pyflowred-node-lowercase

A node package for PyFlowRED, kept deliberately small: it adds one node type, lower-case, which lowercases msg.payload and passes the message on.

It exists to be read. It is the smallest thing that is still a complete node package — a Python file, an edit dialog, and the entry point that makes a distribution a node package — so it can be copied as the starting point for a real one.

Installing it

From the editor: Menu → Manage palette → Install, and search for pyflowred-node-lowercase. Or over the admin API, which is the same path:

curl -X POST localhost:1880/nodes -H 'content-type: application/json' \
     -d '{"module": "pyflowred-node-lowercase"}'

The node appears in the palette under function straight away. PyFlowRED installs it into the environment it keeps beside the flows and writes it down in <userDir>/externalModules/requirements.txt, so a replacement instance installs the same palette rather than coming up without it.

What is in it

src/pyflowred_node_lowercase/
  __init__.py       nothing to declare: the directory is scanned
  lowercase.py      the node
  lowercase.html    the edit dialog, the help text and the palette label

The node itself:

def register(RED):
    class LowerCaseNode(RED.Node):
        def __init__(self, config: dict[str, Any]):
            super().__init__(config)
            self.on("input", self._on_input)

        def _on_input(self, msg, send, done) -> None:
            payload = msg.get("payload")
            if isinstance(payload, str):
                msg["payload"] = payload.lower()
            send(msg)
            done()

    RED.nodes.register_type("lower-case", LowerCaseNode)

A payload that is not a string is passed through untouched rather than coerced: a node that quietly turns a number into "42" is harder to debug than one that leaves it alone.

And what makes the distribution a node package at all:

[project.entry-points."pyflowred.nodes"]
pyflowred-node-lowercase = "pyflowred_node_lowercase"

The entry point name is the module name shown in the palette; the value is an importable package whose directory is scanned for .py/.html pairs.

Writing your own

Everything above is the whole of it: a register(RED) function that declares a class and registers a type, an .html beside it carrying the edit dialog, the help text and the palette label, and the entry point. Copy this package, rename it, and replace the body.

Beyond that - config nodes, HTTP endpoints, icons, translations, shipping example flows, and testing a node - the reference is docs/writing-nodes.md in the PyFlowRED source distribution. See pyflowred on PyPI.