Merge branch 'json-view/12-view-values' into json-view/13-view-dump

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

docs/mkdocs/docs/examples/accept__iterator_pair.cpp

@@ -0,0 +1,15 @@
+#include <iostream>
+#include <vector>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // a buffer containing a JSON text followed by more data
+    std::vector<std::uint8_t> input = {'[', '1', ',', '2', ',', '3', ']', 'o', 't', 'h', 'e', 'r'};
+
+    std::cout << std::boolalpha
+              << json::accept(input.begin(), input.begin() + 7) << ' '
+              << json::accept(input.begin(), input.end()) << '\n';
+}

docs/mkdocs/docs/examples/accept__iterator_pair.output

@@ -0,0 +1 @@
+true false

docs/mkdocs/docs/examples/basic_json__BasicJsonType.cpp

@@ -0,0 +1,22 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+using ordered_json = nlohmann::ordered_json;
+
+int main()
+{
+    // create an ordered_json value; insertion order is preserved
+    ordered_json oj = {{"c", 3}, {"a", 1}, {"b", 2}};
+
+    // convert to json -- overload (4) is used; keys end up sorted
+    json j(oj);
+
+    // convert back to ordered_json -- the original insertion order is lost,
+    // because it was already given up when converting to json
+    ordered_json oj2(j);
+
+    std::cout << oj << '\n';
+    std::cout << j << '\n';
+    std::cout << oj2 << '\n';
+}

docs/mkdocs/docs/examples/basic_json__BasicJsonType.output

@@ -0,0 +1,3 @@
+{"c":3,"a":1,"b":2}
+{"a":1,"b":2,"c":3}
+{"a":1,"b":2,"c":3}

docs/mkdocs/docs/examples/basic_json__CompatibleType.cpp

@@ -44,7 +44,7 @@ int main()
     // create an object from std::unordered_multimap
     std::unordered_multimap<std::string, bool> c_ummap
     {
-        {"one", true}, {"two", true}, {"three", false}, {"three", true}
+        {"one", true}, {"two", true}, {"three", false}, {"three", false}
     };
     json j_ummap(c_ummap); // only one entry for key "three" is used
 
@@ -92,7 +92,7 @@ int main()
     json j_set(c_set); // only one entry for "one" is used
 
     // create an array from std::unordered_set
-    std::unordered_set<std::string> c_uset {"one", "two", "three", "four", "one"};
+    std::unordered_set<std::string> c_uset {"one", "one"};
     json j_uset(c_uset); // only one entry for "one" is used
 
     // create an array from std::multiset
@@ -100,7 +100,7 @@ int main()
     json j_mset(c_mset); // both entries for "one" are used
 
     // create an array from std::unordered_multiset
-    std::unordered_multiset<std::string> c_umset {"one", "two", "one", "four"};
+    std::unordered_multiset<std::string> c_umset {"one", "one"};
     json j_umset(c_umset); // both entries for "one" are used
 
     // serialize the JSON arrays

docs/mkdocs/docs/examples/basic_json__CompatibleType.output

@@ -12,9 +12,9 @@
 [12345678909876,23456789098765,34567890987654,45678909876543]
 [1,2,3,4]
 ["four","one","three","two"]
-["four","three","two","one"]
+["one"]
 ["four","one","one","two"]
-["four","two","one","one"]
+["one","one"]
 
 "The quick brown fox jumps over the lazy dog."
 "The quick brown fox jumps over the lazy dog."

docs/mkdocs/docs/examples/byte_container_with_subtype__operator__equal.cpp

@@ -0,0 +1,23 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+// define a byte container based on std::vector
+using byte_container_with_subtype = nlohmann::byte_container_with_subtype<std::vector<std::uint8_t>>;
+
+int main()
+{
+    std::vector<std::uint8_t> bytes = {{0xca, 0xfe, 0xba, 0xbe}};
+
+    // create containers without and with a subtype
+    auto c1 = byte_container_with_subtype(bytes);
+    auto c2 = byte_container_with_subtype(bytes);
+    auto c3 = byte_container_with_subtype(bytes, 42);
+    auto c4 = byte_container_with_subtype(bytes, 42);
+    auto c5 = byte_container_with_subtype(bytes, 23);
+
+    std::cout << std::boolalpha
+              << "c1 == c2: " << (c1 == c2) << '\n'
+              << "c1 == c3: " << (c1 == c3) << '\n'
+              << "c3 == c4: " << (c3 == c4) << '\n'
+              << "c3 == c5: " << (c3 == c5) << std::endl;
+}

docs/mkdocs/docs/examples/byte_container_with_subtype__operator__equal.output

@@ -0,0 +1,4 @@
+c1 == c2: true
+c1 == c3: false
+c3 == c4: true
+c3 == c5: false

docs/mkdocs/docs/examples/byte_container_with_subtype__operator__notequal.cpp

@@ -0,0 +1,23 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+// define a byte container based on std::vector
+using byte_container_with_subtype = nlohmann::byte_container_with_subtype<std::vector<std::uint8_t>>;
+
+int main()
+{
+    std::vector<std::uint8_t> bytes = {{0xca, 0xfe, 0xba, 0xbe}};
+
+    // create containers without and with a subtype
+    auto c1 = byte_container_with_subtype(bytes);
+    auto c2 = byte_container_with_subtype(bytes);
+    auto c3 = byte_container_with_subtype(bytes, 42);
+    auto c4 = byte_container_with_subtype(bytes, 42);
+    auto c5 = byte_container_with_subtype(bytes, 23);
+
+    std::cout << std::boolalpha
+              << "c1 != c2: " << (c1 != c2) << '\n'
+              << "c1 != c3: " << (c1 != c3) << '\n'
+              << "c3 != c4: " << (c3 != c4) << '\n'
+              << "c3 != c5: " << (c3 != c5) << std::endl;
+}

docs/mkdocs/docs/examples/byte_container_with_subtype__operator__notequal.output

@@ -0,0 +1,4 @@
+c1 != c2: false
+c1 != c3: true
+c3 != c4: false
+c3 != c5: true

docs/mkdocs/docs/examples/custom_string_type.hpp

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <cstddef>
 #include <ostream>
 #include <string>
 
@@ -8,10 +9,10 @@
 // and nothing more of std::string's interface.
 //
 // Covers the "Always required" members, the extras needed for the binary
-// formats, and the extras needed for JSON Pointer / flatten / unflatten /
-// diff. Extending it further (e.g. for std::hash<basic_json> or to_bson) is
-// a matter of adding the extra members listed in the "Required for other
-// functionality" table.
+// formats, JSON Pointer / flatten / unflatten, and the int_to_string overload
+// needed for diff and items. Extending it further (e.g. for
+// std::hash<basic_json> or to_bson) is a matter of adding the extra members
+// listed in the "Required for other functionality" table.
 //
 // See https://json.nlohmann.me/features/types/template_parameters/#stringtype
 class custom_string_type
@@ -93,6 +94,11 @@ class custom_string_type
         data_.append(other.data_);
         return *this;
     }
+    custom_string_type& operator+=(char c)
+    {
+        data_.push_back(c);
+        return *this;
+    }
 
     size_type find_first_of(char c, size_type pos = 0) const
     {
@@ -116,6 +122,12 @@ class custom_string_type
         return data_.end();
     }
 
+    // found by ADL; converts array indices to keys in diff and items
+    friend void int_to_string(custom_string_type& target, std::size_t value)
+    {
+        target.data_ = std::to_string(value);
+    }
+
     friend bool operator==(const custom_string_type& lhs, const custom_string_type& rhs)
     {
         return lhs.data_ == rhs.data_;

docs/mkdocs/docs/examples/flatten__empty.cpp

@@ -0,0 +1,23 @@
+#include <iostream>
+#include <iomanip>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // create a JSON value with an empty object and an empty array
+    json j =
+    {
+        {"empty_object", json::object()},
+        {"empty_array", json::array()},
+        {"name", "Niels"}
+    };
+
+    // call flatten()
+    json flattened = j.flatten();
+    std::cout << std::setw(4) << flattened << "\n\n";
+
+    // the empty containers cannot be restored by unflatten()
+    std::cout << std::setw(4) << flattened.unflatten() << '\n';
+}

docs/mkdocs/docs/examples/flatten__empty.output

@@ -0,0 +1,11 @@
+{
+    "/empty_array": null,
+    "/empty_object": null,
+    "/name": "Niels"
+}
+
+{
+    "empty_array": null,
+    "empty_object": null,
+    "name": "Niels"
+}

docs/mkdocs/docs/examples/get__BasicJsonType.cpp

@@ -0,0 +1,17 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+using ordered_json = nlohmann::ordered_json;
+
+int main()
+{
+    // create a JSON value
+    json j = {{"one", 1}, {"two", 2}, {"three", 3}};
+
+    // convert to a different basic_json specialization
+    ordered_json oj = j.get<ordered_json>();
+
+    std::cout << j << '\n';
+    std::cout << oj << '\n';
+}

docs/mkdocs/docs/examples/get__BasicJsonType.output

@@ -0,0 +1,2 @@
+{"one":1,"three":3,"two":2}
+{"one":1,"three":3,"two":2}

docs/mkdocs/docs/examples/get__ValueType_const.cpp

@@ -1,5 +1,5 @@
 #include <iostream>
-#include <unordered_map>
+#include <map>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;
@@ -29,7 +29,7 @@ int main()
     auto v5 = json_types["number"]["floating-point"].get<int>();
     auto v6 = json_types["string"].get<std::string>();
     auto v7 = json_types["array"].get<std::vector<short>>();
-    auto v8 = json_types.get<std::unordered_map<std::string, json>>();
+    auto v8 = json_types.get<std::map<std::string, json>>();
 
     // print the conversion results
     std::cout << v1 << '\n';

docs/mkdocs/docs/examples/get__ValueType_const.output

@@ -4,8 +4,8 @@
 Hello, world!
 1 2 3 4 5 
 
-number: {"floating-point":17.23,"integer":42}
-null: null
-string: "Hello, world!"
-boolean: true
 array: [1,2,3,4,5]
+boolean: true
+null: null
+number: {"floating-point":17.23,"integer":42}
+string: "Hello, world!"

docs/mkdocs/docs/examples/get_to.cpp

@@ -1,5 +1,5 @@
 #include <iostream>
-#include <unordered_map>
+#include <map>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;
@@ -28,7 +28,7 @@ int main()
     int v5;
     std::string v6;
     std::vector<short> v7;
-    std::unordered_map<std::string, json> v8;
+    std::map<std::string, json> v8;
 
     // use explicit conversions
     json_types["boolean"].get_to(v1);

docs/mkdocs/docs/examples/get_to.output

@@ -4,8 +4,8 @@
 Hello, world!
 1 2 3 4 5 
 
-number: {"floating-point":17.23,"integer":42}
-null: null
-string: "Hello, world!"
-boolean: true
 array: [1,2,3,4,5]
+boolean: true
+null: null
+number: {"floating-point":17.23,"integer":42}
+string: "Hello, world!"

docs/mkdocs/docs/examples/is_discarded__parse.cpp

@@ -0,0 +1,22 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // parsing invalid JSON without exceptions yields a discarded value
+    json j_invalid = json::parse("[1,2,3", nullptr, false);
+
+    // a callback that discards the top-level value does not leave it
+    // "discarded" -- it is replaced by null instead
+    json j_discarded_by_callback = json::parse("[1,2,3]", [](int /*depth*/, json::parse_event_t event, json& /*parsed*/)
+    {
+        return event != json::parse_event_t::array_start;
+    });
+
+    std::cout << std::boolalpha;
+    std::cout << "j_invalid.is_discarded()               = " << j_invalid.is_discarded() << '\n';
+    std::cout << "j_discarded_by_callback                = " << j_discarded_by_callback << '\n';
+    std::cout << "j_discarded_by_callback.is_discarded() = " << j_discarded_by_callback.is_discarded() << '\n';
+}

docs/mkdocs/docs/examples/is_discarded__parse.output

@@ -0,0 +1,3 @@
+j_invalid.is_discarded()               = true
+j_discarded_by_callback                = null
+j_discarded_by_callback.is_discarded() = false

docs/mkdocs/docs/examples/json_pointer__operator_spaceship.c++20.cpp

@@ -0,0 +1,32 @@
+#include <compare>
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+const char* to_string(const std::strong_ordering& so)
+{
+    if (std::is_lt(so))
+    {
+        return "less";
+    }
+    else if (std::is_gt(so))
+    {
+        return "greater";
+    }
+    return "equal";
+}
+
+int main()
+{
+    // different JSON pointers
+    json::json_pointer ptr1("/a/b");
+    json::json_pointer ptr2("/a/c");
+    json::json_pointer ptr3("/a/b/c");
+    json::json_pointer ptr4("/a/b");
+
+    // 3-way compare JSON pointers
+    std::cout << "\"" << ptr1 << "\" <=> \"" << ptr2 << "\": " << to_string(ptr1 <=> ptr2) << '\n' // *NOPAD*
+              << "\"" << ptr1 << "\" <=> \"" << ptr3 << "\": " << to_string(ptr1 <=> ptr3) << '\n' // *NOPAD*
+              << "\"" << ptr1 << "\" <=> \"" << ptr4 << "\": " << to_string(ptr1 <=> ptr4) << std::endl; // *NOPAD*
+}

docs/mkdocs/docs/examples/json_pointer__operator_spaceship.c++20.output

@@ -0,0 +1,3 @@
+"/a/b" <=> "/a/c": less
+"/a/b" <=> "/a/b/c": less
+"/a/b" <=> "/a/b": equal

docs/mkdocs/docs/examples/operator__ValueType.cpp

@@ -1,5 +1,5 @@
 #include <iostream>
-#include <unordered_map>
+#include <map>
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;
@@ -29,7 +29,7 @@ int main()
     int v5 = json_types["number"]["floating-point"];
     std::string v6 = json_types["string"];
     std::vector<short> v7 = json_types["array"];
-    std::unordered_map<std::string, json> v8 = json_types;
+    std::map<std::string, json> v8 = json_types;
 
     // print the conversion results
     std::cout << v1 << '\n';

docs/mkdocs/docs/examples/operator__ValueType.output

@@ -4,9 +4,9 @@
 Hello, world!
 1 2 3 4 5 
 
-number: {"floating-point":17.23,"integer":42}
-null: null
-string: "Hello, world!"
-boolean: true
 array: [1,2,3,4,5]
+boolean: true
+null: null
+number: {"floating-point":17.23,"integer":42}
+string: "Hello, world!"
 [json.exception.type_error.302] type must be boolean, but is string

docs/mkdocs/docs/examples/parse_event_t.cpp

@@ -0,0 +1,44 @@
+#include <iostream>
+#include <string>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+// translate a parse_event_t to a human-readable name
+std::string event_name(json::parse_event_t event)
+{
+    switch (event)
+    {
+        case json::parse_event_t::object_start:
+            return "object_start";
+        case json::parse_event_t::object_end:
+            return "object_end";
+        case json::parse_event_t::array_start:
+            return "array_start";
+        case json::parse_event_t::array_end:
+            return "array_end";
+        case json::parse_event_t::key:
+            return "key";
+        case json::parse_event_t::value:
+            return "value";
+        default:
+            return "unknown";
+    }
+}
+
+int main()
+{
+    // a small JSON text
+    auto text = R"({"pi": 3.141, "numbers": [1, 2]})";
+
+    // parse the text and report every event together with its depth;
+    // returning true keeps every value unchanged
+    json j = json::parse(text, [](int depth, json::parse_event_t event, json& /*parsed*/)
+    {
+        std::cout << depth << " " << event_name(event) << '\n';
+        return true;
+    });
+
+    // the callback did not change anything, so the parsed value is unaffected
+    std::cout << j << '\n';
+}

docs/mkdocs/docs/examples/parse_event_t.output

@@ -0,0 +1,10 @@
+0 object_start
+1 key
+1 value
+1 key
+1 array_start
+2 value
+2 value
+1 array_end
+0 object_end
+{"numbers":[1,2],"pi":3.141}

docs/mkdocs/docs/examples/patch__exception.cpp

@@ -0,0 +1,36 @@
+#include <iostream>
+#include <iomanip>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+using namespace nlohmann::literals;
+
+int main()
+{
+    // the original document
+    json doc = R"(
+        {
+          "a": { "b": 1 }
+        }
+    )"_json;
+
+    // a patch that tries to move "/a" into one of its own children
+    json patch = R"(
+        [
+          { "op": "move", "from": "/a", "path": "/a/b" }
+        ]
+    )"_json;
+
+    // exception out_of_range.414
+    try
+    {
+        json patched_doc = doc.patch(patch);
+    }
+    catch (const json::out_of_range& e)
+    {
+        std::cout << e.what() << '\n';
+    }
+
+    // the original document is unchanged
+    std::cout << std::setw(4) << doc << std::endl;
+}

docs/mkdocs/docs/examples/patch__exception.output

@@ -0,0 +1,6 @@
+[json.exception.out_of_range.414] cannot move value: 'from' path '/a' is a proper prefix of 'path' '/a/b'
+{
+    "a": {
+        "b": 1
+    }
+}

docs/mkdocs/docs/examples/patch_inplace__exception.cpp

@@ -0,0 +1,38 @@
+#include <iostream>
+#include <iomanip>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+using namespace nlohmann::literals;
+
+int main()
+{
+    // the original document
+    json doc = R"(
+        {
+          "a": 1,
+          "b": 2
+        }
+    )"_json;
+
+    // a patch whose second operation fails
+    json patch = R"(
+        [
+          { "op": "replace", "path": "/a", "value": 99 },
+          { "op": "remove", "path": "/nonexistent" }
+        ]
+    )"_json;
+
+    // exception out_of_range.403
+    try
+    {
+        doc.patch_inplace(patch);
+    }
+    catch (const json::out_of_range& e)
+    {
+        std::cout << e.what() << '\n';
+    }
+
+    // the first operation has already been applied to doc
+    std::cout << std::setw(4) << doc << std::endl;
+}

docs/mkdocs/docs/examples/patch_inplace__exception.output

@@ -0,0 +1,5 @@
+[json.exception.out_of_range.403] key 'nonexistent' not found
+{
+    "a": 99,
+    "b": 2
+}

docs/mkdocs/docs/examples/sax_no_exception.cpp

@@ -0,0 +1,40 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+// a DOM parser that reports parse errors instead of throwing
+class sax_no_exception : public nlohmann::detail::json_sax_dom_parser<json, nlohmann::detail::string_input_adapter_type>
+{
+  public:
+    explicit sax_no_exception(json& j)
+        : nlohmann::detail::json_sax_dom_parser<json, nlohmann::detail::string_input_adapter_type>(j, false)
+    {}
+
+    bool parse_error(std::size_t position,
+                     const std::string& last_token,
+                     const json::exception& ex)
+    {
+        std::cout << "parse error at input byte " << position << "\n"
+                  << ex.what() << "\n"
+                  << "last read: \"" << last_token << "\""
+                  << std::endl;
+        return false;
+    }
+};
+
+int main()
+{
+    std::string myinput = "[1,2,3,]";
+
+    json result;
+    sax_no_exception sax(result);
+
+    bool parse_result = json::sax_parse(myinput, &sax);
+    if (!parse_result)
+    {
+        std::cout << "parsing unsuccessful!" << std::endl;
+    }
+
+    std::cout << "parsed value: " << result << std::endl;
+}

docs/mkdocs/docs/examples/sax_no_exception.output

@@ -0,0 +1,5 @@
+parse error at input byte 8
+[json.exception.parse_error.101] parse error at line 1, column 8: syntax error while parsing value - unexpected ']'; expected '[', '{', or a literal
+last read: "3,]"
+parsing unsuccessful!
+parsed value: [1,2,3]

docs/mkdocs/docs/examples/to_bjdata__exception.cpp

@@ -0,0 +1,20 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // create a non-empty JSON array
+    json j = {1, 2, 3};
+
+    // exception other_error.502
+    try
+    {
+        json::to_bjdata(j, false, true);
+    }
+    catch (const json::other_error& e)
+    {
+        std::cout << e.what() << '\n';
+    }
+}

docs/mkdocs/docs/examples/to_bjdata__exception.output

@@ -0,0 +1 @@
+[json.exception.other_error.502] use_type requires use_size = true

docs/mkdocs/docs/examples/to_bon8__exception.cpp

@@ -0,0 +1,22 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // create a JSON string that is not valid UTF-8
+    std::string invalid_utf8;
+    invalid_utf8.push_back(static_cast<char>(0xFF));
+    json j = invalid_utf8;
+
+    // exception type_error.316
+    try
+    {
+        json::to_bon8(j);
+    }
+    catch (const json::type_error& e)
+    {
+        std::cout << e.what() << '\n';
+    }
+}

docs/mkdocs/docs/examples/to_bon8__exception.output

@@ -0,0 +1 @@
+[json.exception.type_error.316] invalid UTF-8 byte at index 0: 0xFF

docs/mkdocs/docs/examples/to_bson__exception.cpp

@@ -0,0 +1,23 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // create a JSON object whose key contains a null byte (U+0000)
+    std::string key = "ab";
+    key.push_back('\0');
+    key.push_back('c');
+    json j = {{key, 1}};
+
+    // exception out_of_range.409
+    try
+    {
+        json::to_bson(j);
+    }
+    catch (const json::out_of_range& e)
+    {
+        std::cout << e.what() << '\n';
+    }
+}

docs/mkdocs/docs/examples/to_bson__exception.output

@@ -0,0 +1 @@
+[json.exception.out_of_range.409] BSON key cannot contain code point U+0000 (at byte 2)

docs/mkdocs/docs/examples/to_msgpack__exception.cpp

@@ -0,0 +1,20 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // create a JSON value with a binary subtype that exceeds 255
+    json j = json::binary({1, 2, 3}, 300);
+
+    // exception out_of_range.415
+    try
+    {
+        json::to_msgpack(j);
+    }
+    catch (const json::out_of_range& e)
+    {
+        std::cout << e.what() << '\n';
+    }
+}

docs/mkdocs/docs/examples/to_msgpack__exception.output

@@ -0,0 +1 @@
+[json.exception.out_of_range.415] subtype 300 is too large for the MessagePack ext type (max 255)

docs/mkdocs/docs/examples/to_ubjson__exception.cpp

@@ -0,0 +1,20 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // create a non-empty JSON array
+    json j = {1, 2, 3};
+
+    // exception other_error.502
+    try
+    {
+        json::to_ubjson(j, false, true);
+    }
+    catch (const json::other_error& e)
+    {
+        std::cout << e.what() << '\n';
+    }
+}

docs/mkdocs/docs/examples/to_ubjson__exception.output

@@ -0,0 +1 @@
+[json.exception.other_error.502] use_type requires use_size = true

docs/mkdocs/docs/examples/value__exception.cpp

@@ -0,0 +1,33 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // create a JSON object with a string value
+    json j = {{"name", "the good"}};
+
+    // exception type_error.302
+    try
+    {
+        int v = j.value("name", 0);
+        std::cout << v << '\n';
+    }
+    catch (const json::type_error& e)
+    {
+        std::cout << e.what() << '\n';
+    }
+
+    // exception type_error.306
+    try
+    {
+        json str = "I am a string";
+        auto v = str.value("name", 0);
+        std::cout << v << '\n';
+    }
+    catch (const json::type_error& e)
+    {
+        std::cout << e.what() << '\n';
+    }
+}

docs/mkdocs/docs/examples/value__exception.output

@@ -0,0 +1,2 @@
+[json.exception.type_error.302] type must be number, but is string
+[json.exception.type_error.306] cannot use value() with string