Architecture of LSPServer

Overview

LSPServer is an implementation of Language Server Protocol for Wolfram Language code.

The server process that is launched by clients is a regular Wolfram kernel.

StdIO

stdin and stdout are used to communicate with the client.

The server kernel has a background thread that blocks reading stdin.

There are functions for checking if there is any traffic and this allows a very simple main loop in the server:

While[True,

	TryQueue["StdIO"];

	ProcessScheduledJobs[];

	If[empty[$ContentQueue],
	  Pause[0.1];
	  Continue[]
	];

	content = $ContentQueue[[1]];
	$ContentQueue = Rest[$ContentQueue];

	contents = LSPEvaluate[content];

	writeLSPResult["StdIO", sock, contents];

]

$ContentQueue is a list of messages waiting to be processed.

Messages

Messages like testDocument/color are expanded into multiple messages:

{
	textDocument/concreteParse,
	textDocument/aggregateParse,
	textDocument/abstractParse,
	textDocument/colorFencepost
}

and these are what are placed in the queue.

textDocument/colorFencepost is where the actual work gets done.

Expanding messages has benefits: If a file closed, then the queue of all messages is cleared, so there is no unnecessary work done.

By sequencing like this, then the implementation of textDocument/colorFencepost can assume that the AST is already present.

This simplifies implementation of textDocument/colorFencepost.

Jobs can be scheduled for the future, such as waiting to display implicit tokens.

$OpenFilesMap

$OpenFilesMap is a global association that contains entries for each file that is currently open.

The key is the URI of the file and the value is an entry that has this structure:

<|

"Text" -> ...,

"CST" -> ...,

"CSTTabs" -> ...,

"Agg" -> ...,

"AggTabs" -> ...,

"AST" -> ...,

"ScopingData" -> ...,

"LastChange" -> ...,

"ScheduledJobs" -> { Function[{entry}, {methods, toRemove}]... },

"SuppressedRegions" -> ...,

"CSTLints" -> ...,

"AggLints" -> ...,

"ASTLints" -> ...,

"ScopingLints" -> ...

|>