ElmLS randomly crashes with Unexpected JSON error

ElmLS runs just fine for a while, but after a couple minutes, something that I do will crash it with the following error:

SyntaxError: Unexpected number in JSON at position 1
    at JSON.parse (<anonymous>)
    at execaError.stderr.split.forEach (/usr/local/lib/node_modules/@elm-tooling/elm-language-server/out/providers/diagnostics/elmMakeDiagnostics.js:146:54)
    at Array.forEach (<anonymous>)
    at ElmMakeDiagnostics.<anonymous> (/usr/local/lib/node_modules/@elm-tooling/elm-language-server/out/providers/diagnostics/elmMakeDiagnostics.js:145:55)
    at Generator.throw (<anonymous>)
    at rejected (/usr/local/lib/node_modules/@elm-tooling/elm-language-server/out/providers/diagnostics/elmMakeDiagnostics.js:6:65)
    at process._tickCallback (internal/process/next_tick.js:68:7)

/usr/local/lib/node_modules/@elm-tooling/elm-language-server/node_modules/web-tree-sitter/tree-sitter.js:1
(function (exports, require, module, __filename, __dirname) { var Module=void 0!==Module?Module:{};!function(e,t){"function"==typeof define&&define.amd?define([],t):"object"==typeof exports?module.exports=t():window.TreeSitter=t()}(0,function(){var e,t={};for(e in Module)Module.hasOwnProperty(e)&&(t[e]=Module[e]);Module.arguments=[],Module.thisProgram="./this.program",Module.quit=function(e,t){throw t},Module.preRun=[],Module.postRun=[];var n,r=!1,a=!1,i=!1;r="object"==typeof window,a="function"==typeof importScripts,i="object"==typeof process&&"function"==typeof require&&!r&&!a,n=!r&&!i&&!a;var o,l,u="";i?(u=__dirname+"/",Module.read=function shell_read(e,t){var n;return o||(o=require("fs")),l||(l=require("path")),e=l.normalize(e),n=o.readFileSync(e),t?n:n.toString()},Module.readBinary=function readBinary(e){var t=Module.read(e,!0);return t.buffer||(t=new Uint8Array(t)),assert(t.buffer),t},process.arg
abort({}). Build with -s ASSERTIONS=1 for more info.
[Error  - 4:03:26 PM] Connection to server got closed. Server will not be restarted.
[Error  - 4:03:26 PM] elm-language-server exited with code: 7

I’m not certain what is triggering this, but it might be the diagnostics.

Expected Behavior

Not to crash, or to restart if it crashes maybe?

Current Behavior

Crashes and I have to do a :CocRestart to fire it up again every couple minutes.

Possible Solution

Figure out what JSON is being returned, though I’m not sure how to do this.

Steps to Reproduce (for bugs)

1. Open a src/test file in https://github.com/jschomay/subway-game/tree/rules-parser in vim using coc (other files may work too)
2. Notice the ElmLS works for a while
3. Make some changes, or maybe just wait for a while or view a diagnostic
4. Notice ElmLS has crashed and :CocInfo shows the error above.

Context

I just want to use ElmLS with coc.

Your Environment

• Version used: ElmLS 1.4.1, Elm elm@0.19.0-no-deps
• Editor used: vim 8.1
• Environment name and version (e.g. node.js 5.4): node v10.10.0
• Operating System and version: OSX 10.11.6

[jschomay]

I tested it out and I think you’ve solved the problem (I am still getting the invalid JSON errors, but elmLS isn’t crashing).

[Info  - 8:02:36 PM] Diagnostics were requested due to a file open or save
[Warn  - 8:02:37 PM] Received an invalid json, skipping error.
[Warn  - 8:02:37 PM] Received an invalid json, skipping error.
[Warn  - 8:02:37 PM] Received an invalid json, skipping error.
... lots of these messages, then more normal logs
[Info  - 8:02:38 PM] Received new elm-analyse report with 24 messages
etc...

Thank you for fixing that. Hopefully the invalid JSON issue gets fixed eventually.

[andys8]

@jschomay I think it’s not possible to install via npm (only). The repository has to be cloned, built and linked. There is a description how to to that here: https://github.com/elm-tooling/elm-language-server/blob/master/README.md#alternative-compile-and-install-from-source

Let me know if it works for you and feel free to ask for help if not.