In a plug-in I am using NPN_Evaluate() to execute some Javascript. How can I detect wether the Javascript raises an exception? Basically I want to execute any piece of Javascript and get the result from it or detect if it raised an exception.
I tried wrapping my Javascript code like this:
try {
// Injected Javascript code here
}
catch (exc) {
exc;
}
That way the result from NPN_Evaluate() will be an NPObject* containing a property "message" with the exception message if something goes wrong. But how can I know that it is an exception? It might as well be a result from the injected Javascript code.
Am I approaching this the wrong way? Can I detect an exception without catching it in Javascript and returning the exception as the result?
Personally I've never been a fan of using NPN_Evaluate; If I needed to do something that couldn't be done using other methods (NPN_Invoke, NPN_GetProperty, etc) I'd use NPN_Evaluate to inject a javascript function into the DOM and then call it using NPN_Invoke; then if it returns false you know it failed. There isn't any really good exception handling across that bridge, unfortunately, but the return value of true or false will tell you if it succeeded -- I suspect this holds true even for just using NPN_Evaluate.
Remember that anything declared global in javascript is a property of the window; thus, if you inject "function foo(bar) { alert(bar); }" with NPN_Evaluate you can use NPN_GetValue to get the Window NPObject and then call GetProperty("foo") to get the foo function. You can then call InvokeDefault on that bar method to call it, passing in whatever value you want for bar as a parameter.
Related
Accessing the local filesystem a la: https://developer.mozilla.org/en-US/docs/Web/API/FileSystemFileHandle
If I inline all my code for the show(Open|Save)FilePicker API logic directly in my button event closure or call plain fn's then things work ok. However, if I define a class w/helper methods and call those from my event-handler, and those helpers call the file pickers, then I get this error:
Uncaught DOMException: Failed to execute 'showOpenFilePicker' on 'Window': Must be handling a user gesture to show a file picker.
I assume the the security system is looking at this to establish the gesture context - is there a way to re-establish this context with code running in my class?
Turns out the class methods were a red herring -- the issue has to do with async code and promises -- this is what looses the context and causes the error.
You need to make any calls to the FS without any promise chaining.
Is it possible to throw an exception in a Logic App?
Specifically, I'm trying to throw an exception inside of a scope. Then in the run after of the scope I'd check if it failed and inspect it for errors. I tried using a terminate inside of a scope, but that terminates the entire logic app run.
As an updated solution we can use Terminate control, Terminate control has 3 status: Failed, Canceled, and Succeeded.
Quick Answer (TL;DR)
Problem: MSFT Azure logic app throwing exceptions
Workaround: Use logic app Scope element to simulate throwing exceptions
Create a scope element to use as your "try-catch" block
Force the scope element to fail with an invalid command to simulate an exception
Allow the scope element to fail naturally and that will count as an exception too
Detailed Answer
Context
MSFT Azure logic app workflows
live version as of 2020-06-14
Problem
Scenario: Developer wishes to throw an exception or use try-catch semantics in a logic app
Solution
As of this writing, the live version of the product does not support this feature. There is a workaround.
Workaround
Use logic app scope element
add a conditional statement inside the scope element
If the conditional statement meets the failure condition, force an exception with a deliberately invalid command
for example create a variable assignment with the value int('__ERROR__')
If the conditional statement does not meet the failure condition, do nothing
The rest of the logic app consists of two paths
The first path runs on the success of the scope element
The second path runs on the failure of the scope element (failed, skipped, timed out)
Example
Create a scope element as a "try-catch" block
Create a variable compose element with an invalid command
int('__ERROR__') ## this will cause the enclosing scope to fail
## the string __ERROR__ cannot be cast to integer
Respond to exit status of the Scope element enclosing your exception
See also
related SO answer about forcing exceptions https://stackoverflow.com/a/61101945/42223
No, there is no Action or Connector directly analogous to something like a throw in C#.
The closest you can get right now would be to do something like use another LogicApp instead of a scope from which you can return a specific status code.
It seems like there still is no option for this inside Logic App or its little brother Power Automate / Microsoft Flow.
The way I have come up with and have used in some flows, is I simply add an action for something I know for a fact will fail.
The simplest (and probably the cheapest as the built-in actions cost less in Logic Apps, even if we are talking fractions of a dollar here either way) is probably to initialize a variable, e.g. called ThrowException with type of integer.
Then a "Set variable" action is added wherever I want my flow to fail, where I set the value (remember it is of type integer) to any string expression. I simply use the expression string('Exception').
Simple example screenshot
Since the value is set via an expression this is still a valid template, but will fail upon runtime when the value is actually being set.
After this, simply use parallel branches, with appropriate Run After settings, as usual.
I've a View and Utility classes and wanted to hook-in the Utility method once View's job is done. So wanted to call the utility method (to add behavior to the view) once View's render call is done.
Using ES6 Proxy API, Is there a way to execute a method before / after executing the main method ? (aka method interceptions)
Similar to YUI3 Do API.
http://yuilibrary.com/yui/docs/api/classes/Do.html
Yes there is a way. Actually I'm trying to build the same thing and as long as you use a synchronous context I already got it working. Have a look at the code examples in the issue I created for my problem: stack overflow when returning an ES6 proxy through a promise
What you need to do to intercept the call is to use the ES6 proxy to get notified of the get-call that takes place to retrieve the function before the method is actually called.
In my example you can see that you get all the information about the call like what method was called with which parameters and also who called it and on which target it was originally called.
On javascript Object i am invoking
obj.requestFileSystem(LOCAL,5*1024*1024) . This method is implemented in PlainNAPI Plugin , now i have to pass one success callback to this function as follows......
obj.requestFileSystem(LOCAL,5*1024*1024,initFS); // initFS is a function in javascript that is an argument to the success callback .
In NPAPI it is an object when the requestFileSystem is completed then initFS function in javascript should be called. How to return from NPAPI plugin to javascript and to execute initFS function.
function initFS(fs) {
alert('Inside the initFS');
alert(fs.root.getFullPath);
}
Please don't tell me what you're actually doing with this plugin, since it sounds like it's something akin to giving people access to things from a web browser that could easily be abused by someone else.
Basically a function is just an NPObject when it gets to your function inside NPRuntime; to call the function you just do a NPN_InvokeDefault on that NPObject.
Note that you must be on the main thread in order to call nearly all NPN_ functions.
EDIT: So if you have to do the callback from a different thread then your easiest solution is to use NPN_PluginThreadAsyncCall; basically you create an object to hold the data you need and call PluginThreadAsyncCall with that pointer as the void* parameter and it will get passed to the function you specify.
Make sure that A) the pointer will still be valid, and B) your function is able to free that memory after it runs. From the callback function you can call NPN_InvokeDefault safely.
Not that NPN_PluginThreadAsyncCall doesn't seem to work on Safari 5.1 anymore. If you need that support or if what I've explained doesn't make sense you might want to consider using FireBreath to build your plugin; it does all of this for you.
public function getTextId():String
{
return val;
}
ExternalInterface.addCallback("getId", getTextId);
I am getting the following error:
Access of undefined property getTextId.
ExternalInterface.addCallback("getId", getTextId);
But I have getTextId defined and all the tutorials indicate this is the correct method to do it.
Is your call to ExternalInterface.addCallback() inside of a method, or are you calling it a the "class level" (for lack of a better term), as shown in your code snippet?
I just tried adding the callback outside of a method, it worked... not surprised but I rarely code that way. However, I added second method as a callback, and got the same error as you at compile time.
Strange that it works for one method but not the other (no matter what I seem to try).
Have you tried moving the addCallback line into a function or the constructor? This fixes the error for me.