MethodError: no method matching String(::Nothing)

[AlexLewandowski]

I get the following error in Emacs with lsp-mode and LanguageServer#v2.0.1 (tried Julia v1.0.5 and Julia v1.4). The error is triggered when I am navigating files in the project associated with the language server.

I am invoking the server as suggested in the README:

Command "julia --startup-file=no --history-file=no -e using LanguageServer; server = LanguageServerInstance( stdin, stdout, false, "$USER/.julia/dev/imputation.jl/"); run(server);" is present on the path.
Found the following clients for $USER/.julia/dev/imputation.jl/src/metrics.jl: (server-id julia-ls, priority 0)
The following clients were selected based on priority: (server-id julia-ls, priority 0)

Here is the stacktrace:

ERROR: MethodError: no method matching String(::Nothing)
Closest candidates are:
  String(!Matched::String) at boot.jl:309
  String(!Matched::Array{UInt8,1}) at strings/string.jl:39
  String(!Matched::Base.CodeUnits{UInt8,String}) at strings/string.jl:75
  ...
Stacktrace:
 [1] _broadcast_getindex_evalf at ./broadcast.jl:582 [inlined]
 [2] _broadcast_getindex at ./broadcast.jl:555 [inlined]
 [3] getindex at ./broadcast.jl:515 [inlined]
 [4] copy at ./broadcast.jl:766 [inlined]
 [5] materialize(::Base.Broadcast.Broadcasted{Base.Broadcast.DefaultArrayStyle{0},Nothing,Type{String},Tuple{Base.RefValue{Nothing}}}) at ./broadcast.jl:756
 [6] LanguageServer.CodeActionContext(::Dict{String,Any}) at $USER/.julia/packages/LanguageServer/ZDdcC/src/protocol/protocol.jl:37 (repeats 2 times)
 [7] parse_params(::Type{Val{Symbol("textDocument/codeAction")}}, ::Dict{String,Any}) at $USER/.julia/packages/LanguageServer/ZDdcC/src/requests/actions.jl:1
 [8] parse(::Type{LanguageServer.JSONRPC.Request}, ::Dict{String,Any}) at $USER/.julia/packages/LanguageServer/ZDdcC/src/jsonrpc.jl:46
 [9] run(::LanguageServerInstance) at $USER/.julia/packages/LanguageServer/ZDdcC/src/languageserverinstance.jl:231
 [10] top-level scope at none:0
ERROR: LoadError: IOError: write: broken pipe (EPIPE)
Stacktrace:
 [1] try_yieldto(::typeof(Base.ensure_rescheduled), ::Base.RefValue{Task}) at ./event.jl:196
 [2] wait() at ./event.jl:255
 [3] uv_write(::Base.PipeEndpoint, ::Ptr{UInt8}, ::UInt64) at ./stream.jl:782
 [4] unsafe_write(::Base.PipeEndpoint, ::Ptr{UInt8}, ::UInt64) at ./stream.jl:830
 [5] macro expansion at ./gcutils.jl:87 [inlined]
 [6] write at ./strings/io.jl:164 [inlined]
 [7] print at ./strings/io.jl:166 [inlined]
 [8] print(::Base.PipeEndpoint, ::String, ::Char) at ./strings/io.jl:42
 [9] println at ./strings/io.jl:69 [inlined]
 [10] cache_package(::Pkg.Types.Context, ::Base.UUID, ::Dict{Any,Any}, ::Base.PipeEndpoint) at $USER/.julia/packages/SymbolServer/aNGJi/src/symbols.jl:265
 [11] cache_package(::Pkg.Types.Context, ::String, ::Dict{Any,Any}, ::Base.PipeEndpoint) at $USER/.julia/packages/SymbolServer/aNGJi/src/symbols.jl:285
 [12] top-level scope at $USER/.julia/packages/SymbolServer/aNGJi/src/server.jl:86
 [13] include at ./boot.jl:317 [inlined]
 [14] include_relative(::Module, ::String) at ./loading.jl:1044
 [15] include(::Module, ::String) at ./sysimg.jl:29
 [16] exec_options(::Base.JLOptions) at ./client.jl:266
 [17] _start() at ./client.jl:425
in expression starting at $USER/.julia/packages/SymbolServer/aNGJi/src/server.jl:57

Process julia-ls stderr finished

[non-Jedi]

@AlexLewandowski could you please set lsp-print-io to t and post the messages from the buffer brought up by M-x lsp-workspace-show-log.

[AlexLewandowski]

Here is the gist for the output of lsp-workspace-show-log up until the crash.

[non-Jedi]

I'm assuming what's causing the error here is the only field being null:

{
  "textDocument": {
    "uri": "file:///home/user/test/src/test.jl"
  },
  "range": {
    "start": {
      "line": 1,
      "character": 0
    },
    "end": {
      "line": 1,
      "character": 0
    }
  },
  "context": {
    "diagnostics": [],
    "only": null
  }
}

According to the lsp spec, the only field must be of type CodeActionKind[] which excludes a null value. I believe this is an lsp-mode bug although it could also be mitigated server-side. Feel free to link this comment in an lsp-mode bug report.

[shaqtsui]

I changed the code to exclude "only": null when no filters given(lsp-mode.el around line 4960) .
This error gone. I also raised a issue 1587 in lsp-mode

[shaqtsui]

That issue be fixed in lsp-mode side. You can update latest lsp-mode to fix this issue