Move the json_view comparison tests into their own file

With the tests this branch adds, the object file of unit-json_view_dump.cpp
got too large for the MinGW x64 assembler ("file too big"). The test case
"json_view comparison" is now unit-json_view_compare.cpp, unchanged and
also built with C++17.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann committed 2026-10-24 20:03:58 +02:00
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// __ _____ _____ _____
// __| | __| | | | JSON for Modern C++ (supporting code)
// | | |__ | | | | | | version 3.12.0
// |_____|_____|_____|_|___| https://github.com/nlohmann/json
//
// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
// SPDX-License-Identifier: MIT
#include "doctest_compatibility.h"
#include <nlohmann/json_view.hpp>
using nlohmann::json;
using nlohmann::ordered_json;
using nlohmann::json_document;
using nlohmann::ordered_json_editable_document;
using nlohmann::json_view;
using nlohmann::ordered_json_document;
#include "json_view_test_helpers.hpp"
using json_view_test::generator;
#include <array>
#include <cstddef>
#include <string>
#include <vector>
// These tests were split off unit-json_view_dump.cpp, whose object file got too
// large for the MinGW assembler ("file too big"). Like that file, this one is
// also built with C++17, as it mentions JSON_HAS_CPP_17.
TEST_CASE("json_view comparison")
{
SECTION("equality of the values parse() produces")
{
generator g;
std::vector<std::string> texts;
for (int i = 0; i < 600; ++i)
{
std::string text;
g.value(text, 0);
texts.push_back(text);
// the same value written differently: sorted keys, canonical numbers
texts.push_back(json::parse(text).dump(1));
}
for (std::size_t i = 0; i + 2 < texts.size(); ++i)
{
for (std::size_t k = i; k < i + 3; ++k)
{
CAPTURE(texts[i])
CAPTURE(texts[k])
const json_document a = json_document::parse(texts[i]);
const json_document b = json_document::parse(texts[k]);
const json ja = json::parse(texts[i]);
const json jb = json::parse(texts[k]);
CHECK((a.root() == b.root()) == (ja == jb));
CHECK((a.root() != b.root()) == (ja != jb));
CHECK((a.root() == jb) == (ja == jb));
CHECK((jb == a.root()) == (ja == jb));
CHECK((a.root() != jb) == (ja != jb));
CHECK((jb != a.root()) == (ja != jb));
// ordered_json compares members in order
const ordered_json_document oa = ordered_json_document::parse(texts[i]);
const ordered_json_document ob = ordered_json_document::parse(texts[k]);
const ordered_json oja = ordered_json::parse(texts[i]);
const ordered_json ojb = ordered_json::parse(texts[k]);
CHECK((oa.root() == ob.root()) == (oja == ojb));
CHECK((oa.root() == ojb) == (oja == ojb));
}
}
}
SECTION("objects whose first keys differ or repeat")
{
const std::array<const char*, 17> texts =
{
{
R"({"a":1,"b":2})", R"({"a":1,"c":2})", R"({"b":1,"a":2})", R"({"a":1,"a":2,"b":3})", R"({"a":2,"b":3})",
R"({"a":1,"b":1,"a":2})", R"({"a":2,"b":1})", R"({"a":1,"a":2})", R"({"b":1})", R"({"a":1,"b":2,"c":3,"d":4,"e":5})",
R"({"a":1,"b":2,"c":3,"d":4,"f":5})", R"({"a":1,"b":2,"c":3,"a":4,"e":5})", R"({"a":4,"b":2,"c":3,"e":5})",
R"({"\u0061":1,"b":2})", R"({})", R"([{"a":1,"b":2}])", R"([{"a":1,"c":2}])"
}
};
for (const char* const x : texts)
{
for (const char* const y : texts)
{
CAPTURE(x)
CAPTURE(y)
const ordered_json_document dx = ordered_json_document::parse(x);
const ordered_json_document dy = ordered_json_document::parse(y);
const ordered_json_editable_document ex = ordered_json_editable_document::parse(x);
const ordered_json jx = ordered_json::parse(x);
const ordered_json jy = ordered_json::parse(y);
CHECK((dx.root() == dy.root()) == (jx == jy));
CHECK((dx.root() == jy) == (jx == jy));
CHECK((ex.root() == dy.root()) == (jx == jy));
}
}
}
SECTION("numbers, duplicate keys, member order")
{
const auto same = [](const char* x, const char* y)
{
const json_document dx = json_document::parse(x);
const json_document dy = json_document::parse(y);
return dx.root() == dy.root();
};
CHECK(same("1", "1.0"));
CHECK(same("[1, -1, 2.5]", "[1.0, -1.0, 25e-1]"));
CHECK(!same("1", "1.5"));
CHECK(same("18446744073709551615", "18446744073709551615"));
CHECK(same(R"({"a": 1, "a": 2})", R"({"a": 2})"));
CHECK(!same(R"({"a": 1, "a": 2})", R"({"a": 1})"));
CHECK(same(R"({"a": 1, "b": 2})", R"({"b": 2, "a": 1})"));
CHECK(!same(R"({"a": 1})", R"({"a": 1, "b": 2})"));
CHECK(!same("[1, 2]", "[2, 1]"));
CHECK(!same("\"a\"", "\"b\""));
CHECK(same("\"\\u00e9\"", "\"\xc3\xa9\""));
CHECK(!same("null", "false"));
CHECK(!same("[]", "{}"));
const ordered_json_document dup = ordered_json_document::parse(R"({"a": 1, "b": 2, "a": 3})");
const ordered_json_document last = ordered_json_document::parse(R"({"a": 3, "b": 2})");
CHECK(dup.root() == last.root());
// (== compares as parse() resolves duplicates, a lookup finds the first)
CHECK(dup.root()["a"].materialize() == 1);
CHECK(dup.root()["a"] != last.root()["a"]);
const ordered_json_document ab = ordered_json_document::parse(R"({"a": 1, "b": 2})");
const ordered_json_document ba = ordered_json_document::parse(R"({"b": 2, "a": 1})");
CHECK(ab.root() != ba.root());
// discarded values compare as basic_json's do
const json discarded(json::value_t::discarded);
CHECK((json_view() == json_view()) == (discarded == discarded)); // NOLINT(readability-container-size-empty): operator== is tested
CHECK((json_view() == discarded) == (discarded == discarded)); // NOLINT(readability-container-size-empty)
const json_document null_document = json_document::parse("null");
CHECK(!(json_view() == null_document.root())); // NOLINT(readability-container-size-empty)
CHECK(!(null_document.root() == discarded));
}
SECTION("values that are the same text, or the same value written differently, at any depth")
{
// nested arrays and objects around depths where the walk over equal text gives up
for (const int depth :
{
1, 5, 47, 48, 49, 50, 60, 300
})
{
CAPTURE(depth)
std::string head;
std::string tail;
for (int i = 0; i < depth; ++i)
{
head += i % 2 == 0 ? R"({"k":[1,"s",{"x":true},)" : R"([null,2.5,{"y":)";
tail.insert(0, i % 2 == 0 ? "]}" : "}]");
}
// the same text, one number changed, and one number written differently
const auto with_number = [&](const char* number)
{
std::string result = head;
result += number;
result += tail;
return result;
};
const std::string text = with_number("7");
const std::string changed = with_number("8");
const std::string spelled = with_number("7.0");
const json_document a = json_document::parse(text);
const json_document b = json_document::parse(text);
const json_document c = json_document::parse(changed);
const json_document d = json_document::parse(spelled);
CHECK(a.root() == b.root());
CHECK(a.root() != c.root());
CHECK(c.root() != a.root());
CHECK(a.root() == d.root());
CHECK(d.root() == a.root());
CHECK(a.root() == json::parse(text));
CHECK(a.root() != json::parse(changed));
CHECK(json::parse(spelled) == a.root());
const nlohmann::json_editable_document e = nlohmann::json_editable_document::parse(text);
CHECK(a.root() == e.root());
CHECK(e.root() == a.root());
CHECK(c.root() != e.root());
CHECK(e.root() == e.root());
const ordered_json_document oa = ordered_json_document::parse(text);
const ordered_json_document oc = ordered_json_document::parse(changed);
CHECK(oa.root() != oc.root());
CHECK(oa.root() == ordered_json::parse(text));
CHECK(oc.root() != ordered_json::parse(text));
}
// not the same text, but the same value
const auto same = [](const char* x, const char* y)
{
const json_document dx = json_document::parse(x);
const json_document dy = json_document::parse(y);
const bool equal = dx.root() == dy.root();
CHECK(equal == (json::parse(x) == json::parse(y)));
CHECK(equal == (dx.root() == json::parse(y)));
return equal;
};
CHECK(same(R"({"a":1,"a":2})", R"({"a":3,"a":2})"));
CHECK(same(R"({"a":1,"b":[1,{"c":2,"c":3}]})", R"({"b":[1,{"c":9,"c":3}],"a":1})"));
CHECK(!same(R"({"a":1,"a":2})", R"({"a":2,"a":3})"));
CHECK(same("[1.0,-0,0,1e2]", "[1.00,0,-0,100.0]"));
CHECK(same(R"(["\u00e9","\n"])", "[\"\xc3\xa9\",\"\\n\"]"));
CHECK(!same(R"({"a":[1,2,{"b":null}]})", R"({"a":[1,2,{"b":false}]})"));
CHECK(!same(R"({"a":[1,2,{"b":null}]})", R"({"a":[1,2,{"c":null}]})"));
CHECK(!same(R"({"a":[1,2,{"b":null}]})", R"({"a":[1,2,{"b":null,"c":1}]})"));
// edited documents: moved sequences, links, and values of new nodes
nlohmann::json_editable_document edited = nlohmann::json_editable_document::parse(R"({"a":[1,2,3],"b":{"c":"d"},"e":0.5})");
const json_document plain = json_document::parse(R"({"a":[1,2,3,4],"b":{"c":"x","y":null},"e":0.5,"z":[]})");
edited.push_back(edited.root()["a"], 4);
edited.set(edited.root()["b"], "c", "x");
edited.set(edited.root()["b"], "y", nullptr);
edited.set(edited.root(), "z", json::array());
CHECK(edited.root() == plain.root());
CHECK(plain.root() == edited.root());
edited.erase(edited.root()["a"], 0);
CHECK(edited.root() != plain.root());
CHECK(edited.root()["a"] == json::parse("[2,3,4]"));
const json_document tail = json_document::parse("[2,3,4]");
CHECK(edited.root()["a"] == tail.root());
}
SECTION("large documents, with a difference at any place")
{
const auto make = [](std::size_t count, std::size_t changed, bool swap_members)
{
std::string text = R"({"b":1,"list":[)";
for (std::size_t i = 0; i < count; ++i)
{
text += (i != 0 ? "," : "");
const std::string id = std::to_string(i == changed ? i + 1 : i);
if (swap_members && i % 3 == 0)
{
text += R"({"v":[1.5,"s",{"k":)";
text += id;
text += R"(}],"id":)";
text += id;
text += "}";
}
else
{
text += R"({"id":)";
text += id;
text += R"(,"v":[1.5,"s",{"k":)";
text += id;
text += "}]}";
}
}
return text + R"(],"a":{"y":2,"x":3}})";
};
const std::size_t count = 3000;
for (const std::size_t changed :
{
count, std::size_t{0}, std::size_t{1}, count / 2, count - 1
})
{
for (const bool swap :
{
false, true
})
{
CAPTURE(changed)
CAPTURE(swap)
const std::string text_a = make(count, count, false);
const std::string text_b = make(count, changed, swap);
const json_document a = json_document::parse(text_a);
const json_document b = json_document::parse(text_b);
const bool equal = changed == count;
CHECK((a.root() == b.root()) == equal);
CHECK((b.root() == a.root()) == equal);
CHECK((a.root() == json::parse(text_b)) == equal);
CHECK((json::parse(text_b) == a.root()) == equal);
CHECK((a.root()["list"] == b.root()["list"]) == equal);
const ordered_json_document oa = ordered_json_document::parse(text_a);
const ordered_json_document ob = ordered_json_document::parse(text_b);
CHECK((oa.root() == ob.root()) == (equal && !swap));
CHECK((oa.root() == ordered_json::parse(text_b)) == (equal && !swap));
}
}
}
SECTION("deep nesting")
{
const std::string deep = std::string(100000, '[') + std::string(100000, ']');
const json_document a = json_document::parse(deep);
const json_document b = json_document::parse(deep);
CHECK(a.root() == b.root());
CHECK(a.root() == json::parse(deep));
const std::string other = std::string(100000, '[') + "1" + std::string(100000, ']');
const json_document c = json_document::parse(other);
CHECK(a.root() != c.root());
}
}
-269
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@@ -432,275 +432,6 @@ TEST_CASE("json_view dump")
}
}
TEST_CASE("json_view comparison")
{
SECTION("equality of the values parse() produces")
{
generator g;
std::vector<std::string> texts;
for (int i = 0; i < 600; ++i)
{
std::string text;
g.value(text, 0);
texts.push_back(text);
// the same value written differently: sorted keys, canonical numbers
texts.push_back(json::parse(text).dump(1));
}
for (std::size_t i = 0; i + 2 < texts.size(); ++i)
{
for (std::size_t k = i; k < i + 3; ++k)
{
CAPTURE(texts[i])
CAPTURE(texts[k])
const json_document a = json_document::parse(texts[i]);
const json_document b = json_document::parse(texts[k]);
const json ja = json::parse(texts[i]);
const json jb = json::parse(texts[k]);
CHECK((a.root() == b.root()) == (ja == jb));
CHECK((a.root() != b.root()) == (ja != jb));
CHECK((a.root() == jb) == (ja == jb));
CHECK((jb == a.root()) == (ja == jb));
CHECK((a.root() != jb) == (ja != jb));
CHECK((jb != a.root()) == (ja != jb));
// ordered_json compares members in order
const ordered_json_document oa = ordered_json_document::parse(texts[i]);
const ordered_json_document ob = ordered_json_document::parse(texts[k]);
const ordered_json oja = ordered_json::parse(texts[i]);
const ordered_json ojb = ordered_json::parse(texts[k]);
CHECK((oa.root() == ob.root()) == (oja == ojb));
CHECK((oa.root() == ojb) == (oja == ojb));
}
}
}
SECTION("objects whose first keys differ or repeat")
{
const std::array<const char*, 17> texts =
{
{
R"({"a":1,"b":2})", R"({"a":1,"c":2})", R"({"b":1,"a":2})", R"({"a":1,"a":2,"b":3})", R"({"a":2,"b":3})",
R"({"a":1,"b":1,"a":2})", R"({"a":2,"b":1})", R"({"a":1,"a":2})", R"({"b":1})", R"({"a":1,"b":2,"c":3,"d":4,"e":5})",
R"({"a":1,"b":2,"c":3,"d":4,"f":5})", R"({"a":1,"b":2,"c":3,"a":4,"e":5})", R"({"a":4,"b":2,"c":3,"e":5})",
R"({"\u0061":1,"b":2})", R"({})", R"([{"a":1,"b":2}])", R"([{"a":1,"c":2}])"
}
};
for (const char* const x : texts)
{
for (const char* const y : texts)
{
CAPTURE(x)
CAPTURE(y)
const ordered_json_document dx = ordered_json_document::parse(x);
const ordered_json_document dy = ordered_json_document::parse(y);
const ordered_json_editable_document ex = ordered_json_editable_document::parse(x);
const ordered_json jx = ordered_json::parse(x);
const ordered_json jy = ordered_json::parse(y);
CHECK((dx.root() == dy.root()) == (jx == jy));
CHECK((dx.root() == jy) == (jx == jy));
CHECK((ex.root() == dy.root()) == (jx == jy));
}
}
}
SECTION("numbers, duplicate keys, member order")
{
const auto same = [](const char* x, const char* y)
{
const json_document dx = json_document::parse(x);
const json_document dy = json_document::parse(y);
return dx.root() == dy.root();
};
CHECK(same("1", "1.0"));
CHECK(same("[1, -1, 2.5]", "[1.0, -1.0, 25e-1]"));
CHECK(!same("1", "1.5"));
CHECK(same("18446744073709551615", "18446744073709551615"));
CHECK(same(R"({"a": 1, "a": 2})", R"({"a": 2})"));
CHECK(!same(R"({"a": 1, "a": 2})", R"({"a": 1})"));
CHECK(same(R"({"a": 1, "b": 2})", R"({"b": 2, "a": 1})"));
CHECK(!same(R"({"a": 1})", R"({"a": 1, "b": 2})"));
CHECK(!same("[1, 2]", "[2, 1]"));
CHECK(!same("\"a\"", "\"b\""));
CHECK(same("\"\\u00e9\"", "\"\xc3\xa9\""));
CHECK(!same("null", "false"));
CHECK(!same("[]", "{}"));
const ordered_json_document dup = ordered_json_document::parse(R"({"a": 1, "b": 2, "a": 3})");
const ordered_json_document last = ordered_json_document::parse(R"({"a": 3, "b": 2})");
CHECK(dup.root() == last.root());
// (== compares as parse() resolves duplicates, a lookup finds the first)
CHECK(dup.root()["a"].materialize() == 1);
CHECK(dup.root()["a"] != last.root()["a"]);
const ordered_json_document ab = ordered_json_document::parse(R"({"a": 1, "b": 2})");
const ordered_json_document ba = ordered_json_document::parse(R"({"b": 2, "a": 1})");
CHECK(ab.root() != ba.root());
// discarded values compare as basic_json's do
const json discarded(json::value_t::discarded);
CHECK((json_view() == json_view()) == (discarded == discarded)); // NOLINT(readability-container-size-empty): operator== is tested
CHECK((json_view() == discarded) == (discarded == discarded)); // NOLINT(readability-container-size-empty)
const json_document null_document = json_document::parse("null");
CHECK(!(json_view() == null_document.root())); // NOLINT(readability-container-size-empty)
CHECK(!(null_document.root() == discarded));
}
SECTION("values that are the same text, or the same value written differently, at any depth")
{
// nested arrays and objects around depths where the walk over equal text gives up
for (const int depth :
{
1, 5, 47, 48, 49, 50, 60, 300
})
{
CAPTURE(depth)
std::string head;
std::string tail;
for (int i = 0; i < depth; ++i)
{
head += i % 2 == 0 ? R"({"k":[1,"s",{"x":true},)" : R"([null,2.5,{"y":)";
tail.insert(0, i % 2 == 0 ? "]}" : "}]");
}
// the same text, one number changed, and one number written differently
const auto with_number = [&](const char* number)
{
std::string result = head;
result += number;
result += tail;
return result;
};
const std::string text = with_number("7");
const std::string changed = with_number("8");
const std::string spelled = with_number("7.0");
const json_document a = json_document::parse(text);
const json_document b = json_document::parse(text);
const json_document c = json_document::parse(changed);
const json_document d = json_document::parse(spelled);
CHECK(a.root() == b.root());
CHECK(a.root() != c.root());
CHECK(c.root() != a.root());
CHECK(a.root() == d.root());
CHECK(d.root() == a.root());
CHECK(a.root() == json::parse(text));
CHECK(a.root() != json::parse(changed));
CHECK(json::parse(spelled) == a.root());
const nlohmann::json_editable_document e = nlohmann::json_editable_document::parse(text);
CHECK(a.root() == e.root());
CHECK(e.root() == a.root());
CHECK(c.root() != e.root());
CHECK(e.root() == e.root());
const ordered_json_document oa = ordered_json_document::parse(text);
const ordered_json_document oc = ordered_json_document::parse(changed);
CHECK(oa.root() != oc.root());
CHECK(oa.root() == ordered_json::parse(text));
CHECK(oc.root() != ordered_json::parse(text));
}
// not the same text, but the same value
const auto same = [](const char* x, const char* y)
{
const json_document dx = json_document::parse(x);
const json_document dy = json_document::parse(y);
const bool equal = dx.root() == dy.root();
CHECK(equal == (json::parse(x) == json::parse(y)));
CHECK(equal == (dx.root() == json::parse(y)));
return equal;
};
CHECK(same(R"({"a":1,"a":2})", R"({"a":3,"a":2})"));
CHECK(same(R"({"a":1,"b":[1,{"c":2,"c":3}]})", R"({"b":[1,{"c":9,"c":3}],"a":1})"));
CHECK(!same(R"({"a":1,"a":2})", R"({"a":2,"a":3})"));
CHECK(same("[1.0,-0,0,1e2]", "[1.00,0,-0,100.0]"));
CHECK(same(R"(["\u00e9","\n"])", "[\"\xc3\xa9\",\"\\n\"]"));
CHECK(!same(R"({"a":[1,2,{"b":null}]})", R"({"a":[1,2,{"b":false}]})"));
CHECK(!same(R"({"a":[1,2,{"b":null}]})", R"({"a":[1,2,{"c":null}]})"));
CHECK(!same(R"({"a":[1,2,{"b":null}]})", R"({"a":[1,2,{"b":null,"c":1}]})"));
// edited documents: moved sequences, links, and values of new nodes
nlohmann::json_editable_document edited = nlohmann::json_editable_document::parse(R"({"a":[1,2,3],"b":{"c":"d"},"e":0.5})");
const json_document plain = json_document::parse(R"({"a":[1,2,3,4],"b":{"c":"x","y":null},"e":0.5,"z":[]})");
edited.push_back(edited.root()["a"], 4);
edited.set(edited.root()["b"], "c", "x");
edited.set(edited.root()["b"], "y", nullptr);
edited.set(edited.root(), "z", json::array());
CHECK(edited.root() == plain.root());
CHECK(plain.root() == edited.root());
edited.erase(edited.root()["a"], 0);
CHECK(edited.root() != plain.root());
CHECK(edited.root()["a"] == json::parse("[2,3,4]"));
const json_document tail = json_document::parse("[2,3,4]");
CHECK(edited.root()["a"] == tail.root());
}
SECTION("large documents, with a difference at any place")
{
const auto make = [](std::size_t count, std::size_t changed, bool swap_members)
{
std::string text = R"({"b":1,"list":[)";
for (std::size_t i = 0; i < count; ++i)
{
text += (i != 0 ? "," : "");
const std::string id = std::to_string(i == changed ? i + 1 : i);
if (swap_members && i % 3 == 0)
{
text += R"({"v":[1.5,"s",{"k":)";
text += id;
text += R"(}],"id":)";
text += id;
text += "}";
}
else
{
text += R"({"id":)";
text += id;
text += R"(,"v":[1.5,"s",{"k":)";
text += id;
text += "}]}";
}
}
return text + R"(],"a":{"y":2,"x":3}})";
};
const std::size_t count = 3000;
for (const std::size_t changed :
{
count, std::size_t{0}, std::size_t{1}, count / 2, count - 1
})
{
for (const bool swap :
{
false, true
})
{
CAPTURE(changed)
CAPTURE(swap)
const std::string text_a = make(count, count, false);
const std::string text_b = make(count, changed, swap);
const json_document a = json_document::parse(text_a);
const json_document b = json_document::parse(text_b);
const bool equal = changed == count;
CHECK((a.root() == b.root()) == equal);
CHECK((b.root() == a.root()) == equal);
CHECK((a.root() == json::parse(text_b)) == equal);
CHECK((json::parse(text_b) == a.root()) == equal);
CHECK((a.root()["list"] == b.root()["list"]) == equal);
const ordered_json_document oa = ordered_json_document::parse(text_a);
const ordered_json_document ob = ordered_json_document::parse(text_b);
CHECK((oa.root() == ob.root()) == (equal && !swap));
CHECK((oa.root() == ordered_json::parse(text_b)) == (equal && !swap));
}
}
}
SECTION("deep nesting")
{
const std::string deep = std::string(100000, '[') + std::string(100000, ']');
const json_document a = json_document::parse(deep);
const json_document b = json_document::parse(deep);
CHECK(a.root() == b.root());
CHECK(a.root() == json::parse(deep));
const std::string other = std::string(100000, '[') + "1" + std::string(100000, ']');
const json_document c = json_document::parse(other);
CHECK(a.root() != c.root());
}
}
TEST_CASE("json_view large objects")
{
// objects with 128 members or more are looked up with a hash index