NestedText — A Human Friendly Data Format

NestedText is a file format for holding structured data. It is similar in concept to JSON, except that NestedText is designed to make it easy for people to enter, edit, or view the data directly. It organizes the data into a nested collection of name-value pairs, lists, and strings. The syntax is intended to be very simple and intuitive for most people.

A unique feature of this file format is that it only supports one scalar type: strings.  As such, quoting strings is unnecessary, and without quoting there is no need for escaping. While the decision to forego other types (integers, reals, dates, etc.) may seem counter productive, it leads to simpler data files and applications that are more robust.

NestedText is convenient for configuration files, address books, account information, and the like. Here is an example of a file that contains a few addresses:

# Contact information for our officers

Katheryn McDaniel:
    position: president
    address:
        > 138 Almond Street
        > Topeka, Kansas 20697
    phone:
        cell: 1-210-555-5297
        home: 1-210-555-8470
            # Katheryn prefers that we always call her on her cell phone.
    email: [email protected]
    additional roles:
        - board member

Margaret Hodge:
    position: vice president
    address:
        > 2586 Marigold Lane
        > Topeka, Kansas 20682
    phone: 1-470-555-0398
    email: [email protected]
    additional roles:
        - new membership task force
        - accounting task force

A strength of NestedText is its lack of quoting and escaping, making it particularly nice for holding code fragments. Here is another example of NestedText that shows off this feature. It holds some Parametrize From File test cases for pytest. In this case a command line program is being tested and its response is checked using regular expressions:

-
    cmd: emborg version
    expected: emborg version: \d+\.\d+(\.\d+(\.?\w+\d+)?)?  \(\d\d\d\d-\d\d-\d\d\)
    expected_type: regex
-
    cmd: emborg --quiet list
    expected: home-\d\d\d\d-\d\d-\d\dT\d\d:\d\d:\d\d
    expected_type: regex
-
    cmd: emborg --quiet borg list --glob-archives "home-*" --short @repo
    expected: home-\d\d\d\d-\d\d-\d\dT\d\d:\d\d:\d\d
    expected_type: regex
-
    cmd: emborg --quiet files -D
    expected:
        > Archive: home-\d\d\d\d-\d\d-\d\dT\d\d:\d\d:\d\d
        > \d\d\d\d-\d\d-\d\dT\d\d:\d\d:\d\d.\d\d\d\d\d\d configs/subdir/(file|)
        > \d\d\d\d-\d\d-\d\dT\d\d:\d\d:\d\d.\d\d\d\d\d\d configs/subdir/(file|)
            # Unfortunately, we cannot check the order as they were both
            # created at the same time.
    expected_type: regex
-
    cmd: emborg due --backup-days 1 --message "{elapsed} since last {action}"
    expected: home: (\d+(\.\d)? (seconds|minutes)) since last backup\.
    expected_type: regex

One particularly attractive use-case for NestedText is command line programs whose output is meant to be consumed by either people or programs. Many programs do so by supporting a --json command-line flag that indicates the output should be computer readable rather than human readable. But, with NestedText it is not necessary to make people choose. Just output the result in NestedText and it can be read by people or computers. For example, consider a program that reads your address list and output particular fields on demand:

> address --email
Katheryn McDaniel: [email protected]
Margaret Hodge: [email protected]

This output could be fed directly into another program that accepts NestedText as input:

> address --email | mail-to-list

Contributing

This package contains a Python reference implementation of NestedText and a test suite. Implementation in many languages is required for NestedText to catch on widely. If you like the format, please consider contributing additional implementations.

Also, please consider using NestedText for any applications you create. It is especially suitable for configuration files.