Bug 1548770 - File.createFile() should not assume that the file doesn't exist, r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D30534

--HG--
extra : moz-landing-system : lando

dom/file/ipc/FileCreatorParent.cpp

@@ -80,13 +80,13 @@ nsresult FileCreatorParent::CreateBlobImpl(
     return rv;
   }
 
-  if (aExistenceCheck) {
-    bool exists;
-    nsresult rv = file->Exists(&exists);
-    if (NS_WARN_IF(NS_FAILED(rv))) {
-      return rv;
-    }
+  bool exists;
+  rv = file->Exists(&exists);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
 
+  if (aExistenceCheck) {
     if (!exists) {
       return NS_ERROR_FILE_NOT_FOUND;
     }
@@ -106,7 +106,9 @@ nsresult FileCreatorParent::CreateBlobImpl(
 
   // If the file doesn't exist, we cannot have its path, its size and so on.
   // Let's set them now.
-  if (!aExistenceCheck) {
+  if (!exists) {
+    MOZ_ASSERT(!aExistenceCheck);
+
     impl->SetMozFullPath(aPath);
     impl->SetLastModified(0);
     impl->SetEmptySize();

dom/file/tests/test_createFile.js

@@ -0,0 +1,31 @@
+async function run_test() {
+  const {Services} = ChromeUtils.import("resource://gre/modules/Services.jsm");
+
+  do_get_profile();
+
+  let existingFile = Services.dirsvc.QueryInterface(Ci.nsIProperties).get("ProfD", Ci.nsIFile);
+  existingFile.append("exists.js");
+  existingFile.createUnique(Ci.nsIFile.NORMAL_FILE_TYPE, 0o600);
+
+  var outStream = Cc["@mozilla.org/network/file-output-stream;1"]
+                      .createInstance(Ci.nsIFileOutputStream);
+  outStream.init(existingFile, 0x02 | 0x08 | 0x20, // write, create, truncate
+                 0666, 0);
+
+  var fileData = "Hello World!";
+  outStream.write(fileData, fileData.length);
+  outStream.close();
+
+  ok(existingFile.exists(), "exists.js exists");
+
+  let unknownFile = Services.dirsvc.QueryInterface(Ci.nsIProperties).get("TmpD", Ci.nsIFile);
+  unknownFile.append("wow.txt");
+
+  ok(!unknownFile.exists(), unknownFile.path + " doesn't exist");
+
+  let a = await File.createFromNsIFile(existingFile, { existenceCheck: false });
+  ok(a.size != 0, "The size is correctly set");
+
+  let b = await File.createFromNsIFile(unknownFile, { existenceCheck: false });
+  ok(b.size == 0, "The size is 0 for unknown file");
+}

dom/file/tests/xpcshell.ini

@@ -1,3 +1,4 @@
 [DEFAULT]
 
 [test_bloburi.js]
+[test_createFile.js]