Add dump() and comparisons to json_view (#5624)

* Add dump() and comparisons to json_view

Add basic_json_view::dump() and the comparison operators, and read
floats from the parser's digit layout instead of rescanning the
token.

dump(indent, indent_char, ensure_ascii, number_format) writes a
value the way ordered_json::parse(text).dump() writes it for the
same arguments: members in document order, all of them should a
key occur more than once; strings escaped by the same rules, using
the library's scanning kernels; floats written with the library's
to_chars conversion, so the output equals basic_json's byte for
byte; integers copied from the source, where they are already
canonical, except -0, which parse() reads as 0. There is no
error_handler argument, because the view only holds valid UTF-8.
number_format::source copies numbers exactly as they appear in the
source (e.g. "1.50", "1E2", "-0"), which basic_json cannot provide.
operator<< takes the indentation from the stream width, as for
basic_json. The writer walks iteratively, so nesting depth is
limited by memory only.

operator== and operator!= compare two views, or a view and a
basic_json value in either order, by the rules basic_json's
operator== uses: numbers compare by value across their types,
objects compare by their members with duplicate keys resolved as
parse() resolves them, member order matters only where the object
type keeps one, and discarded views compare as discarded basic_json
values do, including under JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON.
Nothing is materialized except single scalars.

While parsing, the view now records where the integer digits, the
fraction digits, and the exponent of a float token are, so floats
and doubles with at most 19 digits are read from that layout with
the library's decimal_to_float() instead of rescanning the token.
Both round correctly, so the values are those of parse(). get<double>(),
materialize(), dump(), and the comparisons all use it.

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

* Avoid raw string with escapes inside CHECK macro (MSVC C2017)

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

* Size the dump buffer of a small value by its own extent

The source extent of a value was read from the next node, falling back to the rest of the document when that node held a decoded string. dump() of a small value could thus allocate a buffer as large as the document. Skip a few such nodes, cap the fallback estimate, and shrink a buffer that is much larger than its output.

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

* Hold the documents of the dump and comparison tests in names

root() of a temporary document is deleted: its views would dangle.

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

* Do not shrink the output of dump()

finish() copied the whole output when the buffer was more than twice as
large as the result (citm dump +11%). The tighter source_extent()
estimate already keeps the buffer of a small value small.

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

* Document and test first-wins lookups next to dump() and ==

dump() writes every member and == resolves duplicate keys as parse()
does, whereas lookups find the first member of a duplicate key.

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

* Fix the clang-tidy 22 findings in json_view and its tests

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

* Split the dump and comparison tests off unit-json_view.cpp

The MinGW linker of the Windows clang jobs cannot link object files with more
than 32767 sections ("relocation truncated to fit: IMAGE_REL_AMD64_REL32
against `.rdata'"). unit-json_view.cpp reaches that limit as the stack
grows, so its "json_view dump" and "json_view comparison" test cases move
into unit-json_view_dump.cpp. The test generator and has_duplicate_keys()
that both files use move into json_view_test_helpers.hpp.

The new file mentions JSON_HAS_CPP_17, so it is built for C++17 like the file
it was split from.

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

* Make json_view.hpp pass include-what-you-use

ci_single_binaries runs IWYU with --error on every header. For json_view.hpp
it suggested adding <array> (std::array is used), the headers that json.hpp
already provides (abi_config, abi_macros, input_adapters, json_pointer,
cpp_future, string_concat, value_t, json_fwd), and <version> for
std::nullptr_t, and removing <cstddef>.

- include <array>
- keep <cstddef> (nullptr_t, size_t; IWYU attributes them to <version> and <cstring>)
- tell IWYU not to suggest the headers that json.hpp provides: the amalgamated
  json_view.hpp only includes json.hpp, so including them here would duplicate
  their definitions

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

* Regenerate the amalgamated headers

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

* Follow the renames from the review of the view builder

The review of #5620 renamed document_data's tape/tape_size/tape_cap to
nodes/node_count/node_capacity and made the decode arena a
std::vector<char>; adapt the code of this change to it.

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

* Keep the stream includes of json_view.hpp for IWYU

json_view.hpp uses std::istream and std::ostream itself, but IWYU sees
them through the exported json.hpp and asked to remove both includes,
which fails ci_single_binaries (single_json_view).

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

* Address the review of json_view dump() and comparisons

From gregmarr's review of #5624:

- The output buffer takes string literals without a length.
- write_float() names the IEEE single/double condition once, as the
  library's serializer does.
- equal() checks the types first and compares with !=; the reference to
  the top frame is noted as dangling after pop_back().
- dump.md: one paragraph per case in the notes.

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

* Regenerate the amalgamated headers

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

* Exclude all json_view test files from Infer's reports

The same std::unique_ptr false positive (USE_AFTER_DELETE) also shows for
two json_documents parsed in one lambda in unit-json_view_dump.cpp
(ci_infer). It affects any test that holds several documents, so the
exclusion now covers tests/src/unit-json_view*.cpp; ASan and Valgrind
cover these tests.

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

* Allow the string literal parameter of the view serializer's put() for clang-tidy

The overload takes the literal by array reference so that its length is a
template parameter, like scan_literal() and the C array overloads of
to_json() and from_json().

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

* Bind the serializer's frame only after the check for its end

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

* Regenerate the amalgamated headers

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

---------

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

tests/benchmarks/README.md

@@ -21,6 +21,7 @@ Micro-benchmarks for parsing, serialization and the binary formats, written with
 | `ViewParseIndented` | as `ParseIndented`, with a reused `json_document` |
 | `ViewAccept` | validate with `json_document::accept`; compare with `Accept` |
 | `ViewMaterialize` | convert a parsed `json_document` into a `json` value |
+| `ViewDump` | serialize a parsed `json_document`; compare with `Dump` |
 
 The input files are those of [nativejson-benchmark](https://github.com/miloyip/nativejson-benchmark) (`canada`,
 `citm_catalog`, `twitter`), a large `jeopardy` file, and number-heavy files (`floats`, `signed_ints`, ...).

tests/benchmarks/src/benchmarks_view.cpp

@@ -144,3 +144,37 @@ static void ViewMaterialize(benchmark::State& state, const char* filename)
     state.SetBytesProcessed(state.iterations() * str.size());
 }
 JSON_VIEW_BENCHMARK_FILES(ViewMaterialize);
+
+//////////////////////////////////////////////////////////////////////////////
+// serialize a parsed document (compare with Dump)
+//////////////////////////////////////////////////////////////////////////////
+
+static void ViewDump(benchmark::State& state, const char* filename, int indent)
+{
+    const std::string str = read_file(filename);
+    const json_document d = json_document::parse(str);
+
+    while (state.KeepRunning())
+    {
+        std::string output = d.root().dump(indent);
+        benchmark::DoNotOptimize(output);
+    }
+
+    state.SetBytesProcessed(state.iterations() * d.root().dump(indent).size());
+}
+BENCHMARK_CAPTURE(ViewDump, jeopardy / -,          TEST_DATA_DIRECTORY "/jeopardy/jeopardy.json",                 -1);
+BENCHMARK_CAPTURE(ViewDump, jeopardy / 4,          TEST_DATA_DIRECTORY "/jeopardy/jeopardy.json",                 4);
+BENCHMARK_CAPTURE(ViewDump, canada / -,            TEST_DATA_DIRECTORY "/nativejson-benchmark/canada.json",       -1);
+BENCHMARK_CAPTURE(ViewDump, canada / 4,            TEST_DATA_DIRECTORY "/nativejson-benchmark/canada.json",       4);
+BENCHMARK_CAPTURE(ViewDump, citm_catalog / -,      TEST_DATA_DIRECTORY "/nativejson-benchmark/citm_catalog.json", -1);
+BENCHMARK_CAPTURE(ViewDump, citm_catalog / 4,      TEST_DATA_DIRECTORY "/nativejson-benchmark/citm_catalog.json", 4);
+BENCHMARK_CAPTURE(ViewDump, twitter / -,           TEST_DATA_DIRECTORY "/nativejson-benchmark/twitter.json",      -1);
+BENCHMARK_CAPTURE(ViewDump, twitter / 4,           TEST_DATA_DIRECTORY "/nativejson-benchmark/twitter.json",      4);
+BENCHMARK_CAPTURE(ViewDump, floats / -,            TEST_DATA_DIRECTORY "/regression/floats.json",                 -1);
+BENCHMARK_CAPTURE(ViewDump, floats / 4,            TEST_DATA_DIRECTORY "/regression/floats.json",                 4);
+BENCHMARK_CAPTURE(ViewDump, signed_ints / -,       TEST_DATA_DIRECTORY "/regression/signed_ints.json",            -1);
+BENCHMARK_CAPTURE(ViewDump, signed_ints / 4,       TEST_DATA_DIRECTORY "/regression/signed_ints.json",            4);
+BENCHMARK_CAPTURE(ViewDump, unsigned_ints / -,     TEST_DATA_DIRECTORY "/regression/unsigned_ints.json",          -1);
+BENCHMARK_CAPTURE(ViewDump, unsigned_ints / 4,     TEST_DATA_DIRECTORY "/regression/unsigned_ints.json",          4);
+BENCHMARK_CAPTURE(ViewDump, small_signed_ints / -, TEST_DATA_DIRECTORY "/regression/small_signed_ints.json",      -1);
+BENCHMARK_CAPTURE(ViewDump, small_signed_ints / 4, TEST_DATA_DIRECTORY "/regression/small_signed_ints.json",      4);