feat(@vates/nbd-client): improve error handling

@vates/nbd-client/index.js

@@ -231,15 +231,21 @@ module.exports = class NbdClient {
     buffer.writeInt32BE(size, 24)
 
     return new Promise((resolve, reject) => {
+      function decoratedReject(error) {
+        error.index = index
+        error.size = size
+        reject(error)
+      }
+
       // this will handle one block response, but it can be another block
       // since server does not guaranty to handle query in order
       this.#commandQueryBacklog.set(queryId, {
         size,
         resolve,
-        reject,
+        reject: decoratedReject,
       })
       // really send the command to the server
-      this.#write(buffer).catch(reject)
+      this.#write(buffer).catch(decoratedReject)
 
       // #readBlockResponse never throws directly
       // but if it fails it will reject all the promises in the backlog
@@ -261,34 +267,22 @@ module.exports = class NbdClient {
     }
     const readAhead = []
     const readAheadMaxLength = 10
-    const errors = []
+
+    // read all blocks, but try to keep readAheadMaxLength promise waiting ahead
     for (const { index, size } of indexGenerator()) {
+      // stack readAheadMaxLengthpromise before starting to handle the results
       if (readAhead.length === readAheadMaxLength) {
-        const block = await readAhead.shift()
-        if (block instanceof Error) {
-          break
-        }
-        yield block
+        // any error will stop reading blocks
+        yield readAhead.shift()
       }
-      readAhead.push(
-        this.readBlock(index, size).catch(error => {
-          errors.push(error)
-          return error
-        })
-      )
+
+      // error is handled during unshift
+      const promise = this.readBlock(index, size)
+      promise.catch(() => {})
+      readAhead.push(promise)
     }
     while (readAhead.length > 0) {
-      const block = await readAhead.shift()
-      if (!(block instanceof Error)) {
-        yield block
-      }
-    }
-    // reading a block shoul be quite fast, we wait for all errors
-    // before rethrowing them
-    if (errors.length > 0) {
-      const error = new Error('fail during blocks reading')
-      error.errors = errors
-      throw error
+      yield readAhead.shift()
     }
   }
 }