Hot reloads fail and breakpoints may not be hit if breakpoint scriptUris are prefixed with file://

[DanTup]

Currently when we send breakpoints from Dart Code we send each one in several different formats (local file system path, package: path, device-local path etc,) in an attempt to make sure we get the format the VM expects (since they're not well documented).

I'm trying to remove some of these and clean it up because there are other issues when the breakpoints in the IDE and those in the VM don't map one-to-one. I'm trying to settle on sending file system paths in a single common format, specifically as "URIs" like:

• file:///blah/blah (macOS/Linux)
• file://C:/blah/blah (Windows) Edit: Our test for this is passing on Windows now, so this may be macOS-only

However, if I send breakpoints in this format on Windows then hot reloads will time out (specifically, the PausePostRequest comes in, then we delete/re-add breakpoints, then resume, but it never hits the berakpoint and the hot reload reports a timeout). If I send without the file:// prefix it works fine. I think including the file:// prefix is correct; the field is called scriptUri (and there are other complications elsewhere if I don't send them).

Here are some logs of Flutter Run and Observatory for both with and without the prefixes. Here's how the end of the Flutter Run logs look:

With file:// prefix

[08:11:44]: ==> [{"id":"7","method":"app.restart","params":{"appId":"4e8251e6-1027-4f43-9490-21aad6001ad1","fullRestart":false,"pause":true}}]
[08:11:44]: <== [{"event":"app.progress","params":{"appId":"4e8251e6-1027-4f43-9490-21aad6001ad1","id":"5","progressId":"hot.reload","message":"Initializing hot reload..."}}]
[08:12:15]: <== [{"event":"app.progress","params":{"appId":"4e8251e6-1027-4f43-9490-21aad6001ad1","id":"5","progressId":"hot.reload","finished":true}}]
[08:12:15]: <== [{"id":"7","error":"TimeoutException: Request to Dart VM Service timed out: ext.flutter.evict({value: AssetManifest.json, isolateId: isolates/839716787})"}]

Without file:// prefix

[08:13:44]: ==> [{"id":"7","method":"app.restart","params":{"appId":"34b1335f-7804-48bd-a96a-7d638307f5ed","fullRestart":false,"pause":true}}]
[08:13:44]: <== [{"event":"app.progress","params":{"appId":"34b1335f-7804-48bd-a96a-7d638307f5ed","id":"4","progressId":"hot.reload","message":"Initializing hot reload..."}}]
[08:13:50]: <== [{"event":"app.progress","params":{"appId":"34b1335f-7804-48bd-a96a-7d638307f5ed","id":"4","progressId":"hot.reload","finished":true}}]
[08:13:50]: <== Reloaded 0 of 517 libraries in 5,750ms.
[08:13:50]: <== [{"id":"7","result":{"code":0,"message":"Reloaded 0 of 517 libraries"}}]

And here's what the Observatory log looks like after sending a resume after re-transmitting breakpoints:

Without file://

[08:11:45]: ==> {"id":"546","method":"resume","params":{"isolateId":"isolates/839716787"}}
[08:11:45]: <== {"jsonrpc":"2.0", "result":{"type":"Success"},"id":"546"}
[08:11:45]: <== {"jsonrpc":"2.0","method":"streamNotify","params":{"streamId":"Debug","event":{"type":"Event","kind":"Resume","isolate":{"type":"@Isolate","fixedId":true,"id":"isolates\/839716787","name":"main.dart:main()","number":"839716787"},"timestamp":1528873866356}}}

(it didn't hit a beakpoint, and the hot reload timed out)

Without file:// prefix

[08:13:44]: ==> {"id":"546","method":"resume","params":{"isolateId":"isolates/256354857"}}
[08:13:44]: <== {"jsonrpc":"2.0", "result":{"type":"Success"},"id":"546"}
[08:13:44]: <== {"jsonrpc":"2.0","method":"streamNotify","params":{"streamId":"Debug","event":{"type":"Event","kind":"Resume","isolate":{"type":"@Isolate","fixedId":true,"id":"isolates\/256354857","name":"main.dart:main()","number":"256354857"},"timestamp":1528873986076}}}
[08:13:45]: <== {"jsonrpc":"2.0","method":"streamNotify","params":{"streamId":"Debug","event":{"type":"Event","kind":"PauseBreakpoint","isolate":…

(the hot reload finished and the breakpoint was hit)

[DanTup]

@aam not sure if you have an ideas on this? The format of these paths is not well defined but I think there really should be a common format that works for all types (VM, Flutter Test, Flutter Run, Flutter Run after Hot Reload).

[DanTup]

While trying to write an integration test for this, I found that this might be broken elsewhere too. If I send a breakpoint as a file:// URI on macOS it fails to hit the breakpoint:

final String breakpoint = new Uri.file(fs.path.join(_tempDir.path, 'lib', 'main.dart')).toString();
// final String breakpoint = fs.path.join(_tempDir.path, 'lib', 'main.dart');
await isolate.addBreakpoint(breakpoint, 8);

Depending on which one of those first two lines I uncomment, the test will either pass or time out (waiting for the isolate to pause).

[DanTup]

There's a failing test in flutter_tools for this in #18560.

[DanTup]

Btw, I don't have a Linux machine locally to test, but on the CI it seems like this issue happens on macOS but not on Linux (seems to work fine on Linux).

[DanTup]

Our test that was hitting this on Windows seems to be passing now (see #21201 (comment)) so this may be macOS-only.

[DanTup]

@aam this appears to be not working on macOS. I have an open PR here:

#22510

This changes the tests over to always using file URIs, however on macOS they fail. If you clone that branch on macOS you can repro by running expression_evaluation_test.dart. If you change it to use FS paths (by adding .toFilePath() to the call to isolate.addBreakpoint in test_driver.dart addBreakpoont() then the tests will pass.

[DanTup]

Scratch that - I just re-read what the fix was (symlinks). Same thing may just need applying here - I'll see if I can make the fix it more general.

[DanTup]

Yep, same thing. Sorry for the bother! :)

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