Update loader progress on percent change only

Summary:
A project can have thousands of files. We report loader progress as the VFS loader loads these, presented on the VS Code status bar as a percentage figure.

This means that we send multiple duplicate messages while loading, as the percentage number changes relatively slowly compared to the number of files loaded.

This onslaught of messages can however overload the LSP client, resulting in a status bar that does not accurately reflect the current ELP loading state as it updates from the backlog in a received queue of messages.

## This diff

This diff reduces the number of messages sent, without losing any information, by keeping track of the current percentage value, and only sending a progress message when it changes.

Reviewed By: TheGeorge

Differential Revision: D84140378

fbshipit-source-id: 13fd4e39b87010c70b692abd7aeb15beddef2dbd

Author: alanz

crates/elp/src/server.rs

@@ -957,7 +957,7 @@ impl Server {
                 self.transition(Status::Loading(pb));
             }
             LoadingProgress::Progress(n_done) => {
-                if let Status::Loading(pb) = &self.status {
+                if let Status::Loading(pb) = &mut self.status {
                     pb.report(n_done, n_total);
                 }
             }
@@ -1988,7 +1988,7 @@ impl Server {
 
     fn update_eqwalize_all(
         &mut self,
-        bar: ProgressBar,
+        mut bar: ProgressBar,
         project_id: ProjectId,
         project_name: String,
         mut files: Vec<FileId>,

crates/elp/src/server/progress.rs

@@ -172,6 +172,7 @@ pub struct ProgressBar {
     /// The message sent when sending the final end report.
     /// It is used in e2e tests to check for a specific task being done.
     end_message: String,
+    current_percent: u32,
 }
 
 impl ProgressBar {
@@ -196,21 +197,25 @@ impl ProgressBar {
             token,
             sender,
             end_message: title,
+            current_percent: 0,
         }
     }
 
-    pub fn report(&self, done: usize, total: usize) {
+    pub fn report(&mut self, done: usize, total: usize) {
         let percent_f = done as f64 / total.max(1) as f64;
         let percent = (percent_f * 100.0) as u32;
-        let message = format!("{percent}%");
-        let msg = WorkDoneProgress::Report(WorkDoneProgressReport {
-            cancellable: None,
-            message: Some(message),
-            percentage: Some(percent),
-        });
-        // We do not update any associated telemetry here, it will
-        // report on the whole bar at the end in the drop.
-        send_progress(&self.sender, self.token.clone(), msg);
+        if percent != self.current_percent {
+            self.current_percent = percent;
+            let message = format!("{percent}%");
+            let msg = WorkDoneProgress::Report(WorkDoneProgressReport {
+                cancellable: None,
+                message: Some(message),
+                percentage: Some(percent),
+            });
+            // We do not update any associated telemetry here, it will
+            // report on the whole bar at the end in the drop.
+            send_progress(&self.sender, self.token.clone(), msg);
+        }
     }
 
     pub fn end(self) {