fix(lsp): process Fenced Code Block in JSDoc on completion correctly (#23822)

partially fixing https://github.com/denoland/deno/issues/23820


https://github.com/denoland/deno/assets/41257923/0adb5d4e-cfd5-4195-9045-19d1c0a07a43

BTW, it is out of scope on this PR that to process type of `@param` to
be an code block due to it's a bit complicated.

cli/lsp/tsc.rs

@@ -3283,14 +3283,17 @@ impl CompletionEntryDetails {
       None
     };
     let documentation = if let Some(parts) = &self.documentation {
+      // NOTE: similar as `QuickInfo::to_hover()`
       let mut value = display_parts_to_string(parts, language_server);
       if let Some(tags) = &self.tags {
-        let tag_documentation = tags
+        let tags_preview = tags
           .iter()
           .map(|tag_info| get_tag_documentation(tag_info, language_server))
           .collect::<Vec<String>>()
-          .join("");
-        value = format!("{value}\n\n{tag_documentation}");
+          .join("  \n\n");
+        if !tags_preview.is_empty() {
+          value = format!("{value}\n\n{tags_preview}");
+        }
       }
       Some(lsp::Documentation::MarkupContent(lsp::MarkupContent {
         kind: lsp::MarkupKind::Markdown,

tests/integration/lsp_tests.rs

@@ -6967,7 +6967,7 @@ fn lsp_completions_auto_import() {
       "uri": "file:///a/🦕.ts",
       "languageId": "typescript",
       "version": 1,
-      "text": "export const foo = \"foo\";\n",
+      "text": "/**\n *\n * @example\n * ```ts\n * const result = add(1, 2);\n * console.log(result); // 3\n * ```\n *\n * @param {number} a - The first number\n * @param {number} b - The second number\n */\nexport function add(a: number, b: number) {\n  return a + b;\n}",
     }
   }));
   client.did_open(json!({
@@ -6984,20 +6984,20 @@ fn lsp_completions_auto_import() {
     json!({ "triggerKind": 1 }),
   );
   assert!(!list.is_incomplete);
-  let item = list.items.iter().find(|item| item.label == "foo");
+  let item = list.items.iter().find(|item| item.label == "add");
   let Some(item) = item else {
-    panic!("completions items missing 'foo' symbol");
+    panic!("completions items missing 'add' symbol");
   };
   let mut item_value = serde_json::to_value(item).unwrap();
   item_value["data"]["tsc"]["data"]["exportMapKey"] =
     serde_json::Value::String("".to_string());
 
   let req = json!({
-    "label": "foo",
+    "label": "add",
     "labelDetails": {
       "description": "./🦕.ts",
     },
-    "kind": 6,
+    "kind": 3,
     "sortText": "￿16_0",
     "commitCharacters": [
       ".",
@@ -7009,14 +7009,14 @@ fn lsp_completions_auto_import() {
       "tsc": {
         "specifier": "file:///a/file.ts",
         "position": 12,
-        "name": "foo",
+        "name": "add",
         "source": "./%F0%9F%A6%95.ts",
          "specifierRewrite": [
            "./%F0%9F%A6%95.ts",
            "./🦕.ts",
          ],
         "data": {
-          "exportName": "foo",
+          "exportName": "add",
           "exportMapKey": "",
           "moduleSpecifier": "./%F0%9F%A6%95.ts",
           "fileName": "file:///a/%F0%9F%A6%95.ts"
@@ -7031,15 +7031,15 @@ fn lsp_completions_auto_import() {
   assert_eq!(
     res,
     json!({
-      "label": "foo",
+      "label": "add",
       "labelDetails": {
         "description": "./🦕.ts",
       },
-      "kind": 6,
-      "detail": "const foo: \"foo\"",
+      "kind": 3,
+      "detail": "function add(a: number, b: number): number",
       "documentation": {
         "kind": "markdown",
-        "value": ""
+        "value": "\n\n*@example*  \n```ts\nconst result = add(1, 2);\nconsole.log(result); // 3\n```  \n\n*@param* - a - The first number  \n\n*@param* - b - The second number"
       },
       "sortText": "￿16_0",
       "additionalTextEdits": [
@@ -7048,7 +7048,7 @@ fn lsp_completions_auto_import() {
             "start": { "line": 0, "character": 0 },
             "end": { "line": 0, "character": 0 }
           },
-          "newText": "import { foo } from \"./🦕.ts\";\n\n"
+          "newText": "import { add } from \"./🦕.ts\";\n\n"
         }
       ]
     })
@@ -10161,7 +10161,7 @@ fn lsp_completions_complete_function_calls() {
       "detail": "(method) Array<never>.map<U>(callbackfn: (value: never, index: number, array: never[]) => U, thisArg?: any): U[]",
       "documentation": {
         "kind": "markdown",
-        "value": "Calls a defined callback function on each element of an array, and returns an array that contains the results.\n\n*@param* - callbackfn A function that accepts up to three arguments. The map method calls the callbackfn function one time for each element in the array.*@param* - thisArg An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value."
+        "value": "Calls a defined callback function on each element of an array, and returns an array that contains the results.\n\n*@param* - callbackfn A function that accepts up to three arguments. The map method calls the callbackfn function one time for each element in the array.  \n\n*@param* - thisArg An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value."
       },
       "sortText": "1",
       "insertText": "map(${1:callbackfn})",