zed/crates/git_ui/src/text_diff_view.rs

//! TextDiffView currently provides a UI for displaying differences between the clipboard and selected text.

use anyhow::Result;
use buffer_diff::BufferDiff;
use editor::{
    Editor, EditorEvent, EditorSettings, MultiBuffer, SplittableEditor, ToPoint,
    actions::DiffClipboardWithSelectionData,
};
use futures::{FutureExt, select_biased};
use gpui::{
    AnyElement, App, AppContext as _, AsyncApp, Context, Entity, EventEmitter, FocusHandle,
    Focusable, IntoElement, Render, Task, Window,
};
use language::{self, Buffer, OffsetRangeExt, Point};
use project::Project;
use settings::Settings;
use std::{
    any::{Any, TypeId},
    cmp,
    ops::Range,
    pin::pin,
    sync::Arc,
    time::Duration,
};
use ui::{Color, Icon, IconName, Label, LabelCommon as _, SharedString};
use util::paths::PathExt;

use workspace::{
    Item, ItemNavHistory, Workspace,
    item::{ItemEvent, SaveOptions, TabContentParams},
    searchable::SearchableItemHandle,
};

pub struct TextDiffView {
    diff_editor: Entity<SplittableEditor>,
    title: SharedString,
    path: Option<SharedString>,
    buffer_changes_tx: watch::Sender<()>,
    _recalculate_diff_task: Task<Result<()>>,
}

const RECALCULATE_DIFF_DEBOUNCE: Duration = Duration::from_millis(250);

impl TextDiffView {
    pub fn open(
        diff_data: &DiffClipboardWithSelectionData,
        workspace: &Workspace,
        window: &mut Window,
        cx: &mut App,
    ) -> Option<Task<Result<Entity<Self>>>> {
        let source_editor = diff_data.editor.clone();

        let selection_data = source_editor.update(cx, |editor, cx| {
            let multibuffer = editor.buffer();
            let multibuffer_snapshot = multibuffer.read(cx).snapshot(cx);
            let first_selection = editor.selections.newest_anchor();

            let (source_buffer, buffer_range) = multibuffer_snapshot
                .anchor_range_to_buffer_anchor_range(first_selection.range())?;
            let max_point = source_buffer.max_point();
            let buffer_range = buffer_range.to_point(source_buffer);
            let source_buffer = multibuffer.read(cx).buffer(source_buffer.remote_id())?;

            if buffer_range.is_empty() {
                let full_range = Point::new(0, 0)..max_point;
                return Some((source_buffer, full_range));
            }

            let expanded_start = Point::new(buffer_range.start.row, 0);
            let expanded_end = if buffer_range.end.column > 0 {
                let next_row = buffer_range.end.row + 1;
                cmp::min(max_point, Point::new(next_row, 0))
            } else {
                buffer_range.end
            };
            Some((source_buffer, expanded_start..expanded_end))
        });

        let Some((source_buffer, expanded_selection_range)) = selection_data else {
            log::warn!("There should always be at least one selection in Zed. This is a bug.");
            return None;
        };

        source_editor.update(cx, |source_editor, cx| {
            let multibuffer = source_editor.buffer();
            let mb_range = {
                let mb = multibuffer.read(cx);
                let start_anchor =
                    mb.buffer_point_to_anchor(&source_buffer, expanded_selection_range.start, cx);
                let end_anchor =
                    mb.buffer_point_to_anchor(&source_buffer, expanded_selection_range.end, cx);
                start_anchor.zip(end_anchor).map(|(s, e)| {
                    let snapshot = mb.snapshot(cx);
                    s.to_point(&snapshot)..e.to_point(&snapshot)
                })
            };

            if let Some(range) = mb_range {
                source_editor.change_selections(Default::default(), window, cx, |s| {
                    s.select_ranges(vec![range]);
                });
            }
        });

        let source_buffer_snapshot = source_buffer.read(cx).snapshot();
        let mut clipboard_text = diff_data.clipboard_text.clone();

        if !clipboard_text.ends_with("\n") {
            clipboard_text.push_str("\n");
        }

        let workspace = workspace.weak_handle();
        let diff_buffer = cx.new(|cx| BufferDiff::new(&source_buffer_snapshot.text, cx));
        let clipboard_buffer = build_clipboard_buffer(
            clipboard_text,
            &source_buffer,
            expanded_selection_range.clone(),
            cx,
        );

        let task = window.spawn(cx, async move |cx| {
            update_diff_buffer(&diff_buffer, &source_buffer, &clipboard_buffer, cx).await?;

            workspace.update_in(cx, |workspace, window, cx| {
                let project = workspace.project().clone();
                let workspace_entity = cx.entity();
                let diff_view = cx.new(|cx| {
                    TextDiffView::new(
                        clipboard_buffer,
                        source_editor,
                        source_buffer,
                        expanded_selection_range,
                        diff_buffer,
                        project,
                        workspace_entity,
                        window,
                        cx,
                    )
                });

                let pane = workspace.active_pane();
                pane.update(cx, |pane, cx| {
                    pane.add_item(Box::new(diff_view.clone()), true, true, None, window, cx);
                });

                diff_view
            })
        });

        Some(task)
    }

    pub fn new(
        clipboard_buffer: Entity<Buffer>,
        source_editor: Entity<Editor>,
        source_buffer: Entity<Buffer>,
        source_range: Range<Point>,
        diff_buffer: Entity<BufferDiff>,
        project: Entity<Project>,
        workspace: Entity<Workspace>,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) -> Self {
        let multibuffer = cx.new(|cx| {
            let mut multibuffer = MultiBuffer::new(language::Capability::ReadWrite);

            multibuffer.set_excerpts_for_buffer(source_buffer.clone(), [source_range], 0, cx);

            multibuffer.add_diff(diff_buffer.clone(), cx);
            multibuffer
        });
        let diff_editor = cx.new(|cx| {
            let splittable = SplittableEditor::new(
                EditorSettings::get_global(cx).diff_view_style,
                multibuffer,
                project,
                workspace,
                window,
                cx,
            );
            splittable.set_render_diff_hunk_controls(
                Arc::new(|_, _, _, _, _, _, _, _| gpui::Empty.into_any_element()),
                cx,
            );
            splittable.rhs_editor().update(cx, |editor, cx| {
                editor.start_temporary_diff_override();
                editor.disable_diagnostics(cx);
                editor.set_expand_all_diff_hunks(cx);
            });
            splittable
        });

        let (buffer_changes_tx, mut buffer_changes_rx) = watch::channel(());

        cx.subscribe(&source_buffer, move |this, _, event, _| match event {
            language::BufferEvent::Edited { .. }
            | language::BufferEvent::LanguageChanged(_)
            | language::BufferEvent::Reparsed => {
                this.buffer_changes_tx.send(()).ok();
            }
            _ => {}
        })
        .detach();

        let editor = source_editor.read(cx);
        let title = editor.buffer().read(cx).title(cx).to_string();
        let selection_location_text = selection_location_text(editor, cx);
        let selection_location_title = selection_location_text
            .as_ref()
            .map(|text| format!("{} @ {}", title, text))
            .unwrap_or(title);

        let path = editor
            .buffer()
            .read(cx)
            .as_singleton()
            .and_then(|b| {
                b.read(cx)
                    .file()
                    .map(|f| f.full_path(cx).compact().to_string_lossy().into_owned())
            })
            .unwrap_or("untitled".into());

        let selection_location_path = selection_location_text
            .map(|text| format!("{} @ {}", path, text))
            .unwrap_or(path);

        Self {
            diff_editor,
            title: format!("Clipboard ↔ {selection_location_title}").into(),
            path: Some(format!("Clipboard ↔ {selection_location_path}").into()),
            buffer_changes_tx,
            _recalculate_diff_task: cx.spawn(async move |_, cx| {
                while buffer_changes_rx.recv().await.is_ok() {
                    loop {
                        let mut timer = cx
                            .background_executor()
                            .timer(RECALCULATE_DIFF_DEBOUNCE)
                            .fuse();
                        let mut recv = pin!(buffer_changes_rx.recv().fuse());
                        select_biased! {
                            _ = timer => break,
                            _ = recv => continue,
                        }
                    }

                    log::trace!("start recalculating");
                    update_diff_buffer(&diff_buffer, &source_buffer, &clipboard_buffer, cx).await?;
                    log::trace!("finish recalculating");
                }
                Ok(())
            }),
        }
    }
}

fn build_clipboard_buffer(
    text: String,
    source_buffer: &Entity<Buffer>,
    replacement_range: Range<Point>,
    cx: &mut App,
) -> Entity<Buffer> {
    let source_buffer_snapshot = source_buffer.read(cx).snapshot();
    cx.new(|cx| {
        let mut buffer = language::Buffer::local(source_buffer_snapshot.text(), cx);
        let language = source_buffer.read(cx).language().cloned();
        buffer.set_language(language, cx);

        let range_start = source_buffer_snapshot.point_to_offset(replacement_range.start);
        let range_end = source_buffer_snapshot.point_to_offset(replacement_range.end);
        buffer.edit([(range_start..range_end, text)], None, cx);

        buffer
    })
}

async fn update_diff_buffer(
    diff: &Entity<BufferDiff>,
    source_buffer: &Entity<Buffer>,
    clipboard_buffer: &Entity<Buffer>,
    cx: &mut AsyncApp,
) -> Result<()> {
    let source_buffer_snapshot = source_buffer.read_with(cx, |buffer, _| buffer.snapshot());
    let language = source_buffer_snapshot.language().cloned();
    let language_registry = source_buffer.read_with(cx, |buffer, _| buffer.language_registry());

    let base_buffer_snapshot = clipboard_buffer.read_with(cx, |buffer, _| buffer.snapshot());
    let base_text = base_buffer_snapshot.text();

    let update = diff
        .update(cx, |diff, cx| {
            diff.update_diff(
                source_buffer_snapshot.text.clone(),
                Some(Arc::from(base_text.as_str())),
                Some(true),
                language.clone(),
                cx,
            )
        })
        .await;

    diff.update(cx, |diff, cx| {
        diff.language_changed(language, language_registry, cx);
        diff.set_snapshot(update, &source_buffer_snapshot.text, cx)
    })
    .await;
    Ok(())
}

impl EventEmitter<EditorEvent> for TextDiffView {}

impl Focusable for TextDiffView {
    fn focus_handle(&self, cx: &App) -> FocusHandle {
        self.diff_editor.focus_handle(cx)
    }
}

impl Item for TextDiffView {
    type Event = EditorEvent;

    fn tab_icon(&self, _window: &Window, _cx: &App) -> Option<Icon> {
        Some(Icon::new(IconName::Diff).color(Color::Muted))
    }

    fn tab_content(&self, params: TabContentParams, _window: &Window, cx: &App) -> AnyElement {
        Label::new(self.tab_content_text(params.detail.unwrap_or_default(), cx))
            .color(if params.selected {
                Color::Default
            } else {
                Color::Muted
            })
            .into_any_element()
    }

    fn tab_content_text(&self, _detail: usize, _: &App) -> SharedString {
        self.title.clone()
    }

    fn tab_tooltip_text(&self, _: &App) -> Option<SharedString> {
        self.path.clone()
    }

    fn to_item_events(event: &EditorEvent, f: &mut dyn FnMut(ItemEvent)) {
        Editor::to_item_events(event, f)
    }

    fn telemetry_event_text(&self) -> Option<&'static str> {
        Some("Selection Diff View Opened")
    }

    fn deactivated(&mut self, window: &mut Window, cx: &mut Context<Self>) {
        self.diff_editor
            .update(cx, |editor, cx| editor.deactivated(window, cx));
    }

    fn act_as_type<'a>(
        &'a self,
        type_id: TypeId,
        self_handle: &'a Entity<Self>,
        cx: &'a App,
    ) -> Option<gpui::AnyEntity> {
        if type_id == TypeId::of::<Self>() {
            Some(self_handle.clone().into())
        } else if type_id == TypeId::of::<SplittableEditor>() {
            Some(self.diff_editor.clone().into())
        } else if type_id == TypeId::of::<Editor>() {
            Some(self.diff_editor.read(cx).rhs_editor().clone().into())
        } else {
            None
        }
    }

    fn as_searchable(&self, _: &Entity<Self>, _: &App) -> Option<Box<dyn SearchableItemHandle>> {
        Some(Box::new(self.diff_editor.clone()))
    }

    fn for_each_project_item(
        &self,
        cx: &App,
        f: &mut dyn FnMut(gpui::EntityId, &dyn project::ProjectItem),
    ) {
        self.diff_editor.read(cx).for_each_project_item(cx, f)
    }

    fn set_nav_history(
        &mut self,
        nav_history: ItemNavHistory,
        _: &mut Window,
        cx: &mut Context<Self>,
    ) {
        let rhs = self.diff_editor.read(cx).rhs_editor().clone();
        rhs.update(cx, |editor, _| {
            editor.set_nav_history(Some(nav_history));
        });
    }

    fn navigate(
        &mut self,
        data: Arc<dyn Any + Send>,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) -> bool {
        self.diff_editor
            .update(cx, |editor, cx| editor.navigate(data, window, cx))
    }

    fn added_to_workspace(
        &mut self,
        workspace: &mut Workspace,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        self.diff_editor.update(cx, |editor, cx| {
            editor.added_to_workspace(workspace, window, cx)
        });
    }

    fn can_save(&self, cx: &App) -> bool {
        // The editor handles the new buffer, so delegate to it
        self.diff_editor.read(cx).can_save(cx)
    }

    fn save(
        &mut self,
        options: SaveOptions,
        project: Entity<Project>,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) -> Task<Result<()>> {
        // Delegate saving to the editor, which manages the new buffer
        self.diff_editor
            .update(cx, |editor, cx| editor.save(options, project, window, cx))
    }
}

pub fn selection_location_text(editor: &Editor, cx: &App) -> Option<String> {
    let buffer = editor.buffer().read(cx);
    let buffer_snapshot = buffer.snapshot(cx);
    let first_selection = editor.selections.disjoint_anchors().first()?;

    let selection_start = first_selection.start.to_point(&buffer_snapshot);
    let selection_end = first_selection.end.to_point(&buffer_snapshot);

    let start_row = selection_start.row;
    let start_column = selection_start.column;
    let end_row = selection_end.row;
    let end_column = selection_end.column;

    let range_text = if start_row == end_row {
        format!("L{}:{}-{}", start_row + 1, start_column + 1, end_column + 1)
    } else {
        format!(
            "L{}:{}-L{}:{}",
            start_row + 1,
            start_column + 1,
            end_row + 1,
            end_column + 1
        )
    };

    Some(range_text)
}

impl Render for TextDiffView {
    fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
        self.diff_editor.clone()
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use editor::{MultiBufferOffset, PathKey, test::editor_test_context::assert_state_with_diff};
    use gpui::{BorrowAppContext, TestAppContext, VisualContext};
    use language::Point;
    use project::{FakeFs, Project};
    use serde_json::json;
    use settings::{DiffViewStyle, SettingsStore};
    use unindent::unindent;
    use util::{path, test::marked_text_ranges};
    use workspace::MultiWorkspace;

    fn init_test(cx: &mut TestAppContext) {
        cx.update(|cx| {
            let settings_store = SettingsStore::test(cx);
            cx.set_global(settings_store);
            cx.update_global::<SettingsStore, _>(|store, cx| {
                store.update_user_settings(cx, |settings| {
                    settings.editor.diff_view_style = Some(DiffViewStyle::Unified);
                });
            });
            theme_settings::init(theme::LoadThemes::JustBase, cx);
        });
    }

    #[gpui::test]
    async fn test_diffing_clipboard_against_empty_selection_uses_full_buffer_selection(
        cx: &mut TestAppContext,
    ) {
        base_test(
            path!("/test"),
            path!("/test/text.txt"),
            "def process_incoming_inventory(items, warehouse_id):\n    pass\n",
            "def process_outgoing_inventory(items, warehouse_id):\n    passˇ\n",
            &unindent(
                "
                - def process_incoming_inventory(items, warehouse_id):
                + ˇdef process_outgoing_inventory(items, warehouse_id):
                      pass
                ",
            ),
            "Clipboard ↔ text.txt @ L1:1-L3:1",
            &format!("Clipboard ↔ {} @ L1:1-L3:1", path!("test/text.txt")),
            cx,
        )
        .await;
    }

    #[gpui::test]
    async fn test_diffing_clipboard_against_multiline_selection_expands_to_full_lines(
        cx: &mut TestAppContext,
    ) {
        base_test(
            path!("/test"),
            path!("/test/text.txt"),
            "def process_incoming_inventory(items, warehouse_id):\n    pass\n",
            "«def process_outgoing_inventory(items, warehouse_id):\n    passˇ»\n",
            &unindent(
                "
                - def process_incoming_inventory(items, warehouse_id):
                + ˇdef process_outgoing_inventory(items, warehouse_id):
                      pass
                ",
            ),
            "Clipboard ↔ text.txt @ L1:1-L3:1",
            &format!("Clipboard ↔ {} @ L1:1-L3:1", path!("test/text.txt")),
            cx,
        )
        .await;
    }

    #[gpui::test]
    async fn test_diffing_clipboard_against_single_line_selection(cx: &mut TestAppContext) {
        base_test(
            path!("/test"),
            path!("/test/text.txt"),
            "a",
            "«bbˇ»",
            &unindent(
                "
                - a
                + ˇbb",
            ),
            "Clipboard ↔ text.txt @ L1:1-3",
            &format!("Clipboard ↔ {} @ L1:1-3", path!("test/text.txt")),
            cx,
        )
        .await;
    }

    #[gpui::test]
    async fn test_diffing_clipboard_with_leading_whitespace_against_line(cx: &mut TestAppContext) {
        base_test(
            path!("/test"),
            path!("/test/text.txt"),
            "    a",
            "«bbˇ»",
            &unindent(
                "
                -     a
                + ˇbb",
            ),
            "Clipboard ↔ text.txt @ L1:1-3",
            &format!("Clipboard ↔ {} @ L1:1-3", path!("test/text.txt")),
            cx,
        )
        .await;
    }

    #[gpui::test]
    async fn test_diffing_clipboard_against_line_with_leading_whitespace(cx: &mut TestAppContext) {
        base_test(
            path!("/test"),
            path!("/test/text.txt"),
            "a",
            "    «bbˇ»",
            &unindent(
                "
                - a
                + ˇ    bb",
            ),
            "Clipboard ↔ text.txt @ L1:1-7",
            &format!("Clipboard ↔ {} @ L1:1-7", path!("test/text.txt")),
            cx,
        )
        .await;
    }

    #[gpui::test]
    async fn test_diffing_clipboard_against_line_with_leading_whitespace_included_in_selection(
        cx: &mut TestAppContext,
    ) {
        base_test(
            path!("/test"),
            path!("/test/text.txt"),
            "a",
            "«    bbˇ»",
            &unindent(
                "
                - a
                + ˇ    bb",
            ),
            "Clipboard ↔ text.txt @ L1:1-7",
            &format!("Clipboard ↔ {} @ L1:1-7", path!("test/text.txt")),
            cx,
        )
        .await;
    }

    #[gpui::test]
    async fn test_diffing_clipboard_with_leading_whitespace_against_line_with_leading_whitespace(
        cx: &mut TestAppContext,
    ) {
        base_test(
            path!("/test"),
            path!("/test/text.txt"),
            "    a",
            "    «bbˇ»",
            &unindent(
                "
                -     a
                + ˇ    bb",
            ),
            "Clipboard ↔ text.txt @ L1:1-7",
            &format!("Clipboard ↔ {} @ L1:1-7", path!("test/text.txt")),
            cx,
        )
        .await;
    }

    #[gpui::test]
    async fn test_diffing_clipboard_with_leading_whitespace_against_line_with_leading_whitespace_included_in_selection(
        cx: &mut TestAppContext,
    ) {
        base_test(
            path!("/test"),
            path!("/test/text.txt"),
            "    a",
            "«    bbˇ»",
            &unindent(
                "
                -     a
                + ˇ    bb",
            ),
            "Clipboard ↔ text.txt @ L1:1-7",
            &format!("Clipboard ↔ {} @ L1:1-7", path!("test/text.txt")),
            cx,
        )
        .await;
    }

    #[gpui::test]
    async fn test_diffing_clipboard_against_partial_selection_expands_to_include_trailing_characters(
        cx: &mut TestAppContext,
    ) {
        base_test(
            path!("/test"),
            path!("/test/text.txt"),
            "a",
            "«bˇ»b",
            &unindent(
                "
                - a
                + ˇbb",
            ),
            "Clipboard ↔ text.txt @ L1:1-3",
            &format!("Clipboard ↔ {} @ L1:1-3", path!("test/text.txt")),
            cx,
        )
        .await;
    }

    #[gpui::test]
    async fn test_diffing_clipboard_from_multibuffer_with_selection(cx: &mut TestAppContext) {
        init_test(cx);

        let fs = FakeFs::new(cx.executor());
        fs.insert_tree(
            path!("/project"),
            json!({
                "a.txt": "alpha\nbeta\ngamma",
                "b.txt": "one\ntwo\nthree"
            }),
        )
        .await;

        let project = Project::test(fs, [path!("/project").as_ref()], cx).await;

        let buffer_a = project
            .update(cx, |project, cx| {
                project.open_local_buffer(path!("/project/a.txt"), cx)
            })
            .await
            .unwrap();
        let buffer_b = project
            .update(cx, |project, cx| {
                project.open_local_buffer(path!("/project/b.txt"), cx)
            })
            .await
            .unwrap();

        let (multi_workspace, cx) =
            cx.add_window_view(|window, cx| MultiWorkspace::test_new(project.clone(), window, cx));
        let workspace = multi_workspace.read_with(cx, |mw, _| mw.workspace().clone());

        let editor = cx.new_window_entity(|window, cx| {
            let multibuffer = cx.new(|cx| {
                let mut mb = MultiBuffer::new(language::Capability::ReadWrite);
                mb.set_excerpts_for_path(
                    PathKey::sorted(0),
                    buffer_a.clone(),
                    [Point::new(0, 0)..Point::new(2, 5)],
                    0,
                    cx,
                );
                mb.set_excerpts_for_path(
                    PathKey::sorted(1),
                    buffer_b.clone(),
                    [Point::new(0, 0)..Point::new(2, 5)],
                    0,
                    cx,
                );
                mb
            });

            let mut editor =
                Editor::for_multibuffer(multibuffer, Some(project.clone()), window, cx);
            // Select "beta" inside the first excerpt
            editor.change_selections(Default::default(), window, cx, |s| {
                s.select_ranges([MultiBufferOffset(6)..MultiBufferOffset(10)]);
            });
            editor
        });

        let diff_view = workspace
            .update_in(cx, |workspace, window, cx| {
                TextDiffView::open(
                    &DiffClipboardWithSelectionData {
                        clipboard_text: "REPLACED".to_string(),
                        editor,
                    },
                    workspace,
                    window,
                    cx,
                )
            })
            .unwrap()
            .await
            .unwrap();

        cx.executor().run_until_parked();

        diff_view.read_with(cx, |diff_view, _cx| {
            assert!(
                diff_view.title.contains("Clipboard"),
                "diff view should have opened with a clipboard diff title, got: {}",
                diff_view.title
            );
        });
    }

    #[gpui::test]
    async fn test_diffing_clipboard_from_multibuffer_with_empty_selection(cx: &mut TestAppContext) {
        init_test(cx);

        let fs = FakeFs::new(cx.executor());
        fs.insert_tree(
            path!("/project"),
            json!({
                "a.txt": "alpha\nbeta\ngamma",
                "b.txt": "one\ntwo\nthree"
            }),
        )
        .await;

        let project = Project::test(fs, [path!("/project").as_ref()], cx).await;

        let buffer_a = project
            .update(cx, |project, cx| {
                project.open_local_buffer(path!("/project/a.txt"), cx)
            })
            .await
            .unwrap();
        let buffer_b = project
            .update(cx, |project, cx| {
                project.open_local_buffer(path!("/project/b.txt"), cx)
            })
            .await
            .unwrap();

        let (multi_workspace, cx) =
            cx.add_window_view(|window, cx| MultiWorkspace::test_new(project.clone(), window, cx));
        let workspace = multi_workspace.read_with(cx, |mw, _| mw.workspace().clone());

        let editor = cx.new_window_entity(|window, cx| {
            let multibuffer = cx.new(|cx| {
                let mut mb = MultiBuffer::new(language::Capability::ReadWrite);
                mb.set_excerpts_for_path(
                    PathKey::sorted(0),
                    buffer_a.clone(),
                    [Point::new(0, 0)..Point::new(2, 5)],
                    0,
                    cx,
                );
                mb.set_excerpts_for_path(
                    PathKey::sorted(1),
                    buffer_b.clone(),
                    [Point::new(0, 0)..Point::new(2, 5)],
                    0,
                    cx,
                );
                mb
            });

            let mut editor =
                Editor::for_multibuffer(multibuffer, Some(project.clone()), window, cx);
            // Cursor inside the first excerpt (no selection)
            editor.change_selections(Default::default(), window, cx, |s| {
                s.select_ranges([MultiBufferOffset(6)..MultiBufferOffset(6)]);
            });
            editor
        });

        let diff_view = workspace
            .update_in(cx, |workspace, window, cx| {
                TextDiffView::open(
                    &DiffClipboardWithSelectionData {
                        clipboard_text: "REPLACED".to_string(),
                        editor,
                    },
                    workspace,
                    window,
                    cx,
                )
            })
            .unwrap()
            .await
            .unwrap();

        cx.executor().run_until_parked();

        // Empty selection should diff the full underlying buffer
        diff_view.read_with(cx, |diff_view, _cx| {
            assert!(
                diff_view.title.contains("Clipboard"),
                "diff view should have opened with a clipboard diff title, got: {}",
                diff_view.title
            );
        });
    }

    async fn base_test(
        project_root: &str,
        file_path: &str,
        clipboard_text: &str,
        editor_text: &str,
        expected_diff: &str,
        expected_tab_title: &str,
        expected_tab_tooltip: &str,
        cx: &mut TestAppContext,
    ) {
        init_test(cx);

        let file_name = std::path::Path::new(file_path)
            .file_name()
            .unwrap()
            .to_str()
            .unwrap();

        let fs = FakeFs::new(cx.executor());
        fs.insert_tree(
            project_root,
            json!({
                file_name: editor_text
            }),
        )
        .await;

        let project = Project::test(fs, [project_root.as_ref()], cx).await;

        let (multi_workspace, cx) =
            cx.add_window_view(|window, cx| MultiWorkspace::test_new(project.clone(), window, cx));
        let workspace = multi_workspace.read_with(cx, |mw, _| mw.workspace().clone());

        let buffer = project
            .update(cx, |project, cx| project.open_local_buffer(file_path, cx))
            .await
            .unwrap();

        let editor = cx.new_window_entity(|window, cx| {
            let mut editor = Editor::for_buffer(buffer, None, window, cx);
            let (unmarked_text, selection_ranges) = marked_text_ranges(editor_text, false);
            editor.set_text(unmarked_text, window, cx);
            editor.change_selections(Default::default(), window, cx, |s| {
                s.select_ranges(
                    selection_ranges
                        .into_iter()
                        .map(|range| MultiBufferOffset(range.start)..MultiBufferOffset(range.end)),
                )
            });

            editor
        });

        let diff_view = workspace
            .update_in(cx, |workspace, window, cx| {
                TextDiffView::open(
                    &DiffClipboardWithSelectionData {
                        clipboard_text: clipboard_text.to_string(),
                        editor,
                    },
                    workspace,
                    window,
                    cx,
                )
            })
            .unwrap()
            .await
            .unwrap();

        cx.executor().run_until_parked();

        assert_state_with_diff(
            &diff_view.read_with(cx, |diff_view, cx| {
                diff_view.diff_editor.read(cx).rhs_editor().clone()
            }),
            cx,
            expected_diff,
        );

        diff_view.read_with(cx, |diff_view, cx| {
            assert_eq!(diff_view.tab_content_text(0, cx), expected_tab_title);
            assert_eq!(
                diff_view.tab_tooltip_text(cx).unwrap(),
                expected_tab_tooltip
            );
        });
    }
}