How to validate schema.rb file in rails for any syntax errors?

We have two different apps and both are dependent on each other's database for running the tests.

For example, we create App2's DB before running the specs in App1 using the App2 - schema.rb.

The issue here is that there have been a few scenarios where we faced syntax issues like Mysql2::Error: You have an error in your SQL syntax; while creating the App2 SQL structure in App1's test using the schema.rb.

So, I was thinking is there any way to verify the schema.rb in App2 after someone has updated it? So that we never face any issues while creating the structure in App1.

Assuming that your schema.rb contains only Ruby code and not raw SQL, you can likely safely validate it with Rubocop:

rubocop db/schema.rb

Alternatively, you can use ruby to do the same:

ruby -c db/schema.rb

However two things in your post indicate to me that you may have raw SQL:

1. The error Mysql2::Error: You have an error in your SQL syntax
2. The quote "the App2 SQL structure" which may indicate that you're actually dumping the SQL structure

If you have raw SQL then you may want to consider a SQL linter like sqlfluff which can do the same thing that Rubocop does but for raw SQL:

sqlfluff lint db/structure.sql

Alternatively, you can integrate a step in your test suite that deletes and recreates the test database using the schema to ensure that when the test suite runs it validates the schema:

bundle exec rails db:drop db:create db:schema:load db:migrate

You can run this in one or both of the apps' test suites to ensure that the schema is working as expected.

Finally, you should ensure that changes to the schema are only ever made through ActiveRecord migrations; don't edit the schema file directly and ensure that it only updates via migrations.

Additional advice based on the comments conversation below

If your schema is even slightly complex or includes any raw SQL or Arel commands then use the SQL schema dump option instead to generate raw SQL:

> When the schema format is set to :sql, the database structure will be dumped using a tool specific to the database into db/structure.sql. For example, for PostgreSQL, the pg_dump utility is used. For MySQL and MariaDB, this file will contain the output of SHOW CREATE TABLE for the various tables.

This will mean that your schema is managed in db/structure.sql instead of db/schema.rb going forward.

First, add this to config/application.rb:

config.active_record.schema_format = :sql

Next, dump your schema using the following command:

bundle exec rails db:schema:dump

As described above, you can load this schema using:

bundle exec rails db:schema:load