test case that shows the issue by vorburger · Pull Request #215 · vorburger/ch.vorburger.fswatch

vorburger · 2026-01-03T00:33:15Z

gemini-code-assist · 2026-01-03T00:33:28Z

Summary of Changes

Hello @vorburger, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a targeted test case to validate the file watching mechanism's response to file overwrite operations. By simulating an overwrite using "java.nio.file.Files.move" with the "REPLACE_EXISTING" option, the new test ensures that the "DirectoryWatcher" accurately detects and reports the "ChangeKind.CREATED" event, thereby improving the robustness and reliability of file system change detection.

Highlights

New Test Case for File Overwrite: A new test method, "testOverwriteExistingFile", has been added to "DirectoryAndFileWatcherTest.java" to specifically test the behavior of the file watcher when an existing file is overwritten.
REPLACE_EXISTING Option Usage: The new test case utilizes "java.nio.file.Files.move" with the "REPLACE_EXISTING" option to accurately simulate the file overwrite scenario.
ChangeKind.CREATED Verification: The test asserts that the "DirectoryWatcher" correctly reports a "ChangeKind.CREATED" event when an existing file is overwritten, ensuring proper event handling for such operations.
Code Formatting: Minor formatting adjustments were made to "@BeforeClass" and "@test" annotations, moving the "public" keyword to the same line for consistency.

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Code Review

This pull request adds a new test case to demonstrate an issue with file overwrite detection, and also applies some stylistic changes to existing test methods. My review focuses on improving the new test case by removing debugging artifacts and using modern, non-deprecated APIs. Additionally, I've provided suggestions to revert the stylistic changes to maintain consistency with the existing codebase and adhere to common Java style conventions.

gemini-code-assist · 2026-01-03T00:35:03Z

+        dir.mkdirs();
+        final File file = File.createTempFile("test", "txt");
+        final File to = dir.toPath().resolve("test.txt").toFile();
+        Files.copy(file, to);


The com.google.common.io.Files.copy(File, File) method is deprecated and scheduled for removal. It's better to use the standard java.nio.file.Files.copy() instead. This also improves consistency with other parts of the new test that use java.nio.file.Files.

Suggested change

Files.copy(file, to);

java.nio.file.Files.copy(file.toPath(), to.toPath());

gemini-code-assist · 2026-01-03T00:35:03Z

+        AtomicReference<ChangeKind> change = new AtomicReference<>();
+
+        try (DirectoryWatcher dw = new DirectoryWatcherBuilder().path(dir).listener((p, c) -> {
+            System.out.println("c = " + c);


This System.out.println appears to be a debugging statement. It should be removed to keep the test output clean.

gemini-code-assist · 2026-01-03T00:35:03Z

+            assertableExceptionHandler.assertNoErrorInTheBackgroundThread();
+            java.nio.file.Files.move(file.toPath(), to.toPath(), REPLACE_EXISTING);
+
+//             Files.move(file, to);


This commented-out code should be removed to improve code clarity.

Copilot

Pull request overview

This PR adds a new test case testOverwriteExistingFile() to demonstrate issue #95, which appears to be related to file overwriting behavior in the directory watcher. The test attempts to verify that moving a file to overwrite an existing file is correctly detected as a CREATED event.

Key changes:

New test case added to verify file overwrite detection behavior
Import added for StandardCopyOption.REPLACE_EXISTING to support file move operations
Import added for AtomicReference to track change events in the new test
Minor formatting changes to consolidate annotations with method declarations

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Copilot · 2026-01-03T00:35:46Z

+        AtomicReference<ChangeKind> change = new AtomicReference<>();
+
+        try (DirectoryWatcher dw = new DirectoryWatcherBuilder().path(dir).listener((p, c) -> {
+            System.out.println("c = " + c);


Debug output should be removed or replaced with proper logging. The test already has proper assertion mechanisms, and printing to System.out is not appropriate for production test code.

Suggested change

System.out.println("c = " + c);

Copilot · 2026-01-03T00:35:46Z

+            System.out.println("c = " + c);
+            change.set(c);
+        }).exceptionHandler(assertableExceptionHandler).build()) {
+            // We want it to call the listener once for setup, even without any change


This comment is misleading. The DirectoryWatcherBuilder does not call the listener during setup by default. The existingFiles flag is not set to true in this test, so the listener will only be called when file system events occur. This comment should be corrected or removed.

Suggested change

// We want it to call the listener once for setup, even without any change

// Verify that overwriting an existing file triggers a CREATED event via the listener

Copilot · 2026-01-03T00:35:47Z

+
+//             Files.move(file, to);


Commented-out code should be removed. If this was an alternative implementation being considered, it should either be implemented properly or removed entirely.

Suggested change

// Files.move(file, to);

Copilot · 2026-01-03T00:35:47Z

+        try (DirectoryWatcher dw = new DirectoryWatcherBuilder().path(dir).listener((p, c) -> {
+            System.out.println("c = " + c);
+            change.set(c);
+        }).exceptionHandler(assertableExceptionHandler).build()) {
+            // We want it to call the listener once for setup, even without any change
+            assertableExceptionHandler.assertNoErrorInTheBackgroundThread();
+            java.nio.file.Files.move(file.toPath(), to.toPath(), REPLACE_EXISTING);
+
+//             Files.move(file, to);
+            await().atMost(5, SECONDS).until(change::get, is(ChangeKind.CREATED));


The test expects ChangeKind.CREATED, but the DirectoryWatcherBuilder's default eventKinds only includes DELETED and MODIFIED (not CREATED). You need to explicitly configure the watcher to listen for CREATED events by adding .eventKinds(ChangeKind.CREATED, ChangeKind.MODIFIED, ChangeKind.DELETED) to the builder chain, or at minimum .eventKinds(ChangeKind.CREATED). Without this, the test will timeout waiting for a CREATED event that will never be captured.

Copilot · 2026-01-03T00:35:47Z

+        dir.mkdirs();
+        final File file = File.createTempFile("test", "txt");
+        final File to = dir.toPath().resolve("test.txt").toFile();
+        Files.copy(file, to);


The Guava Files.copy method signature for copying between two File objects requires a target file that doesn't exist, or it will throw an exception. Since this test is intended to demonstrate overwriting an existing file, this line may cause the test to fail. Consider using java.nio.file.Files.copy with appropriate options, or using Files.asCharSink to create the initial file content.

Suggested change

Files.copy(file, to);

java.nio.file.Files.copy(file.toPath(), to.toPath(), REPLACE_EXISTING);

test case that shows the issue

759a857

Copilot AI review requested due to automatic review settings January 3, 2026 00:33

Copilot started reviewing on behalf of vorburger January 3, 2026 00:33 View session

gemini-code-assist Bot reviewed Jan 3, 2026

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Copilot AI reviewed Jan 3, 2026

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vorburger added 2 commits January 3, 2026 01:37

Merge branch 'main' into issue-95

486b0b4

Fix QuietPeriodListener swallowing subsequent events (issue #95)

bbcdc23

	Files.copy(file, to);
	java.nio.file.Files.copy(file.toPath(), to.toPath());

	// We want it to call the listener once for setup, even without any change
	// Verify that overwriting an existing file triggers a CREATED event via the listener

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