helix-term/commands: implement buffer-close (bc, bclose) (#1035)

* helix-view/view: impl method to remove document from jumps

* helix-view/editor: impl close_document

* helix-view/editor: remove close_buffer argument from `close`

According to archseer, this was never implemented or used properly. Now
that we have a proper "buffer close" function, we can get rid of this.

* helix-term/commands: implement buffer-close (bc, bclose)

This behaves the same as Kakoune's `delete-buffer` / `db` command:

* With 3 files opened by the user with `:o ab`, `:o cd`, and `:o ef`:
  * `buffer-close` once closes `ef` and switches to `cd`
  * `buffer-close` again closes `cd` and switches to `ab`
  * `buffer-close` again closes `ab` and switches to a scratch buffer
* With 3 files opened from the command line with `hx -- ab cd ef`:
  * `buffer-close` once closes `ab` and switches to `cd`
  * `buffer-close` again closes `cd` and switches to `ef`
  * `buffer-close` again closes `ef` and switches to a scratch buffer
* With 1 file opened (`ab`):
  * `buffer-close` once closes `ab` and switches to a scratch buffer
  * `buffer-close` again closes the scratch buffer and switches to a new
    scratch buffer

* helix-term/commands: implement buffer-close! (bclose!, bc!)

Namely, if you have a document open in multiple splits, all the splits
will  be closed at the same time, leaving only splits without that
document focused (or a scratch buffer if they were all focused on that
buffer).

* helix-view/tree: reset focus if Tree is empty

4 files changed, 135 insertions, 35 deletions

diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index 8c0a005c..c7aab726 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -1700,8 +1700,7 @@ mod cmd {
             buffers_remaining_impl(cx.editor)?
         }
 
-        cx.editor
-            .close(view!(cx.editor).id, /* close_buffer */ false);
+        cx.editor.close(view!(cx.editor).id);
 
         Ok(())
     }
@@ -1711,8 +1710,7 @@ mod cmd {
         _args: &[&str],
         _event: PromptEvent,
     ) -> anyhow::Result<()> {
-        cx.editor
-            .close(view!(cx.editor).id, /* close_buffer */ false);
+        cx.editor.close(view!(cx.editor).id);
 
         Ok(())
     }
@@ -1730,6 +1728,28 @@ mod cmd {
         Ok(())
     }
 
+    fn buffer_close(
+        cx: &mut compositor::Context,
+        _args: &[&str],
+        _event: PromptEvent,
+    ) -> anyhow::Result<()> {
+        let view = view!(cx.editor);
+        let doc_id = view.doc;
+        cx.editor.close_document(doc_id, false)?;
+        Ok(())
+    }
+
+    fn force_buffer_close(
+        cx: &mut compositor::Context,
+        _args: &[&str],
+        _event: PromptEvent,
+    ) -> anyhow::Result<()> {
+        let view = view!(cx.editor);
+        let doc_id = view.doc;
+        cx.editor.close_document(doc_id, true)?;
+        Ok(())
+    }
+
     fn write_impl<P: AsRef<Path>>(
         cx: &mut compositor::Context,
         path: Option<P>,
@@ -1976,7 +1996,7 @@ mod cmd {
             // close all views
             let views: Vec<_> = cx.editor.tree.views().map(|(view, _)| view.id).collect();
             for view_id in views {
-                cx.editor.close(view_id, false);
+                cx.editor.close(view_id);
             }
         }
 
@@ -2020,7 +2040,7 @@ mod cmd {
         // close all views
         let views: Vec<_> = editor.tree.views().map(|(view, _)| view.id).collect();
         for view_id in views {
-            editor.close(view_id, false);
+            editor.close(view_id);
         }
 
         Ok(())
@@ -2333,6 +2353,20 @@ mod cmd {
             completer: Some(completers::filename),
         },
         TypableCommand {
+          name: "buffer-close",
+          aliases: &["bc", "bclose"],
+          doc: "Close the current buffer.",
+          fun: buffer_close,
+          completer: None, // FIXME: buffer completer
+        },
+        TypableCommand {
+          name: "buffer-close!",
+          aliases: &["bc!", "bclose!"],
+          doc: "Close the current buffer forcefully (ignoring unsaved changes).",
+          fun: force_buffer_close,
+          completer: None, // FIXME: buffer completer
+        },
+        TypableCommand {
             name: "write",
             aliases: &["w"],
             doc: "Write changes to disk. Accepts an optional path (:write some/path.txt)",
@@ -4914,7 +4948,7 @@ fn wclose(cx: &mut Context) {
     }
     let view_id = view!(cx.editor).id;
     // close current split
-    cx.editor.close(view_id, /* close_buffer */ false);
+    cx.editor.close(view_id);
 }
 
 fn wonly(cx: &mut Context) {
@@ -4926,7 +4960,7 @@ fn wonly(cx: &mut Context) {
         .collect::<Vec<_>>();
     for (view_id, focus) in views {
         if !focus {
-            cx.editor.close(view_id, /* close_buffer */ false);
+            cx.editor.close(view_id);
         }
     }
 }
diff --git a/helix-view/src/editor.rs b/helix-view/src/editor.rs
index e4015707..4712c52a 100644
--- a/helix-view/src/editor.rs
+++ b/helix-view/src/editor.rs
@@ -22,7 +22,7 @@ use anyhow::Error;
 pub use helix_core::diagnostic::Severity;
 pub use helix_core::register::Registers;
 use helix_core::syntax;
-use helix_core::Position;
+use helix_core::{Position, Selection};
 
 use serde::Deserialize;
 
@@ -235,9 +235,28 @@ impl Editor {
         }
     }
 
+    fn replace_document_in_view(&mut self, current_view: ViewId, doc_id: DocumentId) {
+        let view = self.tree.get_mut(current_view);
+        view.doc = doc_id;
+        view.offset = Position::default();
+
+        let doc = self.documents.get_mut(&doc_id).unwrap();
+
+        // initialize selection for view
+        doc.selections
+            .entry(view.id)
+            .or_insert_with(|| Selection::point(0));
+        // TODO: reuse align_view
+        let pos = doc
+            .selection(view.id)
+            .primary()
+            .cursor(doc.text().slice(..));
+        let line = doc.text().char_to_line(pos);
+        view.offset.row = line.saturating_sub(view.inner_area().height as usize / 2);
+    }
+
     pub fn switch(&mut self, id: DocumentId, action: Action) {
         use crate::tree::Layout;
-        use helix_core::Selection;
 
         if !self.documents.contains_key(&id) {
             log::error!("cannot switch to document that does not exist (anymore)");
@@ -271,22 +290,9 @@ impl Editor {
                     view.jumps.push(jump);
                     view.last_accessed_doc = Some(view.doc);
                 }
-                view.doc = id;
-                view.offset = Position::default();
-
-                let (view, doc) = current!(self);
 
-                // initialize selection for view
-                doc.selections
-                    .entry(view.id)
-                    .or_insert_with(|| Selection::point(0));
-                // TODO: reuse align_view
-                let pos = doc
-                    .selection(view.id)
-                    .primary()
-                    .cursor(doc.text().slice(..));
-                let line = doc.text().char_to_line(pos);
-                view.offset.row = line.saturating_sub(view.inner_area().height as usize / 2);
+                let view_id = view.id;
+                self.replace_document_in_view(view_id, id);
 
                 return;
             }
@@ -318,11 +324,16 @@ impl Editor {
         self._refresh();
     }
 
-    fn new_file_from_document(&mut self, action: Action, mut document: Document) -> DocumentId {
+    fn new_document(&mut self, mut document: Document) -> DocumentId {
         let id = DocumentId(self.next_document_id);
         self.next_document_id += 1;
         document.id = id;
         self.documents.insert(id, document);
+        id
+    }
+
+    fn new_file_from_document(&mut self, action: Action, document: Document) -> DocumentId {
+        let id = self.new_document(document);
         self.switch(id, action);
         id
     }
@@ -392,7 +403,7 @@ impl Editor {
         Ok(id)
     }
 
-    pub fn close(&mut self, id: ViewId, close_buffer: bool) {
+    pub fn close(&mut self, id: ViewId) {
         let view = self.tree.get(self.tree.focus);
         // remove selection
         self.documents
@@ -401,18 +412,66 @@ impl Editor {
             .selections
             .remove(&id);
 
-        if close_buffer {
-            // get around borrowck issues
-            let doc = &self.documents[&view.doc];
+        self.tree.remove(id);
+        self._refresh();
+    }
 
-            if let Some(language_server) = doc.language_server() {
-                tokio::spawn(language_server.text_document_did_close(doc.identifier()));
-            }
-            self.documents.remove(&view.doc);
+    pub fn close_document(&mut self, doc_id: DocumentId, force: bool) -> anyhow::Result<()> {
+        let doc = match self.documents.get(&doc_id) {
+            Some(doc) => doc,
+            None => anyhow::bail!("document does not exist"),
+        };
+
+        if !force && doc.is_modified() {
+            anyhow::bail!(
+                "buffer {:?} is modified",
+                doc.relative_path()
+                    .map(|path| path.to_string_lossy().to_string())
+                    .unwrap_or_else(|| "[scratch]".into())
+            );
+        }
+
+        if let Some(language_server) = doc.language_server() {
+            tokio::spawn(language_server.text_document_did_close(doc.identifier()));
+        }
+
+        let views_to_close = self
+            .tree
+            .views()
+            .filter_map(|(view, _focus)| {
+                if view.doc == doc_id {
+                    Some(view.id)
+                } else {
+                    None
+                }
+            })
+            .collect::<Vec<_>>();
+
+        for view_id in views_to_close {
+            self.close(view_id);
+        }
+
+        self.documents.remove(&doc_id);
+
+        // If the document we removed was visible in all views, we will have no more views. We don't
+        // want to close the editor just for a simple buffer close, so we need to create a new view
+        // containing either an existing document, or a brand new document.
+        if self.tree.views().peekable().peek().is_none() {
+            let doc_id = self
+                .documents
+                .iter()
+                .map(|(&doc_id, _)| doc_id)
+                .next()
+                .unwrap_or_else(|| self.new_document(Document::default()));
+            let view = View::new(doc_id);
+            let view_id = self.tree.insert(view);
+            let doc = self.documents.get_mut(&doc_id).unwrap();
+            doc.selections.insert(view_id, Selection::point(0));
         }
 
-        self.tree.remove(id);
         self._refresh();
+
+        Ok(())
     }
 
     pub fn resize(&mut self, area: Rect) {
diff --git a/helix-view/src/tree.rs b/helix-view/src/tree.rs
index 064334b1..de5046ac 100644
--- a/helix-view/src/tree.rs
+++ b/helix-view/src/tree.rs
@@ -314,6 +314,9 @@ impl Tree {
 
     pub fn recalculate(&mut self) {
         if self.is_empty() {
+            // There are no more views, so the tree should focus itself again.
+            self.focus = self.root;
+
             return;
         }
 
diff --git a/helix-view/src/view.rs b/helix-view/src/view.rs
index 6a624ded..a77f1562 100644
--- a/helix-view/src/view.rs
+++ b/helix-view/src/view.rs
@@ -54,6 +54,10 @@ impl JumpList {
             None
         }
     }
+
+    pub fn remove(&mut self, doc_id: &DocumentId) {
+        self.jumps.retain(|(other_id, _)| other_id != doc_id);
+    }
 }
 
 #[derive(Debug)]