workspace/executeCommand with ExpandFunction can crash server or deletes comments

[jwortmann]

LanguageServer v3.1.0

Consider the following file:

f(x) = x + 1

# random comment

Problem 1: If the 2nd argument for the workspace/executeCommand request with "command": "ExpandFunction" contains an offset value that points to a position outside of an inline function, the server will crash. This happens even for the position of the first character of the function name. Example:

:: --> julia workspace/executeCommand(19): {'command': 'ExpandFunction', 'arguments': ['file:///D:/julia_test/test.jl', 0]}
julia: ERROR: MethodError: no method matching _get_parent_fexpr(::Nothing, ::typeof(LanguageServer.is_single_line_func))
julia: Closest candidates are:
julia: _get_parent_fexpr(!Matched::CSTParser.EXPR, ::Any) at C:\Users\Janos\.julia\packages\LanguageServer\qudfd\src\requests\actions.jl:188
julia: Stacktrace:
julia: [1] expand_inline_func(::Nothing, ::LanguageServerInstance, ::JSONRPC.JSONRPCEndpoint) at C:\Users\Janos\.julia\packages\LanguageServer\qudfd\src\requests\actions.jl:124
julia: [2] workspace_executeCommand_request(::LanguageServer.ExecuteCommandParams, ::LanguageServerInstance, ::JSONRPC.JSONRPCEndpoint) at C:\Users\Janos\.julia\packages\LanguageServer\qudfd\src\requests\actions.jl:42
julia: [3] (::LanguageServer.var"#8#39"{LanguageServerInstance})(::JSONRPC.JSONRPCEndpoint, ::LanguageServer.ExecuteCommandParams) at C:\Users\Janos\.julia\packages\LanguageServer\qudfd\src\languageserverinstance.jl:270
julia: [4] dispatch_msg(::JSONRPC.JSONRPCEndpoint, ::JSONRPC.MsgDispatcher, ::Dict{String,Any}) at C:\Users\Janos\.julia\packages\JSONRPC\nJmHs\src\typed.jl:63
julia: [5] run(::LanguageServerInstance) at C:\Users\Janos\.julia\packages\LanguageServer\qudfd\src\languageserverinstance.jl:305
julia: [6] top-level scope at none:1

Problem 2: If the subsequent lines contain comments, they will be removed. Example:

:: --> julia workspace/executeCommand(28): {'command': 'ExpandFunction', 'arguments': ['file:///D:/julia_test/test.jl', 5]}
:: <-- julia workspace/applyEdit(b15a33ea-761a-47a9-8732-240dc796fa1a): {'edit': {'changes': None, 'documentChanges': [{'edits': [{'range': {'start': {'line': 0, 'character': 0}, 'end': {'line': 3, 'character': 0}}, 'newText': 'function f(x)\n    x + 1\nend\n'}], 'textDocument': {'version': 145, 'uri': 'file:///d%3A/julia_test/test.jl'}}]}}

I think the line field at end should always be exactly 1 more than at begin, but it is 3 in this example.

In general, consider using Position and Range or even Location for the request arguments instead of using offset values.