making sure bp.actual location is not null/undefined before trying to access its line number

[Shenniey]

Chrome core has a known issue where occasionally it returns an empty locations array: ChromeDevTools/devtools-protocol#103

When this happens, actual location is undefined and throws an error, causing the browser to hang without loading the page. Stack trace from logs:
"aggregated.exceptionStack":"[
"TypeError: Cannot read property 'lineNumber' of undefined\n
at committedBps.filter.bp (breakOnLoadHelper.js:100:96)\n
at Array.filter ()\n
at BreakOnLoadHelper. (breakOnLoadHelper.js:100:65)\n
at Generator.next ()\n at fulfilled (breakOnLoadHelper.js:7:58)\n
at process._tickCallback (internal/process/next_tick.js:68:7)"
]"

This change is just to make sure that the browser doesn't hang

[roblourens]

@digeff can you review?

[roblourens]

The locations array will be empty any time the breakpoint isn't bound to a location, so is this really a bug on their end, or just another case for us to handle?

[Shenniey]

I am leaning more towards bug, but I'm not certain. From the issue it seemed as though the locations array shouldn't be empty. Also, when I was testing with some of the breakpoint locations where we are getting back empty location arrays, if I run the project without debugging through the editor and just use F12 in Chrome, the same breakpoints successfully bind to a location and pause at those locations.

Also, if I debug with Edge, we don't have this issue.

[digeff]

I'm slightly surprised that not all the elements of commitedBps have a valid location. I think this is a valid way to avoid the crash.

The other option we could consider is to modify: https://github.com/Microsoft/vscode-chrome-debug-core/blob/master/src/chrome/chromeDebugAdapter.ts#L1667 so that we don't consider the breakpoints commited if it doesn't have a valid location. I'm not sure what the consequences of that change would be, so I think that the current approach is okay.

👍

[roblourens]

Looks great but can you remove the comment? It's sort of just restating what the code does

[roblourens]

I think that "committed" here means it has been sent to Chrome/Node but not necessarily "bound" to a location.

[roblourens]

I'll merge and remove the comment