Advanced update process

When you run into problems running the nx migrate --run-migrations command, here are some solutions to break the process down into manageable steps.

Make changes easier to review by committing after each migration runs

Depending on the size of the update (e.g. migrating between major versions is likely to require more significant changes than migrating between feature releases), and the size of the workspace, the overall nx migrate process may generate a lot of changes which then need to be reviewed. Particularly if there are then manual changes which need to be made in addition to those made by nx migrate, it can make the associated PR harder to review because of not being able to distinguish between what was changed automatically and what was changed manually.

If you pass --create-commits to the --run-migrations command, Nx will automatically create a dedicated commit for each successfully completed migration, for example:

nx migrate --run-migrations --create-commits

Your git history will then look something like the following:

git log

commit 8c862c780106ab8736985c01de1477309a403548
Author: YOUR_GIT_USERNAME <your_git_email@example.com>
Date:   Thu Apr 14 18:35:44 2022 +0400

    chore: [nx migration] name-of-the-second-migration-which-ran

commit eb83bca97927af26aae731a2cf51ad62cc75efa3
Author: YOUR_GIT_USERNAME <your_git_email@example.com>
Date:   Thu Apr 14 18:35:44 2022 +0400

    chore: [nx migration] name-of-the-first-migration-which-ran

etc

By default, nx will apply the prefix of chore: [nx migration] to each commit in order to clearly identify it, but you can also customize this prefix by passing --commit-prefix to the command:

nx migrate --run-migrations --create-commits --commit-prefix="chore(core): AUTOMATED - "

git log

commit 8c862c780106ab8736985c01de1477309a403548
Author: YOUR_GIT_USERNAME <your_git_email@example.com>
Date:   Thu Apr 14 18:35:44 2022 +0400

    chore(core): AUTOMATED - name-of-the-second-migration-which-ran

commit eb83bca97927af26aae731a2cf51ad62cc75efa3
Author: YOUR_GIT_USERNAME <your_git_email@example.com>
Date:   Thu Apr 14 18:35:44 2022 +0400

    chore(core): AUTOMATED - name-of-the-first-migration-which-ran

etc

Customizing which migrations run by altering `migrations.json`

For small projects, running all the migrations at once often succeeds without any issues. For large projects, more flexibility is sometimes needed, and this is where having the separation between generating the migrations to be run, and actually running them, really shines.

All you need to do is amend the JSON file in whatever way makes sense based on your circumstances, for example:

You may have to skip a migration.
You may want to run one migration at a time to address minor issues.
You may want to reorder migrations.
You may want to run the same migration multiple time if the process takes a long time and you had to rebase.

Because you can run nx migrate --run-migrations as many times as you want, you can achieve all of that by commenting out and reordering items in migrations.json. The migration process can take a long time, depending on the number of migrations, so it is useful to commit the migrations file with the partially-updated repo alongside any changes which were created by previously completed migrations.

You can even provide a custom location for the migrations file if you wish, you simply pass it to the --run-migrations option:

nx migrate --run-migrations=migrations.json

Advanced capabilities & recommendations

One major version at a time, small steps

Migrating Jest, Cypress, ESLint, React, Angular, Next, and more is a difficult task. All the tools change at different rates, they can conflict with each other. In addition, every workspace is different. Even though our goal is for you to update any version of Nx to a newer version of Nx in a single go, sometimes it doesn't work. The following process is better for large workspaces.

Say you want to migrate from Nx 10.1.0 to Nx 11.0.1. The following steps are more likely to work comparing to nx migrate 11.0.1.

Run nx migrate 10.4.5 to update the latest version in the 10.x branch.
Run nx migrate --run-migrations.
Next, run nx migrate 11.0.1.
Run nx migrate --run-migrations.

Overriding versions

Sometimes, you may want to use a different version of a package than what Nx recommends. To do that, specify the package and version:

nx migrate @nrwl/workspace --to="jest@22.0.0,cypress:3.4.0"

By default, Nx uses currently installed packages to calculate what migrations need to run. To override them, override the version:

nx migrate @nrwl/workspace --to="@nrwl/jest@12.0.0"

Reverting a failed update

Updates are best done on a clean git history so that it can be easily reversed if something fails. We try our best to make sure migrations do not fail but if one does, please report it on GitHub.

If an update fails for any reason, you can revert it as you do any other set of changes:

git reset --hard # Reset any changes
git clean -fd # Delete newly added files and directories

--create-commits

If using --create-commits, you will need to first retrieve the SHA of the commit before your first automated migration commit in order to jump back to the point before the migrations ran, e.g. git reset --hard YOUR_APPROPRIATE_SHA_HERE)

Reference

migrate