feat: add support for query isolation

FIXES: #679

adonis-typings/database.ts

@@ -34,6 +34,17 @@ declare module '@ioc:Adonis/Lucid/Database' {
 
   export { SimplePaginatorContract, SimplePaginatorMetaKeys }
 
+  /**
+   * Same as knex. Need to redefine, as knex doesn't export this
+   * type
+   */
+  export type IsolationLevels =
+    | 'read uncommitted'
+    | 'read committed'
+    | 'snapshot'
+    | 'repeatable read'
+    | 'serializable'
+
   /**
    * Migration node returned by the migration source
    * implementation
@@ -64,8 +75,11 @@ declare module '@ioc:Adonis/Lucid/Database' {
    * Shape of the transaction function to create a new transaction
    */
   export interface TransactionFn {
-    <T extends any>(callback: (trx: TransactionClientContract) => Promise<T>): Promise<T>
-    (): Promise<TransactionClientContract>
+    <T extends any>(
+      callback: (trx: TransactionClientContract) => Promise<T>,
+      options?: { isolationLevel?: IsolationLevels }
+    ): Promise<T>
+    (options?: { isolationLevel?: IsolationLevels }): Promise<TransactionClientContract>
   }
 
   /**

src/Database/index.ts

@@ -20,6 +20,8 @@ import {
   DatabaseClientOptions,
   TransactionClientContract,
   ConnectionManagerContract,
+  IsolationLevels,
+  QueryClientContract,
 } from '@ioc:Adonis/Lucid/Database'
 
 import { QueryClient } from '../QueryClient'
@@ -123,7 +125,7 @@ export class Database implements DatabaseContract {
   public connection(
     connection: string = this.primaryConnectionName,
     options?: DatabaseClientOptions
-  ) {
+  ): QueryClientContract | TransactionClientContract {
     options = options || {}
 
     /**
@@ -256,8 +258,16 @@ export class Database implements DatabaseContract {
    * Returns a transaction instance on the default
    * connection
    */
-  public transaction(callback?: (trx: TransactionClientContract) => Promise<any>) {
-    return this.connection().transaction(callback)
+  public transaction(
+    callback?:
+      | { isolationLevel?: IsolationLevels }
+      | ((trx: TransactionClientContract) => Promise<any>),
+    options?: { isolationLevel?: IsolationLevels }
+  ) {
+    const client = this.connection()
+    return typeof callback === 'function'
+      ? client.transaction(callback, options)
+      : client.transaction(callback)
   }
 
   /**

src/QueryClient/index.ts

@@ -15,6 +15,7 @@ import { EmitterContract } from '@ioc:Adonis/Core/Event'
 import { ProfilerRowContract, ProfilerContract } from '@ioc:Adonis/Core/Profiler'
 
 import {
+  IsolationLevels,
   DialectContract,
   ConnectionContract,
   QueryClientContract,
@@ -130,9 +131,12 @@ export class QueryClient implements QueryClientContract {
    * query and hold a single connection for all queries.
    */
   public async transaction(
-    callback?: (trx: TransactionClientContract) => Promise<any>
+    callback?:
+      | { isolationLevel?: IsolationLevels }
+      | ((trx: TransactionClientContract) => Promise<any>),
+    options?: { isolationLevel?: IsolationLevels }
   ): Promise<any> {
-    const trx = await this.getWriteClient().transaction()
+    const trx = await this.getWriteClient().transaction(options)
     const transaction = new TransactionClient(
       trx,
       this.dialect,

src/TransactionClient/index.ts

@@ -13,7 +13,11 @@ import { Knex } from 'knex'
 import { EventEmitter } from 'events'
 import { EmitterContract } from '@ioc:Adonis/Core/Event'
 import { ProfilerRowContract } from '@ioc:Adonis/Core/Profiler'
-import { TransactionClientContract, DialectContract } from '@ioc:Adonis/Lucid/Database'
+import {
+  IsolationLevels,
+  DialectContract,
+  TransactionClientContract,
+} from '@ioc:Adonis/Lucid/Database'
 
 import { ModelQueryBuilder } from '../Orm/QueryBuilder'
 import { RawBuilder } from '../Database/StaticBuilder/Raw'
@@ -180,9 +184,12 @@ export class TransactionClient extends EventEmitter implements TransactionClient
    * Returns another instance of transaction with save point
    */
   public async transaction(
-    callback?: (trx: TransactionClientContract) => Promise<any>
+    callback?:
+      | { isolationLevel?: IsolationLevels }
+      | ((trx: TransactionClientContract) => Promise<any>),
+    options?: { isolationLevel?: IsolationLevels }
   ): Promise<any> {
-    const trx = await this.knexClient.transaction()
+    const trx = await this.knexClient.transaction(options)
     const transaction = new TransactionClient(
       trx,
       this.dialect,