SCR306: message-handler-payload-misuse

Message handler reads a payload key that no sender sends

Code	SCR306
Name	message-handler-payload-misuse
Category	Scripts (SCR)
Default severity	warning
Enabled by default	no
Fix available	no
ign-lint equivalent	none

What it does

Only with strict. For component message handlers and gateway and session message handler scripts, compares the payload keys the handler reads with payload['key'] with the keys of every literal payload sent to it (system.perspective.sendMessage('type', {'key': ...}) for component handlers, system.util.sendMessage(project, 'handler', {...}) for the others), and reports keys that no sender passes.

It only reports when every send of the type to the project is known and passes a dict literal: a payload that is a variable, a send with a computed type, and a handler with no literal sender at all make the rule silent. Reads with a default (payload.get('key')) and keys the handler tests first ('key' in payload) are not reported.

Why is this bad?

payload['key'] raises KeyError when the sender does not pass the key, so the handler fails on every message. This is usually a key that was renamed on one side only.

Example

# sender
system.perspective.sendMessage('selectLine', {'lineId': 3})
# handler
self.view.custom.line = payload['line']

Use instead:

self.view.custom.line = payload['lineId']

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Generated from the rule metadata by iglint generate-docs; iglint rule SCR306 prints the same page in the terminal. Source: docs/rules/SCR306.md.