path type error and not found changes (#13007)

# Description
Instead of an empty string, this PR changes `path type` to return null
if the path does not exist. If some other IO error is encountered, then
that error is bubbled up instead of treating it as a "not found" case.

# User-Facing Changes
- `path type` will now return null instead of an empty string, which is
technically a breaking change. In most cases though, I think this
shouldn't affect the behavior of scripts too much.
- `path type` can now error instead of returning an empty string if some
other IO error besides a "not found" error occurs.

Since this PR introduces breaking changes, it should be merged after the
0.94.1 patch.

crates/nu-command/src/path/type.rs

@@ -1,7 +1,10 @@
 use super::PathSubcommandArguments;
 use nu_engine::command_prelude::*;
 use nu_protocol::engine::StateWorkingSet;
-use std::path::{Path, PathBuf};
+use std::{
+    io,
+    path::{Path, PathBuf},
+};
 
 struct Arguments {
     pwd: PathBuf,
@@ -36,7 +39,7 @@ impl Command for SubCommand {
 
     fn extra_usage(&self) -> &str {
         r#"This checks the file system to confirm the path's object type.
-If nothing is found, an empty string will be returned."#
+If the path does not exist, null will be returned."#
     }
 
     fn is_const(&self) -> bool {
@@ -104,9 +107,11 @@ If nothing is found, an empty string will be returned."#
 
 fn path_type(path: &Path, span: Span, args: &Arguments) -> Value {
     let path = nu_path::expand_path_with(path, &args.pwd, true);
-    let meta = path.symlink_metadata();
-    let ty = meta.as_ref().map(get_file_type).unwrap_or("");
-    Value::string(ty, span)
+    match path.symlink_metadata() {
+        Ok(metadata) => Value::string(get_file_type(&metadata), span),
+        Err(err) if err.kind() == io::ErrorKind::NotFound => Value::nothing(span),
+        Err(err) => Value::error(err.into_spanned(span).into(), span),
+    }
 }
 
 fn get_file_type(md: &std::fs::Metadata) -> &str {