostic_positions_for_json_value(BasicJsonType& v)
{
if (m_lexer_ref)
{
// Lexer has read past the current field value, so set the end position to the current position.
// The start position will be set below based on the length of the string representation
// of the value.
v.end_position = m_lexer_ref->get_position();
switch (v.type())
{
case value_t::boolean:
{
// 4 and 5 are the string length of "true" and "false"
v.start_position = v.end_position - (v.m_data.m_value.boolean ? 4 : 5);
break;
}
case value_t::null:
{
// 4 is the string length of "null"
v.start_position = v.end_position - 4;
break;
}
case value_t::string:
{
// escape sequences make the token longer than the value it
// parses to, so the start position cannot be derived from
// the value; use the offset the lexer recorded instead
v.start_position = m_lexer_ref->get_token_start_position();
break;
}
case value_t::discarded:
{
v.end_position = std::string::npos;
v.start_position = v.end_position;
break;
}
case value_t::binary:
case value_t::number_integer:
case value_t::number_unsigned:
case value_t::number_float:
{
v.start_position = v.end_position - m_lexer_ref->get_string().size();
break;
}
case value_t::object:
case value_t::array:
{
// object and array are handled in start_object() and start_array() handlers
// skip setting the values here.
break;
}
default: // LCOV_EXCL_LINE
// Handle all possible types discretely, default handler should never be reached.
JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert,-warnings-as-errors) LCOV_EXCL_LINE
}
}
}
#endif
/// if there is a pending duplicate-key stash entry for this exact slot,
/// remove it from the stash; if restore_value is true, the stashed
/// previous value is moved back into the slot first (use this when the
@@ -1018,7 +964,7 @@ class json_sax_dom_callback_parser
auto value = BasicJsonType(std::forward<Value>(v));
#if JSON_DIAGNOSTIC_POSITIONS
handle_diagnostic_positions_for_json_value(value);
diagnostic_positions::set_from_lexer(value, m_lexer_ref);
#endif
// check callback
include/nlohmann/json.hpp
+3
View File
@@ -149,6 +149,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
friend class ::nlohmann::detail::json_sax_dom_parser;
template<typename BasicJsonType, typename InputAdapterType>
friend class ::nlohmann::detail::json_sax_dom_callback_parser;
#if JSON_DIAGNOSTIC_POSITIONS
friend struct ::nlohmann::detail::diagnostic_positions;
#endif
friend class ::nlohmann::detail::exception;
/// workaround type for MSVC
single_include/nlohmann/json.hpp
+91 -142
View File
@@ -11589,6 +11589,88 @@ template<typename ArrayType>
inline void reserve_array(ArrayType& /*arr*/, std::size_t /*len*/, priority_tag<0> /*unused*/)
{}
#if JSON_DIAGNOSTIC_POSITIONS
/*!
@brief set the diagnostic positions of a value the DOM SAX parsers just stored
Shared by json_sax_dom_parser and json_sax_dom_callback_parser. basic_json
befriends this struct, as the position members are private.
*/
struct diagnostic_positions
{
/*!
@param[in,out] v the value that was just parsed
@param[in] lexer the lexer that read it, or nullptr to leave @a v alone
*/
template<typename BasicJsonType, typename LexerType>
static void set_from_lexer(BasicJsonType& v, LexerType* lexer)
{
if (lexer)
{
// Lexer has read past the current field value, so set the end position to the current position.
// The start position will be set below based on the length of the string representation
// of the value.
v.end_position = lexer->get_position();
switch (v.type())
{
case value_t::boolean:
{
// 4 and 5 are the string length of "true" and "false"
v.start_position = v.end_position - (v.m_data.m_value.boolean ? 4 : 5);
break;
}
case value_t::null:
{
// 4 is the string length of "null"
v.start_position = v.end_position - 4;
break;
}
case value_t::string:
{
// escape sequences make the token longer than the value it
// parses to, so the start position cannot be derived from
// the value; use the offset the lexer recorded instead
v.start_position = lexer->get_token_start_position();
break;
}
case value_t::discarded:
{
// an object or array the callback of
// json_sax_dom_callback_parser rejected has no position
v.end_position = std::string::npos;
v.start_position = v.end_position;
break;
}
case value_t::binary:
case value_t::number_integer:
case value_t::number_unsigned:
case value_t::number_float:
{
v.start_position = v.end_position - lexer->get_string().size();
break;
}
case value_t::object:
case value_t::array:
{
// object and array are handled in start_object() and start_array() handlers
// skip setting the values here.
break;
}
default: // LCOV_EXCL_LINE
// Handle all possible types discretely, default handler should never be reached.
JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert) LCOV_EXCL_LINE
}
}
}
};
#endif
/*!
@brief SAX implementation to create a JSON value from SAX events
@@ -11790,76 +11872,6 @@ class json_sax_dom_parser
private:
#if JSON_DIAGNOSTIC_POSITIONS
void handle_diagnostic_positions_for_json_value(BasicJsonType& v)
{
if (m_lexer_ref)
{
// Lexer has read past the current field value, so set the end position to the current position.
// The start position will be set below based on the length of the string representation
// of the value.
v.end_position = m_lexer_ref->get_position();
switch (v.type())
{
case value_t::boolean:
{
// 4 and 5 are the string length of "true" and "false"
v.start_position = v.end_position - (v.m_data.m_value.boolean ? 4 : 5);
break;
}
case value_t::null:
{
// 4 is the string length of "null"
v.start_position = v.end_position - 4;
break;
}
case value_t::string:
{
// escape sequences make the token longer than the value it
// parses to, so the start position cannot be derived from
// the value; use the offset the lexer recorded instead
v.start_position = m_lexer_ref->get_token_start_position();
break;
}
// As we handle the start and end positions for values created during parsing,
// we do not expect the following value type to be called. Regardless, set the positions
// in case this is created manually or through a different constructor. Exclude from lcov
// since the exact condition of this switch is esoteric.
// LCOV_EXCL_START
case value_t::discarded:
{
v.end_position = std::string::npos;
v.start_position = v.end_position;
break;
}
// LCOV_EXCL_STOP
case value_t::binary:
case value_t::number_integer:
case value_t::number_unsigned:
case value_t::number_float:
{
v.start_position = v.end_position - m_lexer_ref->get_string().size();
break;
}
case value_t::object:
case value_t::array:
{
// object and array are handled in start_object() and start_array() handlers
// skip setting the values here.
break;
}
default: // LCOV_EXCL_LINE
// Handle all possible types discretely, default handler should never be reached.
JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert,-warnings-as-errors) LCOV_EXCL_LINE
}
}
}
#endif
/*!
@invariant If the ref stack is empty, then the passed value will be the new
root.
@@ -11875,7 +11887,7 @@ class json_sax_dom_parser
root = BasicJsonType(std::forward<Value>(v));
#if JSON_DIAGNOSTIC_POSITIONS
handle_diagnostic_positions_for_json_value(root);
diagnostic_positions::set_from_lexer(root, m_lexer_ref);
#endif
return &root;
@@ -11888,7 +11900,7 @@ class json_sax_dom_parser
ref_stack.back()->m_data.m_value.array->emplace_back(std::forward<Value>(v));
#if JSON_DIAGNOSTIC_POSITIONS
handle_diagnostic_positions_for_json_value(ref_stack.back()->m_data.m_value.array->back());
diagnostic_positions::set_from_lexer(ref_stack.back()->m_data.m_value.array->back(), m_lexer_ref);
#endif
return &(ref_stack.back()->m_data.m_value.array->back());
@@ -11899,7 +11911,7 @@ class json_sax_dom_parser
*object_element = BasicJsonType(std::forward<Value>(v));
#if JSON_DIAGNOSTIC_POSITIONS
handle_diagnostic_positions_for_json_value(*object_element);
diagnostic_positions::set_from_lexer(*object_element, m_lexer_ref);
#endif
return object_element;
@@ -12076,7 +12088,7 @@ class json_sax_dom_callback_parser
#if JSON_DIAGNOSTIC_POSITIONS
// Set start/end positions for discarded object.
handle_diagnostic_positions_for_json_value(*ref_stack.back());
diagnostic_positions::set_from_lexer(*ref_stack.back(), m_lexer_ref);
#endif
}
}
@@ -12192,7 +12204,7 @@ class json_sax_dom_callback_parser
#if JSON_DIAGNOSTIC_POSITIONS
// Set start/end positions for discarded array.
handle_diagnostic_positions_for_json_value(*ref_stack.back());
diagnostic_positions::set_from_lexer(*ref_stack.back(), m_lexer_ref);
#endif
}
}
@@ -12245,72 +12257,6 @@ class json_sax_dom_callback_parser
private:
#if JSON_DIAGNOSTIC_POSITIONS
void handle_diagnostic_positions_for_json_value(BasicJsonType& v)
{
if (m_lexer_ref)
{
// Lexer has read past the current field value, so set the end position to the current position.
// The start position will be set below based on the length of the string representation
// of the value.
v.end_position = m_lexer_ref->get_position();
switch (v.type())
{
case value_t::boolean:
{
// 4 and 5 are the string length of "true" and "false"
v.start_position = v.end_position - (v.m_data.m_value.boolean ? 4 : 5);
break;
}
case value_t::null:
{
// 4 is the string length of "null"
v.start_position = v.end_position - 4;
break;
}
case value_t::string:
{
// escape sequences make the token longer than the value it
// parses to, so the start position cannot be derived from
// the value; use the offset the lexer recorded instead
v.start_position = m_lexer_ref->get_token_start_position();
break;
}
case value_t::discarded:
{
v.end_position = std::string::npos;
v.start_position = v.end_position;
break;
}
case value_t::binary:
case value_t::number_integer:
case value_t::number_unsigned:
case value_t::number_float:
{
v.start_position = v.end_position - m_lexer_ref->get_string().size();
break;
}
case value_t::object:
case value_t::array:
{
// object and array are handled in start_object() and start_array() handlers
// skip setting the values here.
break;
}
default: // LCOV_EXCL_LINE
// Handle all possible types discretely, default handler should never be reached.
JSON_ASSERT(false); // NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert,-warnings-as-errors) LCOV_EXCL_LINE
}
}
}
#endif
/// if there is a pending duplicate-key stash entry for this exact slot,
/// remove it from the stash; if restore_value is true, the stashed
/// previous value is moved back into the slot first (use this when the
@@ -12432,7 +12378,7 @@ class json_sax_dom_callback_parser
auto value = BasicJsonType(std::forward<Value>(v));
#if JSON_DIAGNOSTIC_POSITIONS
handle_diagnostic_positions_for_json_value(value);
diagnostic_positions::set_from_lexer(value, m_lexer_ref);
#endif
// check callback
@@ -26230,6 +26176,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
friend class ::nlohmann::detail::json_sax_dom_parser;
template<typename BasicJsonType, typename InputAdapterType>
friend class ::nlohmann::detail::json_sax_dom_callback_parser;
#if JSON_DIAGNOSTIC_POSITIONS
friend struct ::nlohmann::detail::diagnostic_positions;
#endif
friend class ::nlohmann::detail::exception;
/// workaround type for MSVC