Incorporate PR feedback

Since this is basically the same errors, unify the two
error codes into one. Technically the two are subtly different
(one is trying to format the whole document, while the other
is only trying to format a section), but the underlying cause
is likely the same, so it's fine to merge them. If necessary/required,
they can be disentangled later on too, as currently noone seems to
check them anyway.

src/LanguageServer.jl

@@ -41,6 +41,7 @@ const SERVER_CANCELLED       = -32802
 const REQUEST_FAILED         = -32803
 
 # Specific to our implementation
+const FORMATTING_FAILED  = -33000
 const NO_DOCUMENT        = -33100
 const MISMATCHED_VERSION = -33101
 const SHUTDOWN_REQUEST   = -32600
@@ -50,6 +51,7 @@ const ERROR_CODES = (
     CONTENT_MODIFIED,
     SERVER_CANCELLED,
     REQUEST_FAILED,
+    FORMATTING_FAILED,
     NO_DOCUMENT,
     MISMATCHED_VERSION,
     SHUTDOWN_REQUEST

src/requests/features.jl

@@ -160,7 +160,7 @@ function textDocument_formatting_request(params::DocumentFormattingParams, serve
         format_text(get_text(doc), params, config)
     catch err
         return JSONRPC.JSONRPCError(
-            -32000,
+            FORMATTING_FAILED,
             "Failed to format document: $err.",
             nothing
         )
@@ -210,7 +210,7 @@ function textDocument_range_formatting_request(params::DocumentRangeFormattingPa
         format_text(text_marked, params, config)
     catch err
         return JSONRPC.JSONRPCError(
-            -33000,
+            FORMATTING_FAILED,
             "Failed to format document: $err.",
             nothing
         )