Add test coverage for WAL mode in database_unittest

This change makes it so that all tests in database_unittest.cc now run
both with WAL mode on and off. Better test coverage will help us
transition to using WAL mode by default in the future.

Bug: 78507
Change-Id: I116a8151c1ab4919a78657e46df98b26eddb7f11
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2490664
Commit-Queue: Shubham Aggarwal <shuagga@microsoft.com>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#821790}

sql/internal_api_token.h

@@ -9,6 +9,7 @@ namespace sql {
 
 namespace test {
 struct ColumnInfo;
+bool CorruptSizeInHeader(const base::FilePath&);
 }  // namespace test
 
 // Restricts access to APIs internal to the //sql package.
@@ -23,6 +24,7 @@ class InternalApiToken {
   friend class DatabaseTestPeer;
   friend class Recovery;
   friend struct test::ColumnInfo;
+  friend bool test::CorruptSizeInHeader(const base::FilePath&);
 };
 
 }  // namespace sql

sql/test/test_helpers.cc

@@ -10,12 +10,12 @@
 #include <memory>
 #include <string>
 
+#include "base/check.h"
 #include "base/check_op.h"
 #include "base/files/file_util.h"
 #include "base/files/scoped_file.h"
 #include "base/threading/thread_restrictions.h"
 #include "sql/database.h"
-#include "sql/sql_features.h"
 #include "sql/statement.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/sqlite/sqlite3.h"
@@ -71,21 +71,49 @@ void WriteBigEndian(unsigned val, unsigned char* buf, size_t bytes) {
   }
 }
 
+bool IsWalDatabase(const base::FilePath& db_path) {
+  // The SQLite header is documented at:
+  //   https://www.sqlite.org/fileformat.html#the_database_header
+  //
+  // Read the entire header.
+  constexpr int kHeaderSize = 100;
+  uint8_t header[kHeaderSize];
+  base::ReadFile(db_path, reinterpret_cast<char*>(header), sizeof(header));
+  constexpr int kWriteVersionHeaderOffset = 18;
+  constexpr int kReadVersionHeaderOffset = 19;
+  // If the read version is unsupported, we can't rely on our ability to
+  // interpret anything else in the header.
+  DCHECK_LE(header[kReadVersionHeaderOffset], 2)
+      << "Unsupported SQLite file format";
+  return header[kWriteVersionHeaderOffset] == 2;
+}
+
 }  // namespace
 
 namespace sql {
 namespace test {
 
 bool CorruptSizeInHeader(const base::FilePath& db_path) {
-  // Checkpoint the WAL file in Truncate mode before corrupting to ensure that
-  // any future transaction always touches the DB file and not just the WAL
-  // file.
-  if (base::FeatureList::IsEnabled(sql::features::kEnableWALModeByDefault)) {
+  if (IsWalDatabase(db_path)) {
+    // Checkpoint the WAL file in Truncate mode before corrupting to ensure that
+    // any future transaction always touches the DB file and not just the WAL
+    // file.
     base::ScopedAllowBlockingForTesting allow_blocking;
-    sql::Database db;
+    // TODO: This function doesn't reliably work if connections to the DB are
+    // still open. Change any uses to ensure that we close all database
+    // connections before calling this function.
+    sql::Database db({.exclusive_locking = false, .wal_mode = true});
     if (!db.Open(db_path))
       return false;
-    if (!db.Execute("PRAGMA wal_checkpoint(TRUNCATE)"))
+    int wal_log_size = 0;
+    int checkpointed_frame_count = 0;
+    int truncate_result = sqlite3_wal_checkpoint_v2(
+        db.db(InternalApiToken()), /*zDb=*/nullptr, SQLITE_CHECKPOINT_TRUNCATE,
+        &wal_log_size, &checkpointed_frame_count);
+    // A successful checkpoint in truncate mode sets these to zero.
+    DCHECK(wal_log_size == 0);
+    DCHECK(checkpointed_frame_count == 0);
+    if (truncate_result != SQLITE_OK)
       return false;
     db.Close();
   }