fix (client): solve migration bug with indexes (#471)

This PR solves the index bug described in #457.
The bug was caused by the client migration code which tried to build
table triggers even if the table information is missing. The code was
modified not to build any triggers if the table information is missing.
The table information may be missing e.g. when only creating an index.

.changeset/funny-terms-knock.md

@@ -0,0 +1,5 @@
+---
+"electric-sql": patch
+---
+
+Fix the bug where the client would crash/stop working/stop syncing if it received a migration containing a new index creation.

clients/typescript/src/migrators/builder.ts

@@ -74,6 +74,9 @@ export function makeMigration(migration: MetaData): Migration {
     .map((op) => op.stmts.map((stmt) => stmt.sql))
     .flat()
   const tables = migration.ops
+    // if the operation did not change any table
+    // then ignore it as we don't have to build triggers for it
+    .filter((op) => op.table !== undefined)
     .map((op) => op.table!)
     // remove duplicate tables
     .filter((tbl, idx, arr) => {

clients/typescript/test/migrators/builder.test.ts

@@ -113,6 +113,32 @@ test('generate migration from meta data', (t) => {
   )
 })
 
+test('generate index creation migration from meta data', (t) => {
+  const metaData = parseMetadata({
+    format: 'SatOpMigrate',
+    ops: [
+      encodeSatOpMigrateMsg(
+        SatOpMigrate.fromPartial({
+          version: '20230613112725_814',
+          stmts: [
+            SatOpMigrate_Stmt.create({
+              type: SatOpMigrate_Type.CREATE_INDEX,
+              sql: 'CREATE INDEX idx_stars_username ON stars(username);',
+            }),
+          ],
+        })
+      ),
+    ],
+    protocol_version: 'Electric.Satellite',
+    version: '20230613112725_814',
+  })
+  const migration = makeMigration(metaData)
+  t.assert(migration.version === migrationMetaData.version)
+  t.deepEqual(migration.statements, [
+    'CREATE INDEX idx_stars_username ON stars(username);',
+  ])
+})
+
 const migrationsFolder = path.join('./test/migrators/support/migrations')
 
 test('read migration meta data', async (t) => {