Possible bug on fpjson's TJSONData object
lazarus / 38-Networking and Web Programming

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Gustavo 'Gus' Carreno · 2021-05-20 14:14

Hey all,

Can someone please explain to me what I'm doing wrong here?

Attached is a personal project that aims to implement the JSON-RPC
v2.0 to use in a Stratum protocol.

On the tests you find this
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TNosoPoolStratumJSONRPCRequest.CheckFieldsCreateWithMethod;begin 
AssertEquals('Request '+cjJSONRPC+' is '+cjJSONRPCversion,
cjJSONRPCversion, FRequest.JSONRPC);  AssertEquals('Request
'+cjMethod+' is mining.authorize', 'mining.authorize',
FRequest.Method);  AssertNotNull('Request '+cjParams+' is not null',
FRequest.Params);  AssertEquals('Request '+cjParams+' count is 2', 2,
FRequest.Params.Count);  { TODO 100 -ogcarreno : Why does this go BOOM
only here ?!?!?! }  AssertEquals('Request '+cjParams+' item[0] is
"login""', 'login', FRequest.Params[0].AsString); 
AssertEquals('Request '+cjParams+' item[0] is "password""',
'password', FRequest.Params[1].AsString);  AssertEquals('Request
'+cjID+' is 1', 1, FRequest.ID);end; 
And on that line it gives an Access Violation.

Why is the default property erroring out?

The code that builds the TJSONArray is this(Marked where the
TJSONArray is manipulated):
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TRequestParamsArray.setFromJSONObject(const AJSONObject:
TJSONObject);var  jData: TJSONData;  jParams: TJSONArray;  index:
Integer;begin  jData := AJSONObject.Find(cjJSONRPC);  if
Assigned(jData) then  begin    FJSONRPC:= AJSONObject.Get(cjJSONRPC,
FJSONRPC);  end  else    raise
ERequestMissingMember.Create(Format(rsExceptionMissingMember,
[cjJSONRPC]));   jData := AJSONObject.Find(cjMethod);  if
Assigned(jData) then  begin    FMethod:= AJSONObject.Get(cjMethod,
FMethod);  end  else    raise
ERequestMissingMember.Create(Format(rsExceptionMissingMember,
[cjMethod]));   jData:= AJSONObject.Find(cjParams);  if
Assigned(jData) then  begin    if jData.JSONType = jtArray then   
begin      jParams:= TJSONArray(jData);      FParams.Clear;      for
index:= 0 to Pred(jParams.Count) do      begin       
FParams.Add(jParams[index]);      end;    end;  end  else    raise
ERequestMissingMember.Create(Format(rsExceptionMissingMember,
[cjParams]));   jData:= AJSONObject.Find(cjID);  if Assigned(jData)
then  begin    FID:= AJSONObject.Get(cjID, FID);  end  else   
FNotification:= True;end; 
I've tried many things to debug this but I've exhausted my meagre
means.

Can anyone help please?

Cheers,
Gus

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Gustavo 'Gus' Carreno · 2021-05-22 01:00

Hey all,

I've since modified the names of this code to implement the v2.0 of
JSON-RPC as a stand-alone lib I can then use in other parts.

I've put the code on GitHub:
https://github.com/gcarreno/lazJSONRPCData/

I've also banged my head several times against many floating errors.
The ones you add a blank line and your code explodes in a different
place.

I've even had a private field of TRequest change from TJSONData to
TJSONString after
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
Result.Add(cjJSONRPC, cjJSONRPCversion);)
And those are both string constants. The curious is that the field
would then assume the role of a TJSONString with the value of
cjJSONRPCversion.

I then choose to have FParams as a string, not a TJSONData and ALL my
errors go away!!!

What kind of black magic have the devs used to implement
TJSONData!?!?!?

I'll keep at it, but I really need that FParams is TJSONData and that
just messes up the whole thing!!!

I really need some help here, sorry!!!
I'm really sorry if I seem a desperate beggar, but the fact of the
matter is... well I am!!!

Cheers,
Gus

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Gustavo 'Gus' Carreno · 2021-05-22 01:32

Hey all,

I've solved my problem, but I'm million of miles from understanding
why the code behaved in that way;

In the end my solve was this:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
interfacetype   TRequest = class(TObject)  private  {...}    FParams:
TJSONStringType;  {...}    function GetParams: TJSONData;  public   
property Params: TJSONData      read GetParams; 
end; implementation function TRequest.GetParams: TJSONData;begin 
Result := GetJSONData(FParams);end; 
So storing internally as a TJSONStringType and having a getter return
the TJSONData object that I wanted, miraculously gets all those testes
on the green

I'm baffled and stumped and I can't begin to know where to begin to
investigate  this.

Cheers,
Gus