Lightfoot Parse JSON

A small Symfony console utility to extract key + value pairs from a JSON file and write them to a new JSON file.

This project provides a single command: app:extract-json.

Requirements

• PHP >= 8.2
• Composer dependencies installed (composer install)

Installation

1. Clone the repository
2. Install dependencies:

   composer install

Usage

Run the command via Symfony Console:

php bin/console app:extract-json <file> <key> <value> [--output|-o <path>] [--pretty] [-v|-vv|-vvv]

• file (argument, required): Path to the input JSON file.
• key (argument, required): Field name to use as the "key" in output.
• value (argument, required): Field name to use as the "value" in output.
• --output, -o (option, optional): Path to write the output JSON file. Defaults to <input>.extracted.json (appended to the input filename).
• --pretty (option, flag): Pretty-print the output JSON.
• -v|-vv|-vvv (verbosity): Show warnings for skipped items at verbose levels.

Input expectations

• The input JSON must be an array of objects (or associative arrays).
• Each item should contain both the provided key and value fields.
• Items missing either field, or non-object items, are skipped (warnings shown at -v verbosity).

Output format

The output is a single JSON object mapping the provided key to the provided value:

{
  "<key>": "<value>"
}

Exit codes

• 0 on success
• 1 on failure (e.g., unreadable/missing input file, invalid JSON, failed write)

Examples

Given people.json:

[
  { "id": 1, "name": "Alice", "other": true },
  { "id": 2, "name": "Bob" },
  { "id": 3 }
]

Extract id and name into a new JSON file (pretty-printed):

php bin/console app:extract-json people.json id name --pretty
# Writes people.json.extracted.json in the same directory

Write to a specific output path and show verbose warnings for skipped items:

php bin/console app:extract-json people.json id name -o build/ids-and-names.json -v

Resulting output (pretty-printed):

{
  "1": "Alice",
  "2": "Bob"
}

Development

Run tests:

vendor/bin/phpunit

Notes

• The command attempts to create the output directory if it does not exist.
• The input file path supports tilde (~) expansion (e.g., ~/Downloads/file.json).
• If duplicate keys are encountered, the last occurrence wins (later items overwrite earlier ones).
• Non‑UTF8 characters are preserved; when --pretty is used, slashes and Unicode are not escaped.