Add tests for Shiny Express app detection

Author: wch

tests/test_shiny_express.py

@@ -0,0 +1,52 @@
+from pathlib import Path
+
+from rsconnect import shiny_express as express
+
+def test_is_express_app(tmp_path: Path):
+    tmp_file = str(tmp_path / "app.py")
+
+    def write_tmp_file(s: str):
+        with open(tmp_file, "w") as f:
+            f.write(s)
+
+    write_tmp_file("import shiny.express")
+    assert express.is_express_app(tmp_file, None)
+    # Check that it works when passing in app_path
+    assert express.is_express_app("app.py", str(tmp_path))
+
+    write_tmp_file("# comment\nimport sys\n\nimport shiny.express")
+    assert express.is_express_app(tmp_file, None)
+
+    write_tmp_file("import sys\n\nfrom shiny import App, express")
+    assert express.is_express_app(tmp_file, None)
+
+    write_tmp_file("import sys\n\nfrom shiny.express import layout, input")
+    assert express.is_express_app(tmp_file, None)
+
+    # Shouldn't find in comment
+    write_tmp_file("# import shiny.express")
+    assert not express.is_express_app(tmp_file, None)
+
+    # Shouldn't find in a string, even if it looks like an import
+    write_tmp_file('"""\nimport shiny.express\n"""')
+    assert not express.is_express_app(tmp_file, None)
+
+    # Shouldn't recurse into with, if, for, def, etc.
+    write_tmp_file("with f:\n  from shiny import express")
+    assert not express.is_express_app(tmp_file, None)
+
+    write_tmp_file("if True:\n  import shiny.express")
+    assert not express.is_express_app(tmp_file, None)
+
+    write_tmp_file("for i in range(2):\n  import shiny.express")
+    assert not express.is_express_app(tmp_file, None)
+
+    write_tmp_file("def f():\n  import shiny.express")
+    assert not express.is_express_app(tmp_file, None)
+
+    # Look for magic comment - should override import detection
+    write_tmp_file("\n#shiny_mode: core\nfrom shiny.express import ui")
+    assert not express.is_express_app(tmp_file, None)
+
+    write_tmp_file("#shiny_mode: express\nfrom shiny import ui")
+    assert express.is_express_app(tmp_file, None)