Ok, let me start with the sample code:

import std.stdio;
import std.json;

void main() {
  scope(failure) writeln("FaILED!!");
  string jsonStr = `{ "name": "1", "type": "r" }`;
  auto parsed = parseJSON(jsonStr);
  string s = parsed["fail"].str;
  writeln(s == "");
  writeln(s is null);
  writeln(s);
}

Running "rdmd app.d" doesn't produce any output.
Can anyone explain such a behavior???


PS: Running dmd v2.065 on Linux x64.

On Thu, 24 Jul 2014 15:15:36 +0000, Pavel wrote:

> Ok, let me start with the sample code:
> 
> import std.stdio;
> import std.json;
> 
> void main() {
>    scope(failure) writeln("FaILED!!");
>    string jsonStr = `{ "name": "1", "type": "r" }`;
>    auto parsed = parseJSON(jsonStr);
>    string s = parsed["fail"].str;
>    writeln(s == "");
>    writeln(s is null);
>    writeln(s);
> }
> 
> Running "rdmd app.d" doesn't produce any output.
> Can anyone explain such a behavior???
> 
> 
> PS: Running dmd v2.065 on Linux x64.

That's because it produces a segmentation fault, which rdmd masks for some reason.  The `parsed["fail"]` should throw a range bounds exception-- not sure why it's not.

On Thursday, 24 July 2014 at 15:15:37 UTC, Pavel wrote:
>   string s = parsed["fail"].str;

Since there is no entry "fail" in the object, it returns a null JSON_VALUE pointer. Trying to get the string out of it is then seen as a null pointer access and kills the program.

Check for null on a key before trying to get a value out.

Adam D. Ruppe:

> Check for null on a key before trying to get a value out.

Is something like the get() function usable here?

Bye,
bearophile

On Thursday, 24 July 2014 at 15:22:46 UTC, Adam D. Ruppe wrote:
> On Thursday, 24 July 2014 at 15:15:37 UTC, Pavel wrote:
>>  string s = parsed["fail"].str;
>
> Since there is no entry "fail" in the object, it returns a null JSON_VALUE pointer. Trying to get the string out of it is then seen as a null pointer access and kills the program.
>
> Check for null on a key before trying to get a value out.

Ok, added:

writeln(parsed["fail"] == null);

Now compiler complains:

Error: incompatible types for ((parsed.opIndex("fail")) == (null)): 'JSONValue' and 'typeof(null)'


WAT?!

Am 24.07.2014 17:29, schrieb Pavel:
> On Thursday, 24 July 2014 at 15:22:46 UTC, Adam D. Ruppe wrote:
>> On Thursday, 24 July 2014 at 15:15:37 UTC, Pavel wrote:
>>>  string s = parsed["fail"].str;
>>
>> Since there is no entry "fail" in the object, it returns a null
>> JSON_VALUE pointer. Trying to get the string out of it is then seen as
>> a null pointer access and kills the program.
>>
>> Check for null on a key before trying to get a value out.
>
> Ok, added:
>
> writeln(parsed["fail"] == null);
>
> Now compiler complains:
>
> Error: incompatible types for ((parsed.opIndex("fail")) == (null)):
> 'JSONValue' and 'typeof(null)'
>
>
> WAT?!


"is" instead of "==" ?

On Thursday, 24 July 2014 at 15:15:37 UTC, Pavel wrote:
> Ok, let me start with the sample code:
>
> import std.stdio;
> import std.json;
>
> void main() {
>   scope(failure) writeln("FaILED!!");
>   string jsonStr = `{ "name": "1", "type": "r" }`;
>   auto parsed = parseJSON(jsonStr);
>   string s = parsed["fail"].str;
>   writeln(s == "");
>   writeln(s is null);
>   writeln(s);
> }
>
> Running "rdmd app.d" doesn't produce any output.
> Can anyone explain such a behavior???
>
>
> PS: Running dmd v2.065 on Linux x64.

It's a bug in std.json (you should get a segfault, not no output at all)

It is fixed now and I'm pretty sure it will be in 2.066

std.json has been improved a lot, but I would still recommend using http://vibed.org/api/vibe.data.json/ instead

On Thursday, 24 July 2014 at 15:20:58 UTC, Justin Whear wrote:
> On Thu, 24 Jul 2014 15:15:36 +0000, Pavel wrote:
>
>> Ok, let me start with the sample code:
>> 
>> import std.stdio;
>> import std.json;
>> 
>> void main() {
>>    scope(failure) writeln("FaILED!!");
>>    string jsonStr = `{ "name": "1", "type": "r" }`;
>>    auto parsed = parseJSON(jsonStr);
>>    string s = parsed["fail"].str;
>>    writeln(s == "");
>>    writeln(s is null);
>>    writeln(s);
>> }
>> 
>> Running "rdmd app.d" doesn't produce any output.
>> Can anyone explain such a behavior???
>> 
>> 
>> PS: Running dmd v2.065 on Linux x64.
>
> That's because it produces a segmentation fault, which rdmd masks for
> some reason.  The `parsed["fail"]` should throw a range bounds exception--
> not sure why it's not.

Here's phobos code from github:

/// Hash syntax for json objects.
    /// Throws $(D JSONException) if $(D type) is not $(D JSON_TYPE.OBJECT).
    ref inout(JSONValue) opIndex(string k) inout
    {
        enforceEx!JSONException(type == JSON_TYPE.OBJECT,
                                "JSONValue is not an object");
        return *enforceEx!JSONException(k in store.object,
                                        "Key not found: " ~ k);
    }

Added in https://github.com/D-Programming-Language/phobos/commit/13fbd451bcca923cf8d1028495e58aa88cc7efeb

Maybe phobos is not up to date for me???

On 07/24/2014 08:29 AM, Pavel wrote:

> writeln(parsed["fail"] == null);
>
> Now compiler complains:
>
> Error: incompatible types for ((parsed.opIndex("fail")) == (null)):
> 'JSONValue' and 'typeof(null)'
>
>
> WAT?!

Comparing against null should be done with the 'is' operator, not the == operator:

    if (x is null)

Ali

On Thursday, 24 July 2014 at 15:31:30 UTC, Daniel Gibson wrote:
> Am 24.07.2014 17:29, schrieb Pavel:
>> On Thursday, 24 July 2014 at 15:22:46 UTC, Adam D. Ruppe wrote:
>>> On Thursday, 24 July 2014 at 15:15:37 UTC, Pavel wrote:
>>>> string s = parsed["fail"].str;
>>>
>>> Since there is no entry "fail" in the object, it returns a null
>>> JSON_VALUE pointer. Trying to get the string out of it is then seen as
>>> a null pointer access and kills the program.
>>>
>>> Check for null on a key before trying to get a value out.
>>
>> Ok, added:
>>
>> writeln(parsed["fail"] == null);
>>
>> Now compiler complains:
>>
>> Error: incompatible types for ((parsed.opIndex("fail")) == (null)):
>> 'JSONValue' and 'typeof(null)'
>>
>>
>> WAT?!
>
>
> "is" instead of "==" ?

Nope, the compiler still complains.