chore(format-po): split multi line comments

packages/format-po/src/__snapshots__/po.test.ts.snap

@@ -274,4 +274,10 @@ msgstr "Keeps any flags that are defined"
 msgid "veryLongString"
 msgstr "One morning, when Gregor Samsa woke from troubled dreams, he found himself transformed in his bed into a horrible vermin. He lay on his armour-like back, and if he lifted his head a little he could see his brown belly, slightly domed and divided by arches into stiff sections. The bedding was hardly able to cover it and seemed ready to slide off any moment. His many legs, pitifully thin compared with the size of the rest of him, waved about helplessly as he looked. \\"What's happened to me?\\" he thought. It wasn't a dream. His room, a proper human"
 
+#. hello
+#. world
+#. js-lingui-explicit-id
+msgid "withMultiLineComments"
+msgstr "Message with multi line comments"
+
 `;

packages/format-po/src/po.test.ts

@@ -1,9 +1,9 @@
 import fs from "fs"
 import path from "path"
 
-import { formatter as createFormatter, POCatalogExtra } from "./po"
 import { CatalogFormatter, CatalogType } from "@lingui/conf"
 import MockDate from "mockdate"
+import { formatter as createFormatter, POCatalogExtra } from "./po"
 
 const defaultParseCtx: Parameters<CatalogFormatter["parse"]>[1] = {
   locale: "en",
@@ -87,6 +87,15 @@ describe("pofile format", () => {
           " helplessly as he looked. \"What's happened to me?\" he thought. It wasn't" +
           " a dream. His room, a proper human",
       },
+      withMultiLineComments: {
+        translation: "Message with multi line comments",
+        comments: [
+          `hello
+          world
+
+          `,
+        ],
+      },
     }
 
     const pofile = format.serialize(catalog, defaultSerializeCtx)

packages/format-po/src/po.ts

@@ -11,6 +11,17 @@ const splitOrigin = (origin: string) => {
   return [file, line ? Number(line) : null] as [file: string, line: number]
 }
 
+const splitMultiLineComments = (comments: string[]) => {
+  return comments.flatMap((comment) =>
+    comment.includes("\n")
+      ? comment
+          .split("\n")
+          .map((slice) => slice.trim())
+          .filter(Boolean)
+      : comment
+  )
+}
+
 /**
  * @internal
  */
@@ -96,7 +107,11 @@ const serialize = (catalog: CatalogType, options: PoFormatterOptions) => {
 
     // The extractedComments array may be modified in this method,
     // so create a new array with the message's elements.
-    item.extractedComments = [...(message.comments || [])]
+    item.extractedComments = [
+      ...(message.comments?.length
+        ? splitMultiLineComments(message.comments)
+        : []),
+    ]
 
     item.flags = ((message.extra?.flags || []) as string[]).reduce<
       Record<string, boolean>