schemify-cli

Build JSON Schemas interactively, and fill JSON data from them, from the command line.

Source: github.com/aaltatan/schemify-cli

A web version runs at schemify.surge.sh (source): the same questions as fields, with the schema updating as you type.

Install

uv tool install schemify

Usage

schemify generate -t Person -o person.schema.json   # ask for the properties, write the schema
schemify fill person.schema.json -o person.json     # ask for one object matching it
schemify list person.schema.json -f python          # ask for a list of them

• -o, --output saves to a file (asks before overwriting); without it the result is printed.
• -f, --format picks the output of fill and list: json, python or javascript.

Types: string, integer, number, boolean, date, datetime, enum, array, object, each with its constraints (length, pattern, format, range, items, ...) and an optional default.

Computed properties

A property with x-compute is not asked in fill, it is computed from the other values:

"full_name": {"type": "string", "x-compute": {"fn": "join", "from": ["first", "middle?", "last"]}}

• fn: the computer, from: source paths (a list, or an {alias: path} object for template and expr), options: extra arguments, default: the value when a source is missing.
• Paths are relative to the owning object (address.city, items[0]), or to the root ($.company). items[*].price gives every price; a trailing ? makes a source optional.

Built-in computers:

• Text: join, concat, template, upper, lower, title, capitalize, trim, replace, slice, initials, slug, length, pad, mask
• Numbers: sum, subtract, multiply, divide, average, min, max, abs, round, percent, percent_of, expr
• Dates: today, now, add_days, add_months, add_years, days_between, age, year, month, day, weekday, format_date, start_of_month, end_of_month
• Number to words: words
• Logic, lookup and misc: coalesce, if_else, equals, lookup, constant, count, count_if, unique, uuid

Reusing it in a typer app

schemify.cli.dependencies.schema exposes typer-di dependencies that load a schema file and ask for its data: FilledDataArgumentDI and FilledListArgumentDI take the path as an argument, FilledDataOptionDI and FilledListOptionDI as --js.

Development

uv sync
uv run pytest
uv run ruff check . && uv run mypy src

After changing generators.py, validators.py or computers.py, run pnpm sync && pnpm check in schemify-web so it stays in step.