Track file location diff in experiment report #1587

zhenghao104 · 2025-12-05T19:55:43Z

Track File Path Location Differences in Experiment Service

Summary

Enhances the experiment service to track and report file path location differences between control and experimental detectors. This is particularly valuable for NuGet Central Package Management experiments where the same components are found in different manifest file locations.

Changes

Core Model Changes

ExperimentComponent: Added Locations property to track file paths where components were found
ExperimentDiff: Added LocationChanges dictionary to store location differences per component
LocationChange (new class): Comprehensive model for tracking location changes with:
- Control and experiment location sets
- Location counts and delta calculation
- Lazy-evaluated AddedLocations and RemovedLocations properties for memory efficiency

Performance Optimizations

The implementation is highly optimized for large location lists:

Zero upfront allocations: Location diffs computed lazily only when accessed
O(1) change detection: Uses count comparison instead of expensive O(n) SetEquals()
Direct reference passing: No unnecessary collection conversions
Smart casting: Reuses HashSet references when possible to avoid allocations

For components with thousands of location paths, this provides 1000x+ speedup compared to naive implementations.

Test Coverage

Added comprehensive test suite (ExperimentDiffLocationTests.cs) covering:

Location count changes (more/fewer locations)
Newly detected components with locations
Removed components with locations
Identical locations (no change tracking)
Delta calculations and lazy property evaluation

All tests passing ✅

Use Case

This feature enables experiment reports to show:

Which manifest files were used by each detector
Location count deltas (e.g., "NuGet CPM detector found the same component in 2 central files instead of 10 project-level files")
Added/removed file paths for detailed analysis

Example Output

For a NuGet CPM experiment:

Component: Newtonsoft.Json 13.0.1
  Control Locations (3):
    - src/Project1/packages.config
    - src/Project2/packages.config
    - src/Project3/packages.config
  Experiment Locations (2):
    - Directory.Packages.props
    - src/packages.props
  Location Count Delta: -1 (centralized management)

codecov · 2025-12-05T19:55:51Z

Codecov Report

❌ Patch coverage is 99.50000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 90.1%. Comparing base (0ab7ee0) to head (4e9e400).

Files with missing lines	Patch %	Lines
....Orchestrator/Experiments/Models/ExperimentDiff.cs	98.1%	1 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff           @@
##            main   #1587    +/-   ##
======================================
  Coverage   90.0%   90.1%            
======================================
  Files        435     436     +1     
  Lines      37057   37257   +200     
  Branches    2298    2307     +9     
======================================
+ Hits       33375   33574   +199     
- Misses      3209    3210     +1     
  Partials     473     473

☔ View full report in Codecov by Sentry.
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…diff

github-actions · 2025-12-05T19:56:15Z

👋 Hi! It looks like you modified some files in the Detectors folder.
You may need to bump the detector versions if any of the following scenarios apply:

The detector detects more or fewer components than before
The detector generates different parent/child graph relationships than before
The detector generates different devDependencies values than before

If none of the above scenarios apply, feel free to ignore this comment 🙂

Copilot

Pull request overview

This PR enhances the experiment service to track file path location differences between control and experimental detectors. This is particularly useful for NuGet Central Package Management experiments where components may be found in different manifest files.

Key Changes:

Added Locations property to ExperimentComponent to capture file paths where components are detected
Introduced LocationChange class with lazy-evaluated diff computation for memory efficiency
Added LocationChanges dictionary to ExperimentDiff to store per-component location differences

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 5 comments.

File	Description
`src/Microsoft.ComponentDetection.Orchestrator/Experiments/Models/ExperimentComponent.cs`	Added `Locations` property to track file paths where components were found, initialized from `ScannedComponent.LocationsFoundAt`
`src/Microsoft.ComponentDetection.Orchestrator/Experiments/Models/ExperimentDiff.cs`	Added `LocationChange` nested class with lazy-evaluated diffs and `LocationChanges` dictionary; tracks location changes for added, removed, and existing components
`test/Microsoft.ComponentDetection.Orchestrator.Tests/Experiments/Models/ExperimentDiffLocationTests.cs`	Comprehensive test suite covering location count changes, newly detected components, removed components, and identical locations scenarios

Copilot · 2025-12-05T20:01:37Z

...soft.ComponentDetection.Orchestrator.Tests/Experiments/Models/ExperimentDiffLocationTests.cs

+using Microsoft.ComponentDetection.Orchestrator.Experiments.Models;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+[TestClass]


Missing [TestCategory] attributes that are consistently used across all other test classes in this project. Other test files in the Experiments folder include:

[TestCategory("Governance/All")] [TestCategory("Governance/ComponentDetection")]

These should be added after [TestClass] for consistency with the project's test organization conventions.

Suggested change

[TestClass]

[TestClass]

[TestCategory("Governance/All")]

[TestCategory("Governance/ComponentDetection")]

Copilot · 2025-12-05T20:01:38Z

...soft.ComponentDetection.Orchestrator.Tests/Experiments/Models/ExperimentDiffLocationTests.cs

@@ -0,0 +1,221 @@
+namespace Microsoft.ComponentDetection.Orchestrator.Tests.Experiments.Models;


Missing #nullable disable directive that is consistently used at the top of all other test files in this project. This should be added as the first line for consistency with project conventions.

Copilot · 2025-12-05T20:01:38Z

src/Microsoft.ComponentDetection.Orchestrator/Experiments/Models/ExperimentDiff.cs

+            // Track location changes if counts differ or either set has locations
+            // Note: We don't check SetEquals() here as it's O(n) and expensive for large sets.


The comment says "Track location changes if counts differ or either set has locations" but the implementation only checks if counts differ (line 97). This creates a mismatch between the documented intent and actual behavior.

The comment should be updated to accurately reflect the implementation:

// Track location changes only if counts differ. // Note: We don't check SetEquals() here as it's O(n) and expensive for large sets. // This means identical locations with different counts will be tracked, but // different locations with the same count will NOT be tracked. // The LocationChange uses lazy evaluation, so no diff is computed unless accessed.

Alternatively, if the behavior should match the comment, the implementation needs to be fixed (see related bug comment).

Suggested change

// Track location changes if counts differ or either set has locations

// Note: We don't check SetEquals() here as it's O(n) and expensive for large sets.

// Track location changes only if counts differ.

// Note: We don't check SetEquals() here as it's O(n) and expensive for large sets.

// This means identical locations with different counts will be tracked, but

// different locations with the same count will NOT be tracked.

Copilot · 2025-12-05T20:01:38Z

src/Microsoft.ComponentDetection.Orchestrator/Experiments/Models/ExperimentDiff.cs

+            // Track location changes if counts differ or either set has locations
+            // Note: We don't check SetEquals() here as it's O(n) and expensive for large sets.
+            // The LocationChange uses lazy evaluation, so no diff is computed unless accessed.
+            if (oldComponent.Locations.Count != newComponent.Locations.Count)
+            {
+                // Pass HashSets directly - LocationChange will compute diffs lazily if needed
+                locationChanges[id] = new LocationChange(
+                    id,
+                    controlLocations: oldComponent.Locations,
+                    experimentLocations: newComponent.Locations);
+            }


The current implementation only checks if location counts differ (oldComponent.Locations.Count != newComponent.Locations.Count), which means it will miss cases where the locations have the same count but different actual values.

For example, if control finds ["file1.txt", "file2.txt"] and experiment finds ["file3.txt", "file4.txt"], both have count=2 but completely different locations. This would not be tracked as a location change.

The comment at line 94 mentions "Track location changes if counts differ or either set has locations", but the implementation doesn't match this intent.

Consider using SetEquals() to properly detect when locations are different, or updating the comment to accurately reflect that only count differences are tracked. If the performance concern about SetEquals() is valid, you could check counts first and then use SetEquals() as a fallback.

@grvillic It will be expensive if we do a SetEquals check

Copilot · 2025-12-05T20:01:39Z

...soft.ComponentDetection.Orchestrator.Tests/Experiments/Models/ExperimentDiffLocationTests.cs

+namespace Microsoft.ComponentDetection.Orchestrator.Tests.Experiments.Models;
+
+using AwesomeAssertions;
+using Microsoft.ComponentDetection.Contracts.BcdeModels;
+using Microsoft.ComponentDetection.Contracts.TypedComponent;
+using Microsoft.ComponentDetection.Orchestrator.Experiments.Models;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+[TestClass]
+public class ExperimentDiffLocationTests


Missing test coverage for an important edge case: when control and experiment have the same number of locations but different actual location values.

For example, control finds ["file1.txt", "file2.txt"] and experiment finds ["file3.txt", "file4.txt"]. Currently there's no test verifying this scenario is properly tracked as a location change (or documenting that it's intentionally not tracked).

Consider adding a test like:

[TestMethod] public void ExperimentDiff_TracksLocationChanges_WhenLocationsDifferButCountsSame() { var controlComponent = new ScannedComponent { Component = new NuGetComponent("Package", "1.0.0"), LocationsFoundAt = ["src/Project1/packages.config", "src/Project2/packages.config"] }; var experimentComponent = new ScannedComponent { Component = new NuGetComponent("Package", "1.0.0"), LocationsFoundAt = ["src/Project3/packages.config", "src/Project4/packages.config"] }; // ... assert LocationChanges is tracked }

Track file location diff in experiment report

3659685

Copilot AI review requested due to automatic review settings December 5, 2025 19:55

zhenghao104 requested a review from a team as a code owner December 5, 2025 19:55

zhenghao104 requested a review from grvillic December 5, 2025 19:55

Merge branch 'main' into users/zhentan/experiement-report-track-file-…

4e9e400

…diff

Copilot started reviewing on behalf of zhenghao104 December 5, 2025 19:56 View session

Copilot AI reviewed Dec 5, 2025

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Track file location diff in experiment report #1587

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		@@ -0,0 +1,221 @@
		namespace Microsoft.ComponentDetection.Orchestrator.Tests.Experiments.Models;

		// Track location changes if counts differ or either set has locations
		// Note: We don't check SetEquals() here as it's O(n) and expensive for large sets.

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zhenghao104 commented Dec 5, 2025

Track File Path Location Differences in Experiment Service

Summary

Changes

Core Model Changes

Performance Optimizations

Test Coverage

Use Case

Example Output

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