Filter out empty glob patterns to "glob" command (#6707)

* Filter out empty glob patterns

An empty argument to the "glob" command will now produce an empty result.
Working towards nushell/nushell#6653.

* Run `cargo fmt --all`

Just autoformatted the repo so that CI passes and we have a consistent code
format across modules.

* Treat empty glob argument as error

The glob command will now report an empty string argument as an error instead
of silently ignoring it.

See https://github.com/nushell/nushell/pull/6707#discussion_r993345013.

* Add tests for glob command

Two small tests for the glob command, one to check that the empty string errors
it, and another to sanity check the '*' glob, have been added.

* Rename glob sanity check star test

Co-authored-by: Kyle Anderson <kyle.anderson@uwaterloo.ca>

crates/nu-command/src/filesystem/glob.rs

@@ -99,6 +99,16 @@ impl Command for Glob {
         let glob_pattern: Spanned<String> = call.req(engine_state, stack, 0)?;
         let depth = call.get_flag(engine_state, stack, "depth")?;
 
+        if glob_pattern.item.is_empty() {
+            return Err(ShellError::GenericError(
+                "glob pattern must not be empty".to_string(),
+                "".to_string(),
+                Some(glob_pattern.span),
+                Some("add characters to the glob pattern".to_string()),
+                Vec::new(),
+            ));
+        }
+
         let folder_depth = if let Some(depth) = depth {
             depth
         } else {

crates/nu-command/tests/commands/glob.rs

@@ -0,0 +1,39 @@
+use nu_test_support::fs::Stub::EmptyFile;
+use nu_test_support::playground::Playground;
+use nu_test_support::{nu, pipeline};
+
+#[test]
+fn empty_glob_pattern_triggers_error() {
+    Playground::setup("glob_test_1", |dirs, sandbox| {
+        sandbox.with_files(vec![
+            EmptyFile("yehuda.txt"),
+            EmptyFile("jonathan.txt"),
+            EmptyFile("andres.txt"),
+        ]);
+
+        let actual = nu!(
+            cwd: dirs.test(),
+            "glob ''",
+        );
+
+        assert!(actual.err.contains("must not be empty"));
+    })
+}
+
+#[test]
+fn nonempty_glob_lists_matching_paths() {
+    Playground::setup("glob_sanity_star", |dirs, sandbox| {
+        sandbox.with_files(vec![
+            EmptyFile("yehuda.txt"),
+            EmptyFile("jonathan.txt"),
+            EmptyFile("andres.txt"),
+        ]);
+
+        let actual = nu!(
+            cwd: dirs.test(),
+            pipeline("glob '*' | length"),
+        );
+
+        assert_eq!(actual.out, "3");
+    })
+}

crates/nu-command/tests/commands/mod.rs

@@ -24,6 +24,7 @@ mod flatten;
 mod format;
 mod g;
 mod get;
+mod glob;
 mod group_by;
 mod hash_;
 mod headers;