Update block diagnostics (#28006)

Release Notes:

- "Block" diagnostics (that show up in the diagnostics view, or when
using `f8`/`shift-f8`) are rendered more clearly
- `f8`/`shift-f8` now always go to the "next" or "prev" diagnostic,
regardless of the state of the editor

![Screenshot 2025-04-09 at 16 42
09](https://github.com/user-attachments/assets/ae6d2ff6-5183-4b74-89d0-fefee1aa11e3)

---------

Co-authored-by: Kirill Bulatov <mail4score@gmail.com>
Co-authored-by: Julia Ryan <juliaryan3.14@gmail.com>

crates/editor/src/test.rs

@@ -1,18 +1,25 @@
 pub mod editor_lsp_test_context;
 pub mod editor_test_context;
 
+use std::{rc::Rc, sync::LazyLock};
+
 pub use crate::rust_analyzer_ext::expand_macro_recursively;
 use crate::{
     DisplayPoint, Editor, EditorMode, FoldPlaceholder, MultiBuffer,
-    display_map::{DisplayMap, DisplaySnapshot, ToDisplayPoint},
+    display_map::{
+        Block, BlockPlacement, CustomBlockId, DisplayMap, DisplayRow, DisplaySnapshot,
+        ToDisplayPoint,
+    },
 };
+use collections::HashMap;
 use gpui::{
-    AppContext as _, Context, Entity, Font, FontFeatures, FontStyle, FontWeight, Pixels, Window,
-    font,
+    AppContext as _, Context, Entity, EntityId, Font, FontFeatures, FontStyle, FontWeight, Pixels,
+    VisualTestContext, Window, font, size,
 };
+use multi_buffer::ToPoint;
 use pretty_assertions::assert_eq;
 use project::Project;
-use std::sync::LazyLock;
+use ui::{App, BorrowAppContext, px};
 use util::test::{marked_text_offsets, marked_text_ranges};
 
 #[cfg(test)]
@@ -122,3 +129,126 @@ pub(crate) fn build_editor_with_project(
 ) -> Editor {
     Editor::new(EditorMode::full(), buffer, Some(project), window, cx)
 }
+
+#[derive(Default)]
+struct TestBlockContent(
+    HashMap<(EntityId, CustomBlockId), Rc<dyn Fn(&mut VisualTestContext) -> String>>,
+);
+
+impl gpui::Global for TestBlockContent {}
+
+pub fn set_block_content_for_tests(
+    editor: &Entity<Editor>,
+    id: CustomBlockId,
+    cx: &mut App,
+    f: impl Fn(&mut VisualTestContext) -> String + 'static,
+) {
+    cx.update_default_global::<TestBlockContent, _>(|bc, _| {
+        bc.0.insert((editor.entity_id(), id), Rc::new(f))
+    });
+}
+
+pub fn block_content_for_tests(
+    editor: &Entity<Editor>,
+    id: CustomBlockId,
+    cx: &mut VisualTestContext,
+) -> Option<String> {
+    let f = cx.update(|_, cx| {
+        cx.default_global::<TestBlockContent>()
+            .0
+            .get(&(editor.entity_id(), id))
+            .cloned()
+    })?;
+    Some(f(cx))
+}
+
+pub fn editor_content_with_blocks(editor: &Entity<Editor>, cx: &mut VisualTestContext) -> String {
+    cx.draw(
+        gpui::Point::default(),
+        size(px(3000.0), px(3000.0)),
+        |_, _| editor.clone(),
+    );
+    let (snapshot, mut lines, blocks) = editor.update_in(cx, |editor, window, cx| {
+        let snapshot = editor.snapshot(window, cx);
+        let text = editor.display_text(cx);
+        let lines = text.lines().map(|s| s.to_string()).collect::<Vec<String>>();
+        let blocks = snapshot
+            .blocks_in_range(DisplayRow(0)..snapshot.max_point().row())
+            .map(|(row, block)| (row, block.clone()))
+            .collect::<Vec<_>>();
+        (snapshot, lines, blocks)
+    });
+    for (row, block) in blocks {
+        match block {
+            Block::Custom(custom_block) => {
+                if let BlockPlacement::Near(x) = &custom_block.placement {
+                    if snapshot.intersects_fold(x.to_point(&snapshot.buffer_snapshot)) {
+                        continue;
+                    }
+                };
+                let content = block_content_for_tests(&editor, custom_block.id, cx)
+                    .expect("block content not found");
+                // 2: "related info 1 for diagnostic 0"
+                if let Some(height) = custom_block.height {
+                    if height == 0 {
+                        lines[row.0 as usize - 1].push_str(" § ");
+                        lines[row.0 as usize - 1].push_str(&content);
+                    } else {
+                        let block_lines = content.lines().collect::<Vec<_>>();
+                        assert_eq!(block_lines.len(), height as usize);
+                        lines[row.0 as usize].push_str("§ ");
+                        lines[row.0 as usize].push_str(block_lines[0].trim_end());
+                        for i in 1..height as usize {
+                            lines[row.0 as usize + i].push_str("§ ");
+                            lines[row.0 as usize + i].push_str(block_lines[i].trim_end());
+                        }
+                    }
+                }
+            }
+            Block::FoldedBuffer {
+                first_excerpt,
+                height,
+            } => {
+                lines[row.0 as usize].push_str(&cx.update(|_, cx| {
+                    format!(
+                        "§ {}",
+                        first_excerpt
+                            .buffer
+                            .file()
+                            .unwrap()
+                            .file_name(cx)
+                            .to_string_lossy()
+                    )
+                }));
+                for row in row.0 + 1..row.0 + height {
+                    lines[row as usize].push_str("§ -----");
+                }
+            }
+            Block::ExcerptBoundary {
+                excerpt,
+                height,
+                starts_new_buffer,
+            } => {
+                if starts_new_buffer {
+                    lines[row.0 as usize].push_str(&cx.update(|_, cx| {
+                        format!(
+                            "§ {}",
+                            excerpt
+                                .buffer
+                                .file()
+                                .unwrap()
+                                .file_name(cx)
+                                .to_string_lossy()
+                        )
+                    }));
+                } else {
+                    lines[row.0 as usize].push_str("§ -----")
+                }
+                for row in row.0 + 1..row.0 + height {
+                    lines[row as usize].push_str("§ -----");
+                }
+            }
+        }
+    }
+    lines.join("\n")
+}