Don't register ability to hover, request colors, etc… more than once (#1378)

We're currently re-registering "common" capabilities per workspace
folder. This causes VSCode to make multiple requests to the server for
things like hover causing higher CPU usage. This then results multiple
hovers being displayed. What's worse is that for some scenarios where
the server has to internally do a restart the old registrations weren't
getting disposed of because of a race condition when calling it
concurrently for multiple folders.

I've done two things to address this:
- Common capability registration will only happen after all project
folders have been initialized — hopefully this doesn't cause any
problems (though if it does it's revealing a bigger underlying one)
- Common capabilities will be explicitly disposed before registering
again

This should mean that this only happens one time per server
initialization.

Fixes #1371

Author: thecrypticace

packages/tailwindcss-language-server/src/tw.ts

@@ -174,6 +174,10 @@ export class TW {
       }
     }
 
+    if (results.some((result) => result.status === 'fulfilled')) {
+      await this.updateCommonCapabilities()
+    }
+
     await this.listenForEvents()
   }
 
@@ -628,8 +632,6 @@ export class TW {
 
     console.log(`[Global] Initializing projects...`)
 
-    await this.updateCommonCapabilities()
-
     // init projects for documents that are _already_ open
     let readyDocuments: string[] = []
     let enabledProjectCount = 0
@@ -896,6 +898,7 @@ export class TW {
       capabilities.add(DidChangeConfigurationNotification.type, undefined)
     }
 
+    this.commonRegistrations?.dispose()
     this.commonRegistrations = await this.connection.client.register(capabilities)
   }
 
@@ -907,7 +910,7 @@ export class TW {
   }
 
   private lastTriggerCharacters: Set<string> | undefined
-  private completionRegistration: Disposable | undefined
+  private completionRegistration: Promise<Disposable> | undefined
   private async updateTriggerCharacters() {
     // If the client does not suppory dynamic registration of completions then
     // we cannot update the set of trigger characters
@@ -938,12 +941,27 @@ export class TW {
 
     this.lastTriggerCharacters = chars
 
-    this.completionRegistration?.dispose()
-    this.completionRegistration = await this.connection.client.register(CompletionRequest.type, {
+    let current = this.completionRegistration
+    this.completionRegistration = this.connection.client.register(CompletionRequest.type, {
       documentSelector: null,
       resolveProvider: true,
       triggerCharacters: Array.from(chars),
     })
+
+    // NOTE:
+    // This weird setup works around a race condition where multiple projects
+    // with different separators update their capabilities at the same time. It
+    // is extremely unlikely but it could cause `CompletionRequest` to be
+    // registered more than once with the LSP client.
+    //
+    // We store the promises meaning everything up to this point is synchronous
+    // so it should be fine but really the proper fix here is to:
+    // - Refactor workspace folder initialization so discovery, initialization,
+    //   file events, config watchers, etc… are all shared.
+    // - Remove the need for the "restart" concept in the server for as much as
+    //   possible. Each project should be capable of reloading its modules.
+    await current?.then((r) => r.dispose())
+    await this.completionRegistration
   }
 
   private getProject(document: TextDocumentIdentifier): ProjectService {
@@ -1134,7 +1152,7 @@ export class TW {
     this.commonRegistrations = undefined
 
     this.lastTriggerCharacters.clear()
-    this.completionRegistration?.dispose()
+    this.completionRegistration?.then((r) => r.dispose())
     this.completionRegistration = undefined
 
     this.disposables.forEach((d) => d.dispose())