Validation

Updated Apr 28, 2026

Uptask extracts each function's parameter shape via the TypeScript compiler and builds a runtime zod schema from it. Every CLI-derived value runs through its schema before your function is invoked.

What gets validated

Each parameter — positional argument or option — produces a zod schema:

Optional parameters are wrapped in .optional(). Object parameters with a known property shape recurse — nested port: number inside an object is validated as a number.

What it catches

Commander coerces input first (Number(val), JSON.parse(json), option aggregation), then zod validates the result. The combination catches:

• --port abc → Number("abc") is NaN → zod rejects.
• --config "42" → JSON.parse("42") is 42, not an object → zod rejects.
• --config '{"port": "80"}' declared as { port: number } → zod rejects the string-typed port.

Error format

Validation failures come out as a single line, no stack trace, exit code 1:

error: invalid argument 'concurrency': expected number, received nan

Nested object property failures include the path:

error: invalid argument 'options.port': expected number, received string

The shape mirrors Commander's own errors (error: missing required argument 'target') so users see one consistent style across both kinds of input problems.