Add support for multi-word snippet prefixes (#42398)

Supercedes #41126

Closes #39559, #35397, and #41426

Release Notes:

- Added support for multi-word snippet prefixes

---------

Co-authored-by: Agus Zubiaga <hi@aguz.me>
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>
Co-authored-by: Cole Miller <cole@zed.dev>

crates/project/src/lsp_store.rs

@@ -10143,6 +10143,8 @@ impl LspStore {
                     source: completion.source,
                     documentation: None,
                     label: CodeLabel::default(),
+                    match_start: None,
+                    snippet_deduplication_key: None,
                     insert_text_mode: None,
                     icon_path: None,
                     confirm: None,
@@ -12847,6 +12849,8 @@ async fn populate_labels_for_completions(
                     source: completion.source,
                     icon_path: None,
                     confirm: None,
+                    match_start: None,
+                    snippet_deduplication_key: None,
                 });
             }
             None => {
@@ -12861,6 +12865,8 @@ async fn populate_labels_for_completions(
                     insert_text_mode: None,
                     icon_path: None,
                     confirm: None,
+                    match_start: None,
+                    snippet_deduplication_key: None,
                 });
             }
         }

crates/project/src/project.rs

@@ -103,6 +103,7 @@ use search_history::SearchHistory;
 use settings::{InvalidSettingsError, RegisterSetting, Settings, SettingsLocation, SettingsStore};
 use smol::channel::Receiver;
 use snippet::Snippet;
+pub use snippet_provider;
 use snippet_provider::SnippetProvider;
 use std::{
     borrow::Cow,
@@ -476,6 +477,12 @@ pub struct Completion {
     pub source: CompletionSource,
     /// A path to an icon for this completion that is shown in the menu.
     pub icon_path: Option<SharedString>,
+    /// Text starting here and ending at the cursor will be used as the query for filtering this completion.
+    ///
+    /// If None, the start of the surrounding word is used.
+    pub match_start: Option<text::Anchor>,
+    /// Key used for de-duplicating snippets. If None, always considered unique.
+    pub snippet_deduplication_key: Option<(usize, usize)>,
     /// Whether to adjust indentation (the default) or not.
     pub insert_text_mode: Option<InsertTextMode>,
     /// An optional callback to invoke when this completion is confirmed.
@@ -5643,6 +5650,15 @@ impl Completion {
     }
 
     /// Whether this completion is a snippet.
+    pub fn is_snippet_kind(&self) -> bool {
+        matches!(
+            &self.source,
+            CompletionSource::Lsp { lsp_completion, .. }
+            if lsp_completion.kind == Some(CompletionItemKind::SNIPPET)
+        )
+    }
+
+    /// Whether this completion is a snippet or snippet-style LSP completion.
     pub fn is_snippet(&self) -> bool {
         self.source
             // `lsp::CompletionListItemDefaults` has `insert_text_format` field