Add failing tests for #1677: pdd sync module resolver ambiguous basename

[prompt-driven-github]

Summary

Adds failing tests that detect the bug reported in #1677: pdd sync resolves modules by short leaf basenames (e.g., page) rather than canonical path-qualified IDs, causing wrong-path file generation when multiple modules share the same basename.

Test Files

• Unit test: tests/test_issue_1677_module_resolver.py

What This PR Contains

• Failing unit tests that reproduce all four bugs identified in the root cause analysis
• Tests are verified to fail on current code and will pass once the bugs are fixed
• Sanity checks that must continue passing after the fix (unambiguous basenames, path-qualified names)

Root Cause

Four implementation bugs in the module identity resolution path:

Bug 1 (agentic_sync.py:391): if fp_stem not in basename_counts guard prevents any filepath stem from being counted more than once. Two page.tsx entries in different directories never produce count > 1 for the bare "page" stem.

Bug 2 (agentic_sync.py:394): set(basename_counts.keys()) discards all count data before the validity loop. Even if count reaches 2 (via the filename path), the set conversion makes "page" (count=2) indistinguishable from "page" (count=1).

Bug 3 (sync_determine_operation.py:528): The filepath cross-check safeguard is gated on "/" in basename; bare basenames like "page" fall through to unconditional first-match return, silently selecting the wrong module path.

Bug 4 (agentic_sync.py:2279-2289): AsyncSyncRunner in the agentic code path is constructed without module_targets; _build_command at agentic_sync_runner.py:2098 falls back to bare basename for all child sync subprocesses.

Real production evidence: pdd_cloud PR #1828, PDD bot commits 82f2723b/7782f10c (2026-05-29) generated frontend/src/page.tsx instead of frontend/src/app/login/page.tsx.

Test Results (Current Code)

5 failed, 5 passed in 1.46s

FAILED test_bare_basename_rejected_when_two_entries_share_same_filename   <- Bug 2
FAILED test_bare_basename_rejected_when_two_filepath_stems_match           <- Bug 1
FAILED test_bare_ambiguous_basename_does_not_silently_return_first_match   <- Bug 3
FAILED test_async_runner_receives_module_targets_in_agentic_path           <- Bug 4
FAILED test_ambiguous_bare_page_rejected_not_silently_resolved             <- Bugs 1+2

Next Steps

1. Fix Bug 1: Change if fp_stem not in basename_counts: to if fp_stem: at agentic_sync.py:391
2. Fix Bug 2: Replace set(basename_counts.keys()) with count-aware check at agentic_sync.py:394
3. Fix Bug 3: Remove if "/" in basename: gate at sync_determine_operation.py:528; return (None, None) when multiple entries match a bare basename
4. Fix Bug 4: Build and pass module_targets dict to AsyncSyncRunner in the agentic path (agentic_sync.py:2279-2289)
5. Verify all 10 unit tests pass: pytest -vv tests/test_issue_1677_module_resolver.py
6. Run full test suite: pytest -vv tests/
7. Mark PR as ready for review

Fixes #1677

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