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Add recursive update function (#3069) 

* ✨ add recursive update function
pull/3121/head
Niels Lohmann 2021-11-03 13:52:20 +01:00 committed by GitHub
parent 7440786b81
commit 5d87c4d409
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9 changed files with 243 additions and 128 deletions
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13
doc/examples/update.cpp
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@ -7,12 +7,17 @@ using json = nlohmann::json;
int main()
{
// create two JSON objects
json o1 = R"( {"color": "red", "price": 17.99} )"_json;
json o2 = R"( {"color": "blue", "speed": 100} )"_json;
json o1 = R"( {"color": "red", "price": 17.99, "names": {"de": "Flugzeug"}} )"_json;
json o2 = R"( {"color": "blue", "speed": 100, "names": {"en": "plane"}} )"_json;
json o3 = o1;
// add all keys from o2 to o1 (updating "color")
// add all keys from o2 to o1 (updating "color", replacing "names")
o1.update(o2);
// output updated object o1
// add all keys from o2 to o1 (updating "color", merging "names")
o3.update(o2, true);
// output updated object o1 and o3
std::cout << std::setw(2) << o1 << '\n';
std::cout << std::setw(2) << o3 << '\n';
}

12
doc/examples/update.output
View File

@ -1,5 +1,17 @@
{
"color": "blue",
"names": {
"en": "plane"
},
"price": 17.99,
"speed": 100
}
{
"color": "blue",
"names": {
"de": "Flugzeug",
"en": "plane"
},
"price": 17.99,
"speed": 100
}

13
doc/examples/update__range.cpp
View File

@ -7,12 +7,17 @@ using json = nlohmann::json;
int main()
{
// create two JSON objects
json o1 = R"( {"color": "red", "price": 17.99} )"_json;
json o2 = R"( {"color": "blue", "speed": 100} )"_json;
json o1 = R"( {"color": "red", "price": 17.99, "names": {"de": "Flugzeug"}} )"_json;
json o2 = R"( {"color": "blue", "speed": 100, "names": {"en": "plane"}} )"_json;
json o3 = o1;
// add all keys from o2 to o1 (updating "color")
// add all keys from o2 to o1 (updating "color", replacing "names")
o1.update(o2.begin(), o2.end());
// output updated object o1
// add all keys from o2 to o1 (updating "color", merging "names")
o3.update(o2.begin(), o2.end(), true);
// output updated object o1 and o3
std::cout << std::setw(2) << o1 << '\n';
std::cout << std::setw(2) << o3 << '\n';
}

12
doc/examples/update__range.output
View File

@ -1,5 +1,17 @@
{
"color": "blue",
"names": {
"en": "plane"
},
"price": 17.99,
"speed": 100
}
{
"color": "blue",
"names": {
"de": "Flugzeug",
"en": "plane"
},
"price": 17.99,
"speed": 100
}

72
doc/mkdocs/docs/api/basic_json/update.md
View File

@ -2,14 +2,17 @@
```cpp
// (1)
void update(const_reference j);
void update(const_reference j, bool merge_objects = false);
// (2)
void update(const_iterator first, const_iterator last);
void update(const_iterator first, const_iterator last, bool merge_objects = false);
```
1. Inserts all values from JSON object `j` and overwrites existing keys.
2. Inserts all values from from range `[first, last)` and overwrites existing keys.
1. Inserts all values from JSON object `j`.
2. Inserts all values from from range `[first, last)`
When `merge_objects` is `#!c false` (default), existing keys are overwritten. When `merge_objects` is `#!c true`,
recursively merges objects with common keys.
The function is motivated by Python's [dict.update](https://docs.python.org/3.6/library/stdtypes.html#dict.update)
function.
@ -19,6 +22,10 @@ function.
`j` (in)
: JSON object to read values from
`merge_objects` (in)
: when `#!c true`, existing keys are not overwritten, but contents of objects are merged recursively (default:
`#!c false`)
`first` (in)
: begin of the range of elements to insert
@ -73,6 +80,63 @@ function.
--8<-- "examples/update__range.output"
```
??? example
One common usecase for this function is the handling of user settings. Assume your application can configured in
some aspects:
```json
{
"color": "red",
"active": true,
"name": {"de": "Maus", "en": "mouse"}
}
```
The user may override the default settings selectively:
```json
{
"color": "blue",
"name": {"es": "ratón"},
}
```
Then `update` manages the merging of default settings and user settings:
```cpp
auto user_settings = json::parse("config.json");
auto effective_settings = get_default_settings();
effective_settings.update(user_settings);
```
Now `effective_settings` contains the default settings, but those keys set by the user are overwritten:
```json
{
"color": "blue",
"active": true,
"name": {"es": "ratón"}
}
```
Note existing keys were just overwritten. To merge objects, `merge_objects` setting should be set to `#!c true`:
```cpp
auto user_settings = json::parse("config.json");
auto effective_settings = get_default_settings();
effective_settings.update(user_settings, true);
```
```json
{
"color": "blue",
"active": true,
"name": {"de": "Maus", "en": "mouse", "es": "ratón"}
}
```
## Version history
- Added in version 3.0.0.
- Added `merge_objects` parameter in 3.10.4.

58
include/nlohmann/json.hpp
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@ -5954,6 +5954,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
Inserts all values from JSON object @a j and overwrites existing keys.
@param[in] j JSON object to read values from
@param[in] merge_objects when true, existing keys are not overwritten, but
contents of objects are merged recursively
(default: false)
@throw type_error.312 if called on JSON values other than objects; example:
`"cannot use update() with string"`
@ -5965,34 +5968,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
@sa https://docs.python.org/3.6/library/stdtypes.html#dict.update
@since version 3.0.0
@since version 3.0.0, `merge_objects` parameter added in 3.10.4.
*/
void update(const_reference j)
void update(const_reference j, bool merge_objects = false)
{
// implicitly convert null value to an empty object
if (is_null())
{
m_type = value_t::object;
m_value.object = create<object_t>();
assert_invariant();
}
if (JSON_HEDLEY_UNLIKELY(!is_object()))
{
JSON_THROW(type_error::create(312, "cannot use update() with " + std::string(type_name()), *this));
}
if (JSON_HEDLEY_UNLIKELY(!j.is_object()))
{
JSON_THROW(type_error::create(312, "cannot use update() with " + std::string(j.type_name()), *this));
}
for (auto it = j.cbegin(); it != j.cend(); ++it)
{
m_value.object->operator[](it.key()) = it.value();
#if JSON_DIAGNOSTICS
m_value.object->operator[](it.key()).m_parent = this;
#endif
}
update(j.begin(), j.end(), merge_objects);
}
/*!
@ -6003,12 +5983,14 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
@param[in] first begin of the range of elements to insert
@param[in] last end of the range of elements to insert
@param[in] merge_objects when true, existing keys are not overwritten, but
contents of objects are merged recursively
(default: false)
@throw type_error.312 if called on JSON values other than objects; example:
`"cannot use update() with string"`
@throw invalid_iterator.202 if iterator @a first or @a last does does not
point to an object; example: `"iterators first and last must point to
objects"`
@throw type_error.312 if iterator @a first or @a last does does not
point to an object; example: `"cannot use update() with string"`
@throw invalid_iterator.210 if @a first and @a last do not belong to the
same JSON value; example: `"iterators do not fit"`
@ -6019,9 +6001,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
@sa https://docs.python.org/3.6/library/stdtypes.html#dict.update
@since version 3.0.0
@since version 3.0.0, `merge_objects` parameter added in 3.10.4.
*/
void update(const_iterator first, const_iterator last)
void update(const_iterator first, const_iterator last, bool merge_objects = false)
{
// implicitly convert null value to an empty object
if (is_null())
@ -6043,14 +6025,22 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
}
// passed iterators must belong to objects
if (JSON_HEDLEY_UNLIKELY(!first.m_object->is_object()
|| !last.m_object->is_object()))
if (JSON_HEDLEY_UNLIKELY(!first.m_object->is_object()))
{
JSON_THROW(invalid_iterator::create(202, "iterators first and last must point to objects", *this));
JSON_THROW(type_error::create(312, "cannot use update() with " + std::string(first.m_object->type_name()), *first.m_object));
}
for (auto it = first; it != last; ++it)
{
if (merge_objects && it.value().is_object())
{
auto it2 = m_value.object->find(it.key());
if (it2 != m_value.object->end())
{
it2->second.update(it.value(), true);
continue;
}
}
m_value.object->operator[](it.key()) = it.value();
#if JSON_DIAGNOSTICS
m_value.object->operator[](it.key()).m_parent = this;

58
single_include/nlohmann/json.hpp
View File

@ -23455,6 +23455,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
Inserts all values from JSON object @a j and overwrites existing keys.
@param[in] j JSON object to read values from
@param[in] merge_objects when true, existing keys are not overwritten, but
contents of objects are merged recursively
(default: false)
@throw type_error.312 if called on JSON values other than objects; example:
`"cannot use update() with string"`
@ -23466,34 +23469,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
@sa https://docs.python.org/3.6/library/stdtypes.html#dict.update
@since version 3.0.0
@since version 3.0.0, `merge_objects` parameter added in 3.10.4.
*/
void update(const_reference j)
void update(const_reference j, bool merge_objects = false)
{
// implicitly convert null value to an empty object
if (is_null())
{
m_type = value_t::object;
m_value.object = create<object_t>();
assert_invariant();
}
if (JSON_HEDLEY_UNLIKELY(!is_object()))
{
JSON_THROW(type_error::create(312, "cannot use update() with " + std::string(type_name()), *this));
}
if (JSON_HEDLEY_UNLIKELY(!j.is_object()))
{
JSON_THROW(type_error::create(312, "cannot use update() with " + std::string(j.type_name()), *this));
}
for (auto it = j.cbegin(); it != j.cend(); ++it)
{
m_value.object->operator[](it.key()) = it.value();
#if JSON_DIAGNOSTICS
m_value.object->operator[](it.key()).m_parent = this;
#endif
}
update(j.begin(), j.end(), merge_objects);
}
/*!
@ -23504,12 +23484,14 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
@param[in] first begin of the range of elements to insert
@param[in] last end of the range of elements to insert
@param[in] merge_objects when true, existing keys are not overwritten, but
contents of objects are merged recursively
(default: false)
@throw type_error.312 if called on JSON values other than objects; example:
`"cannot use update() with string"`
@throw invalid_iterator.202 if iterator @a first or @a last does does not
point to an object; example: `"iterators first and last must point to
objects"`
@throw type_error.312 if iterator @a first or @a last does does not
point to an object; example: `"cannot use update() with string"`
@throw invalid_iterator.210 if @a first and @a last do not belong to the
same JSON value; example: `"iterators do not fit"`
@ -23520,9 +23502,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
@sa https://docs.python.org/3.6/library/stdtypes.html#dict.update
@since version 3.0.0
@since version 3.0.0, `merge_objects` parameter added in 3.10.4.
*/
void update(const_iterator first, const_iterator last)
void update(const_iterator first, const_iterator last, bool merge_objects = false)
{
// implicitly convert null value to an empty object
if (is_null())
@ -23544,14 +23526,22 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
}
// passed iterators must belong to objects
if (JSON_HEDLEY_UNLIKELY(!first.m_object->is_object()
|| !last.m_object->is_object()))
if (JSON_HEDLEY_UNLIKELY(!first.m_object->is_object()))
{
JSON_THROW(invalid_iterator::create(202, "iterators first and last must point to objects", *this));
JSON_THROW(type_error::create(312, "cannot use update() with " + std::string(first.m_object->type_name()), *first.m_object));
}
for (auto it = first; it != last; ++it)
{
if (merge_objects && it.value().is_object())
{
auto it2 = m_value.object->find(it.key());
if (it2 != m_value.object->end())
{
it2->second.update(it.value(), true);
continue;
}
}
m_value.object->operator[](it.key()) = it.value();
#if JSON_DIAGNOSTICS
m_value.object->operator[](it.key()).m_parent = this;

16
test/src/unit-diagnostics.cpp
View File

@ -97,6 +97,18 @@ TEST_CASE("Better diagnostics")
CHECK_THROWS_WITH_AS(_ = json::parse(""), "[json.exception.parse_error.101] parse error at line 1, column 1: syntax error while parsing value - unexpected end of input; expected '[', '{', or a literal", json::parse_error);
}
SECTION("Wrong type in update()")
{
json j = {{"foo", "bar"}};
json k = {{"bla", 1}};
CHECK_THROWS_WITH_AS(j.update(k["bla"].begin(), k["bla"].end()), "[json.exception.type_error.312] (/bla) cannot use update() with number", json::type_error);
CHECK_THROWS_WITH_AS(j.update(k["bla"]), "[json.exception.type_error.312] (/bla) cannot use update() with number", json::type_error);
}
}
TEST_CASE("Regression tests for extended diagnostics")
{
SECTION("Regression test for https://github.com/nlohmann/json/pull/2562#pullrequestreview-574858448")
{
CHECK_THROWS_WITH_AS(json({"0", "0"})[1].get<int>(), "[json.exception.type_error.302] (/1) type must be number, but is string", json::type_error);
@ -110,7 +122,7 @@ TEST_CASE("Better diagnostics")
CHECK_THROWS_WITH_AS(j.unflatten(), "[json.exception.type_error.315] (/~1foo) values in object must be primitive", json::type_error);
}
SECTION("Regression test for https://github.com/nlohmann/json/issues/2838")
SECTION("Regression test for issue #2838 - Assertion failure when inserting into arrays with JSON_DIAGNOSTICS set")
{
// void push_back(basic_json&& val)
{
@ -235,7 +247,7 @@ TEST_CASE("Better diagnostics")
}
}
SECTION("Regression test for https://github.com/nlohmann/json/issues/3032")
SECTION("Regression test for issue #3032 - Yet another assertion failure when inserting into arrays with JSON_DIAGNOSTICS set")
{
// reference operator[](size_type idx)
{

117
test/src/unit-modifiers.cpp
View File

@ -796,64 +796,89 @@ TEST_CASE("modifiers")
SECTION("update()")
{
json j_object1 = {{"one", "eins"}, {"two", "zwei"}};
json j_object2 = {{"three", "drei"}, {"two", "zwo"}};
json j_array = {1, 2, 3, 4};
SECTION("const reference")
SECTION("non-recursive (default)")
{
SECTION("proper usage")
{
j_object1.update(j_object2);
CHECK(j_object1 == json({{"one", "eins"}, {"two", "zwo"}, {"three", "drei"}}));
json j_object1 = {{"one", "eins"}, {"two", "zwei"}};
json j_object2 = {{"three", "drei"}, {"two", "zwo"}};
json j_array = {1, 2, 3, 4};
json j_null;
j_null.update(j_object2);
CHECK(j_null == j_object2);
SECTION("const reference")
{
SECTION("proper usage")
{
j_object1.update(j_object2);
CHECK(j_object1 == json({{"one", "eins"}, {"two", "zwo"}, {"three", "drei"}}));
json j_null;
j_null.update(j_object2);
CHECK(j_null == j_object2);
}
SECTION("wrong types")
{
CHECK_THROWS_AS(j_array.update(j_object1), json::type_error&);
CHECK_THROWS_WITH(j_array.update(j_object1), "[json.exception.type_error.312] cannot use update() with array");
CHECK_THROWS_AS(j_object1.update(j_array), json::type_error&);
CHECK_THROWS_WITH(j_object1.update(j_array), "[json.exception.type_error.312] cannot use update() with array");
}
}
SECTION("wrong types")
SECTION("iterator range")
{
CHECK_THROWS_AS(j_array.update(j_object1), json::type_error&);
CHECK_THROWS_WITH(j_array.update(j_object1), "[json.exception.type_error.312] cannot use update() with array");
SECTION("proper usage")
{
j_object1.update(j_object2.begin(), j_object2.end());
CHECK(j_object1 == json({{"one", "eins"}, {"two", "zwo"}, {"three", "drei"}}));
CHECK_THROWS_AS(j_object1.update(j_array), json::type_error&);
CHECK_THROWS_WITH(j_object1.update(j_array), "[json.exception.type_error.312] cannot use update() with array");
json j_null;
j_null.update(j_object2.begin(), j_object2.end());
CHECK(j_null == j_object2);
}
SECTION("empty range")
{
j_object1.update(j_object2.begin(), j_object2.begin());
CHECK(j_object1 == json({{"one", "eins"}, {"two", "zwei"}}));
}
SECTION("invalid iterators")
{
json j_other_array2 = {"first", "second"};
CHECK_THROWS_AS(j_array.update(j_object2.begin(), j_object2.end()), json::type_error&);
CHECK_THROWS_AS(j_object1.update(j_object1.begin(), j_object2.end()), json::invalid_iterator&);
CHECK_THROWS_AS(j_object1.update(j_array.begin(), j_array.end()), json::type_error&);
CHECK_THROWS_WITH(j_array.update(j_object2.begin(), j_object2.end()),
"[json.exception.type_error.312] cannot use update() with array");
CHECK_THROWS_WITH(j_object1.update(j_object1.begin(), j_object2.end()),
"[json.exception.invalid_iterator.210] iterators do not fit");
CHECK_THROWS_WITH(j_object1.update(j_array.begin(), j_array.end()),
"[json.exception.type_error.312] cannot use update() with array");
}
}
}
SECTION("iterator range")
SECTION("recursive")
{
SECTION("proper usage")
SECTION("const reference")
{
j_object1.update(j_object2.begin(), j_object2.end());
CHECK(j_object1 == json({{"one", "eins"}, {"two", "zwo"}, {"three", "drei"}}));
SECTION("extend object")
{
json j1 = {{"string", "s"}, {"numbers", {{"one", 1}}}};
json j2 = {{"string", "t"}, {"numbers", {{"two", 2}}}};
j1.update(j2, true);
CHECK(j1 == json({{"string", "t"}, {"numbers", {{"one", 1}, {"two", 2}}}}));
}
json j_null;
j_null.update(j_object2.begin(), j_object2.end());
CHECK(j_null == j_object2);
}
SECTION("empty range")
{
j_object1.update(j_object2.begin(), j_object2.begin());
CHECK(j_object1 == json({{"one", "eins"}, {"two", "zwei"}}));
}
SECTION("invalid iterators")
{
json j_other_array2 = {"first", "second"};
CHECK_THROWS_AS(j_array.update(j_object2.begin(), j_object2.end()), json::type_error&);
CHECK_THROWS_AS(j_object1.update(j_object1.begin(), j_object2.end()), json::invalid_iterator&);
CHECK_THROWS_AS(j_object1.update(j_array.begin(), j_array.end()), json::invalid_iterator&);
CHECK_THROWS_WITH(j_array.update(j_object2.begin(), j_object2.end()),
"[json.exception.type_error.312] cannot use update() with array");
CHECK_THROWS_WITH(j_object1.update(j_object1.begin(), j_object2.end()),
"[json.exception.invalid_iterator.210] iterators do not fit");
CHECK_THROWS_WITH(j_object1.update(j_array.begin(), j_array.end()),
"[json.exception.invalid_iterator.202] iterators first and last must point to objects");
SECTION("replace object")
{
json j1 = {{"string", "s"}, {"numbers", {{"one", 1}}}};
json j2 = {{"string", "t"}, {"numbers", 1}};
j1.update(j2, true);
CHECK(j1 == json({{"string", "t"}, {"numbers", 1}}));
}
}
}
}