Document clang-tidy exclusions, drop unneeded ones, and clean up doc examples (#5909)

* Document clang-tidy exclusions and drop unneeded ones

Re-enable every excluded check in a run of clang-tidy 22 over all tests
and remove the seven that never fire (cert-err58-cpp,
clang-analyzer-webkit.NoUncountedMemberChecker,
cppcoreguidelines-virtual-class-destructor, google-readability-function-size,
hicpp-function-size, hicpp-no-assembler, readability-function-size).

Document the reason for every remaining exclusion at the top of the file.

Exclude in advance the checks that only exist in clang-tidy 23 and are
noise here (bugprone-signed-bitwise, *-explicit-constructor,
readability-trailing-comma, modernize-use-string-view), plus
modernize-use-integer-sign-comparison, which needs C++20 std::cmp_less
and flags deliberate casts.

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

* Fix clang-tidy findings in documentation examples and replace redundant aliases

Apply clang-tidy fixes to the documentation examples:
- performance-avoid-endl: std::endl -> '\n'
- readability-qualified-auto: auto -> auto* / const auto*
- performance-for-range-copy: copy -> const reference
- google-readability-casting: C-style cast -> static_cast

Replace redundant aliases (readability-redundant-qualified-alias) such as
"using json = nlohmann::json;" with "using nlohmann::json;" in the
documentation, README, examples, tests, and benchmarks. Aliases at class
scope and aliases of other types (with_base_class_t etc.) are kept.

No changes to the library or its public API. All changed examples were
compiled and run; their output matches the stored .output files (except
max_size and meta, which depend on the platform and compiler).

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

* Format doc examples with the pinned astyle

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

---------

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

tests/benchmarks/src/benchmarks.cpp

@@ -21,7 +21,7 @@
 #include <vector>
 #include <test_data.hpp>
 
-using json = nlohmann::json;
+using nlohmann::json;
 
 //////////////////////////////////////////////////////////////////////////////
 // parse JSON from file

tests/benchmarks/src/benchmarks_view.cpp

@@ -17,8 +17,8 @@
 #include <string>
 #include <test_data.hpp>
 
-using json = nlohmann::json;
-using json_document = nlohmann::json_document;
+using nlohmann::json;
+using nlohmann::json_document;
 
 static std::string read_file(const char* filename)
 {

tests/src/fuzzer-json_view_image.cpp

@@ -33,8 +33,8 @@ drivers.
     #error "the fuzzer drivers must be built without NDEBUG"
 #endif
 
-using json = nlohmann::json;
-using json_document = nlohmann::json_document;
+using nlohmann::json;
+using nlohmann::json_document;
 using image_check = json_document::image_check;
 
 // see http://llvm.org/docs/LibFuzzer.html

tests/src/fuzzer-parse_json_view.cpp

@@ -42,8 +42,8 @@ drivers.
     #error "the fuzzer drivers must be built without NDEBUG"
 #endif
 
-using json = nlohmann::json;
-using json_document = nlohmann::json_document;
+using nlohmann::json;
+using nlohmann::json_document;
 
 namespace
 {

tests/src/unit-bjdata.cpp

@@ -19,7 +19,7 @@
 
 #include <nlohmann/json.hpp>
 using nlohmann::json;
-using ordered_json = nlohmann::ordered_json;
+using nlohmann::ordered_json;
 
 #include <algorithm>
 #include <climits>

tests/src/unit-diagnostic-positions.cpp

@@ -14,7 +14,7 @@
 #define JSON_DIAGNOSTIC_POSITIONS 1
 #include <nlohmann/json.hpp>
 
-using json = nlohmann::json;
+using nlohmann::json;
 
 TEST_CASE("Better diagnostics with positions")
 {

tests/src/unit-disabled_exceptions.cpp

@@ -13,7 +13,7 @@ DOCTEST_GCC_SUPPRESS_WARNING_PUSH
 DOCTEST_GCC_SUPPRESS_WARNING("-Wnoexcept")
 
 #include <nlohmann/json.hpp>
-using json = nlohmann::json;
+using nlohmann::json;
 #ifdef JSON_TEST_NO_GLOBAL_UDLS
     using namespace nlohmann::literals; // NOLINT(google-build-using-namespace)
 #endif

tests/src/unit-element_access2.cpp

@@ -1948,7 +1948,7 @@ TEST_CASE_TEMPLATE("element access 2 (additional value() tests)", Json, nlohmann
 #ifdef JSON_HAS_CPP_17
 TEST_CASE("operator[] with user-defined std::string_view-convertible types")
 {
-    using json = nlohmann::json;
+    using nlohmann::json;
 
     class TestClass
     {
@@ -2031,7 +2031,7 @@ TEST_CASE("keys convertible to std::string_view work with all lookup functions (
 
     SECTION("nlohmann::json")
     {
-        using json = nlohmann::json;
+        using nlohmann::json;
 
         SECTION("ViewKey")
         {
@@ -2072,7 +2072,7 @@ TEST_CASE("keys convertible to std::string_view work with all lookup functions (
 
     SECTION("nlohmann::ordered_json")
     {
-        using ordered_json = nlohmann::ordered_json;
+        using nlohmann::ordered_json;
 
         SECTION("ViewKey")
         {

tests/src/unit-explicit_instantiation.cpp

@@ -15,7 +15,7 @@
 #include "doctest_compatibility.h"
 
 #include <nlohmann/json.hpp>
-using json = nlohmann::json;
+using nlohmann::json;
 
 /////////////////////////////////////////////////////////////////////
 // for #4825 - explicitly instantiating basic_json must compile; this

tests/src/unit-format-as.cpp

@@ -9,8 +9,8 @@
 #include "doctest_compatibility.h"
 
 #include <nlohmann/json.hpp>
-using json = nlohmann::json;
-using ordered_json = nlohmann::ordered_json;
+using nlohmann::json;
+using nlohmann::ordered_json;
 
 namespace
 {

tests/src/unit-hash.cpp

@@ -9,8 +9,8 @@
 #include "doctest_compatibility.h"
 
 #include <nlohmann/json.hpp>
-using json = nlohmann::json;
-using ordered_json = nlohmann::ordered_json;
+using nlohmann::json;
+using nlohmann::ordered_json;
 
 #include <limits>
 #include <set>

tests/src/unit-no_automatic_udls.cpp

@@ -19,7 +19,7 @@
 #include <utility>
 
 #include <nlohmann/json.hpp>
-using json = nlohmann::json;
+using nlohmann::json;
 
 // An argument type whose associated namespace is the library namespace, so
 // argument-dependent lookup of a literal operator called by its function name

tests/src/unit-no_io_and_user_exceptions.cpp

@@ -38,7 +38,7 @@ static int json_throw_user_call_count = 0; // NOLINT(cppcoreguidelines-avoid-non
 #include "doctest_compatibility.h"
 
 #include <nlohmann/json.hpp>
-using json = nlohmann::json;
+using nlohmann::json;
 
 TEST_CASE("JSON_NO_IO")
 {

tests/src/unit-regression2.cpp

@@ -33,8 +33,8 @@
 
 #define JSON_TESTS_PRIVATE
 #include <nlohmann/json.hpp>
-using json = nlohmann::json;
-using ordered_json = nlohmann::ordered_json;
+using nlohmann::json;
+using nlohmann::ordered_json;
 #ifdef JSON_TEST_NO_GLOBAL_UDLS
     using namespace nlohmann::literals; // NOLINT(google-build-using-namespace)
 #endif

tests/src/unit-regression3.cpp

@@ -36,8 +36,8 @@
 
 #define JSON_TESTS_PRIVATE
 #include <nlohmann/json.hpp>
-using json = nlohmann::json;
-using ordered_json = nlohmann::ordered_json;
+using nlohmann::json;
+using nlohmann::ordered_json;
 #ifdef JSON_TEST_NO_GLOBAL_UDLS
     using namespace nlohmann::literals; // NOLINT(google-build-using-namespace)
 #endif

tests/src/unit-std-format.cpp

@@ -16,8 +16,8 @@
 #include "doctest_compatibility.h"
 
 #include <nlohmann/json.hpp>
-using json = nlohmann::json;
-using ordered_json = nlohmann::ordered_json;
+using nlohmann::json;
+using nlohmann::ordered_json;
 
 // JSON_HAS_CPP_20 (do not remove; see note at top of file)
 #if JSON_HAS_STD_FORMAT