Add completions.lsp_insert_mode setting to control what ranges are replaced when a completion is inserted (#27453)

This PR adds `completions.lsp_insert_mode` and effectively changes the
default from `"replace"` to `"replace_suffix"`, which automatically
detects whether to use the LSP `replace` range instead of `insert`
range.

`"replace_suffix"` was chosen as a default because it's more
conservative than `"replace_subsequence"`, considering that deleting
text is usually faster and less disruptive than having to rewrite a long
replaced word.

Fixes #27197
Fixes #23395 (again)
Fixes #4816 (again)

Release Notes:

- Added new setting `completions.lsp_insert_mode` that changes what will
be replaced when an LSP completion is accepted. The default is
`"replace_suffix"`, but it accepts 4 values: `"insert"` for replacing
only the text before the cursor, `"replace"` for replacing the whole
text, `"replace_suffix"` that acts like `"replace"` when the text after
the cursor is a suffix of the completion, and `"replace_subsequence"`
that acts like `"replace"` when the text around your cursor is a
subsequence of the completion (similiar to a fuzzy match). Check [the
documentation](https://zed.dev/docs/configuring-zed#LSP-Insert-Mode) for
more information.

---------

Co-authored-by: João Marcos <marcospb19@hotmail.com>
Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>

crates/project/src/lsp_store.rs

@@ -39,7 +39,8 @@ use language::{
     LanguageToolchainStore, LocalFile, LspAdapter, LspAdapterDelegate, Patch, PointUtf16,
     TextBufferSnapshot, ToOffset, ToPointUtf16, Transaction, Unclipped,
     language_settings::{
-        FormatOnSave, Formatter, LanguageSettings, SelectedFormatter, language_settings,
+        AllLanguageSettings, FormatOnSave, Formatter, LanguageSettings, LspInsertMode,
+        SelectedFormatter, language_settings,
     },
     point_to_lsp,
     proto::{deserialize_anchor, deserialize_version, serialize_anchor, serialize_version},
@@ -5151,6 +5152,7 @@ impl LspStore {
                             &buffer_snapshot,
                             completions.clone(),
                             completion_index,
+                            cx,
                         )
                         .await
                         .log_err()
@@ -5184,6 +5186,7 @@ impl LspStore {
         snapshot: &BufferSnapshot,
         completions: Rc<RefCell<Box<[Completion]>>>,
         completion_index: usize,
+        cx: &mut AsyncApp,
     ) -> Result<()> {
         let server_id = server.server_id();
         let can_resolve = server
@@ -5226,7 +5229,15 @@ impl LspStore {
             // language server we currently use that does update `text_edit` in `completionItem/resolve`
             // is `typescript-language-server` and they only update `text_edit.new_text`.
             // But we should not rely on that.
-            let edit = parse_completion_text_edit(text_edit, snapshot);
+            let completion_mode = cx
+                .read_global(|_: &SettingsStore, cx| {
+                    AllLanguageSettings::get_global(cx)
+                        .defaults
+                        .completions
+                        .lsp_insert_mode
+                })
+                .unwrap_or(LspInsertMode::Insert);
+            let edit = parse_completion_text_edit(text_edit, snapshot, completion_mode);
 
             if let Some((old_range, mut new_text)) = edit {
                 LineEnding::normalize(&mut new_text);
@@ -5482,6 +5493,7 @@ impl LspStore {
                     &snapshot,
                     completions.clone(),
                     completion_index,
+                    cx,
                 )
                 .await
                 .context("resolving completion")?;
@@ -7723,7 +7735,16 @@ impl LspStore {
             })??;
 
             if let Some(text_edit) = completion.text_edit.as_ref() {
-                let edit = parse_completion_text_edit(text_edit, &buffer_snapshot);
+                let completion_mode = cx
+                    .read_global(|_: &SettingsStore, cx| {
+                        AllLanguageSettings::get_global(cx)
+                            .defaults
+                            .completions
+                            .lsp_insert_mode
+                    })
+                    .unwrap_or(LspInsertMode::Insert);
+
+                let edit = parse_completion_text_edit(text_edit, &buffer_snapshot, completion_mode);
 
                 if let Some((old_range, mut text_edit_new_text)) = edit {
                     LineEnding::normalize(&mut text_edit_new_text);