How to dev with Error Stacking?

Error Stacking

You may want to be able to retrace each step of you algorithm. For this you may create new errors along the way.

Take this package example

%include_once "/extenso/module/sed/error/package/p_error.sn";
package my_package
 function my_function(my_param)
 // Validate input parameters
 if !my_param then
 return sed_error::new_error(-1, current_function() .+ " - Error: Parameter `my_param` cannot be empty.", my_param);
 endif
  [...]
  // Get stuff
 sql_rs = sql(error: false, "
 SELECT *
 FROM my_table
 WHERE uid = '?'
 ", my_param);
 // Validate query output
 if sql_rs.error then
 return sed_error::new_error(-1, current_function() .+ " - Error: Query failed", sql_rs);
 endif
 if !sql_rs.nbrows then
 return sed_error::new_error(-1, current_function() .+ " - Error: No entry found", sql_rs);
 endif
  return mysql_rs.rows;
 endf
endp

 

Take this resource

 

// file: r_my_resource.sn
%include_once "/extenso/module/sed/error/package/p_error.sn";
%include_once "my_package.sn";

function main(cgidata)
 switch cgidata.operation do
 case "my_case_1":
 my_result = my_package::my_function(cgidata.my_param);
 // You can create a new error by passing the previous error as a `previous` optional named parameter 
 if my_result.type() eq "sed_error::Error" then  // Create a new error by providing the previous error
 return sed_error::new_error(
 -1,  current_function() .+ "r_my_ressource::my_case_1 - Error: Could not get a valid result",  cgidata,  previous: my_result // <-- By adding this, you will link your previous error with the new one
 );
 endif
 // No error
 return my_result;
 endc
 case "my_case_2":
 my_result = my_package::my_function(cgidata.my_param);
 // If you do not want to register this step in the stack, you can simply transfer the original error
 if my_result.type() eq "sed_error::Error" then return my_result; endif
 // No error
 return my_result;
 endc
 ends
endf

cgidata = cgidata();
main(cgidata); // Will output a sed_error::Error or the content of the page

Stack rendering

By default, your error will contains an attribute stack which contains the list or error created along the way. Behind the scene, the function .print() is called when creating a new error. In prod, the print function will cleanup the error by removing all internal information. Only the uid_error and the errcode will be shown. In stage, it will add an attribute error_url that will bring directly to the error page. This is handled automatically.

Error page

An interface is availble to view an error with its full stack in a readable UI.

If the error_url is part of the error sent to the FE, the popup will show a "View error" link that will bring you directly to this error's page.If a user gives you an error code, you can go to the error page by using one of those two methods:   

• Go to Extenso > DEV > Tools > Error (big icons). Enter the error code in the form.    
• Go to Extenso > DEV > Databases management > Errors. Search for your error code and click on the [view] button.

Note that selecting an error that is in the middle of a stack will always show you the first error with the whole stack.

Error example

In prod

{
 "errcode": -1,
 "uid_error": 83758
}

In stage

{
 "errcode": -1,
 "errmesg": "r_my_ressource::my_case_1 - Error: Could not get a valid result",
 "stack": [
 {
 "errcode": "-1",
 "errmesg": "my_package::my_function - Error: Query failed",
 "content": {...},
 "uid_error": "83757",
 "uid_previous": ""
 }
 ],
 "content": {...},
 "uid_error": 83758,
 "uid_previous": 83757,
 "error_url": ".../extenso/secure/module/sed/error/en/print.snc?uid=83758"
}

 

Limitation - Safeguards

As a failsafe, the stack can contain a maximum of 20 items. If you need to increase this number, you can supercharge the package `sed_error::stack_limit` after the `sed_error` include:

%include_once "/extenso/module/sed/error/package/p_error.sn";
sed_error::stack_limit = 100; // Default: 20
[...]