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>

tests/src/json_view_test_helpers.hpp

@@ -0,0 +1,89 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  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
+
+#pragma once
+
+// helpers shared by the unit-json_view*.cpp files, which are split to keep every
+// object file small enough for the MinGW linker (it fails to link objects with
+// more than 32767 sections)
+
+#include <nlohmann/json_view.hpp>
+
+#include <algorithm> // any_of
+#include <random> // mt19937
+#include <string> // string
+
+namespace json_view_test
+{
+// a small deterministic generator of documents
+struct generator
+{
+    std::mt19937 rng{5295}; // NOLINT(cert-msc32-c,cert-msc51-cpp,bugprone-random-generator-seed)
+
+    int r(int n)
+    {
+        return static_cast<int>(rng() % static_cast<unsigned>(n));
+    }
+
+    void str(std::string& o)
+    {
+        static const char* const pieces[] = {"a", "Z", " ", "\\n", "\\\"", "\\u00e9", "\\ud83d\\ude00", "\xc3\xa9", "\xe3\x81\x82", "long text beyond the first sixteen bytes"}; // NOLINT(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays)
+        o += '"';
+        for (int n = r(5); n > 0; --n)
+        {
+            o += pieces[r(10)];
+        }
+        o += '"';
+    }
+
+    void value(std::string& o, int depth)
+    {
+        static const char* const scalars[] = {"0", "-1", "123456789012", "18446744073709551615", "18446744073709551616", "-9223372036854775809", // NOLINT(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays)
+                                              "1.5", "-2.25e-3", "1E2", "0.1", "true", "false", "null"
+                                             };
+        const int k = depth > 5 ? 2 + r(4) : r(6);
+        if (k < 2)
+        {
+            const bool object = k == 0;
+            o += object ? '{' : '[';
+            for (int i = r(5); i > 0; --i)
+            {
+                if (object)
+                {
+                    str(o);
+                    o += r(2) == 0 ? ":" : " : ";
+                }
+                value(o, depth + 1);
+                o += i > 1 ? ", " : "";
+            }
+            o += object ? '}' : ']';
+        }
+        else if (k < 4)
+        {
+            str(o);
+        }
+        else
+        {
+            o += scalars[r(13)];
+        }
+    }
+};
+
+// whether an object of the view repeats a key
+inline bool has_duplicate_keys(const nlohmann::ordered_json_view& v)
+{
+    if (v.is_object() && v.size() != v.materialize().size())
+    {
+        return true;
+    }
+    return std::any_of(v.begin(), v.end(), [](const nlohmann::ordered_json_view e)
+    {
+        return e.is_structured() && has_duplicate_keys(e);
+    });
+}
+} // namespace json_view_test