Parameter System¶

Sayer translates annotated Python function signatures into Click parameters and typed runtime values.

Mental Model¶

• Declaration layer: Python signature + metadata (Option, Argument, Env, JsonParam).
• Parsing layer: Click options/arguments.
• Conversion layer: type coercion and JSON molding.
• Invocation layer: bound arguments passed to your command function.

Data Flow¶

flowchart TD
  Args[argv and env vars] --> Parse[Click parsing]
  Parse --> Meta[Parameter metadata resolution]
  Meta --> Convert[Type conversion]
  Meta --> Json[JSON decode and apply_structure]
  Convert --> Bind[Bound arguments map]
  Json --> Bind
  Bind --> Inject[Context and State injection]
  Inject --> Execute[Command execution]
  Execute --> Result[Output and return value]

Parameter Selection¶

• Option: named values (--region eu-west-1).
• Argument: positional values (deploy billing).
• Env: environment-provided values (API_TOKEN).
• JsonParam: structured JSON payloads.

Related¶

• How-to: Use Parameters
• Feature Guide: Parameters
• API Reference: Params