compose: Skip failing test for windows.

[apoorvapendse]

The attach from camera test fails on
Windows due to the the path separator
used in the split function of the XFile.name
getter in cross_file being \ instead of /.
This results in the getter returning the
entire path on Windows instead of the
last word present after the last '/' in the path.

Read this excellent explanation by
@chrisbobbe for better understanding:
https://chat.zulip.org/#narrow/channel/516-mobile-dev-help/topic/failing.20composebox.20test.20while.20running.20check.20script/near/2000301

[chrisbobbe]

Thanks! Small comment below.

Also a commit message nit: let's make this the summary line:

compose_box [nfc]: On Windows, skip a test that fails

[apoorvapendse]

Thank you for the review @chrisbobbe .

Here is the change summary:

1. Added a comment explaining the reason behind skipping this test on Windows as suggested here.
2. Updated the commit message summary to the one recommended.
3. Fixed the space after , here as suggested here.

[chrisbobbe]

Thanks! Marking for Greg's review; it's possible he'll want to tweak the explanation in the code comment, but the choice to skip this test on Windows seems fine to me.

[apoorvapendse]

Thanks! Marking for Greg's review; it's possible he'll want to tweak the explanation in the code comment, but the choice to skip this test on Windows seems fine to me.

Thanks for the review @chrisbobbe as well as your simple explanation of why it fails on Windows.

[gnprice]

Thanks to you both!

it's possible he'll want to tweak the explanation in the code comment

Indeed. :-) In fact I also went and filed an upstream issue for the underlying bug in [XFile.name]:

• [cross_file] XFile.name should use defaultTargetPlatform path separator, not Platform flutter/flutter#161073

Merging, after those adjustments:

       // TODO test what happens when capturing/uploading fails
-
-      // This test fails on Windows due to the Platform.pathSeparator.
-      // used in the split function of the XFile.name getter in cross_file being '\' instead of '/'.
-      // This results in the getter returning the entire path on Windows instead of the
-      // last word present after the last '/' in the path.
-    }, skip: Platform.isWindows);
+    },
+    // This test fails on Windows because [XFile.name] splits on
+    // [Platform.pathSeparator], corresponding to the actual host platform
+    // the test is running on, instead of the path separator for the
+    // target platform the test is simulating.
+    // TODO(upstream): unskip after fix to https://github.com/flutter/flutter/issues/161073
+    skip: Platform.isWindows);
   });

[gnprice]

nit: this puts the comment inside the test body function, which is potentially confusing about what the comment is referring to; instead, put it after the }, so it's clearly attached to the skip: argument