Append a suffix at then end of a chunk logged by splitLongMultilineMessage

`os_log` truncates trailing whitespace in a log message. If a chunk containing the file contents ends with a newline, this means that the newline will not get logged and thus the file contents read from the log aren't correct. Append an end marker to each chunk to prevent this trimming.

Author: ahoppen

Sources/LSPLogging/SplitLogMessage.swift

@@ -12,8 +12,8 @@
 
 /// Splits `message` on newline characters such that each chunk is at most `maxChunkSize` bytes long.
 ///
-/// The intended use case for this is to split compiler arguments into multiple chunks so that each chunk doesn't exceed
-/// the maximum message length of `os_log` and thus won't get truncated.
+/// The intended use case for this is to split compiler arguments and a file's contents into multiple chunks so
+/// that each chunk doesn't exceed the maximum message length of `os_log` and thus won't get truncated.
 ///
 ///  - Note: This will only split along newline boundary. If a single line is longer than `maxChunkSize`, it won't be
 ///    split. This is fine for compiler argument splitting since a single argument is rarely longer than 800 characters.
@@ -23,6 +23,12 @@ public func splitLongMultilineMessage(message: String, maxChunkSize: Int = 800)
     if let lastChunk = chunks.last, lastChunk.utf8.count + line.utf8.count < maxChunkSize {
       chunks[chunks.count - 1] += "\n" + line
     } else {
+      if !chunks.isEmpty {
+        // Append an end marker to the last chunk so that os_log doesn't truncate trailing whitespace,
+        // which would modify the source contents.
+        // Empty newlines are important so the offset of the request is correct.
+        chunks[chunks.count - 1] += "\n--- End Chunk"
+      }
       chunks.append(String(line))
     }
   }