Fix transpile hanging with incomplete config in non-interactive mode

[moomindani]

Summary

Fixes #2086.

When databricks labs lakebridge transpile is run with missing required configuration (e.g. no --input-source), the checker falls back to prompting the user via input(). However, the Databricks CLI intercepts stdin for the transpile command because it expects a JSON summary written to stdout — so the input() call blocks forever with no output or error message. The user has to ^C to escape.

Stack trace from the issue showing where it hangs:

File ".../cli.py", line 235, in _prompt_input_source
    prompted_input_source = self._prompts.question("Enter input SQL path (directory/file)").strip()
File ".../tui.py", line 125, in question
    res = input(prompt)  # <-- hangs here
KeyboardInterrupt

Root cause

_TranspileConfigChecker uses Prompts.question() / Prompts.choice() as a fallback whenever a required configuration value is absent. These methods call input() which blocks on stdin. When the Databricks CLI runs transpile non-interactively, stdin is not connected to the user's terminal, so the call hangs indefinitely.

Fix

• Add _is_interactive: bool to _TranspileConfigChecker (defaults to sys.stdin.isatty(), injectable via is_interactive kwarg for testing).
• Add _require_interactive(msg): raises a descriptive ValueError immediately if not in a TTY — before any input() is reached.
• Call _require_interactive() before each of the 5 prompt sites:

Prompt site	Non-interactive error message
--input-source missing	"Missing required value for '--input-source': use '--input-source' to specify..."
--output-folder missing	"Missing required value for '--output-folder': use '--output-folder' to specify..."
Multiple dialects available	"Multiple source dialects are available: use '--source-dialect' to specify one of: ..."
Multiple transpilers for dialect	"Multiple transpilers are available for dialect X: use '--transpiler-config-path'..."
Required transpiler option missing	"Missing required transpiler option 'X': use '--target-technology' to provide it." (or install-transpile if no CLI arg exists)

• Add _TRANSPILER_OPTION_CLI_ARGS class-level constant mapping known transpiler option flags to their CLI argument names (overrides-file → --overrides-file, target-tech → --target-technology).
• Remove the pre-existing TODO comment in _handle_missing_transpiler_option (addressed by this PR).

Changes to existing tests

Two existing tests used MockPrompts to simulate interactive prompting and previously passed locally only because a developer terminal has a TTY (sys.stdin.isatty() → True). They would silently fail in CI:

• mock_cli_transpile_no_config fixture: uses MockPrompts to answer dialect/path prompts → patched isatty=True.
• test_transpile_prints_errors: uses MockPrompts to answer an experimental option prompt → patched isatty=True.

New tests

Test	What it covers
test_transpile_non_interactive_missing_input_source	Raises when --input-source absent
test_transpile_non_interactive_missing_output_folder	Raises when --output-folder absent
test_transpile_non_interactive_missing_source_dialect_with_multiple_dialects	Raises when dialect must be chosen from multiple options
test_transpile_non_interactive_missing_required_transpiler_option_with_cli_arg	Raises with correct --target-technology hint when target-tech option is absent

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[codecov]

Codecov Report

❌ Patch coverage is 93.75000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 66.46%. Comparing base (7ff77c2) to head (fd4dd2c).

Files with missing lines	Patch %	Lines
src/databricks/labs/lakebridge/cli.py	93.75%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2326      +/-   ##
==========================================
+ Coverage   66.41%   66.46%   +0.04%     
==========================================
  Files          99       99              
  Lines        9094     9110      +16     
  Branches      974      976       +2     
==========================================
+ Hits         6040     6055      +15     
- Misses       2878     2879       +1     
  Partials      176      176              

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