Trailing whitespace fixer does not work?

Testing it on a simple file with a trailing space:

#' @export 

even when the file is staged,

pre-commit run --all-files -v

returns

Trim Trailing Whitespace.......................................................................................Passed

, but has no visible effect on the file.

[asottile]

What is the extension of the file? Currently (by default) it matches this list here:

https://github.com/pre-commit/pre-commit-hooks/blob/144c3857cdbba0b758f80aeee9f2adf42ea303ee/hooks.yaml#L143

$ hexdump -C test.sh
00000000  23 27 20 40 65 78 70 6f  72 74 20 0a              |#' @export .|
0000000c

$ pre-commit run --all-files
Trim Trailing Whitespace.................................................Failed
hookid: trailing-whitespace

Files were modified by this hook. Additional output:

Fixing test.sh

Fix End of Files.........................................................Passed
autopep8 wrapper.........................................................Passed
Check docstring is first.................................................Passed
Check JSON...............................................................Passed
Check for added large files..............................................Passed
Check Yaml...............................................................Passed
Debug Statements (Python)................................................Passed
Tests should end in _test.py.............................................Passed
Fix requirements.txt.....................................................Passed
Flake8...................................................................Passed
Validate Pre-Commit Config...............................................Passed
Validate Pre-Commit Manifest.............................................Passed
Reorder python imports...................................................Passed`

$ git diff
diff --git a/test.sh b/test.sh
index 9029ebb..05085ee 100644
--- a/test.sh
+++ b/test.sh
@@ -1 +1 @@
-#' @export 
+#' @export

[asottile]

via #126