Log a warning on parse errors, but don't return an LSP error

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 # Development version
 
+- Parse errors in your document no longer trigger an LSP error when you request
+  document or range formatting (which typically would show up as an annoying
+  toast notification in your code editor) (#120).
 
 # 0.1.1
 

crates/lsp/src/handlers_format.rs

@@ -22,17 +22,23 @@ pub(crate) fn document_formatting(
 ) -> anyhow::Result<Option<Vec<lsp_types::TextEdit>>> {
     let doc = state.get_document(&params.text_document.uri)?;
 
+    if doc.parse.has_errors() {
+        // Refuse to format in the face of parse errors, but only log a warning
+        // rather than returning an LSP error, as toast notifications here are distracting.
+        tracing::warn!(
+            "Failed to format {uri}. Can't format when there are parse errors.",
+            uri = params.text_document.uri
+        );
+        return Ok(None);
+    }
+
     let line_width = LineWidth::try_from(80).map_err(|err| anyhow::anyhow!("{err}"))?;
 
     // TODO: Handle FormattingOptions
     let options = RFormatOptions::default()
         .with_indent_style(IndentStyle::Space)
         .with_line_width(line_width);
 
-    if doc.parse.has_errors() {
-        return Err(anyhow::anyhow!("Can't format when there are parse errors."));
-    }
-
     let formatted = format_node(options.clone(), &doc.parse.syntax())?;
     let output = formatted.print()?.into_code();
 
@@ -51,6 +57,16 @@ pub(crate) fn document_range_formatting(
 ) -> anyhow::Result<Option<Vec<lsp_types::TextEdit>>> {
     let doc = state.get_document(&params.text_document.uri)?;
 
+    if doc.parse.has_errors() {
+        // Refuse to format in the face of parse errors, but only log a warning
+        // rather than returning an LSP error, as toast notifications here are distracting.
+        tracing::warn!(
+            "Failed to format {uri}. Can't format when there are parse errors.",
+            uri = params.text_document.uri
+        );
+        return Ok(None);
+    }
+
     let line_width = LineWidth::try_from(80).map_err(|err| anyhow::anyhow!("{err}"))?;
     let range =
         from_proto::text_range(&doc.line_index.index, params.range, doc.line_index.encoding)?;