Fix icon encoding in PL App pretty-print

src/lightning_app/CHANGELOG.md

@@ -65,6 +65,8 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 - Fixed an issue where custom property setters were not being used `LightningWork` class. ([#14259](https://github.com/Lightning-AI/lightning/pull/14259))
 
+- Fixed an issue where some terminals would display broken icons in the PL app CLI. ([#14226](https://github.com/Lightning-AI/lightning/issues/14226))
+
 
 ## [0.6.0] - 2022-09-08
 

src/lightning_app/cli/cmd_pl_init.py

@@ -2,6 +2,7 @@
 import re
 import shutil
 import subprocess
+import sys
 import tarfile
 import urllib.request
 from pathlib import Path
@@ -149,10 +150,21 @@ def print_pretty_report(
         text_pathname.append(f" {padding} {help_text}", "blue")
 
         icon = "📂 " if path.is_dir() else "📄 "
+        icon = icon if _can_encode_icon(icon) else ""
+
         tree.add(Text(icon) + text_pathname)
 
     print("\n")
     print("Done. The app is ready here:\n")
     print(tree)
     print("\nRun it:\n")
     print(Panel(f"[red]lightning run app {directory.relative_to(Path.cwd()) / 'app.py'}"))
+
+
+def _can_encode_icon(icon: str) -> bool:
+    """Helper function to check whether an icon can be encoded."""
+    try:
+        icon.encode(sys.stdout.encoding)
+        return True
+    except UnicodeEncodeError:
+        return False

tests/tests_app/cli/test_cmd_pl_init.py

@@ -1,11 +1,13 @@
 import os
+import sys
 from unittest import mock
+from unittest.mock import Mock
 
 import pytest
 from click.testing import CliRunner
 
 from lightning_app.cli import lightning_cli
-from lightning_app.cli.cmd_pl_init import download_frontend, pl_app
+from lightning_app.cli.cmd_pl_init import _can_encode_icon, download_frontend, pl_app
 
 
 def test_pl_app_input_paths_do_not_exist(tmp_path):
@@ -84,6 +86,19 @@ def test_pl_app_download_frontend(tmp_path):
     assert "static" in contents
 
 
+def test_pl_app_encode_icon(monkeypatch):
+    stdout_mock = Mock(wraps=sys.stdout)
+    monkeypatch.setattr(sys, "stdout", stdout_mock)
+
+    stdout_mock.encoding = "utf-8"
+    assert _can_encode_icon("📂")
+    assert _can_encode_icon("📄")
+
+    stdout_mock.encoding = "ascii"
+    assert not _can_encode_icon("📂")
+    assert not _can_encode_icon("📄")
+
+
 @pytest.mark.parametrize(
     "cwd, source_dir, script_path",
     [