HLS crashes with "The Haskell (<proj>) server crashed 5 times in the last 3 minutes. The server will not be restarted."

[levans]

Your environment

HLS 0.9.0
Running in a stack project sandbox
Hardware is a MacBookPro (2019) with macOS 11.2

Which lsp-client do you use: VSCode (HLS 0.9.0 is automatically downloaded by

Describe your project (alternative: link to the project):
Fails with all my yesod projects, and the basic scaffold project generated with:

stack new nasty yesodweb/postgres

Steps to reproduce

1. Generate a new yesod postgres scaffold project: stack new nasty yesodweb/postgres
2. Open project folder in VSCode and select a .hs file

Hopefully, this is easy to reproduce, given that the entire project can easily be generated from scaffold.
However, I will attempt to narrow the conditions by stripping the project further and will post and insights as addendums.

Expected behaviour

Expected that the metadata would be built successfully and session could continue as normal

Actual behaviour

"Processing" status line message shows stepping though files but resets several times until the final failure notification is displayed and the extension is disabled due to restarts.

Include debug information

Execute in the root of your project the command haskell-language-server --debug . and paste the logs here:

Debug output:

<paste your logs here>

Paste the logs from the lsp-client, e.g. for VS Code

LSP logs:

<paste your logs here>

[jneira]

Hi, thanks for the bug report, there was a similar issue, involving yesod and macos: #230. It was closed as possible duplicate of #469.
We should have the logs to confirming though.

[levans]

Thanks Javier. I don't have have haskell-language-server on my path (was downloaded by the VSCode extension and presumably cached somewhere). If you'd like me to run haskell-language-server --debug ., would you happen to know where the executable is cached?

I've attached the log file generated by setting a file into the VSCode extension settings.
vscode_hls.log

[jneira]

Thanks, the vscode log would be enough to confirm it is not a duplicate of #230. At least the compiler panic is not present.
In fact there is no error logged before the crash afaics 😟
I guess it could be related with the eval plugin, that is inestable and is causing crashes (see #633) but there is no log about it so not sure.

To try to workraround the issue and find the possible cause we can disable all plugins and reenable it one by one.
To do it you can add a settings.json file inside a subdir in the project named .vscode, with this content:

{
    "haskell": {
        "plugin" : {
            "importLens" : {
                "globalOn" : false
            },
            "hlint" : {
                "globalOn" : false
            },
            "eval" : {
                "globalOn" : false
            },
            "moduleName" : {
                "globalOn" : false
            },
            "splice" : {
                "globalOn" : false
            },
            "haddockComments" : {
                "globalOn" : false
            },
            "class" : {
                "globalOn" : false
            },
            "retrie" : {
                "globalOn" : false
            },
            "tactic" : {
                "globalOn" : false
            },
            "pragmas" : {
                "globalOn" : false
            }
        }
    }
}

... and test if the crash is reproduced
As the eval plugin is the main suspect i would start enabling it to reproduce it.

[levans]

Added the settings file and restarted vscode.
Left all the global settings set to false on the first try, but found that there's absolutely no difference in behaviour.

I have attached the log from that run, where you can see the settings reproduced, but the vscode extension still crashes in a loop.

vscode_settings.log

[jneira]

@levans thanks for trying it, from the log we can deduce that the configuration is in effect, cause the specific log for plugins is not included anymore. And as all plugins are disabled the component causing the crash is probably ghcide.

[jneira]

Is there some template haskell used in the module? Iirc yesod make heavy use of th so probably that will be the case.

[levans]

Indeed Yesod makes a good deal of use of TH and quasiquotation for a number of embedded languages (HTML, CSS, data definition). The scaffold creates a range of modules with various examples of these.