Tests for forEachDeltaForwards pt3: early exit

Summary:
# Context

 forEachDelta is a function that allows users to call a callback on each delta recorded in EdenFS Journal starting from the current delta towards a specified point.

The existing implementation has some issues, such as not being able to cancel iteration based on the current conditions(eg. too many results), and needing to reverse the results at the end for desired order.

# This Diff
This diff adds tests for  forEachDeltaForwards

This test case covers the following cases:
1) When a callback returns false, forEachDelta will stop iteration at the current point.

# Discussion

Reviewed By: jdelliot

Differential Revision: D68468618

fbshipit-source-id: c05fff1879cac0e55fd5be5109f30c42ecdea0e0

eden/fs/journal/test/JournalTest.cpp

@@ -968,3 +968,75 @@ TEST_F(JournalDeltaTest, for_each_delta_forwards_no_results) {
   EXPECT_FALSE(truncated);
   checkExpect();
 }
+
+/*
+ * Tests that when the fileChange callback returns false, iteration stops
+ */
+TEST_F(JournalDeltaTest, for_each_delta_forwards_early_exit_file) {
+  // We're using a custom expect values so the input to setupGeneric doesn't
+  // matter
+  setupGeneric(0u);
+
+  // We expect to stop when sequenceID == 7, so only the first entry is
+  // populated
+  expectedFileChangeSequences = {6};
+  expectedFileChangeNames = {"foo3"_relpath};
+  expectedFileChangeDtypes = {dtype_t::Regular};
+  expectedHashUpdateSequences = {};
+  expectedHashUpdateHashes = {};
+
+  bool truncated = journal.forEachDeltaForwards(
+      6u,
+      [&](const FileChangeJournalDelta& current) -> bool {
+        if (current.sequenceID == 7) {
+          return false;
+        }
+        fileChangeSequences.push_back(current.sequenceID);
+        fileChangeNames.push_back(current.path1);
+        fileChangeDtypes.push_back(current.type);
+        return true;
+      },
+      [&](const RootUpdateJournalDelta& current) -> bool {
+        hashUpdateSequences.push_back(current.sequenceID);
+        hashUpdateHashes.push_back(current.fromHash);
+        return true;
+      });
+  EXPECT_FALSE(truncated);
+  checkExpect();
+}
+
+/*
+ * Tests that when the hashUpdate callback returns false, iteration stops
+ */
+TEST_F(JournalDeltaTest, for_each_delta_forwards_early_exit_hash) {
+  // We're using a custom expect values so the input to setupGeneric doesn't
+  // matter
+  setupGeneric(0u);
+
+  // We expect to stop when sequenceID == 9, so only the first entry is
+  // populated in hashUpdate
+  expectedFileChangeSequences = {6, 7};
+  expectedFileChangeNames = {"foo3"_relpath, "foo4"_relpath};
+  expectedFileChangeDtypes = {dtype_t::Regular, dtype_t::Regular};
+  expectedHashUpdateSequences = {8};
+  expectedHashUpdateHashes = {hash1};
+
+  bool truncated = journal.forEachDeltaForwards(
+      6u,
+      [&](const FileChangeJournalDelta& current) -> bool {
+        fileChangeSequences.push_back(current.sequenceID);
+        fileChangeNames.push_back(current.path1);
+        fileChangeDtypes.push_back(current.type);
+        return true;
+      },
+      [&](const RootUpdateJournalDelta& current) -> bool {
+        if (current.sequenceID == 9) {
+          return false;
+        }
+        hashUpdateSequences.push_back(current.sequenceID);
+        hashUpdateHashes.push_back(current.fromHash);
+        return true;
+      });
+  EXPECT_FALSE(truncated);
+  checkExpect();
+}