Fix test discovery to never return root module in fast builds

The test_discovery.py script was incorrectly returning "." (root module)
when root pom.xml was changed, causing fast builds to run ALL tests
instead of being targeted. This defeats the purpose of fast builds.

Key fixes:
- Exclude root pom.xml from relevant file detection
- Never return root module from _find_module_for_file
- Add debugging to show when root module is excluded

This ensures fast builds NEVER run full test suites, even when
version bumps or other root changes occur. The full CI/CD build
will handle comprehensive testing.

Signed-off-by: [email protected]

Author: markpollack

.github/scripts/test_discovery.py

@@ -62,9 +62,9 @@ def _get_changed_files(self, base_ref: Optional[str] = None) -> List[str]:
             pr_head = os.environ.get('GITHUB_HEAD_HEAD')   # PRs  
             branch = os.environ.get('GITHUB_REF_NAME')    # pushes
 
-            # For maintenance branches (cherry-picks), use single commit diff
-            if branch and branch.endswith('.x'):
-                # Maintenance branch - use diff with previous commit
+            # For maintenance branches (cherry-picks) or main branch pushes, use single commit diff
+            if (branch and branch.endswith('.x')) or (branch == 'main'):
+                # Maintenance branch or main branch - use diff with previous commit
                 cmd = ["git", "diff", "--name-only", "HEAD~1", "HEAD"]
             elif base_ref:
                 # Explicit base reference provided - use two-dot diff for direct comparison
@@ -112,9 +112,15 @@ def _discover_affected_modules(self, changed_files: List[str]) -> List[str]:
 
         for file_path in changed_files:
             module = self._find_module_for_file(file_path)
-            if module:
+            # DEBUG: Print what we're finding
+            print(f"DEBUG: file={file_path} -> module={module}", file=sys.stderr)
+            if module and module != ".":  # Exclude root module to prevent full builds
                 modules.add(module)
+                print(f"DEBUG: Added module: {module}", file=sys.stderr)
+            elif module == ".":
+                print(f"DEBUG: Excluded root module for file: {file_path}", file=sys.stderr)
 
+        print(f"DEBUG: Final modules before return: {sorted(list(modules))}", file=sys.stderr)
         return sorted(list(modules))
 
     def _find_module_for_file(self, file_path: str) -> Optional[str]:
@@ -128,25 +134,32 @@ def _find_module_for_file(self, file_path: str) -> Optional[str]:
 
         for i in range(len(path_parts), 0, -1):
             potential_module = '/'.join(path_parts[:i])
+            # Handle root case - empty string becomes "."
+            if not potential_module:
+                potential_module = "."
             pom_path = self.repo_root / potential_module / "pom.xml"
 
             if pom_path.exists():
+                # Never return root module to prevent full builds
+                if potential_module == ".":
+                    return None
                 # Found a module - return the relative path from repo root
                 return potential_module
 
-        # Check if it's in the root module
-        if (self.repo_root / "pom.xml").exists():
-            return "."
-        
+        # Never return root module to prevent full builds
         return None
 
     def _is_relevant_file(self, file_path: str) -> bool:
         """Check if a file is relevant for module discovery"""
+        # Always exclude root pom.xml to prevent full builds
+        if file_path == 'pom.xml':
+            return False
+            
         # Include Java source and test files
         if file_path.endswith('.java'):
             return True
 
-        # Include build files
+        # Include build files (but not root pom.xml - handled above)
         if file_path.endswith('pom.xml'):
             return True
 
@@ -179,8 +192,9 @@ def _detect_default_base(self) -> str:
         branch = os.environ.get('GITHUB_REF_NAME')
 
         # Show the actual strategy being used
-        if branch and branch.endswith('.x'):
-            return f"git diff HEAD~1 HEAD (maintenance branch {branch})"
+        if (branch and branch.endswith('.x')) or (branch == 'main'):
+            branch_type = "maintenance" if branch.endswith('.x') else "main"
+            return f"git diff HEAD~1 HEAD ({branch_type} branch {branch})"
         elif pr_base:
             return f"origin/{pr_base} (PR base)"
         elif branch: