fix(lsp): register formatter dynamically if possible

CHANGELOG.md

@@ -14,6 +14,10 @@ Read our [guidelines for writing a good changelog entry](https://github.com/biom
 
 ### CLI
 
+### LSP
+
+- Fix [#1584](https://github.com/biomejs/biome/issues/1584). Ensure the LSP only registers the formatter once. Contributed by @nhedger
+
 ### Configuration
 
 ### Editors

crates/biome_lsp/src/capabilities.rs

@@ -8,6 +8,48 @@ use tower_lsp::lsp_types::{
 ///
 /// [`InitializeResult`]: lspower::lsp::InitializeResult
 pub(crate) fn server_capabilities(capabilities: &ClientCapabilities) -> ServerCapabilities {
+    let supports_formatter_dynamic_registration = capabilities
+        .text_document
+        .as_ref()
+        .and_then(|text_document| text_document.formatting.as_ref())
+        .and_then(|formatting| formatting.dynamic_registration)
+        .and_then(|supported| {
+            if supported {
+                None
+            } else {
+                Some(OneOf::Left(true))
+            }
+        });
+
+    let supports_range_formatter_dynamic_registration = capabilities
+        .text_document
+        .as_ref()
+        .and_then(|text_document| text_document.range_formatting.as_ref())
+        .and_then(|range_formatting| range_formatting.dynamic_registration)
+        .and_then(|supported| {
+            if supported {
+                None
+            } else {
+                Some(OneOf::Left(true))
+            }
+        });
+
+    let supports_on_type_formatter_dynamic_registration = capabilities
+        .text_document
+        .as_ref()
+        .and_then(|text_document| text_document.on_type_formatting.as_ref())
+        .and_then(|on_type_formatting| on_type_formatting.dynamic_registration)
+        .and_then(|supported| {
+            if supported {
+                None
+            } else {
+                Some(DocumentOnTypeFormattingOptions {
+                    first_trigger_character: String::from("}"),
+                    more_trigger_character: Some(vec![String::from("]"), String::from(")")]),
+                })
+            }
+        });
+
     ServerCapabilities {
         position_encoding: Some(match negotiated_encoding(capabilities) {
             PositionEncoding::Utf8 => PositionEncodingKind::UTF8,
@@ -19,12 +61,9 @@ pub(crate) fn server_capabilities(capabilities: &ClientCapabilities) -> ServerCa
         text_document_sync: Some(TextDocumentSyncCapability::Kind(
             TextDocumentSyncKind::INCREMENTAL,
         )),
-        document_formatting_provider: Some(OneOf::Left(true)),
-        document_range_formatting_provider: Some(OneOf::Left(true)),
-        document_on_type_formatting_provider: Some(DocumentOnTypeFormattingOptions {
-            first_trigger_character: String::from("}"),
-            more_trigger_character: Some(vec![String::from("]"), String::from(")")]),
-        }),
+        document_formatting_provider: supports_formatter_dynamic_registration,
+        document_range_formatting_provider: supports_range_formatter_dynamic_registration,
+        document_on_type_formatting_provider: supports_on_type_formatter_dynamic_registration,
         code_action_provider: Some(CodeActionProviderCapability::Simple(true)),
         rename_provider: None,
         ..Default::default()