Add file watch logging for project switch decisions

Summary:
We already have local logging of changes we receive related to file watching, both from VFS and the LSP client.

To contextualise these, include logging of the decisions made at key points in the project loading lifecyle when ELP is running as an LSP server.

Reviewed By: jcpetruzza

Differential Revision: D86679575

fbshipit-source-id: dc4fb2bdab5b489757a618aefee33f544bce4767

Author: alanz

crates/elp/src/server.rs

@@ -507,6 +507,7 @@ impl Server {
                         a_file_per_project = FxHashSet::default();
                     }
                     spinner.end();
+                    log::info!(target: FILE_WATCH_LOGGER_NAME, "Project reloading complete");
                     self.reload_manager
                         .lock()
                         .set_reload_done(a_file_per_project);
@@ -558,6 +559,7 @@ impl Server {
 
         let to_reload = self.reload_manager.lock().query_changed_files();
         if let Some(to_reload) = to_reload {
+            log::info!(target: FILE_WATCH_LOGGER_NAME, "Asking for project reload");
             let query_config = self.reload_manager.lock().set_reload_active();
             self.reload_project(to_reload, query_config);
         }
@@ -1022,8 +1024,10 @@ impl Server {
                 log::info!(target: FILE_WATCH_LOGGER_NAME, "VFS change:{}:{}", &opened, &path);
             }
             if !opened {
-                // This call will add the file to the changed_files, picked
-                // up in `process_changes`, if it has changed.
+                // This call will add the file to the changed_files,
+                // picked up in `process_changes`, only if the new
+                // content is different from the current, checked via
+                // a hash.
                 vfs.set_file_contents(path, contents);
             }
         }
@@ -1396,9 +1400,11 @@ impl Server {
     fn switch_workspaces(&mut self, spinner: &Spinner, new_projects: Vec<Project>) -> Result<()> {
         if new_projects.is_empty() {
             log::info!("nothing new, not switching workspaces");
+            log::info!(target: FILE_WATCH_LOGGER_NAME, "nothing new, not switching workspaces");
             return Ok(());
         }
         log::info!("will switch workspaces");
+        log::info!(target: FILE_WATCH_LOGGER_NAME, "will switch workspaces");
 
         let mut projects: Vec<Project> = self.projects.iter().cloned().collect();
         for project in new_projects {
@@ -1878,6 +1884,7 @@ impl Server {
         if !self.reload_manager.lock().ok_to_switch_workspace() {
             // There are other changed files, abort this reload, to
             // allow the next one.
+            log::info!(target: FILE_WATCH_LOGGER_NAME, "Not switching workspaces, more changed config files");
             return Ok(false);
         }
         spinner.report("Switching to loaded projects".to_string());