Under which conditions can GlobSetBuilder::build() error?

[konstin]

GlobSetBuilder::build() returns a Result<GlobSet, Error>, even though it's constructed from valid globs. Under which conditions does it raise the error?

[BurntSushi]

This variant:

ripgrep/crates/globset/src/lib.rs

Lines 177 to 178 in 4b0e5a1

	/// An error associated with parsing or compiling a regex.
	Regex(String),

Specifically, from here:

ripgrep/crates/globset/src/lib.rs

Lines 292 to 295 in 4b0e5a1

	.map_err(|err| Error {
	glob: None,
	kind: ErrorKind::Regex(err.to_string()),
	})

Something to note here is that a Glob itself can't do any matching. Basically, a Glob is just the result of converting a glob pattern to a regex. That can fail because of invalid glob syntax. But the process of converting a Glob to a GlobMatcher (for matching one glob) or many Globs to a GlobSet (for matching zero or more globs) can still fail. I believe the only possible error here is if the size limit is exceeded. That size limit is currently hard-coded:

ripgrep/crates/globset/src/lib.rs

Line 286 in 4b0e5a1

.nfa_size_limit(Some(10 * (1 << 20)))

So basically, if your globs combine into one compiled regex that is too big, then this step could fail.

Since Unicode handling is generally disabled in this crate, and since the glob syntax doesn't give you access to things that would otherwise make it easy to build huge regexes (like bounded repetitions), you would likely need many globs to blow the size limit.

[konstin]

Thanks, I'll add an error variant as "glob expressions caused to large regex".