Add an experimental, WIP diagnostics grouping panel (#14515)

Provide a current, broken state as an experimental way to browse
diagnostics.
The diagnostics are grouped by lines and reduced into a block that, in
case of multiple diagnostics per line, could be toggled back and forth
to show more diagnostics on the line.
Use `grouped_diagnostics::Deploy` to show the panel.

Issues remaining:
* panic on warnings toggle due to incorrect excerpt manipulation
* badly styled blocks
* no key bindings to navigate between blocks and toggle them
* overall odd usability gains for certain groups of people

Due to all above, the thing is feature-gated and not exposed to regular
people.


Release Notes:

- N/A

crates/diagnostics/src/diagnostics.rs

@@ -4,6 +4,7 @@ mod toolbar_controls;
 
 #[cfg(test)]
 mod diagnostics_tests;
+mod grouped_diagnostics;
 
 use anyhow::Result;
 use collections::{BTreeSet, HashSet};
@@ -14,6 +15,7 @@ use editor::{
     scroll::Autoscroll,
     Editor, EditorEvent, ExcerptId, ExcerptRange, MultiBuffer, ToOffset,
 };
+use feature_flags::FeatureFlagAppExt;
 use futures::{
     channel::mpsc::{self, UnboundedSender},
     StreamExt as _,
@@ -52,6 +54,9 @@ pub fn init(cx: &mut AppContext) {
     ProjectDiagnosticsSettings::register(cx);
     cx.observe_new_views(ProjectDiagnosticsEditor::register)
         .detach();
+    if !cx.has_flag::<feature_flags::GroupedDiagnostics>() {
+        grouped_diagnostics::init(cx);
+    }
 }
 
 struct ProjectDiagnosticsEditor {
@@ -466,7 +471,9 @@ impl ProjectDiagnosticsEditor {
                                         position: (excerpt_id, entry.range.start),
                                         height: diagnostic.message.matches('\n').count() as u8 + 1,
                                         style: BlockStyle::Fixed,
-                                        render: diagnostic_block_renderer(diagnostic, true),
+                                        render: diagnostic_block_renderer(
+                                            diagnostic, None, true, true,
+                                        ),
                                         disposition: BlockDisposition::Below,
                                     });
                                 }
@@ -798,7 +805,7 @@ impl Item for ProjectDiagnosticsEditor {
 const DIAGNOSTIC_HEADER: &'static str = "diagnostic header";
 
 fn diagnostic_header_renderer(diagnostic: Diagnostic) -> RenderBlock {
-    let (message, code_ranges) = highlight_diagnostic_message(&diagnostic);
+    let (message, code_ranges) = highlight_diagnostic_message(&diagnostic, None);
     let message: SharedString = message;
     Box::new(move |cx| {
         let highlight_style: HighlightStyle = cx.theme().colors().text_accent.into();

crates/diagnostics/src/diagnostics_tests.rs

@@ -973,8 +973,8 @@ fn editor_blocks(
             blocks.extend(
                 snapshot
                     .blocks_in_range(DisplayRow(0)..snapshot.max_point().row())
-                    .enumerate()
-                    .filter_map(|(ix, (row, block))| {
+                    .filter_map(|(row, block)| {
+                        let transform_block_id = block.id();
                         let name: SharedString = match block {
                             TransformBlock::Custom(block) => {
                                 let mut element = block.render(&mut BlockContext {
@@ -984,7 +984,7 @@ fn editor_blocks(
                                     line_height: px(0.),
                                     em_width: px(0.),
                                     max_width: px(0.),
-                                    block_id: ix,
+                                    transform_block_id,
                                     editor_style: &editor::EditorStyle::default(),
                                 });
                                 let element = element.downcast_mut::<Stateful<Div>>().unwrap();