WarpScript is a stack language. Once you've read the basic concepts, you must know how to debug your scripts.
This code has a bug. Click on execute button below:
In the Warp 10 engine, the ADDVALUE raised an exception, with help text
ADDVALUE operates on a single Geo Time Series or GTS Encoder. The error was raised during the execution of line 7 of the script. Why ?
Every WarpScript function expects some parameters on the stack. Look at the
ADDVALUE signature. ADDVALUE expects 6 objects on the stack and will push 1 object on a stack after its execution.
gts tick latitude longitude elevation value ADDVALUE result
ADDVALUE will pop the first element of the stack: value. It will check the type. The allowed types are STRING, a BOOLEAN, a LONG or a DOUBLE. Here we put 42. It's a LONG, it should not be a problem.
ADDVALUE will pop the next element of the stack: elevation. It will check the type. The allowed types are LONG or NaN (Not a Number). Here we put 0. It's a LONG, it should not be a problem.
And so on... In this code, there is a signature error, and ADDVALUE expects somewhere a GTS or an ENCODER. The best way to see the stack before execution is to put a STOP before ADDVALUE, and look carefully at the 6 objects on the top of the stack:
|Stack depth||Content||Types Allowed by ADDVALUE|
|[TOP]||42||STRING, BOOLEAN, LONG, DOUBLE|
"myGTS" is not a GTS. It is a STRING. The GTS is just below in the stack... The author forget to call the
RENAME function. RENAME function pop a string, pop a GTS, and push a GTS on the stack. Here is a possible fix:
LINEON and SECTION instruction
By default, the error has one line and some sections. The line is the line of the script being executed while the exception is raised. If the error is in a macro section called in a foreach loop, the error is on the FOREACH line. Try this code:
ERROR line #13 in section '[TOP]': Exception at statement 'RUN' in section '[TOP]' (Exception at statement '/' in section '[TOP]' (/ by zero)) (Exception at statement '/' in section '[TOP]' (/ by zero))
The error occurred on line #13, two sections below. But the real error is on line 5. The section name is always TOP. To locate the bug, you can use section names:
ERROR line #13 in section '[TOP]': Exception at statement 'RUN' in section 'in my foreach' (Exception at statement '/' in section 'my macro' (/ by zero)) (Exception at statement '/' in section 'my macro' (/ by zero))
SECTION has very few impact on the performance, and will help you to locate the error.
In case you do not have any sections defined in your code, you can use LINEON. LINEON will add one section per line.
ERROR line #13 in section '[Line #9]': Exception at statement 'RUN' in section '[Line #12]' (Exception at statement '/' in section '[Line #5]' (/ by zero)) (Exception at statement '/' in section '[Line #5]' (/ by zero))
LINEON is very handy, but it has an impact on performance, use it carefully, and remove it in production.
JSON object representation, TYPEOF and TDESCRIBE
WarpScript output is a JSON. It means Warp 10 serialize objects to output a string representation of each object on the stack whenever it is possible. For example, a GTS is represented as a MAP. But internally, it is not a MAP, it is a GTS object instance.
Both object have the same representation.
Some objects cannot be represented:
null output can be a real NULL (non existing object), or an object Warp 10 cannot represent in JSON.
TYPEOF function will help you to know what kind of object is on the top of the stack. This function return a string with the type.
Some functions can output LIST of objects, or LIST of LIST of objects. In your debug environment, you can activate
TDESCRIBE extension to get a recursive description of an object.
Raise errors in your code
In unit tests or in your code, you raise an exception with
MSGFAIL. For example, this script will randomly fail:
If your code is running in the background (in a scheduled runner for example), you can also write messages and errors to the standard or error output. See DebugWarpScriptExtension, with functions
If you want to go further in alerting, you can do a WEBCALL to Slack or your favorite alerting channel.
Warp 10 has a try/catch/finally control structure. In the catch, you can get the full error stack with
- STOP allows you to stop execution to check the stack state.
- LINEON allows you to locate an error.
- TYPEOF and TDESCRIBE show you the type of an element.
- TRY is the Warp 10 try/catch/finally control structure.