Merge pull request #7 from github/body-used

Allow body to be consumed only once

fetch.js

@@ -61,6 +61,13 @@
     })
   }
 
+  function consumed(body) {
+    if (body.bodyUsed) {
+      return new Promise.reject(new TypeError('Body already consumed'))
+    }
+    body.bodyUsed = true
+  }
+
   function Body() {
     this.body = null
     this.bodyUsed = false
@@ -70,7 +77,8 @@
     }
 
     this.blob = function() {
-      return Promise.resolve(new Blob([this.body]))
+      var rejected = consumed(this)
+      return rejected ? rejected : Promise.resolve(new Blob([this.body]))
     }
 
     this.formData = function() {
@@ -78,6 +86,11 @@
     }
 
     this.json = function() {
+      var rejected = consumed(this)
+      if (rejected) {
+        return rejected
+      }
+
       var body = this.body
       return new Promise(function(resolve, reject) {
         try {
@@ -89,7 +102,8 @@
     }
 
     this.text = function() {
-      return Promise.resolve(this.body)
+      var rejected = consumed(this)
+      return rejected ? rejected : Promise.resolve(this.body)
     }
 
     return this

test/test.js

@@ -137,3 +137,33 @@ asyncTest('post sets content-type header', 1, function() {
     start()
   })
 })
+
+asyncTest('rejects blob promise after body is consumed', 1, function() {
+  fetch('/hello').then(function(response) {
+    response.blob()
+    return response.blob()
+  }).catch(function(error) {
+    ok(error instanceof TypeError, 'Promise rejected after body consumed')
+    start()
+  })
+})
+
+asyncTest('rejects json promise after body is consumed', 1, function() {
+  fetch('/json').then(function(response) {
+    response.json()
+    return response.json()
+  }).catch(function(error) {
+    ok(error instanceof TypeError, 'Promise rejected after body consumed')
+    start()
+  })
+})
+
+asyncTest('rejects text promise after body is consumed', 1, function() {
+  fetch('/hello').then(function(response) {
+    response.text()
+    return response.text()
+  }).catch(function(error) {
+    ok(error instanceof TypeError, 'Promise rejected after body consumed')
+    start()
+  })
+})