Getting started

What is Valet?

A command-line validation gate for CSV, Parquet, NDJSON or JSON files (local or S3-compatible) before a lakehouse, warehouse or next job. Checks live in YAML or JSON; by default you get one aggregate JSON report on stdout and an exit code, with no rewritten data or output files.

Why Valet?

Readable ≠ correct: checks schemas, missing values, ranges, duplicate keys, references and column relationships before problems propagate. Same versioned rules wherever the file enters.
Caller owns the next step: continue on exit 0, block on failed checks (1), handle execution failures separately (2). Warnings do not block by default; set mandatory rules to level: error.
Self-contained CLI, not a service: no scheduling or lakehouse upload. Keep your uploader; validate the same immutable input before invoking it.

Start here

Installation

Download a release or build the CLI.

Quickstart

Validate the sample, then check its Parquet schema.

Concepts

Pipelines, rules, results and execution.

Schema-only Parquet checks

Check columns and types without scanning rows.

Rules cookbook

Choose schema, row and dataset checks.

Choose the right command

You want to…	Command	Result
Check Parquet columns and types without reading values	`valet schema -p pipeline.yml -i input.parquet`	Schema-only JSON report; no data outputs
Check values without publishing files	`valet validate -p pipeline.yml -i input.parquet`	One aggregate JSON summary on stdout; no manifest
Check row values, conversions, references and dataset rules	`valet validate -p pipeline.yml -i input.parquet -o results/`	Checked rows, issues and a terminal manifest
Preview configuration, schemas, passes and required state	`valet plan -p pipeline.yml -i input.parquet`	Execution-plan JSON; not a validation result

Only schema is Parquet-only; full validation supports all four formats. schema and plan may succeed even when a row value would fail full validation — see schema-only checks.

Full validation lifecycle

Optional: valet plan to see the work and managed state.
valet validate reads, converts and checks the data.
Read results:
- no output URI → aggregate stdout JSON; no files or manifest.
- -o/output.uri → published manifest.json and its artifact references; partial artifacts without it are incomplete.

valet schema is separate: JSON report on stdout only; never publishes row buckets or a manifest.

Exit codes

Exit	`valet schema`	`valet validate`
`0`	Schema compatible; row checks were not evaluated	Completed without error-level violations; warnings allowed
`1`	Error-level schema mismatch; inspect the JSON report	Completed with row, dataset or schema violations; inspect the summary
`2`	Configuration, format, metadata, storage or resource failure	Operational or presentation failure without a committed manifest
`3`	Not used: schema inspection commits no terminal manifest	Manifest committed, but stdout presentation failed
`128+N`	Interrupted by signal `N`	Interrupted by signal `N` before commit

Installation