[3209] feat(lsp): range formatting

Add basic range formatting capabilities when multiple selection
are present.

Related: https://github.com/helix-editor/helix/issues/3209#issue-1318916766

helix-core/src/syntax.rs

@@ -313,6 +313,7 @@ where
 #[serde(rename_all = "kebab-case")]
 pub enum LanguageServerFeature {
     Format,
+    FormatSelection,
     GotoDeclaration,
     GotoDefinition,
     GotoTypeDefinition,
@@ -338,6 +339,7 @@ impl Display for LanguageServerFeature {
         use LanguageServerFeature::*;
         let feature = match self {
             Format => "format",
+            FormatSelection => "format-selection",
             GotoDeclaration => "goto-declaration",
             GotoDefinition => "goto-definition",
             GotoTypeDefinition => "goto-type-definition",

helix-lsp/src/client.rs

@@ -287,6 +287,10 @@ impl Client {
                 capabilities.document_formatting_provider,
                 Some(OneOf::Left(true) | OneOf::Right(_))
             ),
+            LanguageServerFeature::FormatSelection => matches!(
+                capabilities.document_range_formatting_provider,
+                Some(OneOf::Left(true) | OneOf::Right(_))
+            ),
             LanguageServerFeature::GotoDeclaration => matches!(
                 capabilities.declaration_provider,
                 Some(
@@ -662,6 +666,9 @@ impl Client {
                         dynamic_registration: Some(false),
                         resolve_support: None,
                     }),
+                    range_formatting: Some(lsp::DocumentFormattingClientCapabilities {
+                        dynamic_registration: Some(false),
+                    }),
                     ..Default::default()
                 }),
                 window: Some(lsp::WindowClientCapabilities {

helix-term/src/commands.rs

@@ -63,6 +63,7 @@ use crate::{
 };
 
 use crate::job::{self, Jobs};
+use futures_util::future::join_all;
 use std::{
     cmp::Ordering,
     collections::{HashMap, HashSet},
@@ -427,7 +428,7 @@ impl MappableCommand {
         paste_primary_clipboard_before, "Paste primary clipboard before selections",
         indent, "Indent selection",
         unindent, "Unindent selection",
-        format_selections, "Format selection",
+        format_selections, "Format selections",
         join_selections, "Join lines inside selection",
         join_selections_space, "Join lines inside selection and select spaces",
         keep_selections, "Keep selections matching regex",
@@ -4469,25 +4470,11 @@ fn format_selections(cx: &mut Context) {
     let (view, doc) = current!(cx.editor);
     let view_id = view.id;
 
-    // via lsp if available
-    // TODO: else via tree-sitter indentation calculations
+    // TODO: via lsp if available else via tree-sitter indentation calculations
 
-    if doc.selection(view_id).len() != 1 {
-        cx.editor
-            .set_error("format_selections only supports a single selection for now");
-        return;
-    }
-
-    // TODO extra LanguageServerFeature::FormatSelections?
-    // maybe such that LanguageServerFeature::Format contains it as well
     let Some(language_server) = doc
-        .language_servers_with_feature(LanguageServerFeature::Format)
-        .find(|ls| {
-            matches!(
-                ls.capabilities().document_range_formatting_provider,
-                Some(lsp::OneOf::Left(true) | lsp::OneOf::Right(_))
-            )
-        })
+        .language_servers_with_feature(LanguageServerFeature::FormatSelection)
+        .next()
     else {
         cx.editor
             .set_error("No configured language server supports range formatting");
@@ -4498,16 +4485,15 @@ fn format_selections(cx: &mut Context) {
     let ranges: Vec<lsp::Range> = doc
         .selection(view_id)
         .iter()
+        // request and process range formatting in reverse order from last selection
+        // to the first selection to reduce the chances of collisions (change in earlier
+        // sections could cause offsets in later sections, can't happen the other way around).
+        .rev()
         .map(|range| range_to_lsp_range(doc.text(), *range, offset_encoding))
         .collect();
 
-    // TODO: handle fails
-    // TODO: concurrent map over all ranges
-
-    let range = ranges[0];
-
-    let future = language_server
-        .text_document_range_formatting(
+    let futures = ranges.into_iter().filter_map(|range| {
+        language_server.text_document_range_formatting(
             doc.identifier(),
             range,
             lsp::FormattingOptions {
@@ -4517,12 +4503,25 @@ fn format_selections(cx: &mut Context) {
             },
             None,
         )
-        .unwrap();
+    });
 
-    let edits = tokio::task::block_in_place(|| helix_lsp::block_on(future)).unwrap_or_default();
+    let results = helix_lsp::block_on(join_all(futures));
+
+    let all_edits = results
+        .into_iter()
+        .filter_map(|result| {
+            match result {
+                // TODO: handle colliding edits (edits outside the range) and edits that result into collision.
+                // See: https://github.com/helix-editor/helix/issues/3209#issuecomment-1197463913
+                Ok(edits) => Some(edits),
+                Err(_) => None,
+            }
+        })
+        .flatten()
+        .collect();
 
     let transaction =
-        helix_lsp::util::generate_transaction_from_edits(doc.text(), edits, offset_encoding);
+        helix_lsp::util::generate_transaction_from_edits(doc.text(), all_edits, offset_encoding);
 
     doc.apply(&transaction, view_id);
 }