This guide gives a short overview on how to proceed with upgrading PWA dependencies.

Customer Projects

In most cases, customer projects should never do upgrades of dependencies themselves.
Whenever a new PWA version is released, the project should consume it completely, following the recommended importing instructions.
Especially the package-lock.json should be reset to Intershop's version and then (if customized) rewritten using npm install.

PWA Development

The following section should only be abided by Intershop PWA developers and projects that want to disconnect from Intershop's PWA update stream.

Recommendations for the Process of Updating

Always use ng update for upgrading packages, as it also collects and executes possible source code transformers that do some part of automatic code migration.
We would also recommend updating with ng update -C which creates (temporary) commits for each individual update.
This way the process can be tracked easier while doing the update.

After each package update run some form of code check to verify code consistency.
Full checks can be run with npm run check.
You can also run specific subparts of it for verification.

Do not upgrade too many packages at once as you can easily lose track of the process and have to start anew.

Name your GitHub branch for the dependencies update update/... or upgrade/... to run additional 'Updates' checks in the GitHub CI.

0. Before the Update

Check if all third-party libraries for the PWA are compatible with the new version.
This is especially important while doing a major Angular version upgrade.

1. Updating Angular Dependencies

If a new major Angular version should be consumed, follow the steps in the official update guide for advanced app complexity.

ng update gives an overview of available Angular-specific package updates:

$ ng update
...
Found 99 dependencies.
    We analyzed your package.json, there are some packages to update:

      Name                               Version                  Command to update
     --------------------------------------------------------------------------------
      @angular/cli                       9.1.4 -> 9.1.6           ng update @angular/cli
      @angular/core                      9.1.6 -> 9.1.7           ng update @angular/core
      @nguniversal/express-engine        9.1.0 -> 9.1.1           ng update @nguniversal/express-engine

2. Updating Third-Party Project Dependencies

After updating the Angular-specific dependencies, update project libraries (everything you use on the PWA).

npm outdated gives an overview of all upgradable packages in package.json:

$ npm outdated --long
...
@types/jest                          25.2.1    25.2.3   25.2.3  intershop-pwa  devDependencies  https://github.com/DefinitelyTyped/DefinitelyTyped#readme
@types/node                        12.12.38  12.12.39   14.0.1  intershop-pwa  devDependencies  https://github.com/DefinitelyTyped/DefinitelyTyped#readme
angulartics2                          9.0.0     9.0.1    9.0.1  intershop-pwa  dependencies     https://angulartics.github.io/angulartics2/
bootstrap                             4.4.1     4.5.0    4.5.0  intershop-pwa  dependencies     https://getbootstrap.com/
...

Perform updates with ng update as well.

⚠️ @types/node should always remain on the LTS version.
You can upgrade to specific versions with ng update @types/node@12.

3. Update Project Utilities for Testing, Reporting and Linting

Usually utility dependencies can be upgraded individually as they do not interfere with production code directly.
In most cases you can also postpone these updates for a longer time.

4. Cleanup Dependencies

Sometimes build processes and libraries require you to install peer dependencies yourself.
However, this can change after version upgrades and those dependencies become obsolete.
You can check with npm ls <package-name> if a package is used or required.

After removing potential candidates check npm install for peer dependency requirements and also run the responsible process to assure continued functionality.

5. Update Utilities for Formatting

Especially prettier upgrades and applying formatting should be done in individual commits (one for the upgrade and a single one only applying the formatting), so customer projects can ignore the second one and run the formatting independently.

6. Refactoring and Deprecations

Now would be a good time to apply optional code refactoring and replace deprecated code artifacts in individual commits.

7. Restructuring the Update and Documentation

For customer projects it is most important that the process of upgrading is transparent and applicable.
The commits leading to this point should be partially merged and restructured, so that they are importable via cherry-picking.

One recommendation would be to combine all manipulations to package-lock.json in one single commit if no major refactorings or library replacement took place while upgrading.
Further commits should be focused on descriptive commit messages, so the upgrading project can follow them easily.
At the end code re-formatting and optional refactorings should reside in individual commits.

⚠️ Every commit along the way must be consistent. npm run check must be runnable without errors, so the customer project can use it to assure consistency.

Add documentation with migration instructions to the migration guide.

8. Rewrite package-lock.json

Once all dependencies updates are finished it might be a good idea to re-generate the package-lock.json.
For this the node_modules folder and the package-lock.json need to be removed.
Afterwards npm install must be run to get a new clean package-lock.json that can either be amended, if the dependencies update is a single update commit, or as an additional commit.

NOTE

A node script node scripts/upgrade-pwa is provided that is supposed to do the previously explained update steps in an automated fashion.
It can be used to ease the update process but it might need regular adaptions and the results need to be checked.

Security Vulnerabilities

Sometimes npm install reports security vulnerabilities:

$ npm install
...
found 11 vulnerabilities (8 low, 3 high)
  run `npm audit fix` to fix them, or `npm audit` for details

Do not pay too much attention to this.
By doing a complete install on the project, all dependencies (production and development) are audited, but only production dependencies will end up in the production code.
You should, however, pay attention to the production audit:

$ npm audit --production

                       === npm audit security report ===

found 0 vulnerabilities
 in 237 scanned packages

If a package (in most cases a transitive dependency) poses a security risk, most likely an update of the consuming package is already available.
Go ahead and update the package following the steps above.
The output of npm audit will also give useful information about packages.

⚠️ DO NOT RUN npm audit fix!

This would upgrade versions of transitive dependencies directly in package-lock.json and occasionally the affected utilities will stop working.