Implement a JSON::erase_if method for arrays (#1835)

Fixes: #1834
Signed-off-by: Juan Cruz Viotti <jv@jviotti.com>

Author: jviotti

src/core/json/include/sourcemeta/core/json_value.h

@@ -1443,6 +1443,23 @@ class SOURCEMETA_CORE_JSON_EXPORT JSON {
   auto erase(typename Array::const_iterator first,
              typename Array::const_iterator last) -> typename Array::iterator;
 
+  /// This method deletes a set of array elements given a predicate. For
+  /// example:
+  ///
+  /// ```cpp
+  /// #include <sourcemeta/core/json.h>
+  /// #include <cassert>
+  ///
+  /// sourcemeta::core::JSON array =
+  ///   sourcemeta::core::parse_json("[ 1, 2, 3 ]");
+  /// array.erase_if(array,
+  ///   [](const auto &item) { return item.to_integer() % 2 == 0; });
+  /// assert(array.size(), 2);
+  /// assert(array.at(0), 1);
+  /// assert(array.at(1), 3);
+  /// ```
+  auto erase_if(const std::function<bool(const JSON &)> &predicate) -> void;
+
   /// This method deletes all members of an object or all elements of an array,
   /// leaving them empty. For example:
   ///

src/core/json/json_value.cc

@@ -852,6 +852,12 @@ auto JSON::erase(typename JSON::Array::const_iterator first,
   return this->data_array.data.erase(first, last);
 }
 
+auto JSON::erase_if(const std::function<bool(const JSON &)> &predicate)
+    -> void {
+  assert(this->is_array());
+  std::erase_if(this->data_array.data, predicate);
+}
+
 auto JSON::clear() -> void {
   if (this->is_object()) {
     this->data_object.data.clear();

test/json/json_array_test.cc

@@ -534,3 +534,45 @@ TEST(JSON_array, sort_object_items) {
 
   EXPECT_EQ(document, expected);
 }
+
+TEST(JSON_array, erase_if_some) {
+  auto document = sourcemeta::core::parse_json(R"JSON([
+    1, 2, 3, 4, 5
+  ])JSON");
+
+  document.erase_if([](const auto &item) {
+    return item.is_integer() && item.to_integer() % 2 == 0;
+  });
+
+  const auto expected = sourcemeta::core::parse_json(R"JSON([
+    1, 3, 5
+  ])JSON");
+
+  EXPECT_EQ(document, expected);
+}
+
+TEST(JSON_array, erase_if_none) {
+  auto document = sourcemeta::core::parse_json(R"JSON([
+    1, 2, 3, 4, 5
+  ])JSON");
+
+  document.erase_if([](const auto &item) { return item.is_boolean(); });
+
+  const auto expected = sourcemeta::core::parse_json(R"JSON([
+    1, 2, 3, 4, 5
+  ])JSON");
+
+  EXPECT_EQ(document, expected);
+}
+
+TEST(JSON_array, erase_if_all) {
+  auto document = sourcemeta::core::parse_json(R"JSON([
+    1, 2, 3, 4, 5
+  ])JSON");
+
+  document.erase_if([](const auto &item) { return item.is_integer(); });
+
+  const auto expected = sourcemeta::core::parse_json(R"JSON([])JSON");
+
+  EXPECT_EQ(document, expected);
+}