path/filepath: document that WalkDir calls fs.WalkDirFunc with platform-specific paths #52812
Description
The function filepath.WalkDir uses the callback fs.WalkDirFunc.
Within path/filepath, paths generally use the slash separator of the host platform, so the root parameter to filepath.WalkDir is clearly a platform-specific path.
However, it wasn't obvious to me upon reading the documentation whether the path passed to the WalkDirFunc was a platform-specific path or used / as the path separator. In fact, all the paths use the platform separator, but I had to read the code to be sure. Here are some reasons I thought the WalkDirFunc path might be /-separated:
-
Other types/functions inside
io/fs, such asfs.FS, use/-separated paths. -
When the same callback function
fs.WalkDirFuncis called viafs.WalkDir(rather thanfilepath.WalkDir) it sees/-separated paths. -
The
fs.WalkDirFuncdocumentation mentions/-separated paths:The path argument contains the argument to WalkDir as a prefix. That is, if WalkDir is called with root argument "dir" and finds a file named "a" in that directory, the walk function will be called with argument "dir/a".(I believe that on Windows, if this is coming from
filepath.WalkDir, then it would bedir\arather thandir/a.)
I think the documentation of filepath.WalkDir and/or fs.WalkDirFunc could be clearer on this point.
/cc @rsc who wrote most of this stuff as part of io/fs for Go 1.16.