Provide file-picker navigation

We provide the following new keybindings while in a picker:
* `C-e` - Change picker root to one directory in, based on selection
* `C-a` - Change picker root to one directory out

These can be especially useful when combined with the command
`file_picker_in_current_buffer_directory` when navigating library
files.

That is, with this change the following flow is enabled:
1. Perform a `goto_defition` on a symbol defined in an external library.
2. Perform `file_picker_in_current_buffer_directory`, opening a picker
   in the external library.
3. Browse the external library with `C-e` and `C-a`, which is not
   possible without this change.

To accomplish this, we need access to a `FilePickerConfig` not just
when building the picker, but also later, so we add an associated
`Item::Config` type, which is simply `()` for everything except
`PathBuf`.

To make it easier to follow what is going on when navigating the
picker, we set the status bar to the picker's root directory on change.

book/src/keymap.md

@@ -425,6 +425,8 @@ Keys to use within picker. Remapping currently not supported.
 | `Ctrl-v`                     | Open vertically                                            |
 | `Ctrl-t`                     | Toggle preview                                             |
 | `Escape`, `Ctrl-c`           | Close picker                                               |
+| `Ctrl-e`                     | Change picker root to one directory in, based on selection |
+| `Ctrl-a`                     | Change picker root to one directory out                    |
 
 ## Prompt
 

helix-term/src/application.rs

@@ -166,7 +166,7 @@ impl Application {
             if first.is_dir() {
                 helix_loader::set_current_working_dir(first.clone())?;
                 editor.new_file(Action::VerticalSplit);
-                let picker = ui::file_picker(".".into(), &config.load().editor);
+                let picker = ui::file_picker(".".into(), editor.config().file_picker);
                 compositor.push(Box::new(overlaid(picker)));
             } else {
                 let nr_of_files = args.files.len();

helix-term/src/commands.rs

@@ -1194,7 +1194,7 @@ fn goto_file_impl(cx: &mut Context, action: Action) {
         if !p.is_empty() {
             let path = &rel_path.join(p);
             if path.is_dir() {
-                let picker = ui::file_picker(path.into(), &cx.editor.config());
+                let picker = ui::file_picker(path.into(), cx.editor.config().file_picker);
                 cx.push_layer(Box::new(overlaid(picker)));
             } else if let Err(e) = cx.editor.open(path, action) {
                 cx.editor.set_error(format!("Open file failed: {:?}", e));
@@ -2114,6 +2114,7 @@ fn global_search(cx: &mut Context) {
 
     impl ui::menu::Item for FileResult {
         type Data = Option<PathBuf>;
+        type Config = ();
 
         fn format(&self, current_path: &Self::Data) -> Row {
             let relative_path = helix_core::path::get_relative_path(&self.path)
@@ -2649,7 +2650,7 @@ fn file_picker(cx: &mut Context) {
         cx.editor.set_error("Workspace directory does not exist");
         return;
     }
-    let picker = ui::file_picker(root, &cx.editor.config());
+    let picker = ui::file_picker(root, cx.editor.config().file_picker);
     cx.push_layer(Box::new(overlaid(picker)));
 }
 
@@ -2666,7 +2667,7 @@ fn file_picker_in_current_buffer_directory(cx: &mut Context) {
         }
     };
 
-    let picker = ui::file_picker(path, &cx.editor.config());
+    let picker = ui::file_picker(path, cx.editor.config().file_picker);
     cx.push_layer(Box::new(overlaid(picker)));
 }
 
@@ -2677,7 +2678,7 @@ fn file_picker_in_current_directory(cx: &mut Context) {
             .set_error("Current working directory does not exist");
         return;
     }
-    let picker = ui::file_picker(cwd, &cx.editor.config());
+    let picker = ui::file_picker(cwd, cx.editor.config().file_picker);
     cx.push_layer(Box::new(overlaid(picker)));
 }
 
@@ -2694,6 +2695,7 @@ fn buffer_picker(cx: &mut Context) {
 
     impl ui::menu::Item for BufferMeta {
         type Data = ();
+        type Config = ();
 
         fn format(&self, _data: &Self::Data) -> Row {
             let path = self
@@ -2735,7 +2737,7 @@ fn buffer_picker(cx: &mut Context) {
     // mru
     items.sort_unstable_by_key(|item| std::cmp::Reverse(item.focused_at));
 
-    let picker = Picker::new(items, (), |cx, meta, action| {
+    let picker = Picker::new((), items, (), |cx, meta, action| {
         cx.editor.switch(meta.id, action);
     })
     .with_preview(|editor, meta| {
@@ -2761,6 +2763,7 @@ fn jumplist_picker(cx: &mut Context) {
 
     impl ui::menu::Item for JumpMeta {
         type Data = ();
+        type Config = ();
 
         fn format(&self, _data: &Self::Data) -> Row {
             let path = self
@@ -2813,6 +2816,7 @@ fn jumplist_picker(cx: &mut Context) {
     };
 
     let picker = Picker::new(
+        (),
         cx.editor
             .tree
             .views()
@@ -2843,6 +2847,7 @@ fn jumplist_picker(cx: &mut Context) {
 
 impl ui::menu::Item for MappableCommand {
     type Data = ReverseKeymap;
+    type Config = ();
 
     fn format(&self, keymap: &Self::Data) -> Row {
         let fmt_binding = |bindings: &Vec<Vec<KeyEvent>>| -> String {
@@ -2889,7 +2894,7 @@ pub fn command_palette(cx: &mut Context) {
                 }
             }));
 
-            let picker = Picker::new(commands, keymap, move |cx, command, _action| {
+            let picker = Picker::new((), commands, keymap, move |cx, command, _action| {
                 let mut ctx = Context {
                     register,
                     count,

helix-term/src/commands/dap.rs

@@ -24,6 +24,7 @@ use helix_view::handlers::dap::{breakpoints_changed, jump_to_stack_frame, select
 
 impl ui::menu::Item for StackFrame {
     type Data = ();
+    type Config = ();
 
     fn format(&self, _data: &Self::Data) -> Row {
         self.name.as_str().into() // TODO: include thread_states in the label
@@ -32,6 +33,7 @@ impl ui::menu::Item for StackFrame {
 
 impl ui::menu::Item for DebugTemplate {
     type Data = ();
+    type Config = ();
 
     fn format(&self, _data: &Self::Data) -> Row {
         self.name.as_str().into()
@@ -40,6 +42,7 @@ impl ui::menu::Item for DebugTemplate {
 
 impl ui::menu::Item for Thread {
     type Data = ThreadStates;
+    type Config = ();
 
     fn format(&self, thread_states: &Self::Data) -> Row {
         format!(
@@ -73,7 +76,7 @@ fn thread_picker(
             let debugger = debugger!(editor);
 
             let thread_states = debugger.thread_states.clone();
-            let picker = Picker::new(threads, thread_states, move |cx, thread, _action| {
+            let picker = Picker::new((), threads, thread_states, move |cx, thread, _action| {
                 callback_fn(cx.editor, thread)
             })
             .with_preview(move |editor, thread| {
@@ -269,6 +272,7 @@ pub fn dap_launch(cx: &mut Context) {
     let templates = config.templates.clone();
 
     cx.push_layer(Box::new(overlaid(Picker::new(
+        (),
         templates,
         (),
         |cx, template, _action| {
@@ -730,7 +734,7 @@ pub fn dap_switch_stack_frame(cx: &mut Context) {
 
     let frames = debugger.stack_frames[&thread_id].clone();
 
-    let picker = Picker::new(frames, (), move |cx, frame, _action| {
+    let picker = Picker::new((), frames, (), move |cx, frame, _action| {
         let debugger = debugger!(cx.editor);
         // TODO: this should be simpler to find
         let pos = debugger.stack_frames[&thread_id]

helix-term/src/commands/lsp.rs

@@ -70,6 +70,7 @@ macro_rules! language_server_with_feature {
 impl ui::menu::Item for lsp::Location {
     /// Current working directory.
     type Data = PathBuf;
+    type Config = ();
 
     fn format(&self, cwdir: &Self::Data) -> Row {
         // The preallocation here will overallocate a few characters since it will account for the
@@ -109,6 +110,7 @@ struct SymbolInformationItem {
 impl ui::menu::Item for SymbolInformationItem {
     /// Path to currently focussed document
     type Data = Option<lsp::Url>;
+    type Config = ();
 
     fn format(&self, current_doc_path: &Self::Data) -> Row {
         if current_doc_path.as_ref() == Some(&self.symbol.location.uri) {
@@ -145,6 +147,7 @@ struct PickerDiagnostic {
 
 impl ui::menu::Item for PickerDiagnostic {
     type Data = (DiagnosticStyles, DiagnosticsFormat);
+    type Config = ();
 
     fn format(&self, (styles, format): &Self::Data) -> Row {
         let mut style = self
@@ -242,7 +245,7 @@ type SymbolPicker = Picker<SymbolInformationItem>;
 
 fn sym_picker(symbols: Vec<SymbolInformationItem>, current_path: Option<lsp::Url>) -> SymbolPicker {
     // TODO: drop current_path comparison and instead use workspace: bool flag?
-    Picker::new(symbols, current_path, move |cx, item, action| {
+    Picker::new((), symbols, current_path, move |cx, item, action| {
         jump_to_location(
             cx.editor,
             &item.symbol.location,
@@ -292,6 +295,7 @@ fn diag_picker(
     };
 
     Picker::new(
+        (),
         flat_diag,
         (styles, format),
         move |cx,
@@ -512,6 +516,7 @@ struct CodeActionOrCommandItem {
 
 impl ui::menu::Item for CodeActionOrCommandItem {
     type Data = ();
+    type Config = ();
     fn format(&self, _data: &Self::Data) -> Row {
         match &self.lsp_item {
             lsp::CodeActionOrCommand::CodeAction(action) => action.title.as_str().into(),
@@ -754,6 +759,7 @@ pub fn code_action(cx: &mut Context) {
 
 impl ui::menu::Item for lsp::Command {
     type Data = ();
+    type Config = ();
     fn format(&self, _data: &Self::Data) -> Row {
         self.title.as_str().into()
     }
@@ -1029,7 +1035,7 @@ fn goto_impl(
             editor.set_error("No definition found.");
         }
         _locations => {
-            let picker = Picker::new(locations, cwdir, move |cx, location, action| {
+            let picker = Picker::new((), locations, cwdir, move |cx, location, action| {
                 jump_to_location(cx.editor, location, offset_encoding, action)
             })
             .with_preview(move |_editor, location| Some(location_to_file_location(location)));

helix-term/src/commands/typed.rs

@@ -116,7 +116,7 @@ fn open(cx: &mut compositor::Context, args: &[Cow<str>], event: PromptEvent) ->
             let callback = async move {
                 let call: job::Callback = job::Callback::EditorCompositor(Box::new(
                     move |editor: &mut Editor, compositor: &mut Compositor| {
-                        let picker = ui::file_picker(path, &editor.config());
+                        let picker = ui::file_picker(path, editor.config().file_picker);
                         compositor.push(Box::new(overlaid(picker)));
                     },
                 ));
@@ -1404,7 +1404,7 @@ fn lsp_workspace_command(
         let callback = async move {
             let call: job::Callback = Callback::EditorCompositor(Box::new(
                 move |_editor: &mut Editor, compositor: &mut Compositor| {
-                    let picker = ui::Picker::new(commands, (), move |cx, command, _action| {
+                    let picker = ui::Picker::new((), commands, (), move |cx, command, _action| {
                         execute_lsp_command(cx.editor, language_server_id, command.clone());
                     });
                     compositor.push(Box::new(overlaid(picker)))

helix-term/src/ui/completion.rs

@@ -19,6 +19,7 @@ use helix_lsp::{lsp, util, OffsetEncoding};
 
 impl menu::Item for CompletionItem {
     type Data = ();
+    type Config = ();
     fn sort_text(&self, data: &Self::Data) -> Cow<str> {
         self.filter_text(data)
     }

helix-term/src/ui/menu.rs

@@ -11,12 +11,17 @@ use tui::{buffer::Buffer as Surface, widgets::Table};
 
 pub use tui::widgets::{Cell, Row};
 
-use helix_view::{editor::SmartTabConfig, graphics::Rect, Editor};
+use helix_view::{
+    editor::{FilePickerConfig, SmartTabConfig},
+    graphics::Rect,
+    Editor,
+};
 use tui::layout::Constraint;
 
-pub trait Item: Sync + Send + 'static {
+pub trait Item: Sync + Send + Sized + 'static {
     /// Additional editor state that is used for label calculation.
     type Data: Sync + Send + 'static;
+    type Config;
 
     fn format(&self, data: &Self::Data) -> Row;
 
@@ -29,18 +34,30 @@ pub trait Item: Sync + Send + 'static {
         let label: String = self.format(data).cell_text().collect();
         label.into()
     }
+
+    fn goto_parent(_picker: &mut Picker<Self>, _cx: &mut Context) {}
+    fn goto_child(_picker: &mut Picker<Self>, _cx: &mut Context) {}
 }
 
 impl Item for PathBuf {
     /// Root prefix to strip.
     type Data = PathBuf;
+    type Config = FilePickerConfig;
 
     fn format(&self, root_path: &Self::Data) -> Row {
         self.strip_prefix(root_path)
             .unwrap_or(self)
             .to_string_lossy()
             .into()
     }
+
+    fn goto_parent(picker: &mut Picker<PathBuf>, cx: &mut Context) {
+        picker.goto_parent(cx);
+    }
+
+    fn goto_child(picker: &mut Picker<PathBuf>, cx: &mut Context) {
+        picker.goto_child(cx);
+    }
 }
 
 pub type MenuCallback<T> = Box<dyn Fn(&mut Editor, Option<&T>, MenuEvent)>;
@@ -230,7 +247,7 @@ impl<T: Item + PartialEq> Menu<T> {
     }
 }
 
-use super::PromptEvent as MenuEvent;
+use super::{Picker, PromptEvent as MenuEvent};
 
 impl<T: Item + 'static> Component for Menu<T> {
     fn handle_event(&mut self, event: &Event, cx: &mut Context) -> EventResult {