Fix transpile hanging with incomplete config in non-interactive mode

src/databricks/labs/lakebridge/cli.py

@@ -225,12 +225,21 @@ class _TranspileConfigChecker:
     """The source dialect provided on the command-line, if any."""
     _transpiler_repository: TranspilerRepository
     """The repository where available transpilers are installed."""
+    _is_interactive: bool
+    """Whether the CLI is running interactively (stdin is a TTY). When False, prompting is disabled."""
+    _TRANSPILER_OPTION_CLI_ARGS: dict[str, str] = {
+        "overrides-file": "--overrides-file",
+        "target-tech": "--target-technology",
+    }
+    """Mapping from transpiler option flag names to their corresponding CLI argument names."""
 
     def __init__(
         self,
         config: TranspileConfig | None,
         prompts: Prompts,
         transpiler_repository: TranspilerRepository,
+        *,
+        is_interactive: bool | None = None,
     ) -> None:
         if config is None:
             logger.debug("No workspace transpile configuration, starting from defaults.")
@@ -239,6 +248,16 @@ def __init__(
         self._prompts = prompts
         self._transpiler_repository = transpiler_repository
         self._source_dialect_override = None
+        self._is_interactive = sys.stdin.isatty() if is_interactive is None else is_interactive
+
+    def _require_interactive(self, msg: str) -> None:
+        """Raise a validation error if the CLI is not running interactively.
+
+        Call this before any prompt to ensure a clear error is raised instead of hanging when stdin is not a TTY
+        (e.g. when run non-interactively via the Databricks CLI).
+        """
+        if not self._is_interactive:
+            raise_validation_exception(msg)
 
     @staticmethod
     def _validate_transpiler_config_path(transpiler_config_path: str, msg: str) -> None:
@@ -317,6 +336,9 @@ def _prompt_input_source(self) -> None:
     def _check_input_source(self) -> None:
         config_input_source = self._config.input_source
         if config_input_source is None:
+            self._require_interactive(
+                "Missing required value for '--input-source': use '--input-source' to specify the SQL file or directory to convert."
+            )
             self._prompt_input_source()
         else:
             self._validate_input_source(
@@ -348,6 +370,9 @@ def _prompt_output_folder(self) -> None:
     def _check_output_folder(self) -> None:
         config_output_folder = self._config.output_folder
         if config_output_folder is None:
+            self._require_interactive(
+                "Missing required value for '--output-folder': use '--output-folder' to specify the output directory."
+            )
             self._prompt_output_folder()
         else:
             self._validate_output_folder(
@@ -426,6 +451,9 @@ def _configure_transpiler_config_path(self, source_dialect: str) -> TranspileEng
                 logger.debug(
                     f"Multiple transpilers available for dialect {source_dialect!r}: {compatible_transpilers!r}"
                 )
+                self._require_interactive(
+                    f"Multiple transpilers are available for dialect {source_dialect!r}: use '--transpiler-config-path' to specify which one to use."
+                )
                 transpiler_name = self._prompts.choice("Select the transpiler:", list(compatible_transpilers))
         transpiler_config_path = self._transpiler_repository.transpiler_config_path(transpiler_name)
         logger.info(f"Lakebridge will use the {transpiler_name} transpiler.")
@@ -467,6 +495,9 @@ def _prompt_source_dialect(self) -> TranspileEngine:
             case _:
                 # Multiple dialects available, prompt for which to use.
                 logger.debug(f"Multiple source dialects available, choice required: {supported_dialects!r}")
+                self._require_interactive(
+                    f"Multiple source dialects are available: use '--source-dialect' to specify one of: {', '.join(sorted(supported_dialects))}."
+                )
                 source_dialect = self._prompts.choice("Select the source dialect:", list(supported_dialects))
         engine = self._configure_transpiler_config_path(source_dialect)
         assert engine is not None, "No transpiler engine available for a supported dialect; configuration is invalid."
@@ -572,14 +603,17 @@ def _handle_missing_transpiler_option(self, option: LSPConfigOptionV1) -> JsonVa
         #  - If the option has a default of <none> that means that no value is required, no further action is required.
         #  - Otherwise, a value is required: prompt for it.
         #
-        # TODO: When adding non-interactive support, the otherwise branch need to be modified:
-        #     1. If it can be provided by the command-line, fail and ask the user to provide it.
-        #     2. If it cannot be provided by the command-line, prompt for it if we are running interactively.
-        #     3. If we cannot prompt because we are not running interactively, use the default if there is one.
-        #     4. Fail: the only way to provide a value is via the config.yml, which can be set via 'install-transpile'.
-
         if option.is_optional():
             return None
+        cli_arg = self._TRANSPILER_OPTION_CLI_ARGS.get(option.flag)
+        if cli_arg is not None:
+            self._require_interactive(
+                f"Missing required transpiler option {option.flag!r}: use '{cli_arg}' to provide it."
+            )
+        else:
+            self._require_interactive(
+                f"Missing required transpiler option {option.flag!r}: run 'install-transpile' to configure it."
+            )
         return option.prompt_for_value(self._prompts)
 
     def check(self) -> tuple[TranspileConfig, TranspileEngine]:

tests/unit/test_cli_transpile.py

@@ -1,6 +1,7 @@
 import dataclasses
 import json
 import re
+import sys
 from collections.abc import Generator, Callable
 from unittest.mock import create_autospec, patch, ANY, MagicMock
 from pathlib import Path
@@ -155,6 +156,7 @@ async def do_transpile(*args, **kwargs):
     with (
         patch("databricks.labs.lakebridge.cli.do_transpile", new=do_transpile),
         patch("databricks.labs.lakebridge.cli.ApplicationContext", mock_app_context),
+        patch.object(sys.stdin, "isatty", return_value=True),
     ):
         mock_app_context.return_value.workspace_client = mock_workspace_client
         mock_app_context.return_value.prompts = prompts
@@ -433,7 +435,7 @@ def test_transpile_prints_errors(
     prompts = MockPrompts({"Do you want to use the experimental.*": "no"})
     ctx = ApplicationContext(ws=mock_workspace_client).replace(prompts=prompts)
     input_source = test_resources / "lsp_transpiler" / "unsupported_lca.sql"
-    with caplog.at_level("ERROR"):
+    with caplog.at_level("ERROR"), patch.object(sys.stdin, "isatty", return_value=True):
         cli.transpile(
             w=mock_workspace_client,
             transpiler_config_path=str(test_resources / "lsp_transpiler" / "lsp_config.yml"),
@@ -508,6 +510,75 @@ def test_transpile_no_config_with_source_override(
     )
 
 
+@pytest.fixture
+def mock_stdin_non_interactive():
+    """Patch sys.stdin to simulate a non-interactive (non-TTY) environment."""
+    with patch.object(sys.stdin, "isatty", return_value=False):
+        yield
+
+
+def test_transpile_non_interactive_missing_input_source(
+    mock_cli_for_transpile,
+    transpiler_repository: TranspilerRepository,
+    mock_stdin_non_interactive,
+) -> None:
+    """When stdin is not a TTY and --input-source is missing, raise a clear error instead of hanging."""
+    ws, cfg, set_cfg, _ = mock_cli_for_transpile
+    set_cfg(dataclasses.replace(cfg, input_source=None))
+    with pytest.raises(ValueError, match="Missing required value for '--input-source'"):
+        cli.transpile(w=ws, transpiler_repository=transpiler_repository)
+
+
+def test_transpile_non_interactive_missing_output_folder(
+    mock_cli_for_transpile,
+    transpiler_repository: TranspilerRepository,
+    mock_stdin_non_interactive,
+) -> None:
+    """When stdin is not a TTY and --output-folder is missing, raise a clear error instead of hanging."""
+    ws, cfg, set_cfg, _ = mock_cli_for_transpile
+    set_cfg(dataclasses.replace(cfg, output_folder=None))
+    with pytest.raises(ValueError, match="Missing required value for '--output-folder'"):
+        cli.transpile(w=ws, transpiler_repository=transpiler_repository)
+
+
+def test_transpile_non_interactive_missing_source_dialect_with_multiple_dialects(
+    mock_cli_transpile_no_config,
+    transpiler_repository: TranspilerRepository,
+    empty_input_source: Path,
+    output_folder: Path,
+    mock_stdin_non_interactive,
+) -> None:
+    """When stdin is not a TTY and --source-dialect is missing with multiple available dialects, raise a clear error."""
+    ws, _, _ = mock_cli_transpile_no_config
+    # Provide input_source and output_folder so those checks pass; source_dialect remains unspecified.
+    with pytest.raises(ValueError, match="Multiple source dialects are available"):
+        cli.transpile(
+            w=ws,
+            input_source=str(empty_input_source),
+            output_folder=str(output_folder),
+            transpiler_repository=transpiler_repository,
+        )
+
+
+def test_transpile_non_interactive_missing_required_transpiler_option_with_cli_arg(
+    mock_cli_for_transpile,
+    transpiler_repository: TranspilerRepository,
+    mock_stdin_non_interactive,
+) -> None:
+    """When stdin is not a TTY and a required transpiler option with a known CLI arg is missing, raise a clear error."""
+    ws, cfg, set_cfg, _ = mock_cli_for_transpile
+    # Use informatica pc dialect which requires target-tech option
+    set_cfg(
+        dataclasses.replace(
+            cfg,
+            source_dialect="informatica pc",
+            transpiler_options={"overrides-file": None},  # target-tech is missing
+        )
+    )
+    with pytest.raises(ValueError, match=r"Missing required transpiler option 'target-tech'.*--target-technology"):
+        cli.transpile(w=ws, transpiler_repository=transpiler_repository)
+
+
 def test_describe_transpile(mock_cli_transpile_no_config, transpiler_repository: TranspilerRepository, capsys) -> None:
     """Verify that the 'describe-transpile' CLI command produces a JSON summary of installed transpilers."""
     ws, _, _ = mock_cli_transpile_no_config