Generated Code Walkthrough

When you ask the AI to create a Reventless application, it generates a complete set of files. Here's what each file does.

DCB Architecture (Example: Catalog Plugin)

catalog-spec/                          # Extension point types
├── package.json
├── rescript.json
└── src/
    └── Products_ExtensionPoint.res    # Public event API

catalog/                               # Plugin implementation
├── package.json
├── rescript.json
├── __mocks__/emptyModule.js
└── src/
    ├── Product/
    │   ├── StateChangeSlice/
    │   │   ├── AddProduct.res             # Command spec: add a product
    │   │   ├── AddProduct_Behavior.res    # state / evolve / decide
    │   │   ├── ChangeProductName.res      # Command spec: rename
    │   │   ├── ChangeProductName_Behavior.res
    │   │   ├── ChangeProductPrice.res     # Command spec: reprice
    │   │   └── ChangeProductPrice_Behavior.res
    │   └── StateViewSlice/
    │       ├── Products.res               # Query spec: product listings
    │       └── Products_Projection.res    # project function
    ├── ExtensionPoint/
    │   └── Products_ExtensionPointMapping.res  # Internal → public events
    ├── Extension/
    │   └── Orders_Extension.res           # Subscribe to Ordering events
    └── Plugin.res                         # GENERATED — wires everything

platform-local/                    # Platform assembly
├── package.json
├── rescript.json
└── src/
    └── Main.res                       # Starts the platform

Each component is split into a spec file (@@reventless.spec — types only) and a body file (_Behavior.res, _Projection.res, _Translation.res, or _Automation.res — logic only). Plugin.res is generated by generate-plugin from the folder layout and carries an "AUTO-GENERATED — do not edit" banner.

Key Files Explained

StateChangeSlice (e.g., AddProduct.res + AddProduct_Behavior.res)

Handles one command type, split across two files.

The spec (AddProduct.res, @@reventless.spec) declares:

• consumedEvent — events this slice reads from the shared log to build decision state
• command — the command this slice handles
• error — the business errors it can return
• event — the events it produces on success

The behavior (AddProduct_Behavior.res, @@reventless.behavior) declares:

• state — minimal decision state (what's needed to accept/reject)
• initialState — the starting value before any event is replayed
• evolve — builds decision state from consumed events
• decide — business rule: accept or reject the command

StateViewSlice (e.g., Products.res + Products_Projection.res)

Projects events into a queryable read model, split across two files.

The spec (Products.res, @@reventless.spec) declares:

• state — the shape of the view record
• consumedEvent — events this view cares about

The projection (Products_Projection.res, @@reventless.projection) declares:

• project — maps each event to Set/Update/UpdateWithDefault/Delete operations

Plugin Composition (Plugin.res — generated)

The wiring file is generated from the folder layout — do not hand-edit it:

1. Builds each slice/view via Platform.StateChangeSlice.Make(Spec, Behavior) / Platform.StateViewSlice.Make(Spec, Projection) (two args: spec + body)
2. Wires extension point mappings and extensions
3. Assembles everything into Platform.Plugin.make(...) with named arrays

Platform Main (e.g., Main.res)

A few lines that start everything:

1. Create the platform: module Platform = ReventlessLocal.Platform.Make()
2. Build each plugin: module Catalog = CatalogPlugin.Plugin.Make(Platform) (note the .Plugin. segment)
3. Start: Platform.makePlatform(~version=..., ~plugins=[...])

Configuration Files

package.json

Dependencies on Reventless framework packages, spec packages from other plugins, and Jest configuration for testing.

rescript.json

ReScript compiler config with namespace, PPX flags, and dependency ordering. The namespace (CatalogPlugin) combines with the generated Plugin module to give the path CatalogPlugin.Plugin.Make(Platform).

What You Can Modify

All component code is regular ReScript — modify freely:

• Add fields to commands/events
• Add new guard conditions in decide
• Change projection logic in project
• Add new slices or read models (drop a new spec + body into the right folder)

The one exception is Plugin.res — it is generated from the folder layout, so re-run generate-plugin (or pnpm run build, whose prebuild step does it for you) after adding or renaming components rather than editing the wiring by hand.

After modifications, run pnpm run build to verify everything compiles, then pnpm test to run tests.