UTF-8 BOM can break metadata detection

[KwikOne]

When trying to install a user script the @name would be ignored and the script name became the script name (ie 181098.user.js became 181098 for a name) and all @includes and @excludes became ignored such that it indicated that the script runs on everything ( * ).
I discovered that the script appeared to be a UTF-8 with BOM (there was a hidden - character in the front of the file (ahead of the // === Userscript === line and the // appeared to be in character position 1 and 2)

Greasemonkey version 1.12

[arantius]

Cannot reproduce. Please provide an exact file that produces this error. I just wrote this test script which:

$ curl -s http://arantius.com/misc/gm-test/bom-test.user.js | hexdump -C
00000000  ef bb bf 2f 2f 20 3d 3d  55 73 65 72 53 63 72 69  |...// ==UserScri|
00000010  70 74 3d 3d 0a 2f 2f 20  40 6e 61 6d 65 20 20 20  |pt==.// @name   |
00000020  20 20 20 20 20 42 4f 4d  20 54 65 73 74 0a 2f 2f  |     BOM Test.//|
00000030  20 3d 3d 2f 55 73 65 72  53 63 72 69 70 74 3d 3d  | ==/UserScript==|
00000040  0a 0a                                             |..|
00000042

Starts with a valid UTF-8 BOM. And it installs just fine for me, the @name is detected and used.

[KwikOne]

I have the original file, but how do I attach it here? It will only accept an image, not a zip file (since the script is 1.6 million in size). Ah, never mind, the link to the zipped file on dropbox is https://www.dropbox.com/s/nfvdw58t661xkzq/181098-Userscript.zip

[KwikOne]

As for how the script was originally generated to have the invisible (at least to notepad++ but with winmerge it did show up and is how i detected it) character at the front of the file is unknown to me as the script is no longer available on userscript.org. I finally found a good hex editor, and it appears that the file has 2 BOM marks (ef bb bf ef bb bf) prior

But the strange thing is that in chrome, and tampermonkey it installed just fine

[arantius]

Thanks for figuring that out. So, reproduced with http://arantius.com/misc/gm-test/181098.user.js which will not successfully parse the @name from the metadata, but is only 110 bytes. Starting:

$ hexdump -C 181098.user.js | head -n 1
00000000  ef bb bf ef bb bf 2f 2f  20 3d 3d 55 73 65 72 53  |......// ==UserS|

The first four bytes are (I think) handled as a BOM, correctly. But the next four break GM, which wants // =UserScript= to be at the start of a line.