LibSQL+SQLServer+SQLStudio+sql: Propagate connection errors immediately

Currently, when clients connect to SQL server, we inform them of any
errors opening the database via an asynchronous IPC. But we already know
about these errors before returning from the connect() IPC, so this
roundabout propagation is a bit unnecessary. Now if we fail to open the
database, we will simply not send back a valid connection ID.

Disconnect has a similar story. Rather than disconnecting and invoking
an asynchronous IPC to inform the client of the disconnect, make the
disconnect() IPC synchronous (because all it does is remove the database
from the map of open databases). Further, the only user of this command
is the SQL REPL when it wants to connect to a different database, so it
makes sense to block it. This did require moving a bit of logic around
in the REPL to accommodate this change.

6 files changed, 31 insertions, 57 deletions

diff --git a/Userland/Services/SQLServer/ConnectionFromClient.cpp b/Userland/Services/SQLServer/ConnectionFromClient.cpp
index 95d54622da..3c358dd9ae 100644
--- a/Userland/Services/SQLServer/ConnectionFromClient.cpp
+++ b/Userland/Services/SQLServer/ConnectionFromClient.cpp
@@ -37,8 +37,10 @@ void ConnectionFromClient::die()
 Messages::SQLServer::ConnectResponse ConnectionFromClient::connect(DeprecatedString const& database_name)
 {
     dbgln_if(SQLSERVER_DEBUG, "ConnectionFromClient::connect(database_name: {})", database_name);
-    auto database_connection = DatabaseConnection::construct(database_name, client_id());
-    return { database_connection->connection_id() };
+
+    if (auto database_connection = DatabaseConnection::create(database_name, client_id()); !database_connection.is_error())
+        return { database_connection.value()->connection_id() };
+    return { {} };
 }
 
 void ConnectionFromClient::disconnect(u64 connection_id)
diff --git a/Userland/Services/SQLServer/DatabaseConnection.cpp b/Userland/Services/SQLServer/DatabaseConnection.cpp
index ccea8d4061..46f3232000 100644
--- a/Userland/Services/SQLServer/DatabaseConnection.cpp
+++ b/Userland/Services/SQLServer/DatabaseConnection.cpp
@@ -5,7 +5,6 @@
  */
 
 #include <AK/LexicalPath.h>
-#include <SQLServer/ConnectionFromClient.h>
 #include <SQLServer/DatabaseConnection.h>
 #include <SQLServer/SQLStatement.h>
 
@@ -22,64 +21,41 @@ RefPtr<DatabaseConnection> DatabaseConnection::connection_for(u64 connection_id)
     return nullptr;
 }
 
-DatabaseConnection::DatabaseConnection(DeprecatedString database_name, int client_id)
+ErrorOr<NonnullRefPtr<DatabaseConnection>> DatabaseConnection::create(DeprecatedString database_name, int client_id)
+{
+    if (LexicalPath path(database_name); (path.title() != database_name) || (path.dirname() != "."))
+        return Error::from_string_view("Invalid database name"sv);
+
+    auto database = SQL::Database::construct(DeprecatedString::formatted("/home/anon/sql/{}.db", database_name));
+    if (auto result = database->open(); result.is_error()) {
+        warnln("Could not open database: {}", result.error().error_string());
+        return Error::from_string_view("Could not open database"sv);
+    }
+
+    return adopt_nonnull_ref_or_enomem(new (nothrow) DatabaseConnection(move(database), move(database_name), client_id));
+}
+
+DatabaseConnection::DatabaseConnection(NonnullRefPtr<SQL::Database> database, DeprecatedString database_name, int client_id)
     : Object()
+    , m_database(move(database))
     , m_database_name(move(database_name))
     , m_connection_id(s_next_connection_id++)
     , m_client_id(client_id)
 {
-    if (LexicalPath path(m_database_name); (path.title() != m_database_name) || (path.dirname() != ".")) {
-        auto client_connection = ConnectionFromClient::client_connection_for(m_client_id);
-        client_connection->async_connection_error(m_connection_id, SQL::SQLErrorCode::InvalidDatabaseName, m_database_name);
-        return;
-    }
-
-    dbgln_if(SQLSERVER_DEBUG, "DatabaseConnection {} initiating connection with database '{}'", connection_id(), m_database_name);
+    dbgln_if(SQLSERVER_DEBUG, "DatabaseConnection {} initiatedconnection with database '{}'", connection_id(), m_database_name);
     s_connections.set(m_connection_id, *this);
-
-    deferred_invoke([this]() {
-        m_database = SQL::Database::construct(DeprecatedString::formatted("/home/anon/sql/{}.db", m_database_name));
-        auto client_connection = ConnectionFromClient::client_connection_for(m_client_id);
-        if (auto maybe_error = m_database->open(); maybe_error.is_error()) {
-            client_connection->async_connection_error(m_connection_id, maybe_error.error().error(), maybe_error.error().error_string());
-            return;
-        }
-        m_accept_statements = true;
-        if (client_connection)
-            client_connection->async_connected(m_connection_id, m_database_name);
-        else
-            warnln("Cannot notify client of database connection. Client disconnected");
-    });
 }
 
 void DatabaseConnection::disconnect()
 {
     dbgln_if(SQLSERVER_DEBUG, "DatabaseConnection::disconnect(connection_id {}, database '{}'", connection_id(), m_database_name);
-    m_accept_statements = false;
-    deferred_invoke([this]() {
-        m_database = nullptr;
-        s_connections.remove(m_connection_id);
-        auto client_connection = ConnectionFromClient::client_connection_for(client_id());
-        if (client_connection)
-            client_connection->async_disconnected(m_connection_id);
-        else
-            warnln("Cannot notify client of database disconnection. Client disconnected");
-    });
+    s_connections.remove(connection_id());
 }
 
 SQL::ResultOr<u64> DatabaseConnection::prepare_statement(StringView sql)
 {
     dbgln_if(SQLSERVER_DEBUG, "DatabaseConnection::prepare_statement(connection_id {}, database '{}', sql '{}'", connection_id(), m_database_name, sql);
 
-    if (!m_accept_statements)
-        return SQL::Result { SQL::SQLCommand::Unknown, SQL::SQLErrorCode::DatabaseUnavailable };
-
-    auto client_connection = ConnectionFromClient::client_connection_for(client_id());
-    if (!client_connection) {
-        warnln("Cannot notify client of database disconnection. Client disconnected");
-        return SQL::Result { SQL::SQLCommand::Unknown, SQL::SQLErrorCode::InternalError, "Client disconnected"sv };
-    }
-
     auto statement = TRY(SQLStatement::create(*this, sql));
     return statement->statement_id();
 }
diff --git a/Userland/Services/SQLServer/DatabaseConnection.h b/Userland/Services/SQLServer/DatabaseConnection.h
index 3ded1919bc..eea9acbfe2 100644
--- a/Userland/Services/SQLServer/DatabaseConnection.h
+++ b/Userland/Services/SQLServer/DatabaseConnection.h
@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <AK/NonnullRefPtr.h>
 #include <LibCore/Object.h>
 #include <LibSQL/Database.h>
 #include <LibSQL/Result.h>
@@ -14,26 +15,26 @@
 namespace SQLServer {
 
 class DatabaseConnection final : public Core::Object {
-    C_OBJECT(DatabaseConnection)
+    C_OBJECT_ABSTRACT(DatabaseConnection)
 
 public:
+    static ErrorOr<NonnullRefPtr<DatabaseConnection>> create(DeprecatedString database_name, int client_id);
     ~DatabaseConnection() override = default;
 
     static RefPtr<DatabaseConnection> connection_for(u64 connection_id);
     u64 connection_id() const { return m_connection_id; }
     int client_id() const { return m_client_id; }
-    RefPtr<SQL::Database> database() { return m_database; }
+    NonnullRefPtr<SQL::Database> database() { return m_database; }
     void disconnect();
     SQL::ResultOr<u64> prepare_statement(StringView sql);
 
 private:
-    DatabaseConnection(DeprecatedString database_name, int client_id);
+    DatabaseConnection(NonnullRefPtr<SQL::Database> database, DeprecatedString database_name, int client_id);
 
-    RefPtr<SQL::Database> m_database { nullptr };
+    NonnullRefPtr<SQL::Database> m_database;
     DeprecatedString m_database_name;
     u64 m_connection_id { 0 };
     int m_client_id { 0 };
-    bool m_accept_statements { false };
 };
 
 }
diff --git a/Userland/Services/SQLServer/SQLClient.ipc b/Userland/Services/SQLServer/SQLClient.ipc
index e5b87110f4..15d3533333 100644
--- a/Userland/Services/SQLServer/SQLClient.ipc
+++ b/Userland/Services/SQLServer/SQLClient.ipc
@@ -2,11 +2,8 @@
 
 endpoint SQLClient
 {
-    connected(u64 connection_id, DeprecatedString connected_to_database) =|
-    connection_error(u64 connection_id, SQL::SQLErrorCode code, DeprecatedString message) =|
     execution_success(u64 statement_id, u64 execution_id, bool has_results, size_t created, size_t updated, size_t deleted) =|
     next_result(u64 statement_id, u64 execution_id, Vector<DeprecatedString> row) =|
     results_exhausted(u64 statement_id, u64 execution_id, size_t total_rows) =|
     execution_error(u64 statement_id, u64 execution_id, SQL::SQLErrorCode code, DeprecatedString message) =|
-    disconnected(u64 connection_id) =|
 }
diff --git a/Userland/Services/SQLServer/SQLServer.ipc b/Userland/Services/SQLServer/SQLServer.ipc
index ba06d5eb39..2a01ae22f6 100644
--- a/Userland/Services/SQLServer/SQLServer.ipc
+++ b/Userland/Services/SQLServer/SQLServer.ipc
@@ -2,8 +2,8 @@
 
 endpoint SQLServer
 {
-    connect(DeprecatedString name) => (u64 connection_id)
+    connect(DeprecatedString name) => (Optional<u64> connection_id)
     prepare_statement(u64 connection_id, DeprecatedString statement) => (Optional<u64> statement_id)
     execute_statement(u64 statement_id, Vector<SQL::Value> placeholder_values) => (Optional<u64> execution_id)
-    disconnect(u64 connection_id) =|
+    disconnect(u64 connection_id) => ()
 }
diff --git a/Userland/Services/SQLServer/SQLStatement.cpp b/Userland/Services/SQLServer/SQLStatement.cpp
index cce1528f05..a1049bd835 100644
--- a/Userland/Services/SQLServer/SQLStatement.cpp
+++ b/Userland/Services/SQLServer/SQLStatement.cpp
@@ -74,9 +74,7 @@ Optional<u64> SQLStatement::execute(Vector<SQL::Value> placeholder_values)
     m_ongoing_executions.set(execution_id);
 
     deferred_invoke([this, placeholder_values = move(placeholder_values), execution_id] {
-        VERIFY(!connection()->database().is_null());
-
-        auto execution_result = m_statement->execute(connection()->database().release_nonnull(), placeholder_values);
+        auto execution_result = m_statement->execute(connection()->database(), placeholder_values);
         m_ongoing_executions.remove(execution_id);
 
         if (execution_result.is_error()) {