From aa13a35193d747adc7eed20de80a8cb929a5a973 Mon Sep 17 00:00:00 2001
From: Tobias Gurtzick <magic@wizardtales.com>
Date: Thu, 16 May 2019 13:33:16 +0200
Subject: [PATCH] feat(error handling): added advanced error handling and
 rollback

Signed-off-by: Tobias Gurtzick <magic@wizardtales.com>
---
 lib/executors/versioned/v2.js | 19 ++++++++----
 lib/learn.js                  | 55 ++++++++++++++++++++++++++++-------
 2 files changed, 59 insertions(+), 15 deletions(-)

diff --git a/lib/executors/versioned/v2.js b/lib/executors/versioned/v2.js
index 08a0d63c..2958101e 100644
--- a/lib/executors/versioned/v2.js
+++ b/lib/executors/versioned/v2.js
@@ -2,6 +2,7 @@
 
 const Promise = require('bluebird');
 const State = require('../../state');
+const log = require('db-migrate-shared').log;
 const Learn = require('../../learn');
 const Chain = require('../../chain');
 const StateTravel = require('../../methods/v2/statetravel');
@@ -49,11 +50,19 @@ const execUnit = {
     chain.addChain(Migrate);
 
     await State.startMigration(context._driver, file, context.internals);
-    await _file.migrate(chain, {
-      options: context.internals.safeOptions,
-      seedLink: context.seedLink,
-      dbm: context.internals.safeOptions.dbmigrate
-    });
+    try {
+      await _file.migrate(chain, {
+        options: context.internals.safeOptions,
+        seedLink: context.seedLink,
+        dbm: context.internals.safeOptions.dbmigrate
+      });
+    } catch (err) {
+      log.error(
+        'An error occured. No alternative failure strategy defined. Rolling back!'
+      );
+      await execUnit.down(context, driver, file);
+      throw err;
+    }
     return Promise.promisify(context.writeMigrationRecord.bind(context))(file);
     return execUnit.learn(context, driver, file);
 
diff --git a/lib/learn.js b/lib/learn.js
index 0e33eb78..39d2e328 100644
--- a/lib/learn.js
+++ b/lib/learn.js
@@ -3,6 +3,7 @@ const Shadow = require('./driver/shadow');
 
 class STD {
   constructor ({ schema, modSchema: mod }, driver) {
+    this.validations = {};
     this.driver = driver;
     this.indizies = schema.i;
     this.schema = schema.c;
@@ -98,16 +99,50 @@ class STD {
     let alter = {};
     if (this.schema[t]) {
       if (this.schema[t][c].notNull === true) {
-        if (this.driver._meta.supports.optionParam === true) {
-          throw new Error(
-            'Can not drop a notNull column without providing a' +
-              ' recreation strategy.'
-          );
-        } else {
-          throw new Error(
-            'This driver does not support optionParameters which are' +
-              ' required to provide a recreation strategy.'
-          );
+        if (this.validations.columnStrategies !== true) {
+          if (
+            this.driver._meta &&
+            this.driver._meta.supports &&
+            this.driver._meta.supports.optionParam === true
+          ) {
+            /**
+             * This is a validation only, no action will be taken unless throwing
+             * errors.
+             *
+             * The driver needs to respect the options properly.
+             */
+            switch (o.columnStrategy) {
+              case 'defaultValue':
+                break;
+              case 'delay':
+                break;
+              default:
+                if (!o.columnStrategy) {
+                  throw new Error(
+                    'Can not drop a notNull column without providing a' +
+                      ' recreation strategy.'
+                  );
+                }
+                throw new Error(
+                  `There is no such column recreation strategy "${
+                    o.columnStrategy
+                  }!"`
+                );
+            }
+          } else {
+            throw new Error(
+              'This driver does not support optionParameters which are' +
+                ' required to provide a recreation strategy.'
+            );
+          }
+
+          if (!this.driver._meta.supports.columnStrategies) {
+            throw new Error(
+              'This driver does not support column recreation strategies.'
+            );
+          }
+
+          this.validations.columnStrategies = true;
         }
       }
       this.modS[t] = {};