fix(callgraph): Add fallback stdlib check for direct module imports

[shivasurya]

Summary

Fixes stdlib resolution issue where calls like os.path.join() were not being resolved when modules were imported directly with import os.path.

Depends on: #338 (PR #2 - Stdlib loader)

Problem

When Python code imports stdlib modules directly (e.g., import os.path), the resolution logic was failing:

import os.path  # Import os.path directly, not just os

result = os.path.join(a, b)  # Call os.path.join()

Why it failed:

1. importMap has "os.path" → "os.path" mapping
2. When resolving os.path.join, we split into base="os" and rest="path.join"
3. importMap.Resolve("os") returns false (because import is "os.path", not "os")
4. Never reaches stdlib validation → marked as unresolved

Result: 310+ stdlib calls marked as external_framework failures

Solution

Added fallback stdlib check before giving up on resolution:

// builder.go:738-744
// PR #2: Last resort - check if target is a stdlib call (e.g., os.path.join)
// This handles cases where stdlib modules are imported directly (import os.path)
if typeEngine != nil && typeEngine.StdlibRegistry != nil {
    if validateStdlibFQN(target, typeEngine.StdlibRegistry) {
        return target, true, nil
    }
}

This checks the full target string (e.g., os.path.join) against the stdlib registry with platform-specific aliasing (os.path → posixpath).

Impact

Resolution Improvement

Before this fix (PR #2 only):

• Resolution: 66.3% (3,561/5,367 calls)
• Unresolved: 1,806 calls
• os.path.join in top unresolved: 107 occurrences
• external_framework failures: 311 (including os.*: 311)

After this fix:

• Resolution: 72.1% (3,871/5,367 calls)
• Unresolved: 1,496 calls
• os.path.join: FULLY RESOLVED (not in top 20 unresolved)
• external_framework failures: 1 (down from 311)
  • os.*: 1 (99.7% reduction)

Net improvement:

• +310 resolutions (5.8 percentage points)
• Resolved 310 out of 311 os. stdlib calls*

Top 20 Unresolved (After Fix)

Now mostly pytest fixtures and third-party libraries:

1. tmpdir.join (86) - pytest fixture
2. tmp_path.joinpath (71) - pytest fixture
3. in_git_dir.join (42) - pytest fixture
4. cap_out.get (35) - pytest fixture
5. f.read (32) - stdlib, needs type inference
6. f.write (30) - stdlib, needs type inference
7. cfgv.validate (27) - third-party
8. parser.add_argument (22) - stdlib, needs type inference
9. logger.warning (18) - stdlib, needs type inference

Remaining Stdlib Calls Analysis

~135 stdlib calls still unresolved (all require type inference):

• f.read/f.write (62) - need to infer f is a file object
• parser.add_argument (22) - need to infer from type annotation
• logger.warning (18) - need to infer from assignment
• cfg.read/write (33) - need to infer configparser type

These require Phase 3 type inference enhancements (out of scope):

• Variable assignment type inference: logger = logging.getLogger()
• Function parameter annotations: parser: argparse.ArgumentParser
• Context manager types: with open() as f

~361 non-stdlib calls (cannot be resolved without external sources):

• pytest fixtures (214) - dynamically generated
• Third-party libs (68) - cfgv, re_assert
• Custom objects (79) - project-specific

Test Results

Build & Tests

gradle buildGo  # ✅ SUCCESS
gradle testGo   # ✅ ALL TESTS PASS
gradle lintGo   # ✅ 0 ISSUES

Validation (pre-commit codebase - 5,367 calls)

Total improvement from baseline:

• Before PR Tree-Sitter Implementation with Source Sink Analysis #1/Parse full method name as identifier #2: 64.7% (3,471 resolved)
• After this fix: 72.1% (3,871 resolved)
• Net gain: +400 resolutions (+7.4 percentage points)

Files Changed

• graph/callgraph/builder.go - Added fallback stdlib check (8 lines)

Part of Stdlib Registry System

• ✅ PR Tree-Sitter Implementation with Source Sink Analysis #1: Python generator (feat(stdlib): Add generic Python 3.14 stdlib registry generator #337)
• ✅ PR Parse full method name as identifier #2: Go local loader (feat(callgraph): Add local stdlib registry loader with resolution #338)
• ✅ PR Parse full method name as identifier #2.5: Resolution fix (this PR)
• ⏳ PR Added support for method query like interface #3: Remote registry hosting
• ⏳ PR Feature: Add Method Declaration filter based on attributes #4: Automated updates

🤖 Generated with Claude Code

Co-Authored-By: Claude [email protected]

[safedep]

SafeDep Report Summary

No dependency changes detected. Nothing to scan.

_{This report is generated by SafeDep Github App}

[codecov]

Codecov Report

❌ Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.16%. Comparing base (982129c) to head (11c7dbb).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
sourcecode-parser/graph/callgraph/builder.go	0.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #339      +/-   ##
==========================================
- Coverage   74.20%   74.16%   -0.05%     
==========================================
  Files          45       45              
  Lines        5288     5291       +3     
==========================================
  Hits         3924     3924              
- Misses       1199     1201       +2     
- Partials      165      166       +1     

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