Send LSP Completion Item Kind (#11443)

# Description

This commit fills in the completion item kind into the
`textDocument/completion` response so that LSP client can present more
information to the user.

It is an improvement in the context of #10794

# User-Facing Changes

Improved information display in editor's intelli-sense menu


![output](https://github.com/nushell/nushell/assets/16558417/991dc0a9-45d1-4718-8f22-29002d687b93)

crates/nu-lsp/src/lib.rs

@@ -11,18 +11,18 @@ use std::{
 use lsp_server::{Connection, IoThreads, Message, Response, ResponseError};
 use lsp_types::{
     request::{Completion, GotoDefinition, HoverRequest, Request},
-    CompletionItem, CompletionParams, CompletionResponse, CompletionTextEdit, GotoDefinitionParams,
-    GotoDefinitionResponse, Hover, HoverContents, HoverParams, Location, MarkupContent, MarkupKind,
-    OneOf, Range, ServerCapabilities, TextDocumentSyncKind, TextEdit, Url,
+    CompletionItem, CompletionItemKind, CompletionParams, CompletionResponse, CompletionTextEdit,
+    GotoDefinitionParams, GotoDefinitionResponse, Hover, HoverContents, HoverParams, Location,
+    MarkupContent, MarkupKind, OneOf, Range, ServerCapabilities, TextDocumentSyncKind, TextEdit,
+    Url,
 };
 use miette::{IntoDiagnostic, Result};
-use nu_cli::NuCompleter;
+use nu_cli::{NuCompleter, SuggestionKind};
 use nu_parser::{flatten_block, parse, FlatShape};
 use nu_protocol::{
     engine::{EngineState, Stack, StateWorkingSet},
     DeclId, Span, Value, VarId,
 };
-use reedline::Completer;
 use ropey::Rope;
 
 mod diagnostics;
@@ -559,7 +559,8 @@ impl LanguageServer {
 
         let location =
             Self::lsp_position_to_location(&params.text_document_position.position, rope_of_file);
-        let results = completer.complete(&rope_of_file.to_string()[..location], location);
+        let results =
+            completer.fetch_completions_at(&rope_of_file.to_string()[..location], location);
         if results.is_empty() {
             None
         } else {
@@ -568,17 +569,18 @@ impl LanguageServer {
                     .into_iter()
                     .map(|r| {
                         let mut start = params.text_document_position.position;
-                        start.character -= (r.span.end - r.span.start) as u32;
+                        start.character -= (r.suggestion.span.end - r.suggestion.span.start) as u32;
 
                         CompletionItem {
-                            label: r.value.clone(),
-                            detail: r.description,
+                            label: r.suggestion.value.clone(),
+                            detail: r.suggestion.description,
+                            kind: Self::lsp_completion_item_kind(r.kind),
                             text_edit: Some(CompletionTextEdit::Edit(TextEdit {
                                 range: Range {
                                     start,
                                     end: params.text_document_position.position,
                                 },
-                                new_text: r.value,
+                                new_text: r.suggestion.value,
                             })),
                             ..Default::default()
                         }
@@ -587,12 +589,28 @@ impl LanguageServer {
             ))
         }
     }
+
+    fn lsp_completion_item_kind(
+        suggestion_kind: Option<SuggestionKind>,
+    ) -> Option<CompletionItemKind> {
+        suggestion_kind.and_then(|suggestion_kind| match suggestion_kind {
+            SuggestionKind::Type(t) => match t {
+                nu_protocol::Type::String => Some(CompletionItemKind::VARIABLE),
+                _ => None,
+            },
+            SuggestionKind::Command(c) => match c {
+                nu_protocol::engine::CommandType::Keyword => Some(CompletionItemKind::KEYWORD),
+                nu_protocol::engine::CommandType::Builtin => Some(CompletionItemKind::FUNCTION),
+                _ => None,
+            },
+        })
+    }
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
-    use assert_json_diff::assert_json_eq;
+    use assert_json_diff::{assert_json_eq, assert_json_include};
     use lsp_types::{
         notification::{
             DidChangeTextDocument, DidOpenTextDocument, Exit, Initialized, Notification,
@@ -1078,7 +1096,8 @@ mod tests {
                         "start": { "character": 5, "line": 2 },
                         "end": { "character": 9, "line": 2 }
                      }
-                  }
+                  },
+                  "kind": 6
                }
             ])
         );
@@ -1115,7 +1134,8 @@ mod tests {
                         "end": { "line": 0, "character": 8 },
                      },
                      "newText": "config nu"
-                  }
+                  },
+                  "kind": 3
                }
             ])
         );
@@ -1152,7 +1172,45 @@ mod tests {
                         "end": { "line": 0, "character": 14 },
                      },
                      "newText": "str trim"
-                  }
+                  },
+                  "kind": 3
+               }
+            ])
+        );
+    }
+
+    #[test]
+    fn complete_keyword() {
+        let (client_connection, _recv) = initialize_language_server();
+
+        let mut script = fixtures();
+        script.push("lsp");
+        script.push("completion");
+        script.push("keyword.nu");
+        let script = Url::from_file_path(script).unwrap();
+
+        open_unchecked(&client_connection, script.clone());
+
+        let resp = complete(&client_connection, script, 0, 2);
+        let result = if let Message::Response(response) = resp {
+            response.result
+        } else {
+            panic!()
+        };
+
+        assert_json_include!(
+            actual: result,
+            expected: serde_json::json!([
+               {
+                  "label": "def",
+                  "textEdit": {
+                     "newText": "def",
+                     "range": {
+                        "start": { "character": 0, "line": 0 },
+                        "end": { "character": 2, "line": 0 }
+                     }
+                  },
+                  "kind": 14
                }
             ])
         );