If save-ing with non-existing parent dir, return directory_not_found (#15961)

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

@@ -91,7 +91,8 @@ impl Command for Save {
             PipelineData::ByteStream(stream, metadata) => {
                 check_saving_to_source_file(metadata.as_ref(), &path, stderr_path.as_ref())?;
 
-                let (file, stderr_file) = get_files(&path, stderr_path.as_ref(), append, force)?;
+                let (file, stderr_file) =
+                    get_files(engine_state, &path, stderr_path.as_ref(), append, force)?;
 
                 let size = stream.known_size();
                 let signals = engine_state.signals();
@@ -201,7 +202,8 @@ impl Command for Save {
                     stderr_path.as_ref(),
                 )?;
 
-                let (mut file, _) = get_files(&path, stderr_path.as_ref(), append, force)?;
+                let (mut file, _) =
+                    get_files(engine_state, &path, stderr_path.as_ref(), append, force)?;
                 for val in ls {
                     file.write_all(&value_to_bytes(val)?)
                         .map_err(&from_io_error)?;
@@ -226,7 +228,8 @@ impl Command for Save {
                     input_to_bytes(input, Path::new(&path.item), raw, engine_state, stack, span)?;
 
                 // Only open file after successful conversion
-                let (mut file, _) = get_files(&path, stderr_path.as_ref(), append, force)?;
+                let (mut file, _) =
+                    get_files(engine_state, &path, stderr_path.as_ref(), append, force)?;
 
                 file.write_all(&bytes).map_err(&from_io_error)?;
                 file.flush().map_err(&from_io_error)?;
@@ -422,13 +425,14 @@ fn prepare_path(
     }
 }
 
-fn open_file(path: &Path, span: Span, append: bool) -> Result<File, ShellError> {
-    let file: Result<File, nu_protocol::shell_error::io::ErrorKind> = match (append, path.exists())
-    {
-        (true, true) => std::fs::OpenOptions::new()
-            .append(true)
-            .open(path)
-            .map_err(|err| err.into()),
+fn open_file(
+    engine_state: &EngineState,
+    path: &Path,
+    span: Span,
+    append: bool,
+) -> Result<File, ShellError> {
+    let file: std::io::Result<File> = match (append, path.exists()) {
+        (true, true) => std::fs::OpenOptions::new().append(true).open(path),
         _ => {
             // This is a temporary solution until `std::fs::File::create` is fixed on Windows (rust-lang/rust#134893)
             // A TOCTOU problem exists here, which may cause wrong error message to be shown
@@ -438,22 +442,51 @@ fn open_file(path: &Path, span: Span, append: bool) -> Result<File, ShellError>
                     deprecated,
                     reason = "we don't get a IsADirectory error, so we need to provide it"
                 )]
-                Err(nu_protocol::shell_error::io::ErrorKind::from_std(
-                    std::io::ErrorKind::IsADirectory,
-                ))
+                Err(std::io::ErrorKind::IsADirectory.into())
             } else {
-                std::fs::File::create(path).map_err(|err| err.into())
+                std::fs::File::create(path)
             }
             #[cfg(not(target_os = "windows"))]
-            std::fs::File::create(path).map_err(|err| err.into())
+            std::fs::File::create(path)
         }
     };
 
-    file.map_err(|err_kind| ShellError::Io(IoError::new(err_kind, span, PathBuf::from(path))))
+    match file {
+        Ok(file) => Ok(file),
+        Err(err) => {
+            // In caase of NotFound, search for the missing parent directory.
+            // This also presents a TOCTOU (or TOUTOC, technically?)
+            if err.kind() == std::io::ErrorKind::NotFound {
+                if let Some(missing_component) =
+                    path.ancestors().skip(1).filter(|dir| !dir.exists()).last()
+                {
+                    // By looking at the postfix to remove, rather than the prefix
+                    // to keep, we are able to handle relative paths too.
+                    let components_to_remove = path
+                        .strip_prefix(missing_component)
+                        .expect("Stripping ancestor from a path should never fail")
+                        .as_os_str()
+                        .as_encoded_bytes();
+
+                    return Err(ShellError::Io(IoError::new(
+                        ErrorKind::DirectoryNotFound,
+                        engine_state
+                            .span_match_postfix(span, components_to_remove)
+                            .map(|(pre, _post)| pre)
+                            .unwrap_or(span),
+                        PathBuf::from(missing_component),
+                    )));
+                }
+            }
+
+            Err(ShellError::Io(IoError::new(err, span, PathBuf::from(path))))
+        }
+    }
 }
 
 /// Get output file and optional stderr file
 fn get_files(
+    engine_state: &EngineState,
     path: &Spanned<PathBuf>,
     stderr_path: Option<&Spanned<PathBuf>>,
     append: bool,
@@ -467,7 +500,7 @@ fn get_files(
         .transpose()?;
 
     // Only if both files can be used open and possibly truncate them
-    let file = open_file(path, path_span, append)?;
+    let file = open_file(engine_state, path, path_span, append)?;
 
     let stderr_file = stderr_path_and_span
         .map(|(stderr_path, stderr_path_span)| {
@@ -480,7 +513,7 @@ fn get_files(
                     inner: vec![],
                 })
             } else {
-                open_file(stderr_path, stderr_path_span, append)
+                open_file(engine_state, stderr_path, stderr_path_span, append)
             }
         })
         .transpose()?;

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

@@ -536,6 +536,39 @@ fn parent_redirection_doesnt_affect_save() {
     })
 }
 
+#[test]
+fn save_missing_parent_dir() {
+    Playground::setup("save_test_24", |dirs, sandbox| {
+        sandbox.with_files(&[]);
+
+        let actual = nu!(
+            cwd: dirs.root(),
+            r#"'hello' | save save_test_24/foobar/hello.txt"#,
+        );
+
+        assert!(actual.err.contains("nu::shell::io::directory_not_found"));
+        assert!(actual.err.contains("foobar' does not exist"));
+    })
+}
+
+#[test]
+fn save_missing_ancestor_dir() {
+    Playground::setup("save_test_24", |dirs, sandbox| {
+        sandbox.with_files(&[]);
+
+        std::fs::create_dir(dirs.test().join("foo"))
+            .expect("should have been able to create subdir for test");
+
+        let actual = nu!(
+            cwd: dirs.root(),
+            r#"'hello' | save save_test_24/foo/bar/baz/hello.txt"#,
+        );
+
+        assert!(actual.err.contains("nu::shell::io::directory_not_found"));
+        assert!(actual.err.contains("bar' does not exist"));
+    })
+}
+
 #[test]
 fn force_save_to_dir() {
     let actual = nu!(cwd: "crates/nu-command/tests/commands", r#"

crates/nu-protocol/src/engine/engine_state.rs

@@ -768,6 +768,30 @@ impl EngineState {
         &[0u8; 0]
     }
 
+    /// If the span's content starts with the given prefix, return two subspans
+    /// corresponding to this prefix, and the rest of the content.
+    pub fn span_match_prefix(&self, span: Span, prefix: &[u8]) -> Option<(Span, Span)> {
+        let contents = self.get_span_contents(span);
+
+        if contents.starts_with(prefix) {
+            span.split_at(prefix.len())
+        } else {
+            None
+        }
+    }
+
+    /// If the span's content ends with the given postfix, return two subspans
+    /// corresponding to the rest of the content, and this postfix.
+    pub fn span_match_postfix(&self, span: Span, prefix: &[u8]) -> Option<(Span, Span)> {
+        let contents = self.get_span_contents(span);
+
+        if contents.ends_with(prefix) {
+            span.split_at(span.len() - prefix.len())
+        } else {
+            None
+        }
+    }
+
     /// Get the global config from the engine state.
     ///
     /// Use [`Stack::get_config()`] instead whenever the `Stack` is available, as it takes into

crates/nu-protocol/src/span.rs

@@ -132,6 +132,45 @@ impl Span {
         Self::new(self.start - offset, self.end - offset)
     }
 
+    /// Return length of the slice.
+    pub fn len(&self) -> usize {
+        self.end - self.start
+    }
+
+    /// Indicate if slice has length 0.
+    pub fn is_empty(&self) -> bool {
+        self.start == self.end
+    }
+
+    /// Return another span fully inside the [`Span`].
+    ///
+    /// `start` and `end` are relative to `self.start`, and must lie within the `Span`.
+    /// In other words, both `start` and `end` must be `<= self.len()`.
+    pub fn subspan(&self, offset_start: usize, offset_end: usize) -> Option<Self> {
+        let len = self.len();
+
+        if offset_start > len || offset_end > len || offset_start > offset_end {
+            None
+        } else {
+            Some(Self::new(
+                self.start + offset_start,
+                self.start + offset_end,
+            ))
+        }
+    }
+
+    /// Return two spans that split the ['Span'] at the given position.
+    pub fn split_at(&self, offset: usize) -> Option<(Self, Self)> {
+        if offset < self.len() {
+            Some((
+                Self::new(self.start, self.start + offset),
+                Self::new(self.start + offset, self.end),
+            ))
+        } else {
+            None
+        }
+    }
+
     pub fn contains(&self, pos: usize) -> bool {
         self.start <= pos && pos < self.end
     }