Add check for pending migrations

[nkwtnb]

First, thank you for creating nice library.

Summary

Compare existing migration files and migration version of DB to check if there is pending migration.

Tests were added as follows

• The test case of applying all migrations
  • Expect that No pending migrations exist (return false)
• The test case of rollbacking all migrations
  • Expect that pending migrations exist (return true)

Thank you!

[witsch]

This, along with perhaps an option to have goose status set its status code to something other than 0 when there are pending migrations would be very helpful.

Our use case is to make some Kubernetes deployments wait for migrations to finish before they are started themselves (using a simple shell loop in most cases). So a straight-forward way to check if the database is "ready" would be great – instead of "grepping" for "pending" that is… 😊

And yes, thanks for all your work on this!

[mfridman]

Note that goose.NewProvider has a method called .Status(ctx) which returns a slice of []*MigrationStatus,

type MigrationStatus struct {
	Source    *Source
	State     State
	AppliedAt time.Time
}

This allows you to quickly loop over all migrations and check for State, which is one of StatePending and StateApplied.

I presume we could add another method called .Pending() that returns only the migrations that are pending.

In the next few weeks I'll be working on #663 to plug the goose.Provider into the CLI code which enables us to expose much of this functionality, and output it as JSON (#350) so you can programmatically goose status | jq .... Would that help in your case?

[witsch]

In the next few weeks I'll be working on #663 to plug the goose.Provider into the CLI code which enables us to expose much of this functionality, and output it as JSON (#350) so you can programmatically goose status | jq .... Would that help in your case?

Yes, it surely would. In fact, #225 (which is linked in #350) sounds very close to what we're doing. I just hadn't seen it before, but the JSON output would totally do the trick for us as well! 😊

[mfridman]

Thank you so much for putting up a PR with tests! I'd prefer to focus our efforts on the goose.Provider which has a bit more knobs and functionality.

At some point we can re-use the .HasPending() method added in #751.

func (p *Provider) HasPending(context.Context) (bool, error) {}

Dropped a #225 (comment) in a related issue.