fix: avoid reading files when the size is empty (#134)

* fix: avoid reading files when the size is empty

* also use stat.size for checking if it is modified

* bump minor version number

* Don't push empty chunks into the array (creates faster reads)

* reverted back to avoid making a if check

Author: jimmywarting

from.js

@@ -65,6 +65,9 @@ class BlobDataItem {
     this.#start = options.start
     this.size = options.size
     this.lastModified = options.lastModified
+    this.originalSize = options.originalSize === undefined
+      ? options.size
+      : options.originalSize
   }
 
   /**
@@ -75,16 +78,19 @@ class BlobDataItem {
     return new BlobDataItem({
       path: this.#path,
       lastModified: this.lastModified,
+      originalSize: this.originalSize,
       size: end - start,
       start: this.#start + start
     })
   }
 
   async * stream () {
-    const { mtimeMs } = await stat(this.#path)
-    if (mtimeMs > this.lastModified) {
+    const { mtimeMs, size } = await stat(this.#path)
+
+    if (mtimeMs > this.lastModified || this.originalSize !== size) {
       throw new DOMException('The requested file could not be read, typically due to permission problems that have occurred after a reference to a file was acquired.', 'NotReadableError')
     }
+
     yield * createReadStream(this.#path, {
       start: this.#start,
       end: this.#start + this.size - 1

index.js

@@ -83,8 +83,12 @@ const _Blob = class Blob {
         part = encoder.encode(`${element}`)
       }
 
-      this.#size += ArrayBuffer.isView(part) ? part.byteLength : part.size
-      this.#parts.push(part)
+      const size = ArrayBuffer.isView(part) ? part.byteLength : part.size
+      // Avoid pushing empty parts into the array to better GC them
+      if (size) {
+        this.#size += size
+        this.#parts.push(part)
+      }
     }
 
     this.#endings = `${options.endings === undefined ? 'transparent' : options.endings}`

package.json

@@ -1,6 +1,6 @@
 {
     "name": "fetch-blob",
-    "version": "3.1.4",
+    "version": "3.1.5",
     "description": "Blob & File implementation in Node.js, originally from node-fetch.",
     "main": "index.js",
     "type": "module",

test/own-misc-test.js

@@ -189,6 +189,12 @@ promise_test(async () => {
   assert_equals(await (await fileFrom('./LICENSE')).text(), license.toString())
 }, 'blob part backed up by filesystem slice correctly')
 
+promise_test(async () => {
+  fs.writeFileSync('temp', '')
+  await blobFromSync('./temp').text()
+  fs.unlinkSync('./temp')
+}, 'can read empty files')
+
 test(async () => {
   const blob = blobFromSync('./LICENSE')
   await new Promise(resolve => setTimeout(resolve, 2000))