feat(read-chunk/readChunkStrict): attach read chunk to error if small text

@vates/read-chunk/index.js

@@ -1,6 +1,7 @@
 'use strict'
 
 const assert = require('assert')
+const isUtf8 = require('isutf8')
 
 /**
  * Read a chunk of data from a stream.
@@ -80,7 +81,15 @@ exports.readChunkStrict = async function readChunkStrict(stream, size) {
   }
 
   if (size !== undefined && chunk.length !== size) {
-    const error = new Error(`stream has ended with not enough data (actual: ${chunk.length}, expected: ${size})`)
+    // Buffer.isUtf8 is too recent for now
+    // @todo : replace external package by Buffer.isUtf8 when the supported version of node reach 18
+
+    // cut the message to a sane length and make it usable
+    const content = chunk.subarray(0, 128).toString(isUtf8(chunk) ? 'utf-8' : 'base64')
+
+    const error = new Error(
+      `stream has ended with not enough data (actual: ${chunk.length}, expected: ${size}). Received: ${content}`
+    )
     Object.defineProperties(error, {
       chunk: {
         value: chunk,

@vates/read-chunk/index.test.js

@@ -102,12 +102,39 @@ describe('readChunkStrict', function () {
     assert.strictEqual(error.chunk, undefined)
   })
 
-  it('throws if stream ends with not enough data', async () => {
+  it('throws if stream ends with not enough data, utf8', async () => {
     const error = await rejectionOf(readChunkStrict(makeStream(['foo', 'bar']), 10))
     assert(error instanceof Error)
-    assert.strictEqual(error.message, 'stream has ended with not enough data (actual: 6, expected: 10)')
+    assert.strictEqual(
+      error.message,
+      'stream has ended with not enough data (actual: 6, expected: 10). Received: foobar'
+    )
     assert.deepEqual(error.chunk, Buffer.from('foobar'))
   })
+
+  it('throws if stream ends with not enough data, non utf8 ', async () => {
+    const source = [Buffer.alloc(10, 128), Buffer.alloc(10, 128)]
+    const error = await rejectionOf(readChunkStrict(makeStream(source), 30))
+    assert(error instanceof Error)
+    assert.strictEqual(
+      error.message,
+      'stream has ended with not enough data (actual: 20, expected: 30). Received: gICAgICAgICAgICAgICAgICAgIA='
+    )
+    assert.deepEqual(error.chunk, Buffer.concat(source))
+  })
+
+  it('throws if stream ends with not enough data, non utf8 , long data', async () => {
+    const source = Buffer.alloc(256, 128)
+    const error = await rejectionOf(readChunkStrict(makeStream([source]), 512))
+    assert(error instanceof Error)
+    assert.strictEqual(
+      error.message,
+      `stream has ended with not enough data (actual: 256, expected: 512). Received: ${source
+        .subarray(128)
+        .toString('base64')}`
+    )
+    assert.deepEqual(error.chunk, source)
+  })
 })
 
 describe('skip', function () {

@vates/read-chunk/package.json

@@ -33,5 +33,8 @@
   },
   "devDependencies": {
     "test": "^3.2.1"
+  },
+  "dependencies": {
+    "isutf8": "^4.0.0"
   }
 }

CHANGELOG.unreleased.md

@@ -15,6 +15,7 @@
 
 - [Incremental Backup & Replication] Attempt to work around HVM multiplier issues when creating VMs on older XAPIs (PR [#6866](https://github.com/vatesfr/xen-orchestra/pull/6866))
 - [REST API] Fix VDI export when NBD is enabled
+- [Backup/exports] Show more information on error ` stream has ended with not enough data (actual: xxx, expected: 512)` (PR [#6940](https://github.com/vatesfr/xen-orchestra/pull/6940))
 
 ### Packages to release
 
@@ -34,6 +35,7 @@
 
 - @xen-orchestra/backups minor
 - @xen-orchestra/xapi major
+- @vates/read-chunk minor
 - complex-matcher patch
 - xo-server patch
 - xo-web minor