From 22263e8ff974e6ad5cf0a914c6b7c4197678ec66 Mon Sep 17 00:00:00 2001
From: Adam Obuchowicz <adam.obuchowicz@enso.org>
Date: Tue, 20 Aug 2024 16:42:25 +0200
Subject: [PATCH] Y-docs: Fix write capability recovery (#10851)

When receiving no write capability in `text/openFile` response, the method returned error without synchronizing, but session state stayed at 'Opening' - this resulted in automatic success on the next retry without actually trying.

Added additional state to handle recovery from missing write capability errors.

# Important Notes
tested by applying the patch below (which simulates problem reported by James):

```diff
diff --git a/app/ydoc-shared/src/languageServer.ts b/app/ydoc-shared/src/languageServer.ts
index e1403f50420247575b437df8c603e5f1701b5e1d..753bbf9f9f449f6130c79040e44607ce0c308f7f 100644
--- a/app/ydoc-shared/src/languageServer.ts
+++ b/app/ydoc-shared/src/languageServer.ts
@@ -3,6 +3,7 @@ import { bytesToHex } from '@noble/hashes/utils'
import { Client, RequestManager } from '@open-rpc/client-js'
import debug from 'debug'
import { ObservableV2 } from 'lib0/observable'
+import { wait } from 'lib0/promise.js'
import { uuidv4 } from 'lib0/random'
import { z } from 'zod'
import { walkFs } from './languageServer/files'
@@ -268,9 +269,25 @@ export class LanguageServer extends ObservableV2<Notifications & TransportEvents
return this.request('session/initProtocolConnection', { clientId }, false)
}

+  private openCalls = 0
/** [Documentation](https://github.com/enso-org/enso/blob/develop/docs/language-server/protocol-language-server.md#textopenfile) */
openTextFile(path: Path): Promise<LsRpcResult<response.OpenTextFile>> {
-    return this.request<response.OpenTextFile>('text/openFile', { path })
+    if (this.openCalls === 0) {
+      this.openCalls = 1
+      return wait(1000).then(() =>
+        Err(new LsRpcError('Simluated timeout', 'text/openFile', { path })),
+      )
+    } else if (this.openCalls === 1) {
+      this.openCalls = 2
+      return this.request<response.OpenTextFile>('text/openFile', { path }).then(value => {
+        if (value.ok) {
+          value.value.writeCapability = null
+        }
+        return value
+      })
+    } else {
+      return this.request<response.OpenTextFile>('text/openFile', { path })
+    }
}

/** [Documentation](https://github.com/enso-org/enso/blob/develop/docs/language-server/protocol-language-server.md#textclosefile) */
```
---
 app/ydoc-server/src/languageServerSession.ts | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/app/ydoc-server/src/languageServerSession.ts b/app/ydoc-server/src/languageServerSession.ts
index 0455cd892cd6..130ebe9c6f5d 100644
--- a/app/ydoc-server/src/languageServerSession.ts
+++ b/app/ydoc-server/src/languageServerSession.ts
@@ -277,6 +277,7 @@ enum LsSyncState {
   Synchronized,
   WritingFile,
   WriteError,
+  CapabilityError,
   Reloading,
   Closing,
   Disposed,
@@ -402,6 +403,7 @@ class ModulePersistence extends ObservableV2<{ removed: () => void }> {
               const result = await promise
               if (!result.ok) return result
               if (!result.value.writeCapability) {
+                this.setState(LsSyncState.CapabilityError)
                 return Err(
                   `Could not acquire write capability for module '${this.path.segments.join('/')}'`,
                 )
@@ -410,6 +412,8 @@ class ModulePersistence extends ObservableV2<{ removed: () => void }> {
               return Ok()
             })
           }
+          case LsSyncState.CapabilityError:
+            return this.reload()
           default: {
             assertNever(this.state)
           }
@@ -655,6 +659,7 @@ class ModulePersistence extends ObservableV2<{ removed: () => void }> {
         }
         return
       }
+      case LsSyncState.CapabilityError:
       case LsSyncState.WriteError:
       case LsSyncState.Synchronized: {
         this.setState(LsSyncState.Closing)
@@ -703,6 +708,7 @@ class ModulePersistence extends ObservableV2<{ removed: () => void }> {
               return Ok()
             })
           }
+          case LsSyncState.CapabilityError:
           case LsSyncState.WriteError: {
             return this.withState(LsSyncState.Reloading, async () => {
               const path = this.path.segments.join('/')