Merge pull request #2252 from jfinkels/realpath-simplify

realpath: use uucore::fs::canonicalize() to reduce code duplication

src/uu/realpath/src/realpath.rs

@@ -11,7 +11,6 @@
 extern crate uucore;
 
 use clap::{App, Arg};
-use std::fs;
 use std::path::{Path, PathBuf};
 use uucore::fs::{canonicalize, CanonicalizeMode};
 
@@ -75,64 +74,35 @@ pub fn uumain(args: impl uucore::Args) -> i32 {
     let quiet = matches.is_present(OPT_QUIET);
     let mut retcode = 0;
     for path in &paths {
-        if !resolve_path(path, strip, zero, quiet) {
+        if let Err(e) = resolve_path(path, strip, zero) {
+            if !quiet {
+                show_error!("{}: {}", e, path.display());
+            }
             retcode = 1
         };
     }
     retcode
 }
 
-fn resolve_path(p: &Path, strip: bool, zero: bool, quiet: bool) -> bool {
-    let abs = canonicalize(p, CanonicalizeMode::Normal).unwrap();
-
-    if strip {
-        if zero {
-            print!("{}\0", p.display());
-        } else {
-            println!("{}", p.display())
-        }
-        return true;
-    }
-
-    let mut result = PathBuf::new();
-    let mut links_left = 256;
-
-    for part in abs.components() {
-        result.push(part.as_os_str());
-        loop {
-            if links_left == 0 {
-                if !quiet {
-                    show_error!("Too many symbolic links: {}", p.display())
-                };
-                return false;
-            }
-            match fs::metadata(result.as_path()) {
-                Err(_) => break,
-                Ok(ref m) if !m.file_type().is_symlink() => break,
-                Ok(_) => {
-                    links_left -= 1;
-                    match fs::read_link(result.as_path()) {
-                        Ok(x) => {
-                            result.pop();
-                            result.push(x.as_path());
-                        }
-                        _ => {
-                            if !quiet {
-                                show_error!("Invalid path: {}", p.display())
-                            };
-                            return false;
-                        }
-                    }
-                }
-            }
-        }
-    }
-
-    if zero {
-        print!("{}\0", result.display());
+/// Resolve a path to an absolute form and print it.
+///
+/// If `strip` is `true`, then this function does not attempt to resolve
+/// symbolic links in the path. If `zero` is `true`, then this function
+/// prints the path followed by the null byte (`'\0'`) instead of a
+/// newline character (`'\n'`).
+///
+/// # Errors
+///
+/// This function returns an error if there is a problem resolving
+/// symbolic links.
+fn resolve_path(p: &Path, strip: bool, zero: bool) -> std::io::Result<()> {
+    let mode = if strip {
+        CanonicalizeMode::None
     } else {
-        println!("{}", result.display());
-    }
-
-    true
+        CanonicalizeMode::Normal
+    };
+    let abs = canonicalize(p, mode)?;
+    let line_ending = if zero { '\0' } else { '\n' };
+    print!("{}{}", abs.display(), line_ending);
+    Ok(())
 }

src/uucore/src/lib/features/fs.rs

@@ -54,11 +54,19 @@ pub fn resolve_relative_path(path: &Path) -> Cow<Path> {
     result.into()
 }
 
+/// Controls how symbolic links should be handled when canonicalizing a path.
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
 pub enum CanonicalizeMode {
+    /// Do not resolve any symbolic links.
     None,
+
+    /// Resolve all symbolic links.
     Normal,
+
+    /// Resolve symbolic links, ignoring errors on the final component.
     Existing,
+
+    /// Resolve symbolic links, ignoring errors on the non-final components.
     Missing,
 }
 
@@ -125,6 +133,24 @@ fn resolve<P: AsRef<Path>>(original: P) -> IOResult<PathBuf> {
     Ok(result)
 }
 
+/// Return the canonical, absolute form of a path.
+///
+/// This function is a generalization of [`std::fs::canonicalize`] that
+/// allows controlling how symbolic links are resolved and how to deal
+/// with missing components. It returns the canonical, absolute form of
+/// a path. The `can_mode` parameter controls how symbolic links are
+/// resolved:
+///
+/// * [`CanonicalizeMode::Normal`] makes this function behave like
+///   [`std::fs::canonicalize`], resolving symbolic links and returning
+///   an error if the path does not exist.
+/// * [`CanonicalizeMode::Missing`] makes this function ignore non-final
+///   components of the path that could not be resolved.
+/// * [`CanonicalizeMode::Existing`] makes this function return an error
+///   if the final component of the path does not exist.
+/// * [`CanonicalizeMode::None`] makes this function not try to resolve
+///   any symbolic links.
+///
 pub fn canonicalize<P: AsRef<Path>>(original: P, can_mode: CanonicalizeMode) -> IOResult<PathBuf> {
     // Create an absolute path
     let original = original.as_ref();
@@ -180,6 +206,10 @@ pub fn canonicalize<P: AsRef<Path>>(original: P, can_mode: CanonicalizeMode) ->
 
         result.push(parts.last().unwrap());
 
+        if can_mode == CanonicalizeMode::None {
+            return Ok(result);
+        }
+
         match resolve(&result) {
             Err(e) => {
                 if can_mode == CanonicalizeMode::Existing {