Small fixes and refactors to paths & source command (#3998)

* Expand path when converting value -> PathBuf

Also includes Tagged<PathBuf>.

Fixes #3605

* Expand path for PATH env. variable

Fixes #1834

* Remove leftover Cows after nu-path refactor

There were some unnecessary Cow conversions leftover from the old
nu-path implementation.

* Use canonicalize in source command; Improve errors

Previously, `source` used `expand_path()` which does not follow
symlinks.

As a follow up, I improved the source error messages so they now tell
why the source file could not be canonicalized or read into string.

crates/nu-command/src/commands/core_commands/source.rs

@@ -2,11 +2,11 @@ use crate::prelude::*;
 use nu_engine::{script, WholeStreamCommand};
 
 use nu_errors::ShellError;
-use nu_path::expand_path;
+use nu_path::{canonicalize, canonicalize_with};
 use nu_protocol::{Signature, SyntaxShape};
 use nu_source::Tagged;
 
-use std::{borrow::Cow, path::Path, path::PathBuf};
+use std::path::Path;
 
 pub struct Source;
 
@@ -69,11 +69,15 @@ pub fn source(args: CommandArgs) -> Result<OutputStream, ShellError> {
         for lib_path in dir {
             match lib_path {
                 Ok(name) => {
-                    let path = PathBuf::from(name).join(source_file);
+                    let path = canonicalize_with(&source_file, name).map_err(|e| {
+                        ShellError::labeled_error(
+                            format!("Can't load source file. Reason: {}", e.to_string()),
+                            "Can't load this file",
+                            filename.span(),
+                        )
+                    })?;
 
-                    if let Ok(contents) =
-                        std::fs::read_to_string(&expand_path(Cow::Borrowed(path.as_path())))
-                    {
+                    if let Ok(contents) = std::fs::read_to_string(path) {
                         let result = script::run_script_standalone(contents, true, ctx, false);
 
                         if let Err(err) = result {
@@ -89,9 +93,15 @@ pub fn source(args: CommandArgs) -> Result<OutputStream, ShellError> {
         }
     }
 
-    let path = Path::new(source_file);
+    let path = canonicalize(source_file).map_err(|e| {
+        ShellError::labeled_error(
+            format!("Can't load source file. Reason: {}", e.to_string()),
+            "Can't load this file",
+            filename.span(),
+        )
+    })?;
 
-    let contents = std::fs::read_to_string(&expand_path(Cow::Borrowed(path)));
+    let contents = std::fs::read_to_string(path);
 
     match contents {
         Ok(contents) => {
@@ -102,10 +112,10 @@ pub fn source(args: CommandArgs) -> Result<OutputStream, ShellError> {
             }
             Ok(OutputStream::empty())
         }
-        Err(_) => {
+        Err(e) => {
             ctx.error(ShellError::labeled_error(
-                "Can't load file to source",
-                "can't load file",
+                format!("Can't load source file. Reason: {}", e.to_string()),
+                "Can't load this file",
                 filename.span(),
             ));
 

crates/nu-command/src/commands/path/expand.rs

@@ -5,7 +5,7 @@ use nu_errors::ShellError;
 use nu_path::{canonicalize, expand_path};
 use nu_protocol::{ColumnPath, Signature, SyntaxShape, UntaggedValue, Value};
 use nu_source::Span;
-use std::{borrow::Cow, path::Path};
+use std::path::Path;
 
 pub struct PathExpand;
 
@@ -105,7 +105,7 @@ fn action(path: &Path, tag: Tag, args: &PathExpandArguments) -> Value {
             tag.span,
         ))
     } else {
-        UntaggedValue::filepath(expand_path(Cow::Borrowed(path))).into_value(tag)
+        UntaggedValue::filepath(expand_path(path)).into_value(tag)
     }
 }