Cleanup ErrorCodes

protocol/src/main/scala/sbt/internal/langserver/ErrorCodes.scala

@@ -9,18 +9,39 @@ package sbt
 package internal
 package langserver
 
+/** Holds the error codes for the LSP implementation here. */
 object ErrorCodes {
-  // Defined by JSON RPC
-  val ParseError = -32700L
-  val InvalidRequest = -32600L
-  val MethodNotFound = -32601L
-  val InvalidParams = -32602L
-  val InternalError = -32603L
-  val serverErrorStart = -32099L
-  val serverErrorEnd = -32000L
-  val ServerNotInitialized = -32002L
-  val UnknownErrorCode = -32001L
+  // this is essentially a lookup table encoded in Scala,
+  // so heavy usage of vertical alignment is beneficial
+  // format: off
 
-  // Defined by the protocol.
-  val RequestCancelled = -32800L
+  // Defined by the JSON-RPC 2.0 Specification
+  // http://www.jsonrpc.org/specification#error_object
+  //
+  // The error codes from and including -32768 to -32000 are reserved for pre-defined errors.
+  // Any code within this range, but not defined explicitly below is reserved for future use.
+  //
+  // The error codes are nearly the same as those suggested for XML-RPC at the following url:
+  // http://xmlrpc-epi.sourceforge.net/specs/rfc.fault_codes.php
+  //
+  val ParseError     = -32700L       // Invalid JSON was received by the server.
+                                     // An error occurred on the server while parsing the JSON text.
+  val InvalidRequest = -32600L       // The JSON sent is not a valid Request object.
+  val MethodNotFound = -32601L       // The method does not exist / is not available.
+  val InvalidParams  = -32602L       // Invalid method parameter(s).
+  val InternalError  = -32603L       // Internal JSON-RPC error.
+
+
+  // The range -32000 to -32099 are reserved for implementation-defined server-errors.
+  val serverErrorStart = -32099L     // from LSP's spec code snippet
+  val serverErrorEnd   = -32000L     // from LSP's spec code snippet
+
+  val UnknownErrorCode     = -32001L // Defined by LSP
+  val ServerNotInitialized = -32002L // Defined by LSP
+
+
+  // The remainder of the space is available for application defined errors.
+  val RequestCancelled = -32800L     // Defined by LSP
+
+  // format: on
 }