Handling Duplicate Keys in INI to JSON Conversion

Duplicate Keys in INI Files

Some INI-style configuration files use duplicate keys within the same section to represent lists. For example, the PHP error_handler or Samba's interfaces directive may appear multiple times. The converter provides two strategies for handling this.

Example INI

[dns]
nameserver=8.8.8.8
nameserver=8.8.4.4
nameserver=1.1.1.1

[allowed_hosts]
host=web1.example.com
host=web2.example.com
host=web3.example.com
host=web4.example.com

[app]
log_level=debug
log_level=info

Strategy 1: Last Wins (Default)

Standard INI behavior --- when a key appears multiple times, only the last value is kept.

{
  "dns": {
    "nameserver": "1.1.1.1"
  },
  "allowed_hosts": {
    "host": "web4.example.com"
  },
  "app": {
    "log_level": "info"
  }
}

Strategy 2: As Array

All values for duplicate keys are collected into a JSON array, preserving the order.

{
  "dns": {
    "nameserver": ["8.8.8.8", "8.8.4.4", "1.1.1.1"]
  },
  "allowed_hosts": {
    "host": [
      "web1.example.com",
      "web2.example.com",
      "web3.example.com",
      "web4.example.com"
    ]
  },
  "app": {
    "log_level": ["debug", "info"]
  }
}

Choosing a Strategy

Use "Last wins" when...	Use "As array" when...
You want standard INI semantics	Keys represent lists of values
Override patterns are intentional	All values should be preserved
Simpler JSON output is preferred	The consuming app expects arrays

Round-Trip Behavior

When converting "As array" JSON back to INI, each array element is emitted as a separate line with the same key, faithfully reproducing the original multi-value structure.