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fix: skip identical session autosave writes (#1732)

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* test: cover repeated identical session saves

* fix: skip identical session snapshot writes

---------

Co-authored-by: Lawrence Chen <lawrencecchen@users.noreply.github.com>
This commit is contained in:
Lawrence Chen 2026-03-18 03:24:40 -07:00 • committed by GitHub
parent 8a74dc2d05
commit 8512e6d8a5
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GPG key ID: B5690EEEBB952194
2 changed files with 37 additions and 3 deletions
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13
Sources/SessionPersistence.swift
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@ -377,9 +377,10 @@ enum SessionPersistenceStore {
let directory = fileURL.deletingLastPathComponent()
do {
try FileManager.default.createDirectory(at: directory, withIntermediateDirectories: true, attributes: nil)
let encoder = JSONEncoder()
encoder.outputFormatting = [.sortedKeys]
let data = try encoder.encode(snapshot)
let data = try encodedSnapshotData(snapshot)
if let existingData = try? Data(contentsOf: fileURL), existingData == data {
return true
}
try data.write(to: fileURL, options: .atomic)
return true
} catch {
@ -387,6 +388,12 @@ enum SessionPersistenceStore {
}
}
private static func encodedSnapshotData(_ snapshot: AppSessionSnapshot) throws -> Data {
let encoder = JSONEncoder()
encoder.outputFormatting = [.sortedKeys]
return try encoder.encode(snapshot)
}
static func removeSnapshot(fileURL: URL? = nil) {
guard let fileURL = fileURL ?? defaultSnapshotFileURL() else { return }
try? FileManager.default.removeItem(at: fileURL)

27
cmuxTests/SessionPersistenceTests.swift
View file

@ -86,6 +86,28 @@ final class SessionPersistenceTests: XCTestCase {
)
}
func testSaveSkipsRewritingIdenticalSnapshotData() throws {
let tempDir = FileManager.default.temporaryDirectory
.appendingPathComponent("cmux-session-tests-\(UUID().uuidString)", isDirectory: true)
try FileManager.default.createDirectory(at: tempDir, withIntermediateDirectories: true)
defer { try? FileManager.default.removeItem(at: tempDir) }
let snapshotURL = tempDir.appendingPathComponent("session.json", isDirectory: false)
let snapshot = makeSnapshot(version: SessionSnapshotSchema.currentVersion)
XCTAssertTrue(SessionPersistenceStore.save(snapshot, fileURL: snapshotURL))
let firstFileNumber = try fileNumber(for: snapshotURL)
XCTAssertTrue(SessionPersistenceStore.save(snapshot, fileURL: snapshotURL))
let secondFileNumber = try fileNumber(for: snapshotURL)
XCTAssertEqual(
secondFileNumber,
firstFileNumber,
"Saving identical session data should not replace the snapshot file"
)
}
func testWorkspaceCustomColorDecodeSupportsMissingLegacyField() throws {
var snapshot = makeSnapshot(version: SessionSnapshotSchema.currentVersion)
snapshot.windows[0].tabManager.workspaces[0].customColor = nil
@ -780,6 +802,11 @@ final class SessionPersistenceTests: XCTestCase {
windows: [window]
)
}
private func fileNumber(for fileURL: URL) throws -> Int {
let attributes = try FileManager.default.attributesOfItem(atPath: fileURL.path)
return try XCTUnwrap(attributes[.systemFileNumber] as? Int)
}
}
final class SocketListenerAcceptPolicyTests: XCTestCase {