Major Description
We have encountered a number of problems using ResolvingDecoder in the C++ project that we can trace to
1. Incorrectly swapped reader/writer arguments passed to ResolvingGrammarGenerator::generate()
2. Using the wrong tree in ResolvingGrammarGenerator::generate() to generate the backup parsing stack
3. A decoder has no "hook" into the generated codec_traits decode methods for Specific that advances the resolved parse tree through the Symbol::sSkipStart nodes to ignore extra or unknown fields in the writer's data.
4. A resolving decoder can generate a valid decoded object even if there are garbage characters at the end of the input stream if those characters appear in a field that the reader schema is unaware of
Reader/Writer schemas that fail to parse properly below. First example is the writer adding a field to a record that is inside an array
Added field to record inside array
{
std::string readerString("{\"type\":\"record\",\"name\":\"Outer\",\"fields\":[{\"name\":\"outerArray\",\"type\":{\"type\":\"array\",\"items\":{\"type\":\"record\",\"name\":\"InArray\",\"fields\":[{\"name\":\"first\",\"type\":{\"type\":\"record\",\"name\":\"Inner1\",\"fields\":[{\"name\":\"field\",\"type\":\"string\"}]}},{\"name\":\"second\",\"type\":{\"type\":\"record\",\"name\":\"Inner2\",\"fields\":[{\"name\":\"field\",\"type\":\"string\"}]}}]}}}]}");
std::string writerString("{\"type\":\"record\",\"name\":\"Outer\",\"fields\":[{\"name\":\"outerArray\",\"type\":{\"type\":\"array\",\"items\":{\"type\":\"record\",\"name\":\"InArray\",\"fields\":[{\"name\":\"first\",\"type\":{\"type\":\"record\",\"name\":\"Inner1\",\"fields\":[{\"name\":\"field\",\"type\":\"string\"}]}},{\"name\":\"second\",\"type\":{\"type\":\"record\",\"name\":\"Inner2\",\"fields\":[{\"name\":\"field\",\"type\":\"string\"}]}},{\"name\":\"third\",\"type\":{\"type\":\"record\",\"name\":\"Inner3\",\"fields\":[{\"name\":\"number\",\"type\":\"int\"}]}}]}}}]}");
std::stringstream readerStream(readerString);
std::stringstream writerStream(writerString);
avro::ValidSchema readerSchema;
avro::ValidSchema writerSchema;
avro::compileJsonSchema(readerStream, readerSchema);
avro::compileJsonSchema(writerStream, writerSchema);
avro::DecoderPtr decoder = avro::resolvingDecoder(writerSchema, readerSchema, avro::jsonDecoder(writerSchema));
struct Outer outer;
std::stringstream jsonStream("{\"outerArray\":[{\"first\":{\"field\":\"here is a string field\"},\"second\":{\"field\":\"here is another string field\"},\"third\":{\"number\":3}},{\"first\":{\"field\":\"cool\"},\"second\":{\"field\":\"beans\"},\"third\":{\"number\":4}}]}");
std::auto_ptr<avro::InputStream> input = avro::istreamInputStream(jsonStream);
decoder->init(*input);
avro::decode(*decoder, outer);
}
Additional array of writer-only record
{
std::string readerString("{\"type\":\"record\",\"name\":\"OuterExtra\",\"fields\":[{\"name\":\"extraArray\",\"type\":{\"type\":\"array\",\"items\":{\"type\":\"record\",\"name\":\"InArrayExtraArray\",\"fields\":[{\"name\":\"first\",\"type\":{\"type\":\"record\",\"name\":\"Inner1\",\"fields\":[{\"name\":\"field\",\"type\":\"string\"}]}},{\"name\":\"second\",\"type\":{\"type\":\"record\",\"name\":\"Inner2\",\"fields\":[{\"name\":\"field\",\"type\":\"string\"}]}}]}}}]}");
std::string writerString("{\"type\":\"record\",\"name\":\"OuterExtra\",\"fields\":[{\"name\":\"extraArray\",\"type\":{\"type\":\"array\",\"items\":{\"type\":\"record\",\"name\":\"InArrayExtraArray\",\"fields\":[{\"name\":\"first\",\"type\":{\"type\":\"record\",\"name\":\"Inner1\",\"fields\":[{\"name\":\"field\",\"type\":\"string\"}]}},{\"name\":\"second\",\"type\":{\"type\":\"record\",\"name\":\"Inner2\",\"fields\":[{\"name\":\"field\",\"type\":\"string\"}]}},{\"name\":\"innerArray\",\"type\":{\"type\":\"array\",\"items\":{\"type\":\"record\",\"name\":\"Inner3\",\"fields\":[{\"name\":\"number\",\"type\":\"int\"}]}}}]}}}]}");
std::stringstream readerStream(readerString);
std::stringstream writerStream(writerString);
avro::ValidSchema readerSchema;
avro::ValidSchema writerSchema;
avro::compileJsonSchema(readerStream, readerSchema);
avro::compileJsonSchema(writerStream, writerSchema);
avro::DecoderPtr decoder = avro::resolvingDecoder(writerSchema, readerSchema, avro::jsonDecoder(writerSchema));
struct Outer outer;
std::stringstream jsonStream("{\"extraArray\":[{\"first\":{\"field\":\"here is a string field\"},\"second\":{\"field\":\"here is another string field\"},\"innerArray\":[{\"number\":1},{\"number\":2},{\"number\":3}]},{\"first\":{\"field\":\"second item in array\"},\"second\":{\"field\":\"inner2 field of 2\"},\"innerArray\":[{\"number\":4},{\"number\":5}]},{\"first\":{\"field\":\"third item in array\"},\"second\":{\"field\":\"inner2 field of 3\"},\"innerArray\":[{\"number\":6}]}]}");
std::auto_ptr<avro::InputStream> input = avro::istreamInputStream(jsonStream);
decoder->init(*input);
avro::decode(*decoder, outer);
}
Multiple nesting of unknown records
{
std::string readerString("{\"type\":\"record\",\"name\":\"CombinationExtra\",\"fields\":[{\"name\":\"outerAsField\",\"type\":{\"type\":\"record\",\"name\":\"OuterExtra\",\"fields\":[{\"name\":\"extraArray\",\"type\":{\"type\":\"array\",\"items\":{\"type\":\"record\",\"name\":\"InArrayExtraArray\",\"fields\":[{\"name\":\"first\",\"type\":{\"type\":\"record\",\"name\":\"Inner1\",\"fields\":[{\"name\":\"field\",\"type\":\"string\"}]}},{\"name\":\"second\",\"type\":{\"type\":\"record\",\"name\":\"Inner2\",\"fields\":[{\"name\":\"field\",\"type\":\"string\"}]}}]}}}]}}]}");
std::string writerString("{\"type\":\"record\",\"name\":\"CombinationExtra\",\"fields\":[{\"name\":\"outerAsField\",\"type\":{\"type\":\"record\",\"name\":\"OuterExtra\",\"fields\":[{\"name\":\"extraArray\",\"type\":{\"type\":\"array\",\"items\":{\"type\":\"record\",\"name\":\"InArrayExtraArray\",\"fields\":[{\"name\":\"first\",\"type\":{\"type\":\"record\",\"name\":\"Inner1\",\"fields\":[{\"name\":\"field\",\"type\":\"string\"}]}},{\"name\":\"second\",\"type\":{\"type\":\"record\",\"name\":\"Inner2\",\"fields\":[{\"name\":\"field\",\"type\":\"string\"}]}},{\"name\":\"innerArray\",\"type\":{\"type\":\"array\",\"items\":{\"type\":\"record\",\"name\":\"Inner3\",\"fields\":[{\"name\":\"number\",\"type\":\"int\"}]}}}]}}}]}}]}");
std::stringstream readerStream(readerString);
std::stringstream writerStream(writerString);
avro::ValidSchema readerSchema;
avro::ValidSchema writerSchema;
avro::compileJsonSchema(readerStream, readerSchema);
avro::compileJsonSchema(writerStream, writerSchema);
avro::DecoderPtr decoder = avro::resolvingDecoder(writerSchema, readerSchema, avro::jsonDecoder(writerSchema));
struct Outer outer;
std::stringstream jsonStream("{\"outerAsField\":{\"extraArray\":[{\"first\":{\"field\":\"here is a string field\"},\"second\":{\"field\":\"here is another string field\"},\"innerArray\":[{\"number\":1},{\"number\":2},{\"number\":3}]}]}}");
std::auto_ptr<avro::InputStream> input = avro::istreamInputStream(jsonStream);
decoder->init(*input);
avro::decode(*decoder, outer);
}
The following will generate a proper object according to the reader schema and completely ignores the extraneous characters at the end of the stream.
Garbage after appended field of new record
{
std::string readerString("{\"type\":\"record\",\"name\":\"InArray\",\"fields\":[{\"name\":\"first\",\"type\":{\"type\":\"record\",\"name\":\"Inner1\",\"fields\":[{\"name\":\"field\",\"type\":\"string\"}]}},{\"name\":\"second\",\"type\":{\"type\":\"record\",\"name\":\"Inner2\",\"fields\":[{\"name\":\"field\",\"type\":\"string\"}]}}]}");
std::string writerString("{\"type\":\"record\",\"name\":\"InArray\",\"fields\":[{\"name\":\"first\",\"type\":{\"type\":\"record\",\"name\":\"Inner1\",\"fields\":[{\"name\":\"field\",\"type\":\"string\"}]}},{\"name\":\"second\",\"type\":{\"type\":\"record\",\"name\":\"Inner2\",\"fields\":[{\"name\":\"field\",\"type\":\"string\"}]}},{\"name\":\"third\",\"type\":{\"type\":\"record\",\"name\":\"Inner3\",\"fields\":[{\"name\":\"number\",\"type\":\"int\"}]}}]}");
std::stringstream readerStream(readerString);
std::stringstream writerStream(writerString);
avro::ValidSchema readerSchema;
avro::ValidSchema writerSchema;
avro::compileJsonSchema(readerStream, readerSchema);
avro::compileJsonSchema(writerStream, writerSchema);
avro::DecoderPtr decoder = avro::resolvingDecoder(writerSchema, readerSchema, avro::jsonDecoder(writerSchema));
struct Outer outer;
std::stringstream jsonStream("{\"first\":{\"field\":\"here is a string field\"},\"second\":{\"field\":\"here is another string field\"},\"third\":{\"number\":3} GARBAGE_HERE}");
std::auto_ptr<avro::InputStream> input = avro::istreamInputStream(jsonStream);
decoder->init(*input);
avro::decode(*decoder, outer);
}