Mark buffers created from stdin as modified (helix-editor#7431)

This resolves some confusing behavior where a scratch document created
by piping into hx is discarded when navigating away from that document.

We discard any scratch documents that are not modified and the original
`Editor::new_file_from_stdin` would create unmodified documents. We
refactor this function to create an empty document first and then to
apply the text from stdin as a change.

helix-view/src/document.rs

@@ -397,33 +397,11 @@ pub fn from_reader<R: std::io::Read + ?Sized>(
     let mut buf_out = [0u8; BUF_SIZE];
     let mut builder = RopeBuilder::new();
 
-    // By default, the encoding of the text is auto-detected by
-    // `encoding_rs` for_bom, and if it fails, from `chardetng`
-    // crate which requires sample data from the reader.
-    // As a manual override to this auto-detection is possible, the
-    // same data is read into `buf` to ensure symmetry in the upcoming
-    // loop.
-    let (encoding, has_bom, mut decoder, mut slice, mut is_empty) = {
-        let read = reader.read(&mut buf)?;
-        let is_empty = read == 0;
-        let (encoding, has_bom) = encoding
-            .map(|encoding| (encoding, false))
-            .or_else(|| {
-                encoding::Encoding::for_bom(&buf).map(|(encoding, _bom_size)| (encoding, true))
-            })
-            .unwrap_or_else(|| {
-                let mut encoding_detector = chardetng::EncodingDetector::new();
-                encoding_detector.feed(&buf, is_empty);
-                (encoding_detector.guess(None, true), false)
-            });
-
-        let decoder = encoding.new_decoder();
+    let (encoding, has_bom, mut decoder, read) =
+        read_and_detect_encoding(reader, encoding, &mut buf)?;
 
-        // If the amount of bytes read from the reader is less than
-        // `buf.len()`, it is undesirable to read the bytes afterwards.
-        let slice = &buf[..read];
-        (encoding, has_bom, decoder, slice, is_empty)
-    };
+    let mut slice = &buf[..read];
+    let mut is_empty = read == 0;
 
     // `RopeBuilder::append()` expects a `&str`, so this is the "real"
     // output buffer. When decoding, the number of bytes in the output
@@ -493,6 +471,81 @@ pub fn from_reader<R: std::io::Read + ?Sized>(
     Ok((rope, encoding, has_bom))
 }
 
+pub fn read_to_string<R: std::io::Read + ?Sized>(
+    reader: &mut R,
+    encoding: Option<&'static Encoding>,
+) -> Result<(String, &'static Encoding, bool), Error> {
+    let mut buf = [0u8; BUF_SIZE];
+
+    let (encoding, has_bom, mut decoder, read) =
+        read_and_detect_encoding(reader, encoding, &mut buf)?;
+
+    let mut slice = &buf[..read];
+    let mut is_empty = read == 0;
+    let mut buf_string = String::with_capacity(buf.len());
+
+    loop {
+        let mut total_read = 0usize;
+
+        loop {
+            let (result, read, ..) =
+                decoder.decode_to_string(&slice[total_read..], &mut buf_string, is_empty);
+
+            total_read += read;
+
+            match result {
+                encoding::CoderResult::InputEmpty => {
+                    debug_assert_eq!(slice.len(), total_read);
+                    break;
+                }
+                encoding::CoderResult::OutputFull => {
+                    debug_assert!(slice.len() > total_read);
+                    buf_string.reserve(buf.len())
+                }
+            }
+        }
+
+        if is_empty {
+            debug_assert_eq!(reader.read(&mut buf)?, 0);
+            break;
+        }
+
+        let read = reader.read(&mut buf)?;
+        slice = &buf[..read];
+        is_empty = read == 0;
+    }
+    Ok((buf_string, encoding, has_bom))
+}
+
+/// Reads the first chunk from a Reader into the given buffer
+/// and detects the encoding.
+///
+/// By default, the encoding of the text is auto-detected by
+/// `encoding_rs` for_bom, and if it fails, from `chardetng`
+/// crate which requires sample data from the reader.
+/// As a manual override to this auto-detection is possible, the
+/// same data is read into `buf` to ensure symmetry in the upcoming
+/// loop.
+fn read_and_detect_encoding<R: std::io::Read + ?Sized>(
+    reader: &mut R,
+    encoding: Option<&'static Encoding>,
+    buf: &mut [u8],
+) -> Result<(&'static Encoding, bool, encoding::Decoder, usize), Error> {
+    let read = reader.read(buf)?;
+    let is_empty = read == 0;
+    let (encoding, has_bom) = encoding
+        .map(|encoding| (encoding, false))
+        .or_else(|| encoding::Encoding::for_bom(buf).map(|(encoding, _bom_size)| (encoding, true)))
+        .unwrap_or_else(|| {
+            let mut encoding_detector = chardetng::EncodingDetector::new();
+            encoding_detector.feed(buf, is_empty);
+            (encoding_detector.guess(None, true), false)
+        });
+    let decoder = encoding.new_decoder();
+
+    Ok((encoding, has_bom, decoder, read))
+}
+
 // The documentation and implementation of this function should be up-to-date with
 // its sibling function, `from_reader()`.
 //

helix-view/src/editor.rs

@@ -1386,11 +1386,22 @@ impl Editor {
     }
 
     pub fn new_file_from_stdin(&mut self, action: Action) -> Result<DocumentId, Error> {
-        let (rope, encoding, has_bom) = crate::document::from_reader(&mut stdin(), None)?;
-        Ok(self.new_file_from_document(
-            action,
-            Document::from(rope, Some((encoding, has_bom)), self.config.clone()),
-        ))
+        let (stdin, encoding, has_bom) = crate::document::read_to_string(&mut stdin(), None)?;
+        let doc = Document::from(
+            helix_core::Rope::default(),
+            Some((encoding, has_bom)),
+            self.config.clone(),
+        );
+        let doc_id = self.new_file_from_document(action, doc);
+        let doc = doc_mut!(self, &doc_id);
+        let view = view_mut!(self);
+        doc.ensure_view_init(view.id);
+        let transaction =
+            helix_core::Transaction::insert(doc.text(), doc.selection(view.id), stdin.into())
+                .with_selection(Selection::point(0));
+        doc.apply(&transaction, view.id);
+        doc.append_changes_to_history(view);
+        Ok(doc_id)
     }
 
     // ??? possible use for integration tests