Improve lsp hover definition comment formatting (#3411)

Author: hirasawayuki

private/buf/buflsp/symbol.go

@@ -566,24 +566,12 @@ func (s *symbol) FormatDocs(ctx context.Context) string {
 	var printed bool
 	for _, comments := range allComments {
 		for i := 0; i < comments.Len(); i++ {
-			comment := comments.Index(i).RawText()
-
 			// The compiler does not currently provide comments without their
 			// delimited removed, so we have to do this ourselves.
-			if strings.HasPrefix(comment, "//") {
-				// NOTE: We do not trim the space here, because indentation is
-				// significant for Markdown code fences, and if every line
-				// starts with a space, Markdown will trim it for us, even off
-				// of code blocks.
-				comment = strings.TrimPrefix(comment, "//")
-			} else {
-				comment = strings.TrimSuffix(strings.TrimPrefix(comment, "/*"), "*/")
-			}
-
+			comment := commentToMarkdown(comments.Index(i).RawText())
 			if comment != "" {
 				printed = true
 			}
-
 			// No need to process Markdown in comment; this Just Works!
 			fmt.Fprintln(&tooltip, comment)
 		}
@@ -596,6 +584,41 @@ func (s *symbol) FormatDocs(ctx context.Context) string {
 	return tooltip.String()
 }
 
+// commentToMarkdown processes comment strings and formats them for markdown display.
+func commentToMarkdown(comment string) string {
+	if strings.HasPrefix(comment, "//") {
+		// NOTE: We do not trim the space here, because indentation is
+		// significant for Markdown code fences, and if every line
+		// starts with a space, Markdown will trim it for us, even off
+		// of code blocks.
+		return strings.TrimPrefix(comment, "//")
+	}
+
+	if strings.HasPrefix(comment, "/**") && !strings.HasPrefix(comment, "/**/") {
+		// NOTE: Doxygen-style comments (/** ... */) to Markdown format
+		// by removing comment delimiters and formatting the content.
+		//
+		// Example:
+		// /**
+		//  * This is a Doxygen comment
+		//  * with multiple lines
+		//  */
+		comment = strings.TrimSuffix(strings.TrimPrefix(comment, "/**"), "*/")
+
+		lines := strings.Split(strings.TrimSpace(comment), "\n")
+		for i, line := range lines {
+			line = strings.TrimSpace(line)
+			line = strings.TrimPrefix(line, "*")
+			lines[i] = line
+		}
+
+		return strings.Join(lines, "\n")
+	}
+
+	// Handle standard multi-line comments (/* ... */)
+	return strings.TrimSuffix(strings.TrimPrefix(comment, "/*"), "*/")
+}
+
 // symbolWalker is an AST walker that generates the symbol table for a file in IndexSymbols().
 type symbolWalker struct {
 	file    *file

private/buf/buflsp/symbol_test.go

@@ -0,0 +1,101 @@
+// Copyright 2020-2024 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// This file defines all of the message handlers that involve symbols.
+//
+// In particular, this file handles semantic information in fileManager that have been
+// *opened by the editor*, and thus do not need references to Buf modules to find.
+// See imports.go for that part of the LSP.
+package buflsp
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCommentToMarkdown(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{
+			name:     "single-line-comment",
+			input:    "// this is a single-line comment",
+			expected: " this is a single-line comment",
+		},
+		{
+			name: "multi-line-comment",
+			input: `/*
+ this is a
+ multi-line comment
+*/`,
+			expected: `
+ this is a
+ multi-line comment
+`,
+		},
+		{
+			name: "doxygen-style-comment",
+			input: `/**
+ * Documentation comment
+ * with asterisks
+ */`,
+			expected: ` Documentation comment
+ with asterisks`,
+		},
+		{
+			name: "doxygen-mixed-indentation",
+			input: `/**
+ * First line
+ * - Second line
+ *   - Third line
+ */`,
+			expected: ` First line
+ - Second line
+   - Third line`,
+		},
+		{
+			name:     "markdown-emphasis",
+			input:    "/*This is *important**/",
+			expected: "This is *important*",
+		},
+		{
+			name:     "single-line-doxygen",
+			input:    "/** Single line doc comment */",
+			expected: "Single line doc comment",
+		},
+		{
+			name:     "empty-comment",
+			input:    "/**/",
+			expected: "",
+		},
+		{
+			name:     "only-space",
+			input:    "/* */",
+			expected: " ",
+		},
+	}
+
+	for _, test := range tests {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
+			assert.Equal(t, test.expected, commentToMarkdown(test.input))
+		})
+	}
+}