Make file preview callback optional

When Picker and FilePicker are merged, not all Pickers will be able to
show a preview.

Co-authored-by: Gokul Soumya <gokulps15@gmail.com>

5 files changed, 121 insertions, 138 deletions

diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index 5fb4a70e..b760b692 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -2184,11 +2184,9 @@ fn global_search(cx: &mut Context) {
 
                         doc.set_selection(view.id, Selection::single(start, end));
                         align_view(doc, view, Align::Center);
-                    },
-                    |_editor, FileResult { path, line_num }| {
+                    }).with_preview(|_editor, FileResult { path, line_num }| {
                         Some((path.clone().into(), Some((*line_num, *line_num))))
-                    },
-                );
+                    });
                 compositor.push(Box::new(overlaid(picker)));
             },
         ));
@@ -2579,22 +2577,18 @@ fn buffer_picker(cx: &mut Context) {
     // mru
     items.sort_unstable_by_key(|item| std::cmp::Reverse(item.focused_at));
 
-    let picker = FilePicker::new(
-        items,
-        (),
-        |cx, meta, action| {
-            cx.editor.switch(meta.id, action);
-        },
-        |editor, meta| {
-            let doc = &editor.documents.get(&meta.id)?;
-            let &view_id = doc.selections().keys().next()?;
-            let line = doc
-                .selection(view_id)
-                .primary()
-                .cursor_line(doc.text().slice(..));
-            Some((meta.id.into(), Some((line, line))))
-        },
-    );
+    let picker = FilePicker::new(items, (), |cx, meta, action| {
+        cx.editor.switch(meta.id, action);
+    })
+    .with_preview(|editor, meta| {
+        let doc = &editor.documents.get(&meta.id)?;
+        let &view_id = doc.selections().keys().next()?;
+        let line = doc
+            .selection(view_id)
+            .primary()
+            .cursor_line(doc.text().slice(..));
+        Some((meta.id.into(), Some((line, line))))
+    });
     cx.push_layer(Box::new(overlaid(picker)));
 }
 
@@ -2678,12 +2672,12 @@ fn jumplist_picker(cx: &mut Context) {
             doc.set_selection(view.id, meta.selection.clone());
             view.ensure_cursor_in_view_center(doc, config.scrolloff);
         },
-        |editor, meta| {
-            let doc = &editor.documents.get(&meta.id)?;
-            let line = meta.selection.primary().cursor_line(doc.text().slice(..));
-            Some((meta.id.into(), Some((line, line))))
-        },
-    );
+    )
+    .with_preview(|editor, meta| {
+        let doc = &editor.documents.get(&meta.id)?;
+        let line = meta.selection.primary().cursor_line(doc.text().slice(..));
+        Some((meta.id.into(), Some((line, line))))
+    });
     cx.push_layer(Box::new(overlaid(picker)));
 }
 
diff --git a/helix-term/src/commands/dap.rs b/helix-term/src/commands/dap.rs
index 84794bed..2684e946 100644
--- a/helix-term/src/commands/dap.rs
+++ b/helix-term/src/commands/dap.rs
@@ -73,21 +73,19 @@ fn thread_picker(
             let debugger = debugger!(editor);
 
             let thread_states = debugger.thread_states.clone();
-            let picker = FilePicker::new(
-                threads,
-                thread_states,
-                move |cx, thread, _action| callback_fn(cx.editor, thread),
-                move |editor, thread| {
-                    let frames = editor.debugger.as_ref()?.stack_frames.get(&thread.id)?;
-                    let frame = frames.get(0)?;
-                    let path = frame.source.as_ref()?.path.clone()?;
-                    let pos = Some((
-                        frame.line.saturating_sub(1),
-                        frame.end_line.unwrap_or(frame.line).saturating_sub(1),
-                    ));
-                    Some((path.into(), pos))
-                },
-            );
+            let picker = FilePicker::new(threads, thread_states, move |cx, thread, _action| {
+                callback_fn(cx.editor, thread)
+            })
+            .with_preview(move |editor, thread| {
+                let frames = editor.debugger.as_ref()?.stack_frames.get(&thread.id)?;
+                let frame = frames.get(0)?;
+                let path = frame.source.as_ref()?.path.clone()?;
+                let pos = Some((
+                    frame.line.saturating_sub(1),
+                    frame.end_line.unwrap_or(frame.line).saturating_sub(1),
+                ));
+                Some((path.into(), pos))
+            });
             compositor.push(Box::new(picker));
         },
     );
@@ -728,39 +726,35 @@ pub fn dap_switch_stack_frame(cx: &mut Context) {
 
     let frames = debugger.stack_frames[&thread_id].clone();
 
-    let picker = FilePicker::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]
-                .iter()
-                .position(|f| f.id == frame.id);
-            debugger.active_frame = pos;
-
-            let frame = debugger.stack_frames[&thread_id]
-                .get(pos.unwrap_or(0))
-                .cloned();
-            if let Some(frame) = &frame {
-                jump_to_stack_frame(cx.editor, frame);
-            }
-        },
-        move |_editor, frame| {
-            frame
-                .source
-                .as_ref()
-                .and_then(|source| source.path.clone())
-                .map(|path| {
-                    (
-                        path.into(),
-                        Some((
-                            frame.line.saturating_sub(1),
-                            frame.end_line.unwrap_or(frame.line).saturating_sub(1),
-                        )),
-                    )
-                })
-        },
-    );
+    let picker = FilePicker::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]
+            .iter()
+            .position(|f| f.id == frame.id);
+        debugger.active_frame = pos;
+
+        let frame = debugger.stack_frames[&thread_id]
+            .get(pos.unwrap_or(0))
+            .cloned();
+        if let Some(frame) = &frame {
+            jump_to_stack_frame(cx.editor, frame);
+        }
+    })
+    .with_preview(move |_editor, frame| {
+        frame
+            .source
+            .as_ref()
+            .and_then(|source| source.path.clone())
+            .map(|path| {
+                (
+                    path.into(),
+                    Some((
+                        frame.line.saturating_sub(1),
+                        frame.end_line.unwrap_or(frame.line).saturating_sub(1),
+                    )),
+                )
+            })
+    });
     cx.push_layer(Box::new(picker))
 }
diff --git a/helix-term/src/commands/lsp.rs b/helix-term/src/commands/lsp.rs
index 8c3fd13b..7cc2eaf8 100644
--- a/helix-term/src/commands/lsp.rs
+++ b/helix-term/src/commands/lsp.rs
@@ -240,44 +240,40 @@ type SymbolPicker = FilePicker<SymbolInformationItem>;
 
 fn sym_picker(symbols: Vec<SymbolInformationItem>, current_path: Option<lsp::Url>) -> SymbolPicker {
     // TODO: drop current_path comparison and instead use workspace: bool flag?
-    FilePicker::new(
-        symbols,
-        current_path.clone(),
-        move |cx, item, action| {
-            let (view, doc) = current!(cx.editor);
-            push_jump(view, doc);
-
-            if current_path.as_ref() != Some(&item.symbol.location.uri) {
-                let uri = &item.symbol.location.uri;
-                let path = match uri.to_file_path() {
-                    Ok(path) => path,
-                    Err(_) => {
-                        let err = format!("unable to convert URI to filepath: {}", uri);
-                        cx.editor.set_error(err);
-                        return;
-                    }
-                };
-                if let Err(err) = cx.editor.open(&path, action) {
-                    let err = format!("failed to open document: {}: {}", uri, err);
-                    log::error!("{}", err);
+    FilePicker::new(symbols, current_path.clone(), move |cx, item, action| {
+        let (view, doc) = current!(cx.editor);
+        push_jump(view, doc);
+
+        if current_path.as_ref() != Some(&item.symbol.location.uri) {
+            let uri = &item.symbol.location.uri;
+            let path = match uri.to_file_path() {
+                Ok(path) => path,
+                Err(_) => {
+                    let err = format!("unable to convert URI to filepath: {}", uri);
                     cx.editor.set_error(err);
                     return;
                 }
+            };
+            if let Err(err) = cx.editor.open(&path, action) {
+                let err = format!("failed to open document: {}: {}", uri, err);
+                log::error!("{}", err);
+                cx.editor.set_error(err);
+                return;
             }
+        }
 
-            let (view, doc) = current!(cx.editor);
+        let (view, doc) = current!(cx.editor);
 
-            if let Some(range) =
-                lsp_range_to_range(doc.text(), item.symbol.location.range, item.offset_encoding)
-            {
-                // we flip the range so that the cursor sits on the start of the symbol
-                // (for example start of the function).
-                doc.set_selection(view.id, Selection::single(range.head, range.anchor));
-                align_view(doc, view, Align::Center);
-            }
-        },
-        move |_editor, item| Some(location_to_file_location(&item.symbol.location)),
-    )
+        if let Some(range) =
+            lsp_range_to_range(doc.text(), item.symbol.location.range, item.offset_encoding)
+        {
+            // we flip the range so that the cursor sits on the start of the symbol
+            // (for example start of the function).
+            doc.set_selection(view.id, Selection::single(range.head, range.anchor));
+            align_view(doc, view, Align::Center);
+        }
+    })
+    .with_preview(move |_editor, item| Some(location_to_file_location(&item.symbol.location)))
     .truncate_start(false)
 }
 
@@ -345,11 +341,11 @@ fn diag_picker(
                 align_view(doc, view, Align::Center);
             }
         },
-        move |_editor, PickerDiagnostic { url, diag, .. }| {
-            let location = lsp::Location::new(url.clone(), diag.range);
-            Some(location_to_file_location(&location))
-        },
     )
+    .with_preview(move |_editor, PickerDiagnostic { url, diag, .. }| {
+        let location = lsp::Location::new(url.clone(), diag.range);
+        Some(location_to_file_location(&location))
+    })
     .truncate_start(false)
 }
 
@@ -1047,14 +1043,10 @@ fn goto_impl(
             editor.set_error("No definition found.");
         }
         _locations => {
-            let picker = FilePicker::new(
-                locations,
-                cwdir,
-                move |cx, location, action| {
-                    jump_to_location(cx.editor, location, offset_encoding, action)
-                },
-                move |_editor, location| Some(location_to_file_location(location)),
-            );
+            let picker = FilePicker::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)));
             compositor.push(Box::new(overlaid(picker)));
         }
     }
diff --git a/helix-term/src/ui/mod.rs b/helix-term/src/ui/mod.rs
index ec328ec5..c5e66d86 100644
--- a/helix-term/src/ui/mod.rs
+++ b/helix-term/src/ui/mod.rs
@@ -217,21 +217,17 @@ pub fn file_picker(root: PathBuf, config: &helix_view::editor::Config) -> FilePi
 
     log::debug!("file_picker init {:?}", Instant::now().duration_since(now));
 
-    FilePicker::new(
-        files,
-        root,
-        move |cx, path: &PathBuf, action| {
-            if let Err(e) = cx.editor.open(path, action) {
-                let err = if let Some(err) = e.source() {
-                    format!("{}", err)
-                } else {
-                    format!("unable to open \"{}\"", path.display())
-                };
-                cx.editor.set_error(err);
-            }
-        },
-        |_editor, path| Some((path.clone().into(), None)),
-    )
+    FilePicker::new(files, root, move |cx, path: &PathBuf, action| {
+        if let Err(e) = cx.editor.open(path, action) {
+            let err = if let Some(err) = e.source() {
+                format!("{}", err)
+            } else {
+                format!("unable to open \"{}\"", path.display())
+            };
+            cx.editor.set_error(err);
+        }
+    })
+    .with_preview(|_editor, path| Some((path.clone().into(), None)))
 }
 
 pub mod completers {
diff --git a/helix-term/src/ui/picker.rs b/helix-term/src/ui/picker.rs
index c06918d4..001526c4 100644
--- a/helix-term/src/ui/picker.rs
+++ b/helix-term/src/ui/picker.rs
@@ -141,7 +141,7 @@ pub struct FilePicker<T: Item> {
     preview_cache: HashMap<PathBuf, CachedPreview>,
     read_buffer: Vec<u8>,
     /// Given an item in the picker, return the file path and line number to display.
-    file_fn: FileCallback<T>,
+    file_fn: Option<FileCallback<T>>,
 }
 
 impl<T: Item + 'static> FilePicker<T> {
@@ -149,7 +149,6 @@ impl<T: Item + 'static> FilePicker<T> {
         options: Vec<T>,
         editor_data: T::Data,
         callback_fn: impl Fn(&mut Context, &T, Action) + 'static,
-        preview_fn: impl Fn(&Editor, &T) -> Option<FileLocation> + 'static,
     ) -> Self {
         let prompt = Prompt::new(
             "".into(),
@@ -173,7 +172,7 @@ impl<T: Item + 'static> FilePicker<T> {
             widths: Vec::new(),
             preview_cache: HashMap::new(),
             read_buffer: Vec::with_capacity(1024),
-            file_fn: Box::new(preview_fn),
+            file_fn: None,
 
             picker: unimplemented!(),
         };
@@ -202,6 +201,14 @@ impl<T: Item + 'static> FilePicker<T> {
         self
     }
 
+    pub fn with_preview(
+        mut self,
+        preview_fn: impl Fn(&Editor, &T) -> Option<FileLocation> + 'static,
+    ) -> Self {
+        self.file_fn = Some(Box::new(preview_fn));
+        self
+    }
+
     pub fn set_options(&mut self, new_options: Vec<T>) {
         self.options = new_options;
         self.cursor = 0;
@@ -372,7 +379,7 @@ impl<T: Item + 'static> FilePicker<T> {
     fn current_file(&self, editor: &Editor) -> Option<FileLocation> {
         self.picker
             .selection()
-            .and_then(|current| (self.file_fn)(editor, current))
+            .and_then(|current| (self.file_fn.as_ref()?)(editor, current))
             .and_then(|(path_or_id, line)| path_or_id.get_canonicalized().ok().zip(Some(line)))
     }