copy triggers in sqlite table recreation (#39)

### Description of change

Copies triggers when recreating a table in SQLite.

Previously, any DSL migration operations that resulted in recreating the
table would drop the triggers, because they weren't being properly
copied over.

Fixes https://linear.app/n8n/issue/CAT-1709.

Verified in n8n.


### Pull-Request Checklist

<!--
  Please make sure to review and check all of the following.

  If an item is not applicable, you can add "N/A" to the end.
-->

- [ ] Code is up-to-date with the `master` branch
- [ ] `npm run format` to apply prettier formatting
- [ ] `npm run test` passes with this change
- [ ] This pull request links relevant issues as `Fixes #0000`
- [ ] There are new or updated unit tests validating the change
- [ ] Documentation has been updated to reflect this change
- [ ] The new commits follow conventions explained in
[CONTRIBUTING.md](https://github.com/typeorm/typeorm/blob/master/CONTRIBUTING.md)

<!--
  🎉 Thank you for contributing and making TypeORM even better!
-->

Author: mfsiega

src/driver/sqlite-abstract/AbstractSqliteQueryRunner.ts

@@ -2005,6 +2005,14 @@ export abstract class AbstractSqliteQueryRunner
         const upQueries: Query[] = []
         const downQueries: Query[] = []
 
+        // query triggers from old table before recreation
+        const [, tableNameOldInitial] = this.splitTablePath(oldTable.name)
+        const triggerQuery = `SELECT name, sql FROM sqlite_master WHERE type = 'trigger' AND tbl_name = ?`
+        const triggers: { name: string; sql: string }[] = await this.query(
+            triggerQuery,
+            [tableNameOldInitial],
+        )
+
         // drop old table indices
         oldTable.indices.forEach((index) => {
             upQueries.push(this.dropIndexSql(index))
@@ -2112,6 +2120,14 @@ export abstract class AbstractSqliteQueryRunner
             downQueries.push(this.dropIndexSql(index))
         })
 
+        // recreate table triggers
+        triggers.forEach((trigger) => {
+            // upQueries: recreate triggers on the new table (forward migration)
+            upQueries.push(new Query(trigger.sql))
+            // downQueries: recreate triggers on the old table (rollback)
+            downQueries.push(new Query(trigger.sql))
+        })
+
         // update generated columns in "typeorm_metadata" table
         // Step 1: clear data for removed generated columns
         oldTable.columns

test/functional/query-runner/drop-column.ts

@@ -111,6 +111,57 @@ describe("query runner > drop column", () => {
             ))
     })
 
+    it("should preserve triggers when recreating table in sqlite", () =>
+        Promise.all(
+            connections
+            // Only run this test for sqlite-based connections
+                .filter(
+                    (connection) =>
+                        connection.options.type === "sqlite" ||
+                        connection.options.type === "sqlite-pooled",
+                )
+                .map(async (connection) => {
+                    const queryRunner = connection.createQueryRunner()
+
+                    // Get the post table
+                    let table = await queryRunner.getTable("post")
+                    expect(table).to.exist
+
+                    // Create a trigger on the table
+                    const triggerName = "test_insert_trigger"
+                    const triggerSql = `CREATE TRIGGER ${triggerName} AFTER INSERT ON "${table!.name}" BEGIN SELECT 1; END`
+                    await queryRunner.query(triggerSql)
+
+                    // Verify trigger exists before column drop
+                    const triggersBefore: { name: string; sql: string }[] =
+                        await queryRunner.query(
+                            `SELECT name, sql FROM sqlite_master WHERE type = 'trigger' AND tbl_name = ?`,
+                            [table!.name],
+                        )
+                    expect(triggersBefore).to.have.length(1)
+                    expect(triggersBefore[0].name).to.equal(triggerName)
+
+                    // Drop a column, which triggers recreateTable in SQLite
+                    await queryRunner.dropColumn(table!, "version")
+
+                    // Verify trigger still exists after table recreation
+                    table = await queryRunner.getTable("post")
+                    const triggersAfter: { name: string; sql: string }[] =
+                        await queryRunner.query(
+                            `SELECT name, sql FROM sqlite_master WHERE type = 'trigger' AND tbl_name = ?`,
+                            [table!.name],
+                        )
+                    expect(triggersAfter).to.have.length(1)
+                    expect(triggersAfter[0].name).to.equal(triggerName)
+                    expect(triggersAfter[0].sql).to.equal(triggerSql)
+
+                    // Clean up
+                    await queryRunner.query(`DROP TRIGGER ${triggerName}`)
+                    await queryRunner.executeMemoryDownSql()
+                    await queryRunner.release()
+                }),
+        ))
+
     it("should safely handle SQL injection in hasEnumType", () =>
         Promise.all(
             connections