fix(@angular/cli): chunk log so output is piped properly

Previously the output of some commands with long one-line log would not be
drained properly when piping it, causing it to be truncated.

Author: hansl

packages/angular/cli/lib/cli/index.ts

@@ -93,6 +93,32 @@ function initializeLogging(logger: logging.Logger) {
           break;
       }
 
-      output.write(color(entry.message) + '\n');
+      // If we do console.log(message) or process.stdout.write(message + '\n'), the process might
+      // stop before the whole message is written and the stream is flushed. This happens when
+      // streams are asynchronous.
+      //
+      // NodeJS IO streams are different depending on platform and usage. In POSIX environment,
+      // for example, they're asynchronous when writing to a pipe, but synchronous when writing
+      // to a TTY. In windows, it's the other way around. You can verify which is which with
+      // stream.isTTY and platform, but this is not good enough.
+      // In the async case, one should wait for the callback before sending more data or
+      // continuing the process. In our case it would be rather hard to do (but not impossible).
+      //
+      // Instead we take the easy way out and simply chunk the message and call the write
+      // function while the buffer drain itself asynchronously. With a smaller chunk size than
+      // the buffer, we are mostly certain that it works. In this case, the chunk has been picked
+      // as half a page size (4096/2 = 2048), minus some bytes for the color formatting.
+      // On POSIX it seems the buffer is 2 pages (8192), but just to be sure (could be different
+      // by platform).
+      //
+      // For more details, see https://nodejs.org/api/process.html#process_a_note_on_process_i_o
+      const chunkSize = 2000;  // Small chunk.
+      let message = entry.message;
+      while (message) {
+        const chunk = message.slice(0, chunkSize);
+        message = message.slice(chunkSize);
+        output.write(color(chunk));
+      }
+      output.write('\n');
     });
 }