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use diagnostic positions in exceptions (#4585)
* add a ci step for Json_Diagnostic_Positions Signed-off-by: Harinath Nampally <[email protected]> * Update ci.cmake to address review comments Signed-off-by: Harinath Nampally <[email protected]> * address review comment Signed-off-by: Harinath Nampally <[email protected]> * fix typo in the comment Signed-off-by: Harinath Nampally <[email protected]> * fix typos in ci.cmake Signed-off-by: Harinath Nampally <[email protected]> * invoke the new ci step from ubuntu.yml Signed-off-by: Harinath Nampally <[email protected]> * issue4561 - use diagnostic positions for exceptions Signed-off-by: Harinath Nampally <[email protected]> * fix ci_test_documentation check Signed-off-by: Harinath Nampally <[email protected]> * address review comments Signed-off-by: Harinath Nampally <[email protected]> * fix ci check failures for unit-diagnostic-postions.cpp Signed-off-by: Harinath Nampally <[email protected]> * improvements based on review comments Signed-off-by: Harinath Nampally <[email protected]> * fix const correctness string Signed-off-by: Harinath Nampally <[email protected]> * further refinements based on reviews Signed-off-by: Harinath Nampally <[email protected]> * add one more test case for full coverage Signed-off-by: Harinath Nampally <[email protected]> * ci check fix - add const Signed-off-by: Harinath Nampally <[email protected]> * add unit tests for json_diagnostic_postions only Signed-off-by: Harinath Nampally <[email protected]> * fix ci_test_diagnostics Signed-off-by: Harinath Nampally <[email protected]> * fix ci_test_build_documentation check Signed-off-by: Harinath Nampally <[email protected]> --------- Signed-off-by: Harinath Nampally <[email protected]>
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‎docs/mkdocs/docs/api/macros/json_diagnostic_positions.md

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@@ -81,6 +81,33 @@ When the macro is not defined, the library will define it to its default value.
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The output shows the start/end positions of all the objects and fields in the JSON string.
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??? example "Example 2: using only diagnostic positions in exceptions"
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```cpp
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--8<-- "examples/diagnostic_positions_exception.cpp"
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```
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Output:
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```
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--8<-- "examples/diagnostic_positions_exception.output"
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```
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The output shows the exception with start/end positions only.
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??? example "Example 3: using extended diagnostics with positions enabled in exceptions"
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```cpp
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--8<-- "examples/diagnostics_extended_positions.cpp"
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```
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Output:
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```
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--8<-- "examples/diagnostics_extended_positions.output"
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```
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The output shows the exception with diagnostic path info and start/end positions.
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## Version history
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- Added in version 3.12.0.

‎docs/mkdocs/docs/api/macros/json_diagnostics.md

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Now the exception message contains a JSON Pointer `/address/housenumber` that indicates which value has the wrong type.
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??? example "Example 3: using only diagnostic positions in exceptions"
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```cpp
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--8<-- "examples/diagnostic_positions_exception.cpp"
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```
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Output:
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```
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--8<-- "examples/diagnostic_positions_exception.output"
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```
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The output shows the exception with start/end positions only.
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## Version history
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- Added in version 3.10.0.

‎docs/mkdocs/docs/examples/diagnostic_positions_exception.cpp

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#include <iostream>
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#define JSON_DIAGNOSTIC_POSITIONS 1
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#include <nlohmann/json.hpp>
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using json = nlohmann::json;
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/* Demonstration of type error exception with diagnostic postions support enabled */
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int main()
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{
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//Invalid json string - housenumber type must be int instead of string
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const std::string json_invalid_string = R"(
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{
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"address": {
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"street": "Fake Street",
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"housenumber": "1"
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}
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}
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)";
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json j = json::parse(json_invalid_string);
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try
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{
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int housenumber = j["address"]["housenumber"];
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std::cout << housenumber;
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}
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catch (const json::exception& e)
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{
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std::cout << e.what() << '\n';
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}
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}

‎docs/mkdocs/docs/examples/diagnostic_positions_exception.output

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[json.exception.type_error.302] (bytes 92-95) type must be number, but is string

‎docs/mkdocs/docs/examples/diagnostics_extended_positions.cpp

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#include <iostream>
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#define JSON_DIAGNOSTICS 1
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#define JSON_DIAGNOSTIC_POSITIONS 1
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#include <nlohmann/json.hpp>
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using json = nlohmann::json;
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/* Demonstration of type error exception with diagnostic postions support enabled */
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int main()
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{
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//Invalid json string - housenumber type must be int instead of string
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const std::string json_invalid_string = R"(
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{
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"address": {
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"street": "Fake Street",
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"housenumber": "1"
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}
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}
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)";
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json j = json::parse(json_invalid_string);
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try
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{
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int housenumber = j["address"]["housenumber"];
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std::cout << housenumber;
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}
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catch (const json::exception& e)
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{
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std::cout << e.what() << '\n';
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}
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}

‎docs/mkdocs/docs/examples/diagnostics_extended_positions.output

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[json.exception.type_error.302] (/address/housenumber) (bytes 92-95) type must be number, but is string

‎include/nlohmann/detail/exceptions.hpp

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{
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return concat(a, '/', detail::escape(b));
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});
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return concat('(', str, ") ");
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return concat('(', str, ") ", get_byte_positions(leaf_element));
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#else
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static_cast<void>(leaf_element);
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return "";
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return get_byte_positions(leaf_element);
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#endif
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}
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private:
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/// an exception object as storage for error messages
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std::runtime_error m;
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#if JSON_DIAGNOSTIC_POSITIONS
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template<typename BasicJsonType>
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static std::string get_byte_positions(const BasicJsonType* leaf_element)
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{
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if ((leaf_element->start_pos() != std::string::npos) && (leaf_element->end_pos() != std::string::npos))
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{
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return concat("(bytes ", std::to_string(leaf_element->start_pos()), "-", std::to_string(leaf_element->end_pos()), ") ");
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}
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return "";
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}
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#else
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template<typename BasicJsonType>
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static std::string get_byte_positions(const BasicJsonType* leaf_element)
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{
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static_cast<void>(leaf_element);
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return "";
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}
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#endif
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};
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/// @brief exception indicating a parse error

‎single_include/nlohmann/json.hpp

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{
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return concat(a, '/', detail::escape(b));
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});
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return concat('(', str, ") ");
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return concat('(', str, ") ", get_byte_positions(leaf_element));
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#else
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static_cast<void>(leaf_element);
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return "";
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return get_byte_positions(leaf_element);
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#endif
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}
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private:
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/// an exception object as storage for error messages
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std::runtime_error m;
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#if JSON_DIAGNOSTIC_POSITIONS
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template<typename BasicJsonType>
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static std::string get_byte_positions(const BasicJsonType* leaf_element)
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{
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if ((leaf_element->start_pos() != std::string::npos) && (leaf_element->end_pos() != std::string::npos))
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{
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return concat("(bytes ", std::to_string(leaf_element->start_pos()), "-", std::to_string(leaf_element->end_pos()), ") ");
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}
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return "";
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}
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#else
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template<typename BasicJsonType>
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static std::string get_byte_positions(const BasicJsonType* leaf_element)
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{
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static_cast<void>(leaf_element);
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return "";
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}
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#endif
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};
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/// @brief exception indicating a parse error

‎tests/src/unit-diagnostic-positions-only.cpp

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// __ _____ _____ _____
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// __| | __| | | | JSON for Modern C++ (supporting code)
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// | | |__ | | | | | | version 3.11.3
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// |_____|_____|_____|_|___| https://github.com/nlohmann/json
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//
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// SPDX-FileCopyrightText: 2013 - 2024 Niels Lohmann <https://nlohmann.me>
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// SPDX-License-Identifier: MIT
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#include "doctest_compatibility.h"
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#ifdef JSON_DIAGNOSTICS
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#undef JSON_DIAGNOSTICS
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#endif
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#define JSON_DIAGNOSTICS 0
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#define JSON_DIAGNOSTIC_POSITIONS 1
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#include <nlohmann/json.hpp>
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using json = nlohmann::json;
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TEST_CASE("Better diagnostics with positions only")
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{
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SECTION("invalid type")
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{
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const std::string json_invalid_string = R"(
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{
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"address": {
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"street": "Fake Street",
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"housenumber": "1"
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}
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}
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)";
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json j = json::parse(json_invalid_string);
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CHECK_THROWS_WITH_AS(j.at("address").at("housenumber").get<int>(),
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"[json.exception.type_error.302] (bytes 108-111) type must be number, but is string", json::type_error);
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}
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SECTION("invalid type without positions")
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{
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const json j = "foo";
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CHECK_THROWS_WITH_AS(j.get<int>(),
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"[json.exception.type_error.302] type must be number, but is string", json::type_error);
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}
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}

‎tests/src/unit-diagnostic-positions.cpp

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// __ _____ _____ _____
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// __| | __| | | | JSON for Modern C++ (supporting code)
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// | | |__ | | | | | | version 3.11.3
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// |_____|_____|_____|_|___| https://github.com/nlohmann/json
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//
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// SPDX-FileCopyrightText: 2013 - 2024 Niels Lohmann <https://nlohmann.me>
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// SPDX-License-Identifier: MIT
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#include "doctest_compatibility.h"
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#define JSON_DIAGNOSTICS 1
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#define JSON_DIAGNOSTIC_POSITIONS 1
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#include <nlohmann/json.hpp>
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using json = nlohmann::json;
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TEST_CASE("Better diagnostics with positions")
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{
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SECTION("invalid type")
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{
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const std::string json_invalid_string = R"(
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{
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"address": {
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"street": "Fake Street",
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"housenumber": "1"
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}
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}
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)";
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json j = json::parse(json_invalid_string);
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CHECK_THROWS_WITH_AS(j.at("address").at("housenumber").get<int>(),
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"[json.exception.type_error.302] (/address/housenumber) (bytes 108-111) type must be number, but is string", json::type_error);
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}
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SECTION("invalid type without positions")
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{
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const json j = "foo";
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CHECK_THROWS_WITH_AS(j.get<int>(),
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"[json.exception.type_error.302] type must be number, but is string", json::type_error);
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}
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}

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