Interface WalkDirFunc

WalkDirFunc is the type of the function called by [WalkDir] to visit each file or directory.

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".

The d argument is the [DirEntry] for the named path.

The error result returned by the function controls how [WalkDir] continues. If the function returns the special value [SkipDir], WalkDir skips the current directory (path if d.IsDir() is true, otherwise path's parent directory). If the function returns the special value [SkipAll], WalkDir skips all remaining files and directories. Otherwise, if the function returns a non-nil error, WalkDir stops entirely and returns that error.

The err argument reports an error related to path, signaling that [WalkDir] will not walk into that directory. The function can decide how to handle that error; as described earlier, returning the error will cause WalkDir to stop walking the entire tree.

[WalkDir] calls the function with a non-nil err argument in two cases.

First, if the initial [Stat] on the root directory fails, WalkDir calls the function with path set to root, d set to nil, and err set to the error from [fs.Stat].

Second, if a directory's ReadDir method (see [ReadDirFile]) fails, WalkDir calls the function with path set to the directory's path, d set to an [DirEntry] describing the directory, and err set to the error from ReadDir. In this second case, the function is called twice with the path of the directory: the first call is before the directory read is attempted and has err set to nil, giving the function a chance to return [SkipDir] or [SkipAll] and avoid the ReadDir entirely. The second call is after a failed ReadDir and reports the error from ReadDir. (If ReadDir succeeds, there is no second call.)

The differences between WalkDirFunc compared to [path/filepath.WalkFunc] are:

  - The second argument has type [DirEntry] instead of [FileInfo].
  - The function is called before reading a directory, to allow [SkipDir]
    or [SkipAll] to bypass the directory read entirely or skip all remaining
    files and directories respectively.
  - If a directory read fails, the function is called a second time
    for that directory to report the error.
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