Custom hooks

[icebob]

• Start Date: 2020-03-08
• Target Version: 0.14
• Reference Issues: -
• Implementation PR: -

Summary

We should extend the current Action Hooks feature. It is used by the ActionHook middleware and it can be defined only before, after & error hooks for actions.

For some major components, it would be good if the user can define custom hooks for the custom functions, e.g. define a beforeTransform or afterPopulate hook in moleculer-db.

Basic example

module.exports = {
    name: "posts",
    mixins: [DbService],
    hooks: {
        // It will be called before transforming
        beforeTransform(ctx, params, doc) {
            doc.id = encrypt(doc._id);
            delete doc._id;
        },

        // It will be called after populating
        afterPopulate(ctx, populate, doc) {
            if (doc.author) {
                delete doc.authorID;
            }
        }
    },
};

function transformDocuments(ctx, params, doc) {
  // Call beforeTransform hook
  if (this.hooks.beforeTransform) {
    await this.hooks.beforeTransform(ctx, params, doc);
  }

  //  Do transforming

  // Call afterTransform hook
  if (this.hooks.afterTransform) {
    await this.hooks.afterTransform(ctx, params, doc);
  }
}

Motivation

Detailed design

Drawbacks

Alternatives

Adoption strategy

Unresolved questions