Message: An error occurred while handling textDocument/references request Code: -32001

[leaf-node]

In VSCodium version 1.96.4.25026-el9 and VSCodium Insiders version 1.97.0.25026-el9 on OpenSUSE Tumbleweed, with Dart 3.6.1 installed by Flutter 3.27.3, I am no longer able to find references to Dart code that exists in other files. The LSP log in VSCodium shows the following after trying to search for a variable reference:

[Error - 6:16:14 PM] Request textDocument/references failed.
  Message: An error occurred while handling textDocument/references request
  Code: -32001 
[Error - 6:16:14 PM] An error occurred while handling textDocument/references request: Null check operator used on a null value
#0      Search._searchReferences_Local (package:analyzer/src/dart/analysis/search.dart:761:33)
#1      Search._searchReferences_Parameter (package:analyzer/src/dart/analysis/search.dart:801:26)
#2      Search.references (package:analyzer/src/dart/analysis/search.dart:386:14)
#3      SearchEngineImpl.searchReferences (package:analysis_server/src/services/search/search_engine_internal.dart:119:41)
#4      ElementReferencesComputer._findSingleElementReferences (package:analysis_server/src/search/element_references.dart:61:25)
#5      ElementReferencesComputer._findElementsReferences.<anonymous closure> (package:analysis_server/src/search/element_references.dart:52:18)
#6      OperationPerformanceImpl.runAsync (package:analyzer/src/util/performance/operation_performance.dart:174:29)
#7      ElementReferencesComputer._findElementsReferences (package:analysis_server/src/search/element_references.dart:50:46)
<asynchronous suspension>
#8      OperationPerformanceImpl.runAsync (package:analyzer/src/util/performance/operation_performance.dart:174:14)
<asynchronous suspension>
#9      ElementReferencesComputer.compute (package:analysis_server/src/search/element_references.dart:25:20)
<asynchronous suspension>
#10     OperationPerformanceImpl.runAsync (package:analyzer/src/util/performance/operation_performance.dart:174:14)
<asynchronous suspension>
#11     ReferencesHandler._getReferences (package:analysis_server/src/lsp/handlers/handler_references.dart:84:19)
<asynchronous suspension>
#12     ErrorOrRecord2Extension.mapResults (package:analysis_server/src/lsp/error_or.dart:125:12)
<asynchronous suspension>
#13     OperationPerformanceImpl.runAsync (package:analyzer/src/util/performance/operation_performance.dart:174:14)
<asynchronous suspension>
#14     ReferencesHandler.handle (package:analysis_server/src/lsp/handlers/handler_references.dart:42:12)
<asynchronous suspension>
#15     ServerStateMessageHandler.handleMessage (package:analysis_server/src/lsp/handlers/handlers.dart:452:11)
<asynchronous suspension>
#16     LspAnalysisServer._handleRequestMessage (package:analysis_server/src/lsp/lsp_analysis_server.dart:1068:18)
<asynchronous suspension>
#17     LspAnalysisServer.handleMessage.<anonymous closure>.<anonymous closure> (package:analysis_server/src/lsp/lsp_analysis_server.dart:509:15)
<asynchronous suspension>
#18     OperationPerformanceImpl.runAsync (package:analyzer/src/util/performance/operation_performance.dart:174:14)
<asynchronous suspension>
#19     LspAnalysisServer.handleMessage.<anonymous closure> (package:analysis_server/src/lsp/lsp_analysis_server.dart:491:11)
<asynchronous suspension>

I see that the LSP is running in my process list:

andrew      5234  1.5  0.7 1580044 511784 ?      Sl   17:26   0:06 /home/andrew/.local/lib/flutter/bin/cache/dart-sdk/bin/dart language-server --protocol=lsp --client-id=VS-Code --client-version=3.102.0

In the helix editor, version 25.1 (dabfb6ce), I see the following when I try to lookup a reference that exists outside of the file currently in view:

protocol error: ServerError(-32001): An error occurred while handling textDocument/references request

As an example, this error occurs when finding references (by right clicking) for allowClickAccept in the following project, file and line number: https://github.com/okcode-studio/open_alert_viewer/blob/main/lib/ui/settings/cubit/account_settings_cubit.dart#L157, but I'm seeing this in other files and for other references too.

I have tried clearing my ~/.dart*, ~/.pub-cache, ~/.cache and ran git clean -fxd in my Flutter checkout, but the problem persists.

This issue started probably within the last few hours or so, even before updating VSCodium from 1.95 to the most recent version, 1.96. Testing VSCodium Insiders did not resolve the issue either.

[pq]

@DanTup @scheglov

[leaf-node]

I'm also seeing this on Flutter 3.29.0-0.2.pre, with Dart SDK version: 3.7.0-323.1.beta, from the Flutter beta channel.

[DanTup]

I don't suppose either of you have a code sample that triggers this?

@scheglov the exception is occurring on the assertion that source is not-null here:

https://github.com/dart-lang/sdk/blob/3.6.1/pkg/analyzer/lib/src/dart/analysis/search.dart#L761

It's not clear to me in what situations source would be null though (the docs are on AnalysisTarget and only say "null if this target is not associated with a source").

[leaf-node]

I don't suppose either of you have a code sample that triggers this?

I have a part of my repo that runs into this problem (right click on allowClickAccept and search for references):

https://github.com/okcode-studio/open_alert_viewer/blob/main/lib/ui/settings/cubit/account_settings_cubit.dart#L157

I suppose there could be a security risk in running the LSP on untrusted code, but is there a way to test it in a Docker container, or in a VM?

[leaf-node]

@DanTup I made a simple demo with the freezed and bloc libraries, and was able to reproduce the error:

leaf-node/dart_lsp_test@4598d2c

If you right-click on foo in:

https://github.com/leaf-node/dart_lsp_test/blob/main/lib/foo_cubit.dart#L5

The error is reproduced.

[DanTup]

@leaf-node thanks! Although I don't seem able to reproduce it. I checked out that commit from your repository and I can fetch references fine (I'm using Flutter stable 3.27.3 which I think matches you):

references.mp4

Does it repro for you in a clean clone of that repository? If not, could you try copying your pubspec.lock file into the clean clone and flutter pub get to see if that then causes the issue (in case it's triggered by something in specific dependency version and I've solved to different versions).

[leaf-node]

@leaf-node thanks! Although I don't seem able to reproduce it. I checked out that commit from your repository and I can fetch references fine (I'm using Flutter stable 3.27.3 which I think matches you):

@DanTup Oops, it looks like I gave you the wrong line to test. If you right click on foo on line 12, and select "Find All References" rather than just showing definitions, the bug should reproduce:

https://github.com/leaf-node/dart_lsp_test/blob/8149548e773f0d73ee771fedec279430e4997050/lib/foo_cubit.dart#L12

[leaf-node]

Oh, I should also mention that if you view the "Output" tab in VSCodium, you can select from the drop-down on the right to show "LSP" logs once an error occurs.

[DanTup]

@leaf-node thanks, I can repro now. I tried but failed to reduce the example to something smaller by removing some of the additional layers. I'll wait for @scheglov's input, as he might have a better idea of why this element might not have a source (I wonder if it's related to the callable classes - though I retained them as I tried to reduce the code, but the issue stopped occurring).

[scheglov]

We probably don't have a source because the formal parameter element is synthetic.

[bwilkerson]

We need to fix the case where the exception is being thrown, and we need to do so in a way that allows us to find all of the references to a parameter, even when the formal parameter element is synthetic. Those might have to be done in two steps, depending on how long it will take to fix the exception.