Support serialising/deserializing the JSONPath class

src/core/jsonpath/include/sourcemeta/core/jsonpath.h

@@ -293,7 +293,35 @@ class SOURCEMETA_CORE_JSONPATH_EXPORT JSONPath {
   [[nodiscard]] static auto normalize(const WeakPointer &location)
       -> JSON::String;
 
+  /// Serialize the query into its expression string as JSON. For example:
+  ///
+  /// ```cpp
+  /// #include <sourcemeta/core/jsonpath.h>
+  /// #include <cassert>
+  ///
+  /// const sourcemeta::core::JSONPath path{"$.foo[0]"};
+  /// const sourcemeta::core::JSON result{path.to_json()};
+  /// assert(result.is_string());
+  /// assert(result.to_string() == "$.foo[0]");
+  /// ```
+  [[nodiscard]] auto to_json() const -> JSON;
+
+  /// Deserialize a query from its expression string as JSON, returning no
+  /// result on invalid input. For example:
+  ///
+  /// ```cpp
+  /// #include <sourcemeta/core/jsonpath.h>
+  /// #include <cassert>
+  ///
+  /// const sourcemeta::core::JSON input{"$.foo[0]"};
+  /// const auto path{sourcemeta::core::JSONPath::from_json(input)};
+  /// assert(path.has_value());
+  /// ```
+  [[nodiscard]] static auto from_json(const JSON &value)
+      -> std::optional<JSONPath>;
+
 private:
+  JSON::String expression_;
   Query query_;
 };
 

src/core/jsonpath/jsonpath.cc

@@ -1363,7 +1363,7 @@ inline auto evaluate_segments(const std::vector<JSONPath::Segment> &segments,
 } // namespace
 
 JSONPath::JSONPath(const JSON::StringView expression)
-    : query_{parse_jsonpath(expression)} {}
+    : expression_{expression}, query_{parse_jsonpath(expression)} {}
 
 auto JSONPath::evaluate(const JSON &document, const Callback &callback) const
     -> void {
@@ -1429,4 +1429,18 @@ auto JSONPath::normalize(const WeakPointer &location) -> JSON::String {
   return result;
 }
 
+auto JSONPath::to_json() const -> JSON { return JSON{this->expression_}; }
+
+auto JSONPath::from_json(const JSON &value) -> std::optional<JSONPath> {
+  if (!value.is_string()) {
+    return std::nullopt;
+  }
+
+  try {
+    return JSONPath{value.to_string()};
+  } catch (const JSONPathParseError &) {
+    return std::nullopt;
+  }
+}
+
 } // namespace sourcemeta::core

test/jsonpath/CMakeLists.txt

@@ -3,7 +3,8 @@ sourcemeta_test(NAMESPACE sourcemeta PROJECT core NAME jsonpath
     jsonpath_parse_test.cc
     jsonpath_evaluate_test.cc
     jsonpath_filter_test.cc
-    jsonpath_normalize_test.cc)
+    jsonpath_normalize_test.cc
+    jsonpath_json_auto_test.cc)
 
 target_link_libraries(sourcemeta_core_jsonpath_unit
   PRIVATE sourcemeta::core::json)

test/jsonpath/jsonpath_json_auto_test.cc

@@ -0,0 +1,77 @@
+#include <sourcemeta/core/json.h>
+#include <sourcemeta/core/jsonpath.h>
+#include <sourcemeta/core/test.h>
+
+TEST(jsonpath_to_json_single_name) {
+  const sourcemeta::core::JSONPath path{"$.foo"};
+  const auto result{sourcemeta::core::to_json(path)};
+  EXPECT_TRUE(result.is_string());
+  EXPECT_EQ(result.to_string(), "$.foo");
+}
+
+TEST(jsonpath_to_json_filter_expression) {
+  const sourcemeta::core::JSONPath path{
+      "$..books[?@.price < 10 && match(@.category, 'fic.*')]"};
+  const auto result{sourcemeta::core::to_json(path)};
+  EXPECT_TRUE(result.is_string());
+  EXPECT_EQ(result.to_string(),
+            "$..books[?@.price < 10 && match(@.category, 'fic.*')]");
+}
+
+TEST(jsonpath_from_json_valid) {
+  const sourcemeta::core::JSON input{"$.foo[0]"};
+  const auto path{
+      sourcemeta::core::from_json<sourcemeta::core::JSONPath>(input)};
+  EXPECT_TRUE(path.has_value());
+  const auto result{sourcemeta::core::to_json(path.value())};
+  EXPECT_TRUE(result.is_string());
+  EXPECT_EQ(result.to_string(), "$.foo[0]");
+}
+
+TEST(jsonpath_from_json_round_trip_evaluate) {
+  const sourcemeta::core::JSONPath path{"$.foo[0]"};
+  const auto back{sourcemeta::core::from_json<sourcemeta::core::JSONPath>(
+      sourcemeta::core::to_json(path))};
+  EXPECT_TRUE(back.has_value());
+  const auto document{
+      sourcemeta::core::parse_json(R"JSON({ "foo": [ 1, 2 ] })JSON")};
+  std::size_t count{0};
+  back.value().evaluate(
+      document,
+      [&count](const sourcemeta::core::JSON &value,
+               const sourcemeta::core::WeakPointer &location) -> void {
+        EXPECT_TRUE(value.is_integer());
+        EXPECT_EQ(value.to_integer(), 1);
+        EXPECT_EQ(location.size(), 2);
+        count += 1;
+      });
+  EXPECT_EQ(count, 1);
+}
+
+TEST(jsonpath_from_json_invalid_type_integer) {
+  const sourcemeta::core::JSON input{1};
+  const auto path{
+      sourcemeta::core::from_json<sourcemeta::core::JSONPath>(input)};
+  EXPECT_FALSE(path.has_value());
+}
+
+TEST(jsonpath_from_json_invalid_type_array) {
+  const auto input{sourcemeta::core::parse_json(R"JSON([ "$.foo" ])JSON")};
+  const auto path{
+      sourcemeta::core::from_json<sourcemeta::core::JSONPath>(input)};
+  EXPECT_FALSE(path.has_value());
+}
+
+TEST(jsonpath_from_json_invalid_expression) {
+  const sourcemeta::core::JSON input{"foo"};
+  const auto path{
+      sourcemeta::core::from_json<sourcemeta::core::JSONPath>(input)};
+  EXPECT_FALSE(path.has_value());
+}
+
+TEST(jsonpath_from_json_empty_string) {
+  const sourcemeta::core::JSON input{""};
+  const auto path{
+      sourcemeta::core::from_json<sourcemeta::core::JSONPath>(input)};
+  EXPECT_FALSE(path.has_value());
+}