Glob: Double asterisk is not matching zero directories

[eWert-Online]

Using the latest (unreleased) version with #172 already merged, I would expect ** to match zero or more directories.

Given the following two paths

/project/path/test/lib/test.ml
/project/path/test/lib/deep/test2.ml

with the pattern test/lib/**/*.ml, I would expect both to be true.
Right now however, only the second (deep) one matches.

Doing the same without the lib like this test/**/*.ml returns both paths as true.

This leads me to the conclusion, that ** right now means one or more directories.

(Related to #171)

[rgrinberg]

@sliquister do you agree that this is a bug?

[v-gb]

@rgrinberg did you actually mean to ask me?

I don't know how globs are documented right now, but both git and hg would interpret ** as matching >= 0 number of directories, so in terms of expectations, it's likely less surprising to interpret ** similarly, as @eWert-Online is requesting. (I also looked at fnmatch but it doesn't have ** or equivalent, so no comparison possible)

[rgrinberg]

I wrongly recalled that it was you who contributed many improvements to the glob api. It was actually another JaneStreet employee. In any case, I assume you are still using Re.Glob, in which case we don't want to change the behavior and subtly break things for you.

@eWert-Online since we all seem agree with your assessment, would you like to contribute a fix?

[eWert-Online]

My OCaml isn't that good, but I can at least try 🙂

[eWert-Online]

I looked into this, but I think solving this is currently a bit too much for me 😄

I think the problem is, that the parser currently sees the /'s as explicitly set characters that need to be present in the path.
In my understanding it should however "swallow" the path segments recursively until it finds its match or runs out of characters. If it encounters a .. or . it should also fail.

I did write some tests, which test all of the above mentioned.

  assert (re_match    (glob ~anchored "foo/**/bar/**/baz") "foo/bar/baz");
  assert (re_match    (glob ~anchored "foo/**/bar/**/baz") "foo/bar/x/y/z/baz");
  assert (re_match    (glob ~anchored "foo/**/bar/**/baz") "foo/x/y/z/bar/baz");
  assert (re_match    (glob ~anchored "foo/**/bar/**/baz") "foo/bar/x/bar/x/baz");
  assert (re_mismatch (glob ~anchored "foo/**/bar/**/baz") "foo/bar/../x/baz");
  assert (re_mismatch (glob ~anchored "foo/**/bar/**/baz") "foo/bar/./x/baz");