`:reload` (#374)

* reloading functionality

* fn with_newline_eof()

* fmt

* wip

* wip

* wip

* wip

* moved to core, added simd feature for encoding_rs

* wip

* rm

* .gitignore

* wip

* local wip

* wip

* wip

* no features

* wip

* nit

* remove simd

* doc

* clippy

* clippy

* address comments

* add indentation & line ending change

1 files changed, 53 insertions, 8 deletions

diff --git a/helix-view/src/document.rs b/helix-view/src/document.rs
index 0f1f3a8f..f85ded11 100644
--- a/helix-view/src/document.rs
+++ b/helix-view/src/document.rs
@@ -307,6 +307,19 @@ pub async fn to_writer<'a, W: tokio::io::AsyncWriteExt + Unpin + ?Sized>(
     Ok(())
 }
 
+/// Inserts the final line ending into `rope` if it's missing. [Why?](https://stackoverflow.com/questions/729692/why-should-text-files-end-with-a-newline)
+pub fn with_line_ending(rope: &mut Rope) -> LineEnding {
+    // search for line endings
+    let line_ending = auto_detect_line_ending(rope).unwrap_or(DEFAULT_LINE_ENDING);
+
+    // add missing newline at the end of file
+    if rope.len_bytes() == 0 || !char_is_line_ending(rope.char(rope.len_chars() - 1)) {
+        rope.insert(rope.len_chars(), line_ending.as_str());
+    }
+
+    line_ending
+}
+
 /// Like std::mem::replace() except it allows the replacement value to be mapped from the
 /// original value.
 fn take_with<T, F>(mut_ref: &mut T, closure: F)
@@ -449,14 +462,7 @@ impl Document {
 
         let mut file = std::fs::File::open(&path).context(format!("unable to open {:?}", path))?;
         let (mut rope, encoding) = from_reader(&mut file, encoding)?;
-
-        // search for line endings
-        let line_ending = auto_detect_line_ending(&rope).unwrap_or(DEFAULT_LINE_ENDING);
-
-        // add missing newline at the end of file
-        if rope.len_bytes() == 0 || !char_is_line_ending(rope.char(rope.len_chars() - 1)) {
-            rope.insert(rope.len_chars(), line_ending.as_str());
-        }
+        let line_ending = with_line_ending(&mut rope);
 
         let mut doc = Self::from(rope, Some(encoding));
 
@@ -586,6 +592,45 @@ impl Document {
         }
     }
 
+    /// Reload the document from its path.
+    pub fn reload(&mut self, view_id: ViewId) -> Result<(), Error> {
+        let encoding = &self.encoding;
+        let path = self.path().filter(|path| path.exists());
+
+        // If there is no path or the path no longer exists.
+        if path.is_none() {
+            return Err(anyhow!("can't find file to reload from"));
+        }
+
+        let mut file = std::fs::File::open(path.unwrap())?;
+        let (mut rope, ..) = from_reader(&mut file, Some(encoding))?;
+        let line_ending = with_line_ending(&mut rope);
+
+        let transaction = helix_core::diff::compare_ropes(self.text(), &rope);
+        self.apply(&transaction, view_id);
+        self.append_changes_to_history(view_id);
+
+        // Detect indentation style and set line ending.
+        self.detect_indent_style();
+        self.line_ending = line_ending;
+
+        Ok(())
+    }
+
+    /// Sets the [`Document`]'s encoding with the encoding correspondent to `label`.
+    pub fn set_encoding(&mut self, label: &str) -> Result<(), Error> {
+        match encoding_rs::Encoding::for_label(label.as_bytes()) {
+            Some(encoding) => self.encoding = encoding,
+            None => return Err(anyhow::anyhow!("unknown encoding")),
+        }
+        Ok(())
+    }
+
+    /// Returns the [`Document`]'s current encoding.
+    pub fn encoding(&self) -> &'static encoding_rs::Encoding {
+        self.encoding
+    }
+
     fn detect_indent_style(&mut self) {
         // Build a histogram of the indentation *increases* between
         // subsequent lines, ignoring lines that are all whitespace.