Debug Failure. False expression: `JsxText` tokens should not be the first child of `JsxElement | JsxSelfClosingElement` in `findRightmostChildNodeWithTokens` during `getQuickInfoAtPosition`

[aozgaa]

tsserver version: 2.6.1
hitting sessions: 6483
stack:

Error: Debug Failure. False expression: `JsxText` tokens should not be the first child of `JsxElement | JsxSelfClosingElement`
    at findRightmostChildNodeWithTokens (tsserver.js:62901:30)
    at find (tsserver.js:62893:33)
    at findPrecedingToken (tsserver.js:62859:22)
    at getTokenAtPositionWorker (tsserver.js:62822:41)
    at getTouchingToken (tsserver.js:62794:16)
    at Object.getTouchingPropertyName (tsserver.js:62790:16)
    at Object.getQuickInfoAtPosition (tsserver.js:79791:27)
    at IOSession.Session.getQuickInfoWorker (tsserver.js:86102:62)
    at Session.handlers.ts.createMapFromTemplate._a.(anonymous function) (tsserver.js:85266:61)
    at tsserver.js:86669:88
    at IOSession.Session.executeWithRequestId (tsserver.js:86660:28)
    at IOSession.Session.executeCommand (tsserver.js:86669:33)
    at IOSession.Session.onMessage (tsserver.js:86689:35)
    at Interface.<anonymous> (tsserver.js:87881:27)
    at emitOne (events.js:96:13)
    at Interface.emit (events.js:191:7)
    at Interface._onLine (readline.js:241:10)
    at Interface._normalWrite (readline.js:384:12)
    at Socket.ondata (readline.js:101:10)
    at emitOne (events.js:96:13)
    at Socket.emit (events.js:191:7)
    at readableAddChunk (_stream_readable.js:178:18)
    at Socket.Readable.push (_stream_readable.js:136:10)
    at Pipe.onread (net.js:560:20)

[mhegazy]

The Source: Telemetry have limited information. we only have the call stack from the crash report. We need to either mitigate the crash, or add additional asserts to get more information in future crash reports.

The assertion was added in #16385. Since then we've added JSX fragment syntax (#19249), so that might have to do with the error. The first child of some node is a JSXText with containsOnlyWhiteSpaces set --
the error message assumes its parent is JsxElement | JsxSelfClosingElement but it may be a JsxFragment.

@uniqueiniquity Do you think this might have been fixed by #20912?

If it helps, I wrote this helper method in class TestState in fourslash.ts to look for errors:

public verifyPreceding() {
    for (const fileName of this.getProgram().getRootFileNames()) {
        const file = this.getProgram().getSourceFile(fileName);
        for (let i = 0; i < file.text.length; i++) {
            ts.findPrecedingToken(i, file);
        }
    };
}

You also need to add in class Verify: public preceding() { this.state.verifyPreceding(); }

[uniqueiniquity]

@Andy-MS I doubt #20912 would have fixed this since it was just related to behavior on format.

[uniqueiniquity]

I am looking into this further.

[uniqueiniquity]

@Andy-MS your helper function will not behave the same as the case in the stack trace; the caller of findPrecedingToken provides a third argument.

[uniqueiniquity]

Worked on this with @RyanCavanaugh and could not find a case that would locally repro.
Might be worth adding additional asserts as @mhegazy suggests.

Maybe add the assert in the parser -- on finishing a jsx node, assert that the first child is not whitespace-only?

[mhegazy]

Asserts in the parser would be bad. if they fail nothing will work in the program. at least with this assert, some operations work.

@mhegazy Can we have informational-only asserts? We don't necessarily need to throw an exception, just report in telemetry that there was an error.

[mhegazy]

but we have no way of getting the info really.. we log the failures, but the info can go to the log, and we have no way on getting that afterwards.