Path expand fixes (#3505)

* Throw an error if path failed to expand

Previously, it just repeated the non-expanded path.

* Allow expanding non-existent paths

This commit has a strange error in examples.

* Specify span manually in examples; Add an example

* Expand relative path without requiring cwd

* Remove redundant tilde expansion

This makes the tilde expansion in relative paths dependant on "dirs"
feature.

* Add missing example result

* Adjust path expand description

* Fix import error with missing feature

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

@@ -1,13 +1,18 @@
 use super::{operate, PathSubcommandArguments};
 use crate::prelude::*;
+#[cfg(feature = "dirs")]
+use nu_engine::filesystem::path::expand_tilde;
+use nu_engine::filesystem::path::resolve_dots;
 use nu_engine::WholeStreamCommand;
 use nu_errors::ShellError;
 use nu_protocol::{ColumnPath, Signature, SyntaxShape, UntaggedValue, Value};
-use std::path::{Path, PathBuf};
+use nu_source::Span;
+use std::path::Path;
 
 pub struct PathExpand;
 
 struct PathExpandArguments {
+    strict: bool,
     rest: Vec<ColumnPath>,
 }
 
@@ -24,17 +29,23 @@ impl WholeStreamCommand for PathExpand {
 
     fn signature(&self) -> Signature {
         Signature::build("path expand")
+            .switch(
+                "strict",
+                "Throw an error if the path could not be expanded",
+                Some('s'),
+            )
             .rest(SyntaxShape::ColumnPath, "Optionally operate by column path")
     }
 
     fn usage(&self) -> &str {
-        "Expand a path to its absolute form"
+        "Try to expand a path to its absolute form"
     }
 
     fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
         let tag = args.call_info.name_tag.clone();
         let args = args.evaluate_once()?;
         let cmd_args = Arc::new(PathExpandArguments {
+            strict: args.has_flag("strict"),
             rest: args.rest(0)?,
         });
 
@@ -43,32 +54,65 @@ impl WholeStreamCommand for PathExpand {
 
     #[cfg(windows)]
     fn examples(&self) -> Vec<Example> {
-        vec![Example {
-            description: "Expand relative directories",
-            example: "echo 'C:\\Users\\joe\\foo\\..\\bar' | path expand",
-            result: None,
-            // fails to canonicalize into Some(vec![Value::from("C:\\Users\\joe\\bar")]) due to non-existing path
-        }]
+        vec![
+            Example {
+                description: "Expand an absolute path",
+                example: r"'C:\Users\joe\foo\..\bar' | path expand",
+                result: Some(vec![
+                    UntaggedValue::filepath(r"C:\Users\joe\bar").into_value(Span::new(0, 25))
+                ]),
+            },
+            Example {
+                description: "Expand a relative path",
+                example: r"'foo\..\bar' | path expand",
+                result: Some(vec![
+                    UntaggedValue::filepath("bar").into_value(Span::new(0, 12))
+                ]),
+            },
+        ]
     }
 
     #[cfg(not(windows))]
     fn examples(&self) -> Vec<Example> {
-        vec![Example {
-            description: "Expand relative directories",
-            example: "echo '/home/joe/foo/../bar' | path expand",
-            result: None,
-            // fails to canonicalize into Some(vec![Value::from("/home/joe/bar")]) due to non-existing path
-        }]
+        vec![
+            Example {
+                description: "Expand an absolute path",
+                example: "'/home/joe/foo/../bar' | path expand",
+                result: Some(vec![
+                    UntaggedValue::filepath("/home/joe/bar").into_value(Span::new(0, 22))
+                ]),
+            },
+            Example {
+                description: "Expand a relative path",
+                example: "'foo/../bar' | path expand",
+                result: Some(vec![
+                    UntaggedValue::filepath("bar").into_value(Span::new(0, 12))
+                ]),
+            },
+        ]
     }
 }
 
-fn action(path: &Path, tag: Tag, _args: &PathExpandArguments) -> Value {
-    let ps = path.to_string_lossy();
-    let expanded = shellexpand::tilde(&ps);
-    let path: &Path = expanded.as_ref().as_ref();
+fn action(path: &Path, tag: Tag, args: &PathExpandArguments) -> Value {
+    if let Ok(p) = dunce::canonicalize(path) {
+        UntaggedValue::filepath(p).into_value(tag)
+    } else if args.strict {
+        Value::error(ShellError::labeled_error(
+            "Could not expand path",
+            "could not be expanded (path might not exist, non-final \
+                    component is not a directory, or other cause)",
+            tag.span,
+        ))
+    } else {
+        // "best effort" mode, just expand tilde and resolve single/double dots
+        #[cfg(feature = "dirs")]
+        let path = match expand_tilde(path) {
+            Some(expanded) => expanded,
+            None => path.into(),
+        };
 
-    UntaggedValue::filepath(dunce::canonicalize(path).unwrap_or_else(|_| PathBuf::from(path)))
-        .into_value(tag)
+        UntaggedValue::filepath(resolve_dots(&path)).into_value(tag)
+    }
 }
 
 #[cfg(test)]

crates/nu-engine/src/filesystem/path.rs

@@ -1,6 +1,25 @@
 use std::io;
 use std::path::{Component, Path, PathBuf};
 
+pub fn resolve_dots<P>(path: P) -> PathBuf
+where
+    P: AsRef<Path>,
+{
+    let mut result = PathBuf::new();
+
+    path.as_ref()
+        .components()
+        .for_each(|component| match component {
+            Component::ParentDir => {
+                result.pop();
+            }
+            Component::CurDir => {}
+            _ => result.push(component),
+        });
+
+    dunce::simplified(&result).to_path_buf()
+}
+
 pub fn absolutize<P, Q>(relative_to: P, path: Q) -> PathBuf
 where
     P: AsRef<Path>,
@@ -67,7 +86,7 @@ where
 
 // borrowed from here https://stackoverflow.com/questions/54267608/expand-tilde-in-rust-path-idiomatically
 #[cfg(feature = "dirs")]
-fn expand_tilde<P: AsRef<Path>>(path_user_input: P) -> Option<PathBuf> {
+pub fn expand_tilde<P: AsRef<Path>>(path_user_input: P) -> Option<PathBuf> {
     let p = path_user_input.as_ref();
     if !p.starts_with("~") {
         return Some(p.to_path_buf());