feat: Show filepath context in bufferline

book/src/editor.md

@@ -3,6 +3,7 @@
 - [`[editor]` Section](#editor-section)
 - [`[editor.clipboard-provider]` Section](#editorclipboard-provider-section)
 - [`[editor.statusline]` Section](#editorstatusline-section)
+- [`[editor.bufferline]` Section](#editorbufferline-section)
 - [`[editor.lsp]` Section](#editorlsp-section)
 - [`[editor.cursor-shape]` Section](#editorcursor-shape-section)
 - [`[editor.file-picker]` Section](#editorfile-picker-section)
@@ -147,6 +148,32 @@ The following statusline elements can be configured:
 | `version-control` | The current branch name or detached commit hash of the opened workspace |
 | `register` | The current selected register |
 
+### `[editor.bufferline]` Section
+
+For simplicity, `editor.bufferline` accepts a render mode, which will use
+default settings for the rest of the configuration.
+
+```toml
+[editor]
+bufferline = "always"
+```
+
+To customize the behavior of the bufferline, the `[editor.bufferline]` section
+must be used.
+
+| Key       | Description                                    | Default     |
+| --------- | ---------------------------------------------- | ----------- |
+| `show`    | When to show the bufferline                    | `"never"`   |
+| `context` | Whether to provide additional filepath context | `"minimal"` |
+
+Example:
+
+```toml
+[editor.bufferline]
+show = "always"
+context = "none"
+```
+
 ### `[editor.lsp]` Section
 
 | Key                   | Description                                                 | Default |

helix-term/src/ui/editor.rs

@@ -25,13 +25,15 @@ use helix_core::{
 use helix_view::{
     annotations::diagnostics::DiagnosticFilter,
     document::{Mode, SCRATCH_BUFFER_NAME},
-    editor::{CompleteAction, CursorShapeConfig},
+    editor::{BufferLineContextMode, CompleteAction, CursorShapeConfig},
     graphics::{Color, CursorKind, Modifier, Rect, Style},
     input::{KeyEvent, MouseButton, MouseEvent, MouseEventKind},
     keyboard::{KeyCode, KeyModifiers},
-    Document, Editor, Theme, View,
+    Document, DocumentId, Editor, Theme, View,
+};
+use std::{
+    collections::HashMap, ffi::OsString, mem::take, num::NonZeroUsize, ops, path::PathBuf, rc::Rc,
 };
-use std::{mem::take, num::NonZeroUsize, ops, path::PathBuf, rc::Rc};
 
 use tui::{buffer::Buffer as Surface, text::Span};
 
@@ -559,8 +561,12 @@ impl EditorView {
     }
 
     /// Render bufferline at the top
-    pub fn render_bufferline(editor: &Editor, viewport: Rect, surface: &mut Surface) {
-        let scratch = PathBuf::from(SCRATCH_BUFFER_NAME); // default filename to use for scratch buffer
+    pub fn render_bufferline(
+        editor: &Editor,
+        viewport: Rect,
+        surface: &mut Surface,
+        context: &BufferLineContextMode,
+    ) {
         surface.clear_with(
             viewport,
             editor
@@ -582,14 +588,27 @@ impl EditorView {
         let mut x = viewport.x;
         let current_doc = view!(editor).doc;
 
+        let fnames = match context {
+            BufferLineContextMode::None => {
+                let scratch = PathBuf::from(SCRATCH_BUFFER_NAME); // default filename to use for scratch buffer
+                HashMap::<DocumentId, String>::from_iter(editor.documents().map(|doc| {
+                    (
+                        doc.id(),
+                        doc.path()
+                            .unwrap_or(&scratch)
+                            .file_name()
+                            .unwrap_or_default()
+                            .to_str()
+                            .unwrap_or_default()
+                            .to_owned(),
+                    )
+                }))
+            }
+            BufferLineContextMode::Minimal => expand_fname_contexts(editor, SCRATCH_BUFFER_NAME),
+        };
+
         for doc in editor.documents() {
-            let fname = doc
-                .path()
-                .unwrap_or(&scratch)
-                .file_name()
-                .unwrap_or_default()
-                .to_str()
-                .unwrap_or_default();
+            let fname = fnames.get(&doc.id()).unwrap();
 
             let style = if current_doc == doc.id() {
                 bufferline_active
@@ -1494,10 +1513,10 @@ impl Component for EditorView {
         let config = cx.editor.config();
 
         // check if bufferline should be rendered
-        use helix_view::editor::BufferLine;
-        let use_bufferline = match config.bufferline {
-            BufferLine::Always => true,
-            BufferLine::Multiple if cx.editor.documents.len() > 1 => true,
+        use helix_view::editor::BufferLineRenderMode;
+        let use_bufferline = match config.bufferline.show {
+            BufferLineRenderMode::Always => true,
+            BufferLineRenderMode::Multiple if cx.editor.documents.len() > 1 => true,
             _ => false,
         };
 
@@ -1511,7 +1530,12 @@ impl Component for EditorView {
         cx.editor.resize(editor_area);
 
         if use_bufferline {
-            Self::render_bufferline(cx.editor, area.with_height(1), surface);
+            Self::render_bufferline(
+                cx.editor,
+                area.with_height(1),
+                surface,
+                &config.bufferline.context,
+            );
         }
 
         for (view, is_focused) in cx.editor.tree.views() {
@@ -1615,3 +1639,72 @@ fn canonicalize_key(key: &mut KeyEvent) {
         key.modifiers.remove(KeyModifiers::SHIFT)
     }
 }
+
+#[derive(Default)]
+struct PathTrie {
+    parents: HashMap<OsString, PathTrie>,
+    visits: u32,
+}
+
+/// Returns a unique path ending for the current set of documents in the
+/// editor. For example, documents `a/b` and `c/d` would resolve to `b` and `d`
+/// respectively, while `a/b/c` and `a/d/c` would resolve to `b/c` and `d/c`
+/// respectively.
+fn expand_fname_contexts<'a>(editor: &'a Editor, scratch: &'a str) -> HashMap<DocumentId, String> {
+    let mut trie = HashMap::new();
+
+    // Build out a reverse prefix trie for all documents
+    for doc in editor.documents() {
+        let Some(path) = doc.path() else {
+            continue;
+        };
+
+        let mut current_subtrie = &mut trie;
+
+        for component in path.components().rev() {
+            let segment = component.as_os_str().to_os_string();
+            let subtrie = current_subtrie
+                .entry(segment)
+                .or_insert_with(PathTrie::default);
+
+            subtrie.visits += 1;
+            current_subtrie = &mut subtrie.parents;
+        }
+    }
+
+    let mut fnames = HashMap::new();
+
+    // Navigate the built reverse prefix trie to find the smallest unique path
+    for doc in editor.documents() {
+        let Some(path) = doc.path() else {
+            fnames.insert(doc.id(), scratch.to_owned());
+            continue;
+        };
+
+        let mut current_subtrie = &trie;
+        let mut built_path = vec![];
+
+        for component in path.components().rev() {
+            let segment = component.as_os_str().to_os_string();
+            let subtrie = current_subtrie
+                .get(&segment)
+                .expect("should have contained segment");
+
+            built_path.insert(0, segment);
+
+            if subtrie.visits == 1 {
+                fnames.insert(
+                    doc.id(),
+                    PathBuf::from_iter(built_path.iter())
+                        .to_string_lossy()
+                        .into_owned(),
+                );
+                break;
+            }
+
+            current_subtrie = &subtrie.parents;
+        }
+    }
+
+    fnames
+}

helix-view/src/editor.rs

@@ -56,7 +56,11 @@ use helix_dap as dap;
 use helix_lsp::lsp;
 use helix_stdx::path::canonicalize;
 
-use serde::{ser::SerializeMap, Deserialize, Deserializer, Serialize, Serializer};
+use serde::{
+    de::{self, IntoDeserializer},
+    ser::SerializeMap,
+    Deserialize, Deserializer, Serialize, Serializer,
+};
 
 use arc_swap::{
     access::{DynAccess, DynGuard},
@@ -162,6 +166,40 @@ where
     deserializer.deserialize_any(GutterVisitor)
 }
 
+fn deserialize_bufferline_show_or_struct<'de, D>(deserializer: D) -> Result<BufferLine, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    struct BufferLineVisitor;
+
+    impl<'de> serde::de::Visitor<'de> for BufferLineVisitor {
+        type Value = BufferLine;
+
+        fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
+            write!(
+                formatter,
+                "a bufferline render mode or a detailed bufferline configuration"
+            )
+        }
+
+        fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
+        where
+            E: serde::de::Error,
+        {
+            Ok(BufferLineRenderMode::deserialize(v.into_deserializer())?.into())
+        }
+
+        fn visit_map<A>(self, map: A) -> Result<Self::Value, A::Error>
+        where
+            A: serde::de::MapAccess<'de>,
+        {
+            BufferLine::deserialize(de::value::MapAccessDeserializer::new(map))
+        }
+    }
+
+    deserializer.deserialize_any(BufferLineVisitor)
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
 #[serde(rename_all = "kebab-case", default, deny_unknown_fields)]
 pub struct GutterLineNumbersConfig {
@@ -334,6 +372,7 @@ pub struct Config {
     #[serde(default)]
     pub whitespace: WhitespaceConfig,
     /// Persistently display open buffers along the top
+    #[serde(deserialize_with = "deserialize_bufferline_show_or_struct")]
     pub bufferline: BufferLine,
     /// Vertical indent width guides.
     pub indent_guides: IndentGuidesConfig,
@@ -671,10 +710,27 @@ impl Default for CursorShapeConfig {
     }
 }
 
+/// Bufferline configuration
+#[derive(Debug, Default, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "kebab-case")]
+pub struct BufferLine {
+    pub show: BufferLineRenderMode,
+    pub context: BufferLineContextMode,
+}
+
+impl From<BufferLineRenderMode> for BufferLine {
+    fn from(show: BufferLineRenderMode) -> Self {
+        Self {
+            show,
+            ..Default::default()
+        }
+    }
+}
+
 /// bufferline render modes
 #[derive(Debug, Default, Clone, PartialEq, Eq, Serialize, Deserialize)]
 #[serde(rename_all = "kebab-case")]
-pub enum BufferLine {
+pub enum BufferLineRenderMode {
     /// Don't render bufferline
     #[default]
     Never,
@@ -684,6 +740,18 @@ pub enum BufferLine {
     Multiple,
 }
 
+/// Bufferline filename context modes
+#[derive(Debug, Default, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "kebab-case")]
+pub enum BufferLineContextMode {
+    /// Don't expand filenames to be unique
+    None,
+
+    /// Expand filenames to the smallest unique path
+    #[default]
+    Minimal,
+}
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Serialize, Deserialize)]
 #[serde(rename_all = "kebab-case")]
 pub enum LineNumber {