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Deduplicate the strict-EOF/release_lookahead/error block in parser::parse()

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json_sax_dom_callback_parser and json_sax_dom_parser branches of
parser::parse() ran the same ~25 lines after sax_parse_internal():
the strict-mode EOF check (raising parse_error.101 through the SAX
parser), release_lookahead() in non-strict mode, and mapping an
errored SAX parser to a discarded result. The two copies had already
drifted apart in formatting and in the second copy's "see above"
comment.

Add a private parse_dom(DomSax&, strict) member that runs this shared
sequence once and returns whether the SAX parser did not error; both
branches of parse() now only construct their DOM SAX parser, call
parse_dom(), and (for the callback parser) map a discarded top-level
value to null. sax_parse() is left untouched, since it only runs the
EOF check and release_lookahead() when sax_parse_internal() succeeded,
unlike parse(), which runs them unconditionally.

Behavior-preserving: same operations in the same order for both SAX
parser kinds. Verified with unit-class_parser (strict/non-strict,
callback and non-callback), unit-deserialization and
unit-disabled_exceptions (JSON_NOEXCEPTION), plus a clean
make amalgamate / make check-amalgamation diff.

Overlaps #5601, which touches the same lines.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

#5712 item 2
This commit is contained in:
Niels Lohmann
2026-09-30 17:58:49 +02:00
parent e0d1123acd
commit 32d5540d37
2 changed files with 84 additions and 76 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/nlohmann/detail/input/parser.hpp
+42 -38
View File
@@ -99,28 +99,9 @@ class parser
if (callback)
{
json_sax_dom_callback_parser<BasicJsonType, InputAdapterType> sdp(result, callback, allow_exceptions, &m_lexer);
sax_parse_internal(&sdp);
if (strict)
{
// in strict mode, input must be completely read
if (get_token() != token_type::end_of_input)
{
sdp.parse_error(m_lexer.get_position(),
m_lexer.get_token_string(),
parse_error::create(101, m_lexer.get_position(),
exception_message(token_type::end_of_input, "value"), nullptr));
}
}
else
{
// the caller keeps using the input: position it right after
// the value by leaving the character that terminated it
m_lexer.release_lookahead();
}
// in case of an error, return a discarded value
if (sdp.is_errored())
if (!parse_dom(sdp, strict))
{
result = value_t::discarded;
return;
@@ -136,26 +117,9 @@ class parser
else
{
json_sax_dom_parser<BasicJsonType, InputAdapterType> sdp(result, allow_exceptions, &m_lexer);
sax_parse_internal(&sdp);
if (strict)
{
// in strict mode, input must be completely read
if (get_token() != token_type::end_of_input)
{
sdp.parse_error(m_lexer.get_position(),
m_lexer.get_token_string(),
parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr));
}
}
else
{
// see above
m_lexer.release_lookahead();
}
// in case of an error, return a discarded value
if (sdp.is_errored())
if (!parse_dom(sdp, strict))
{
result = value_t::discarded;
return;
@@ -208,6 +172,46 @@ class parser
}
private:
/*!
@brief run a DOM SAX parser to completion and position the lexer
Shared by both branches of @ref parse(): builds no SAX parser itself,
but drives an already-constructed @a json_sax_dom_parser or
@ref json_sax_dom_callback_parser through @ref sax_parse_internal(),
then applies the strict-EOF check (reporting parse_error.101 through
@a sdp on failure) or, in non-strict mode, releases the lookahead so
the caller can keep reading the input right after the parsed value.
@param[in,out] sdp the DOM SAX parser to run
@param[in] strict whether to expect the last token to be EOF
@return whether @a sdp did not report an error
*/
template<typename DomSax>
bool parse_dom(DomSax& sdp, const bool strict)
{
sax_parse_internal(&sdp);
if (strict)
{
// in strict mode, input must be completely read
if (get_token() != token_type::end_of_input)
{
sdp.parse_error(m_lexer.get_position(),
m_lexer.get_token_string(),
parse_error::create(101, m_lexer.get_position(),
exception_message(token_type::end_of_input, "value"), nullptr));
}
}
else
{
// the caller keeps using the input: position it right after
// the value by leaving the character that terminated it
m_lexer.release_lookahead();
}
return !sdp.is_errored();
}
template<typename SAX>
JSON_HEDLEY_NON_NULL(2)
bool sax_parse_internal(SAX* sax)
single_include/nlohmann/json.hpp
+42 -38
View File
@@ -17175,28 +17175,9 @@ class parser
if (callback)
{
json_sax_dom_callback_parser<BasicJsonType, InputAdapterType> sdp(result, callback, allow_exceptions, &m_lexer);
sax_parse_internal(&sdp);
if (strict)
{
// in strict mode, input must be completely read
if (get_token() != token_type::end_of_input)
{
sdp.parse_error(m_lexer.get_position(),
m_lexer.get_token_string(),
parse_error::create(101, m_lexer.get_position(),
exception_message(token_type::end_of_input, "value"), nullptr));
}
}
else
{
// the caller keeps using the input: position it right after
// the value by leaving the character that terminated it
m_lexer.release_lookahead();
}
// in case of an error, return a discarded value
if (sdp.is_errored())
if (!parse_dom(sdp, strict))
{
result = value_t::discarded;
return;
@@ -17212,26 +17193,9 @@ class parser
else
{
json_sax_dom_parser<BasicJsonType, InputAdapterType> sdp(result, allow_exceptions, &m_lexer);
sax_parse_internal(&sdp);
if (strict)
{
// in strict mode, input must be completely read
if (get_token() != token_type::end_of_input)
{
sdp.parse_error(m_lexer.get_position(),
m_lexer.get_token_string(),
parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr));
}
}
else
{
// see above
m_lexer.release_lookahead();
}
// in case of an error, return a discarded value
if (sdp.is_errored())
if (!parse_dom(sdp, strict))
{
result = value_t::discarded;
return;
@@ -17284,6 +17248,46 @@ class parser
}
private:
/*!
@brief run a DOM SAX parser to completion and position the lexer
Shared by both branches of @ref parse(): builds no SAX parser itself,
but drives an already-constructed @a json_sax_dom_parser or
@ref json_sax_dom_callback_parser through @ref sax_parse_internal(),
then applies the strict-EOF check (reporting parse_error.101 through
@a sdp on failure) or, in non-strict mode, releases the lookahead so
the caller can keep reading the input right after the parsed value.
@param[in,out] sdp the DOM SAX parser to run
@param[in] strict whether to expect the last token to be EOF
@return whether @a sdp did not report an error
*/
template<typename DomSax>
bool parse_dom(DomSax& sdp, const bool strict)
{
sax_parse_internal(&sdp);
if (strict)
{
// in strict mode, input must be completely read
if (get_token() != token_type::end_of_input)
{
sdp.parse_error(m_lexer.get_position(),
m_lexer.get_token_string(),
parse_error::create(101, m_lexer.get_position(),
exception_message(token_type::end_of_input, "value"), nullptr));
}
}
else
{
// the caller keeps using the input: position it right after
// the value by leaving the character that terminated it
m_lexer.release_lookahead();
}
return !sdp.is_errored();
}
template<typename SAX>
JSON_HEDLEY_NON_NULL(2)
bool sax_parse_internal(SAX* sax)