From c40c33467875a50f11e939d53e5d1c51dec41f1c Mon Sep 17 00:00:00 2001
From: Kyle Edwards <kyle.edwards@kitware.com>
Date: Tue, 6 Apr 2021 16:11:35 -0400
Subject: [PATCH] CharReader: Add StructuredError

---
 include/json/reader.h        | 13 +++++++++++++
 src/lib_json/json_reader.cpp | 18 +++++++++---------
 src/test_lib_json/main.cpp   | 37 ++++++++++++++++++++++++++++++++++++
 3 files changed, 59 insertions(+), 9 deletions(-)

diff --git a/include/json/reader.h b/include/json/reader.h
index 917546608..847cd3777 100644
--- a/include/json/reader.h
+++ b/include/json/reader.h
@@ -244,6 +244,13 @@ class JSONCPP_DEPRECATED(
  */
 class JSON_API CharReader {
 public:
+  class JSON_API StructuredError {
+  public:
+    ptrdiff_t offset_start;
+    ptrdiff_t offset_limit;
+    String message;
+  };
+
   virtual ~CharReader() = default;
   /** \brief Read a Value from a <a HREF="http://www.json.org">JSON</a>
    * document. The document must be a UTF-8 encoded string containing the
@@ -264,6 +271,12 @@ class JSON_API CharReader {
   virtual bool parse(char const* beginDoc, char const* endDoc, Value* root,
                      String* errs) = 0;
 
+  /** \brief Get a list of structured error messages from parsing the document.
+   *
+   * \return list of error messages.
+   */
+  virtual std::vector<StructuredError> getStructuredErrors() const = 0;
+
   class JSON_API Factory {
   public:
     virtual ~Factory() = default;
diff --git a/src/lib_json/json_reader.cpp b/src/lib_json/json_reader.cpp
index a34017d99..63fc11603 100644
--- a/src/lib_json/json_reader.cpp
+++ b/src/lib_json/json_reader.cpp
@@ -884,17 +884,12 @@ class OurReader {
 public:
   using Char = char;
   using Location = const Char*;
-  struct StructuredError {
-    ptrdiff_t offset_start;
-    ptrdiff_t offset_limit;
-    String message;
-  };
 
   explicit OurReader(OurFeatures const& features);
   bool parse(const char* beginDoc, const char* endDoc, Value& root,
              bool collectComments = true);
   String getFormattedErrorMessages() const;
-  std::vector<StructuredError> getStructuredErrors() const;
+  std::vector<CharReader::StructuredError> getStructuredErrors() const;
 
 private:
   OurReader(OurReader const&);      // no impl
@@ -1849,10 +1844,11 @@ String OurReader::getFormattedErrorMessages() const {
   return formattedMessage;
 }
 
-std::vector<OurReader::StructuredError> OurReader::getStructuredErrors() const {
-  std::vector<OurReader::StructuredError> allErrors;
+std::vector<CharReader::StructuredError>
+OurReader::getStructuredErrors() const {
+  std::vector<CharReader::StructuredError> allErrors;
   for (const auto& error : errors_) {
-    OurReader::StructuredError structured;
+    CharReader::StructuredError structured;
     structured.offset_start = error.token_.start_ - begin_;
     structured.offset_limit = error.token_.end_ - begin_;
     structured.message = error.message_;
@@ -1876,6 +1872,10 @@ class OurCharReader : public CharReader {
     }
     return ok;
   }
+
+  std::vector<StructuredError> getStructuredErrors() const override {
+    return reader_.getStructuredErrors();
+  }
 };
 
 CharReaderBuilder::CharReaderBuilder() { setDefaults(&settings_); }
diff --git a/src/test_lib_json/main.cpp b/src/test_lib_json/main.cpp
index d0f5364ac..d75cddf5c 100644
--- a/src/test_lib_json/main.cpp
+++ b/src/test_lib_json/main.cpp
@@ -3903,6 +3903,43 @@ JSONTEST_FIXTURE_LOCAL(FuzzTest, fuzzDoesntCrash) {
                              example.size()));
 }
 
+struct ParseWithStructuredErrorsTest : JsonTest::TestCase {
+  void
+  testErrors(const std::string& doc, bool success,
+             const std::vector<Json::CharReader::StructuredError>& errors) {
+    Json::CharReaderBuilder b;
+    CharReaderPtr reader(b.newCharReader());
+    Json::Value root;
+    JSONTEST_ASSERT_EQUAL(
+        success,
+        reader->parse(doc.data(), doc.data() + doc.length(), &root, nullptr));
+    auto actualErrors = reader->getStructuredErrors();
+    JSONTEST_ASSERT_EQUAL(errors.size(), actualErrors.size());
+    for (std::size_t i = 0; i < errors.size() && i < actualErrors.size(); i++) {
+      JSONTEST_ASSERT_EQUAL(errors[i].offset_start,
+                            actualErrors[i].offset_start);
+      JSONTEST_ASSERT_EQUAL(errors[i].offset_limit,
+                            actualErrors[i].offset_limit);
+      JSONTEST_ASSERT_STRING_EQUAL(errors[i].message, actualErrors[i].message);
+    }
+  }
+};
+
+JSONTEST_FIXTURE_LOCAL(ParseWithStructuredErrorsTest, success) {
+  testErrors("{}", true, {});
+}
+
+JSONTEST_FIXTURE_LOCAL(ParseWithStructuredErrorsTest, singleError) {
+  testErrors("{ 1 : 2 }", false,
+             {
+                 {
+                     /*offset_start=*/2,
+                     /*offset_limit=*/3,
+                     /*message=*/"Missing '}' or object member name",
+                 },
+             });
+}
+
 int main(int argc, const char* argv[]) {
   JsonTest::Runner runner;