Thanks for the idea! That's similar to what I thought would be necessary. I was hoping to monkey patch `fetch()` to have it get the trace if any `fetch` call, but they would not be async stack traces. For async traces it would require instrumentation by injecting code similar to yours (I want to detect traces in third-party code installed locally).
#!/JoePea On Wed, Jul 8, 2020, 2:13 AM kai zhu <[email protected]> wrote: > here's a simple throwaway-function you can wrap around promises like fetch > to get the caller's async-stack-trace `promiseWithErrorStack`: > > ```html > <!doctype html> > <html lang="en"> > <body> > <h1>test.html</h1> > <script> > (async function foo() { > function promiseWithErrorStack(promise) { > /* > * this function will append current-stack to any err caught from > <promise> > */ > let errStack; > errStack = new Error().stack; > return new Promise(function (resolve, reject) { > promise.then(resolve).catch(function (err) { > // append current errStack to err.stack > if (err && typeof err.stack === "string") { > err.stack += "\n" + errStack; > } > reject(err); > }); > }); > } > await promiseWithErrorStack(fetch("https://example.com";)); // at foo > (test.html:23) > > /* > console-output: > > Uncaught (in promise) TypeError: Failed to fetch > Error > at promiseWithErrorStack (test.html:12) > at foo (test.html:23) // async-stack-trace > at test.html:32 > */ > }()); > </script> > </body> > ``` > > On Tue, Jul 7, 2020 at 11:54 PM #!/JoePea <[email protected]> wrote: > >> Is there some way (perhaps by patching methods on objects?) so we can >> track async call stacks? >> >> When we pause code in devtools, we are able to see the async stack >> trace of the code. >> >> What I'd like to do is to effectively detect the same thing as >> devtools does at some point in any code. As a specific example, I'd >> like to detect the async stack trace of any call to `fetch`. >> >> Is such a thing possible with runtime code? >> >> Or would it require instrumentation of the source code? >> >> #!/JoePea >> _______________________________________________ >> es-discuss mailing list >> [email protected] >> https://mail.mozilla.org/listinfo/es-discuss >> >
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