dynamic palette

Design notes for #322

Currently, the palette of nodes is loaded when the runtime starts and does not change.

The runtime needs to allow nodes to be added/removed dynamically.

Some points that need to be considered:

• nodes can be added by dropping files into the node path, or by npm. Both of these mechanisms should be supported by this feature
  • adding by file will expect the file to have already been copied into node path
  • adding by npm will trigger an npm install of the module
  • future support for importing a zip or files themselves?
• removing a node cannot 'unload' the module - care must be taken if the node creates any 'static' resources
• removing a node in the editor must allow it to remove any artefacts added to the page (eg, debug node's tab)
• a node file or module can contain multiple nodes. Making a request to remove a single node type may trigger the removal of multiple node types.
• what to do if the node is being used in the current flow? Safest option is to reject the removal.
• removing a node, without also removing the files, will mean it returns to the palette on the next restart. That would be unexpected.

On the packaging of nodes

node

A node is defined in an html file and a js file. The js file will include a call to the runtime's version of RED.nodes.registerType. The html file will contain the template and help script blocks, along with a call to the editor's version of RED.nodes.registerType.

node set

A js/html file pair may contain multiple nodes. This is called a node set. Any error loading the js/html files will cause all nodes in a node set to be unavailable.

node module

An npm node module may contain multiple js/html file pairs - each identified in the package.json file. Hence, an npm module may contain multiple node sets, each containing 1 or more nodes.

node pack

A node pack is a collection of similarly-themed nodes that a user might want to install together. It is structurally the same as a node module, but acts as a meta-package that pulls in multiple specific node modules using the standard package dependency mechanism.

Add/Remove vs Enable/Disable

The Add/Remove api is for getting new nodes installed into the runtime as well as removing them. It operates at either the js/html level, or the node module level.

The Enable/Disable api is used with node sets. This is how a user can install a node module using the Add/Remove API, then elect to disable one or more of the node sets it contains so they don't appear in the palette.

Adding a node set/module

To add a new node to the palette:

1. a request is POSTed to {admin root}/nodes to trigger the add. The post body is a JSON structure that identifies where the node information comes from, either a local file (file) or an npm module (module).

    {
        file: "path to local node .js file or package.json",
        module: "npm module name"
    }
   

2. The response to this request is a json object containing the node set id, a list of the specific types in the set and a boolean flag to show if it is enabled or not. If not enabled, it may also list an error message describing why it is not enabled - unless if has been disabled by the user.

3. An event is fired over the comms link telling any connected editors that nodes have been added. This triggers a HTTP Get back to {admin root}/nodes/{node-set-id} to load the node definition/help/edit template.

Remove node set/module

To remove a node from the palette:

1. a DELETE http request is sent to {admin root}/nodes/{node-set-id} to trigger the removal.
2. If the any of the corresponding nodes are in use, the request is rejected
3. The runtime registry removes the corresponding nodes.
4. An event is fired over the comms link telling any connected editors that the nodes have been removed.

Enable a node set

TBD

• need a persistence mechanism to remember the enabled/disabled state of nodes over restarts.

Disable a node set

TBD

• as with remove, cannot disable a node set that contains an in-use type