Rework editors to register and query buffers on scroll (#40388)

Preparation to https://github.com/zed-industries/zed/pull/40183
Moves https://github.com/zed-industries/zed/pull/22958 further: now,
instead of selection, scrolling the buffer into view is enough to get
registered and, later, be queried for its LSP data such as inlay hints,
diagnostics and document colors.

This effectively undoes https://github.com/zed-industries/zed/pull/28855
as now we try to register whatever's visible more aggressively, instead
of implicitly via inlay hints.

Release Notes:

- Reworked editors to register and query buffers on scroll

crates/project/src/lsp_store.rs

@@ -3495,12 +3495,6 @@ struct CodeLensData {
     update: Option<(Global, CodeLensTask)>,
 }
 
-#[derive(Debug, PartialEq, Eq, Clone, Copy)]
-pub enum LspFetchStrategy {
-    IgnoreCache,
-    UseCache { known_cache_version: Option<usize> },
-}
-
 #[derive(Debug)]
 pub enum LspStoreEvent {
     LanguageServerAdded(LanguageServerId, LanguageServerName, Option<WorktreeId>),
@@ -6498,47 +6492,35 @@ impl LspStore {
 
     pub fn document_colors(
         &mut self,
-        fetch_strategy: LspFetchStrategy,
+        known_cache_version: Option<usize>,
         buffer: Entity<Buffer>,
         cx: &mut Context<Self>,
     ) -> Option<DocumentColorTask> {
         let version_queried_for = buffer.read(cx).version();
         let buffer_id = buffer.read(cx).remote_id();
 
-        match fetch_strategy {
-            LspFetchStrategy::IgnoreCache => {}
-            LspFetchStrategy::UseCache {
-                known_cache_version,
-            } => {
-                if let Some(cached_data) = self.lsp_document_colors.get(&buffer_id)
-                    && !version_queried_for.changed_since(&cached_data.colors_for_version)
-                {
-                    let has_different_servers = self.as_local().is_some_and(|local| {
-                        local
-                            .buffers_opened_in_servers
-                            .get(&buffer_id)
-                            .cloned()
-                            .unwrap_or_default()
-                            != cached_data.colors.keys().copied().collect()
-                    });
-                    if !has_different_servers {
-                        if Some(cached_data.cache_version) == known_cache_version {
-                            return None;
-                        } else {
-                            return Some(
-                                Task::ready(Ok(DocumentColors {
-                                    colors: cached_data
-                                        .colors
-                                        .values()
-                                        .flatten()
-                                        .cloned()
-                                        .collect(),
-                                    cache_version: Some(cached_data.cache_version),
-                                }))
-                                .shared(),
-                            );
-                        }
-                    }
+        if let Some(cached_data) = self.lsp_document_colors.get(&buffer_id)
+            && !version_queried_for.changed_since(&cached_data.colors_for_version)
+        {
+            let has_different_servers = self.as_local().is_some_and(|local| {
+                local
+                    .buffers_opened_in_servers
+                    .get(&buffer_id)
+                    .cloned()
+                    .unwrap_or_default()
+                    != cached_data.colors.keys().copied().collect()
+            });
+            if !has_different_servers {
+                if Some(cached_data.cache_version) == known_cache_version {
+                    return None;
+                } else {
+                    return Some(
+                        Task::ready(Ok(DocumentColors {
+                            colors: cached_data.colors.values().flatten().cloned().collect(),
+                            cache_version: Some(cached_data.cache_version),
+                        }))
+                        .shared(),
+                    );
                 }
             }
         }
@@ -6564,13 +6546,12 @@ impl LspStore {
                     .map_err(Arc::new);
                 let fetched_colors = match fetched_colors {
                     Ok(fetched_colors) => {
-                        if fetch_strategy != LspFetchStrategy::IgnoreCache
-                            && Some(true)
-                                == buffer
-                                    .update(cx, |buffer, _| {
-                                        buffer.version() != query_version_queried_for
-                                    })
-                                    .ok()
+                        if Some(true)
+                            == buffer
+                                .update(cx, |buffer, _| {
+                                    buffer.version() != query_version_queried_for
+                                })
+                                .ok()
                         {
                             return Ok(DocumentColors::default());
                         }

crates/project/src/manifest_tree/server_tree.rs

@@ -47,7 +47,7 @@ pub struct LanguageServerTree {
 /// A node in language server tree represents either:
 /// - A language server that has already been initialized/updated for a given project
 /// - A soon-to-be-initialized language server.
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub struct LanguageServerTreeNode(Weak<InnerTreeNode>);
 
 /// Describes a request to launch a language server.