Foundations for Open All the Things (#9353)

This is the beginning of setting up a flexible way to open items beyond
the text buffer -- think notebooks, images, GeoJSON, etc. The primary
requirement to allow opening an arbitrary file is `try_open` on the
`project::Item` trait. Now we can make new `Item`s for other types with
their own ways to render.

Under the hood, `register_project_item` uses this new opening scheme. It
supports a dynamic array of opener functions, that will handle specific
item types. By default, a `Buffer` should be able to be able to open any
file that another opener did not.

A key detail here is that the order of registration matters. The last
item has primacy. Here's an example:

```rust
workspace::register_project_item::<Editor>(cx);
workspace::register_project_item::<Notebook>(cx);
workspace::register_project_item::<ImageViewer>(cx);
```

When a project item (file) is attempted to be opened, it's first tried
with the `ImageViewer`, followed by the `Notebook`, then the `Editor`.

The tests are set up in a way that should make it _hopefully_ easy to
learn how to write a new opener. First to go after should probably be
image files.

Release Notes:

N/A

---------

Co-authored-by: Antonio Scandurra <me@as-cii.com>
Co-authored-by: Mikayla Maki <mikayla@zed.dev>

crates/project/src/project.rs

@@ -118,6 +118,13 @@ const SERVER_LAUNCHING_BEFORE_SHUTDOWN_TIMEOUT: Duration = Duration::from_secs(5
 pub const SERVER_PROGRESS_DEBOUNCE_TIMEOUT: Duration = Duration::from_millis(100);
 
 pub trait Item {
+    fn try_open(
+        project: &Model<Project>,
+        path: &ProjectPath,
+        cx: &mut AppContext,
+    ) -> Option<Task<Result<Model<Self>>>>
+    where
+        Self: Sized;
     fn entry_id(&self, cx: &AppContext) -> Option<ProjectEntryId>;
     fn project_path(&self, cx: &AppContext) -> Option<ProjectPath>;
 }
@@ -9616,6 +9623,14 @@ fn resolve_path(base: &Path, path: &Path) -> PathBuf {
 }
 
 impl Item for Buffer {
+    fn try_open(
+        project: &Model<Project>,
+        path: &ProjectPath,
+        cx: &mut AppContext,
+    ) -> Option<Task<Result<Model<Self>>>> {
+        Some(project.update(cx, |project, cx| project.open_buffer(path.clone(), cx)))
+    }
+
     fn entry_id(&self, cx: &AppContext) -> Option<ProjectEntryId> {
         File::from_dyn(self.file()).and_then(|file| file.project_entry_id(cx))
     }

crates/workspace/src/item.rs

@@ -32,6 +32,7 @@ use std::{
     time::Duration,
 };
 use theme::Theme;
+use ui::Element as _;
 
 pub const LEADER_UPDATE_THROTTLE: Duration = Duration::from_millis(200);
 
@@ -100,6 +101,15 @@ pub struct BreadcrumbText {
 
 pub trait Item: FocusableView + EventEmitter<Self::Event> {
     type Event;
+    fn tab_content(
+        &self,
+        _detail: Option<usize>,
+        _selected: bool,
+        _cx: &WindowContext,
+    ) -> AnyElement {
+        gpui::Empty.into_any()
+    }
+    fn to_item_events(_event: &Self::Event, _f: impl FnMut(ItemEvent)) {}
 
     fn deactivated(&mut self, _: &mut ViewContext<Self>) {}
     fn workspace_deactivated(&mut self, _: &mut ViewContext<Self>) {}
@@ -112,9 +122,10 @@ pub trait Item: FocusableView + EventEmitter<Self::Event> {
     fn tab_description(&self, _: usize, _: &AppContext) -> Option<SharedString> {
         None
     }
-    fn tab_content(&self, detail: Option<usize>, selected: bool, cx: &WindowContext) -> AnyElement;
 
-    fn telemetry_event_text(&self) -> Option<&'static str>;
+    fn telemetry_event_text(&self) -> Option<&'static str> {
+        None
+    }
 
     /// (model id, Item)
     fn for_each_project_item(
@@ -170,8 +181,6 @@ pub trait Item: FocusableView + EventEmitter<Self::Event> {
         unimplemented!("reload() must be implemented if can_save() returns true")
     }
 
-    fn to_item_events(event: &Self::Event, f: impl FnMut(ItemEvent));
-
     fn act_as_type<'a>(
         &'a self,
         type_id: TypeId,
@@ -847,6 +856,14 @@ pub mod test {
     }
 
     impl project::Item for TestProjectItem {
+        fn try_open(
+            _project: &Model<Project>,
+            _path: &ProjectPath,
+            _cx: &mut AppContext,
+        ) -> Option<Task<gpui::Result<Model<Self>>>> {
+            None
+        }
+
         fn entry_id(&self, _: &AppContext) -> Option<ProjectEntryId> {
             self.entry_id
         }

crates/workspace/src/workspace.rs

@@ -26,13 +26,13 @@ use futures::{
     Future, FutureExt, StreamExt,
 };
 use gpui::{
-    actions, canvas, div, impl_actions, point, size, Action, AnyElement, AnyModel, AnyView,
-    AnyWeakView, AppContext, AsyncAppContext, AsyncWindowContext, Bounds, Context, Div,
-    DragMoveEvent, Element, ElementContext, Entity, EntityId, EventEmitter, FocusHandle,
-    FocusableView, Global, GlobalPixels, InteractiveElement, IntoElement, KeyContext, Keystroke,
-    LayoutId, ManagedView, Model, ModelContext, ParentElement, PathPromptOptions, Pixels, Point,
-    PromptLevel, Render, SharedString, Size, Styled, Subscription, Task, View, ViewContext,
-    VisualContext, WeakView, WindowContext, WindowHandle, WindowOptions,
+    actions, canvas, div, impl_actions, point, size, Action, AnyElement, AnyView, AnyWeakView,
+    AppContext, AsyncAppContext, AsyncWindowContext, Bounds, Context, Div, DragMoveEvent, Element,
+    ElementContext, Entity, EntityId, EventEmitter, FocusHandle, FocusableView, Global,
+    GlobalPixels, InteractiveElement, IntoElement, KeyContext, Keystroke, LayoutId, ManagedView,
+    Model, ModelContext, ParentElement, PathPromptOptions, Pixels, Point, PromptLevel, Render,
+    SharedString, Size, Styled, Subscription, Task, View, ViewContext, VisualContext, WeakView,
+    WindowContext, WindowHandle, WindowOptions,
 };
 use item::{FollowableItem, FollowableItemHandle, Item, ItemHandle, ItemSettings, ProjectItem};
 use itertools::Itertools;
@@ -275,17 +275,37 @@ pub fn init(app_state: Arc<AppState>, cx: &mut AppContext) {
 }
 
 #[derive(Clone, Default, Deref, DerefMut)]
-struct ProjectItemBuilders(
-    HashMap<TypeId, fn(Model<Project>, AnyModel, &mut ViewContext<Pane>) -> Box<dyn ItemHandle>>,
-);
+struct ProjectItemOpeners(Vec<ProjectItemOpener>);
 
-impl Global for ProjectItemBuilders {}
+type ProjectItemOpener = fn(
+    &Model<Project>,
+    &ProjectPath,
+    &mut WindowContext,
+)
+    -> Option<Task<Result<(Option<ProjectEntryId>, WorkspaceItemBuilder)>>>;
 
+type WorkspaceItemBuilder = Box<dyn FnOnce(&mut ViewContext<Pane>) -> Box<dyn ItemHandle>>;
+
+impl Global for ProjectItemOpeners {}
+
+/// Registers a [ProjectItem] for the app. When opening a file, all the registered
+/// items will get a chance to open the file, starting from the project item that
+/// was added last.
 pub fn register_project_item<I: ProjectItem>(cx: &mut AppContext) {
-    let builders = cx.default_global::<ProjectItemBuilders>();
-    builders.insert(TypeId::of::<I::Item>(), |project, model, cx| {
-        let item = model.downcast::<I::Item>().unwrap();
-        Box::new(cx.new_view(|cx| I::for_project_item(project, item, cx)))
+    let builders = cx.default_global::<ProjectItemOpeners>();
+    builders.push(|project, project_path, cx| {
+        let project_item = <I::Item as project::Item>::try_open(&project, project_path, cx)?;
+        let project = project.clone();
+        Some(cx.spawn(|cx| async move {
+            let project_item = project_item.await?;
+            let project_entry_id: Option<ProjectEntryId> =
+                project_item.read_with(&cx, |item, cx| project::Item::entry_id(item, cx))?;
+            let build_workspace_item = Box::new(|cx: &mut ViewContext<Pane>| {
+                Box::new(cx.new_view(|cx| I::for_project_item(project, project_item, cx)))
+                    as Box<dyn ItemHandle>
+            }) as Box<_>;
+            Ok((project_entry_id, build_workspace_item))
+        }))
     });
 }
 
@@ -2051,26 +2071,17 @@ impl Workspace {
         &mut self,
         path: ProjectPath,
         cx: &mut WindowContext,
-    ) -> Task<
-        Result<(
-            Option<ProjectEntryId>,
-            impl 'static + Send + FnOnce(&mut ViewContext<Pane>) -> Box<dyn ItemHandle>,
-        )>,
-    > {
+    ) -> Task<Result<(Option<ProjectEntryId>, WorkspaceItemBuilder)>> {
         let project = self.project().clone();
-        let project_item = project.update(cx, |project, cx| project.open_path(path, cx));
-        cx.spawn(|mut cx| async move {
-            let (project_entry_id, project_item) = project_item.await?;
-            let build_item = cx.update(|cx| {
-                cx.default_global::<ProjectItemBuilders>()
-                    .get(&project_item.entity_type())
-                    .ok_or_else(|| anyhow!("no item builder for project item"))
-                    .cloned()
-            })??;
-            let build_item =
-                move |cx: &mut ViewContext<Pane>| build_item(project, project_item, cx);
-            Ok((project_entry_id, build_item))
-        })
+        let project_item_builders = cx.default_global::<ProjectItemOpeners>().clone();
+        let Some(open_project_item) = project_item_builders
+            .iter()
+            .rev()
+            .find_map(|open_project_item| open_project_item(&project, &path, cx))
+        else {
+            return Task::ready(Err(anyhow!("cannot open file {:?}", path.path)));
+        };
+        open_project_item
     }
 
     pub fn open_project_item<T>(
@@ -4811,7 +4822,7 @@ mod tests {
         },
     };
     use fs::FakeFs;
-    use gpui::{px, DismissEvent, TestAppContext, VisualTestContext};
+    use gpui::{px, DismissEvent, Empty, TestAppContext, VisualTestContext};
     use project::{Project, ProjectEntryId};
     use serde_json::json;
     use settings::SettingsStore;
@@ -5787,6 +5798,293 @@ mod tests {
         });
     }
 
+    mod register_project_item_tests {
+        use super::*;
+
+        const TEST_PNG_KIND: &str = "TestPngItemView";
+        // View
+        struct TestPngItemView {
+            focus_handle: FocusHandle,
+        }
+        // Model
+        struct TestPngItem {}
+
+        impl project::Item for TestPngItem {
+            fn try_open(
+                _project: &Model<Project>,
+                path: &ProjectPath,
+                cx: &mut AppContext,
+            ) -> Option<Task<gpui::Result<Model<Self>>>> {
+                if path.path.extension().unwrap() == "png" {
+                    Some(cx.spawn(|mut cx| async move { cx.new_model(|_| TestPngItem {}) }))
+                } else {
+                    None
+                }
+            }
+
+            fn entry_id(&self, _: &AppContext) -> Option<ProjectEntryId> {
+                None
+            }
+
+            fn project_path(&self, _: &AppContext) -> Option<ProjectPath> {
+                None
+            }
+        }
+
+        impl Item for TestPngItemView {
+            type Event = ();
+
+            fn serialized_item_kind() -> Option<&'static str> {
+                Some(TEST_PNG_KIND)
+            }
+        }
+        impl EventEmitter<()> for TestPngItemView {}
+        impl FocusableView for TestPngItemView {
+            fn focus_handle(&self, _cx: &AppContext) -> FocusHandle {
+                self.focus_handle.clone()
+            }
+        }
+
+        impl Render for TestPngItemView {
+            fn render(&mut self, _cx: &mut ViewContext<Self>) -> impl IntoElement {
+                Empty
+            }
+        }
+
+        impl ProjectItem for TestPngItemView {
+            type Item = TestPngItem;
+
+            fn for_project_item(
+                _project: Model<Project>,
+                _item: Model<Self::Item>,
+                cx: &mut ViewContext<Self>,
+            ) -> Self
+            where
+                Self: Sized,
+            {
+                Self {
+                    focus_handle: cx.focus_handle(),
+                }
+            }
+        }
+
+        const TEST_IPYNB_KIND: &str = "TestIpynbItemView";
+        // View
+        struct TestIpynbItemView {
+            focus_handle: FocusHandle,
+        }
+        // Model
+        struct TestIpynbItem {}
+
+        impl project::Item for TestIpynbItem {
+            fn try_open(
+                _project: &Model<Project>,
+                path: &ProjectPath,
+                cx: &mut AppContext,
+            ) -> Option<Task<gpui::Result<Model<Self>>>> {
+                if path.path.extension().unwrap() == "ipynb" {
+                    Some(cx.spawn(|mut cx| async move { cx.new_model(|_| TestIpynbItem {}) }))
+                } else {
+                    None
+                }
+            }
+
+            fn entry_id(&self, _: &AppContext) -> Option<ProjectEntryId> {
+                None
+            }
+
+            fn project_path(&self, _: &AppContext) -> Option<ProjectPath> {
+                None
+            }
+        }
+
+        impl Item for TestIpynbItemView {
+            type Event = ();
+
+            fn serialized_item_kind() -> Option<&'static str> {
+                Some(TEST_IPYNB_KIND)
+            }
+        }
+        impl EventEmitter<()> for TestIpynbItemView {}
+        impl FocusableView for TestIpynbItemView {
+            fn focus_handle(&self, _cx: &AppContext) -> FocusHandle {
+                self.focus_handle.clone()
+            }
+        }
+
+        impl Render for TestIpynbItemView {
+            fn render(&mut self, _cx: &mut ViewContext<Self>) -> impl IntoElement {
+                Empty
+            }
+        }
+
+        impl ProjectItem for TestIpynbItemView {
+            type Item = TestIpynbItem;
+
+            fn for_project_item(
+                _project: Model<Project>,
+                _item: Model<Self::Item>,
+                cx: &mut ViewContext<Self>,
+            ) -> Self
+            where
+                Self: Sized,
+            {
+                Self {
+                    focus_handle: cx.focus_handle(),
+                }
+            }
+        }
+
+        struct TestAlternatePngItemView {
+            focus_handle: FocusHandle,
+        }
+
+        const TEST_ALTERNATE_PNG_KIND: &str = "TestAlternatePngItemView";
+        impl Item for TestAlternatePngItemView {
+            type Event = ();
+
+            fn serialized_item_kind() -> Option<&'static str> {
+                Some(TEST_ALTERNATE_PNG_KIND)
+            }
+        }
+        impl EventEmitter<()> for TestAlternatePngItemView {}
+        impl FocusableView for TestAlternatePngItemView {
+            fn focus_handle(&self, _cx: &AppContext) -> FocusHandle {
+                self.focus_handle.clone()
+            }
+        }
+
+        impl Render for TestAlternatePngItemView {
+            fn render(&mut self, _cx: &mut ViewContext<Self>) -> impl IntoElement {
+                Empty
+            }
+        }
+
+        impl ProjectItem for TestAlternatePngItemView {
+            type Item = TestPngItem;
+
+            fn for_project_item(
+                _project: Model<Project>,
+                _item: Model<Self::Item>,
+                cx: &mut ViewContext<Self>,
+            ) -> Self
+            where
+                Self: Sized,
+            {
+                Self {
+                    focus_handle: cx.focus_handle(),
+                }
+            }
+        }
+
+        #[gpui::test]
+        async fn test_register_project_item(cx: &mut TestAppContext) {
+            init_test(cx);
+
+            cx.update(|cx| {
+                register_project_item::<TestPngItemView>(cx);
+                register_project_item::<TestIpynbItemView>(cx);
+            });
+
+            let fs = FakeFs::new(cx.executor());
+            fs.insert_tree(
+                "/root1",
+                json!({
+                    "one.png": "BINARYDATAHERE",
+                    "two.ipynb": "{ totally a notebook }",
+                    "three.txt": "editing text, sure why not?"
+                }),
+            )
+            .await;
+
+            let project = Project::test(fs, ["root1".as_ref()], cx).await;
+            let (workspace, cx) = cx.add_window_view(|cx| Workspace::test_new(project.clone(), cx));
+
+            let worktree_id = project.update(cx, |project, cx| {
+                project.worktrees().next().unwrap().read(cx).id()
+            });
+
+            let handle = workspace
+                .update(cx, |workspace, cx| {
+                    let project_path = (worktree_id, "one.png");
+                    workspace.open_path(project_path, None, true, cx)
+                })
+                .await
+                .unwrap();
+
+            // Now we can check if the handle we got back errored or not
+            assert_eq!(handle.serialized_item_kind().unwrap(), TEST_PNG_KIND);
+
+            let handle = workspace
+                .update(cx, |workspace, cx| {
+                    let project_path = (worktree_id, "two.ipynb");
+                    workspace.open_path(project_path, None, true, cx)
+                })
+                .await
+                .unwrap();
+
+            assert_eq!(handle.serialized_item_kind().unwrap(), TEST_IPYNB_KIND);
+
+            let handle = workspace
+                .update(cx, |workspace, cx| {
+                    let project_path = (worktree_id, "three.txt");
+                    workspace.open_path(project_path, None, true, cx)
+                })
+                .await;
+            assert!(handle.is_err());
+        }
+
+        #[gpui::test]
+        async fn test_register_project_item_two_enter_one_leaves(cx: &mut TestAppContext) {
+            init_test(cx);
+
+            cx.update(|cx| {
+                register_project_item::<TestPngItemView>(cx);
+                register_project_item::<TestAlternatePngItemView>(cx);
+            });
+
+            let fs = FakeFs::new(cx.executor());
+            fs.insert_tree(
+                "/root1",
+                json!({
+                    "one.png": "BINARYDATAHERE",
+                    "two.ipynb": "{ totally a notebook }",
+                    "three.txt": "editing text, sure why not?"
+                }),
+            )
+            .await;
+
+            let project = Project::test(fs, ["root1".as_ref()], cx).await;
+            let (workspace, cx) = cx.add_window_view(|cx| Workspace::test_new(project.clone(), cx));
+
+            let worktree_id = project.update(cx, |project, cx| {
+                project.worktrees().next().unwrap().read(cx).id()
+            });
+
+            let handle = workspace
+                .update(cx, |workspace, cx| {
+                    let project_path = (worktree_id, "one.png");
+                    workspace.open_path(project_path, None, true, cx)
+                })
+                .await
+                .unwrap();
+
+            // This _must_ be the second item registered
+            assert_eq!(
+                handle.serialized_item_kind().unwrap(),
+                TEST_ALTERNATE_PNG_KIND
+            );
+
+            let handle = workspace
+                .update(cx, |workspace, cx| {
+                    let project_path = (worktree_id, "three.txt");
+                    workspace.open_path(project_path, None, true, cx)
+                })
+                .await;
+            assert!(handle.is_err());
+        }
+    }
+
     pub fn init_test(cx: &mut TestAppContext) {
         cx.update(|cx| {
             let settings_store = SettingsStore::test(cx);