perf(compile): cache file walk and fix placement for narrow patterns by Roozi489 · Pull Request #871 · microsoft/apm

Roozi489 · 2026-04-23T09:31:33Z

Depends on #870.

Build a single _directory_files_cache during project analysis and use it for all subsequent glob matching, eliminating repeated os.walk/iterdir() calls. Also fixes instruction files with narrow applyTo globs (e.g. Engine/Plugins/PCG*/**/*) incorrectly landing at ./ instead of their target subtree -- _optimize_low_distribution_placement now uses _find_minimal_coverage_placement (lowest common ancestor) instead of a pollution-scored search that biased toward root. Stats loop rewritten from O(N^2) to O(N).

Replace glob.glob(recursive=True) in find_primitive_files() with an os.walk loop that prunes directories before descending into them. This allows compilation.exclude patterns (and the new DEFAULT_SKIP_DIRS constant) to short-circuit traversal into large subtrees -- e.g. a UE5 game repo with 265 K files no longer hangs because node_modules / build / apm_modules are skipped at the first encountered node. Changes: - constants.py: add DEFAULT_SKIP_DIRS frozenset (replaces duplicate inline sets in discovery.py and context_optimizer.py) - discovery.py: os.walk + early prune; thread exclude_patterns into traversal so callers no longer need a post-filter pass; add _glob_match() helper for ** zero-segment matching - test_discovery_walk.py: new unit tests covering prune behaviour, exclude_patterns, symlink rejection, and ** pattern matching Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Build a _directory_files_cache during _analyze_project_structure() so that _cached_glob(), _find_matching_directories(), and _directory_matches_pattern() all work from the same in-memory file list instead of issuing repeated os.walk / iterdir() calls against disk. Key changes in context_optimizer.py: - _analyze_project_structure: move dirs[:] pruning BEFORE the depth / exclusion checks so os.walk never descends into excluded subtrees; populate _directory_files_cache[dir] = [file, ...] for later use - _cached_glob: replaces glob.glob(cwd=base_dir) with a scan of _directory_files_cache using _glob_match() from discovery.py - _find_matching_directories: fast path for ** patterns derives directory hits from the cached glob set (no iterdir()); slow path for non-recursive patterns iterates cached files - _calculate_optimization_stats: rewrite O(N^2) efficiency loop to O(N) using pre-computed pattern_dir_sets from _pattern_cache - _optimize_low_distribution_placement: go straight to _find_minimal_coverage_placement (lowest common ancestor) instead of the pollution-scored candidate search that biased toward root; fixes instruction files for narrow applyTo globs landing at ./ when all matching files live under a specific subtree - Drop local DEFAULT_EXCLUDED_DIRNAMES; use DEFAULT_SKIP_DIRS from constants (introduced in perf/discovery-prune) Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

microsoft-github-policy-service · 2026-04-23T09:31:44Z

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Copilot

Pull request overview

This PR improves apm compile performance and correctness by caching filesystem traversal results and adjusting low-distribution instruction placement to use lowest-common-ancestor coverage, reducing repeated os.walk/iterdir() work and avoiding incorrect root placements for narrow applyTo patterns.

Changes:

Switch primitive discovery find_primitive_files() from glob.glob(recursive=True) to os.walk with early directory pruning and shared skip dirs.
Add DEFAULT_SKIP_DIRS constant and use it to prune traversal in both primitives discovery and compilation analysis.
Update ContextOptimizer to cache per-directory file lists and use them for glob matching, directory matching, and stats computation; adjust low-distribution placement to use minimal-coverage (LCA) placement.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
tests/unit/primitives/test_discovery_walk.py	Adds unit tests for the new walk-based discovery helpers and verifies ContextOptimizer’s cached glob behavior.
src/apm_cli/primitives/discovery.py	Implements `_glob_match` and updates `find_primitive_files()` to walk/prune instead of `glob.glob()`.
src/apm_cli/constants.py	Introduces `DEFAULT_SKIP_DIRS` to centralize unconditional traversal skips.
src/apm_cli/compilation/context_optimizer.py	Adds `_directory_files_cache` and rewires `_cached_glob` / matching / stats; changes single-point placement to use LCA.
CHANGELOG.md	Documents the behavior/perf changes under Unreleased.

Copilot · 2026-04-23T09:41:15Z

+        Strategy: Place at the lowest common ancestor of all matching directories.
+        This is the most specific directory that still provides full hierarchical
+        coverage, avoiding pollution of unrelated subtrees.
        """
-        candidates = self._generate_all_candidates(matching_directories, instruction)
+        # Find the deepest directory that covers all matches
+        minimal_coverage = self._find_minimal_coverage_placement(matching_directories)
+        if minimal_coverage and minimal_coverage in self._directory_cache:
+            return [minimal_coverage]


_optimize_single_point_placement() now uses lowest-common-ancestor placement, which is the crux of the bugfix described in the PR. There are existing tests for single-point placement and for LCA-at-root sibling coverage, but there is no test that asserts a non-root LCA is chosen when multiple matching directories exist under a deep subtree (the regression you mention like Engine/Plugins/PCG*/**/*). Add a unit test that constructs such a tree and asserts the placement directory is that subtree LCA, not the project root.

Copilot · 2026-04-23T09:41:15Z

+### Changed
+
+- `find_primitive_files()` now uses `os.walk` with early directory pruning instead of `glob.glob(recursive=True)`, so `compilation.exclude` patterns prevent traversal into expensive subtrees (e.g. large game-engine asset trees). Adds shared `DEFAULT_SKIP_DIRS` constant used by both discovery and compilation.
+- `ContextOptimizer` now builds a `_directory_files_cache` during `_analyze_project_structure()` and uses it for `_cached_glob`, `_find_matching_directories`, and `_directory_matches_pattern`, eliminating repeated `os.walk` / `iterdir()` calls. Directory pruning is moved before the depth check so excluded subtrees are never descended into. Stats loop rewritten from O(N^2) per-directory inheritance walk to O(N) with pre-computed pattern sets. Low-distribution placement now uses `_find_minimal_coverage_placement` directly instead of a pollution-scored candidate search that incorrectly biased toward the project root.


The new changelog bullets under ## [Unreleased] do not follow the repo format rules: each entry should end with a PR reference like (#<number>), and be one logical change per line. Please add the appropriate PR number(s) to these entries (and consider splitting the long ContextOptimizer bullet if needed).

Copilot · 2026-04-23T09:41:15Z

+        # Match files against the requested patterns
+        for file_name in files:
+            file_path = current / file_name
+            rel_str = str(file_path.relative_to(base_path)).replace(os.sep, '/')
+            for pattern in patterns:
+                if _glob_match(rel_str, pattern):
+                    all_files.append(file_path)
+                    break


find_primitive_files() iterates files from os.walk() without sorting, which can make primitive discovery order nondeterministic across filesystems. Because local primitives with the same name are conflict-resolved by first-seen order, this can lead to different winners on different machines. Sort files (and ideally return a consistently sorted valid_files) to preserve deterministic behavior similar to the old glob.glob() path ordering.

Copilot · 2026-04-23T09:41:15Z

 def _should_skip_directory(dir_path: str) -> bool:
    """Check if a directory should be skipped during scanning.

    Args:
        dir_path (str): Directory path to check.

    Returns:
        bool: True if directory should be skipped, False otherwise.
    """
-    skip_patterns = {
-        '.git',
-        'node_modules',
-        '__pycache__',
-        '.pytest_cache',
-        '.venv',
-        'venv',
-        '.tox',
-        'build',
-        'dist',
-        '.mypy_cache'
-    }
-
    dir_name = os.path.basename(dir_path)
-    return dir_name in skip_patterns
+    return dir_name in DEFAULT_SKIP_DIRS


_should_skip_directory() is now unused (no references in the repo) and duplicates the DEFAULT_SKIP_DIRS check already done inline during traversal. Consider removing it to avoid dead code, or reintroduce a call site if it is meant to be the canonical skip check.

Copilot · 2026-04-23T09:41:16Z

+# These never contain APM primitives or user source files and can be
+# very large (e.g. node_modules, .git objects).  Used by discovery,
+# compilation, and content hashing to avoid expensive walks.
+# NOTE: .apm is intentionally absent -- it is where primitives live.


The comment for DEFAULT_SKIP_DIRS says these directories "never contain APM primitives", but apm_modules/ can contain dependency primitives (it is just intentionally excluded from local traversal). Reword the comment to reflect that these dirs are skipped because they are not relevant for project-source analysis / local primitive discovery. Also consider updating the docs default-exclusions list (e.g. reference/cli-commands.md) since venv/ is now an unconditional skip.

Suggested change

# These never contain APM primitives or user source files and can be

# very large (e.g. node_modules, .git objects). Used by discovery,

# compilation, and content hashing to avoid expensive walks.

# NOTE: .apm is intentionally absent -- it is where primitives live.

# These directories are not relevant to project-source analysis or local

# primitive discovery and may be very large (e.g. node_modules, .git

# objects). Used by discovery, compilation, and content hashing to avoid

# expensive walks.

# NOTE: .apm is intentionally absent because local project primitives may

# live there and should still be discovered.

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Roozi489 · 2026-04-23T10:35:29Z

@microsoft-github-policy-service agree

Martin Matouš and others added 2 commits April 23, 2026 11:26

Copilot AI review requested due to automatic review settings April 23, 2026 09:31

Roozi489 requested review from danielmeppiel and sergio-sisternes-epam as code owners April 23, 2026 09:31

Copilot started reviewing on behalf of Roozi489 April 23, 2026 09:32 View session

Copilot AI reviewed Apr 23, 2026

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Roozi489 mentioned this pull request Apr 23, 2026

perf(discovery): prune excluded subtrees during traversal #870

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perf(compile): cache file walk and fix placement for narrow patterns#871

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-# These never contain APM primitives or user source files and can be
-# very large (e.g. node_modules, .git objects).  Used by discovery,
-# compilation, and content hashing to avoid expensive walks.
-# NOTE: .apm is intentionally absent -- it is where primitives live.
+# These directories are not relevant to project-source analysis or local
+# primitive discovery and may be very large (e.g. node_modules, .git
+# objects). Used by discovery, compilation, and content hashing to avoid
+# expensive walks.
+# NOTE: .apm is intentionally absent because local project primitives may
+# live there and should still be discovered.

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