Am 25.08.2014 15:07, schrieb Don:
On Thursday, 21 August 2014 at 22:35:18 UTC, Sönke Ludwig wrote:
Following up on the recent "std.jgrandson" thread [1], I've picked up
the work (a lot earlier than anticipated) and finished a first version
of a loose blend of said std.jgrandson, vibe.data.json and some
changes that I had planned for vibe.data.json for a while. I'm quite
pleased by the results so far, although without a serialization
framework it still misses a very important building block.
Code: https://github.com/s-ludwig/std_data_json
Docs: http://s-ludwig.github.io/std_data_json/
DUB: http://code.dlang.org/packages/std_data_json
The new code contains:
- Lazy lexer in the form of a token input range (using slices of the
input if possible)
- Lazy streaming parser (StAX style) in the form of a node input range
- Eager DOM style parser returning a JSONValue
- Range based JSON string generator taking either a token range, a
node range, or a JSONValue
- Opt-out location tracking (line/column) for tokens, nodes and values
- No opDispatch() for JSONValue - this has shown to do more harm than
good in vibe.data.json
The DOM style JSONValue type is based on std.variant.Algebraic. This
currently has a few usability issues that can be solved by
upgrading/fixing Algebraic:
- Operator overloading only works sporadically
- No "tag" enum is supported, so that switch()ing on the type of a
value doesn't work and an if-else cascade is required
- Operations and conversions between different Algebraic types is not
conveniently supported, which gets important when other similar
formats get supported (e.g. BSON)
Assuming that those points are solved, I'd like to get some early
feedback before going for an official review. One open issue is how to
handle unescaping of string literals. Currently it always unescapes
immediately, which is more efficient for general input ranges when the
unescaped result is needed, but less efficient for string inputs when
the unescaped result is not needed. Maybe a flag could be used to
conditionally switch behavior depending on the input range type.
Destroy away! ;)
[1]: http://forum.dlang.org/thread/[email protected]
One missing feature (which is also missing from the existing std.json)
is support for NaN and Infinity as JSON values. Although they are not
part of the formal JSON spec (which is a ridiculous omission, the
argument given for excluding them is fallacious), they do get generated
if you use Javascript's toString to create the JSON. Many JSON libraries
(eg Google's) also generate them, so they are frequently encountered in
practice. So a JSON parser should at least be able to lex them.
ie this should be parsable:
{"foo": NaN, "bar": Infinity, "baz": -Infinity}
This would probably best added as another (CT) optional feature. I think
the default should strictly adhere to the JSON specification, though.
You should also put tests in for what happens when you pass NaN or
infinity to toJSON. It shouldn't silently generate invalid JSON.
Good point. The current solution to just use formattedWrite("%.16g") is
also not ideal.
