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IfThenElseSchema.md

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IfThenElseSchema

The IfThenElseSchema applies one of two schemas depending on a condition: when the if schema matches, the then schema is applied, otherwise the else schema. It covers the JSON Schema if / then / else keywords.

Basic Usage

use Chubbyphp\Parsing\Parser;

$p = new Parser();

$schema = $p->if($p->string())
    ->then($p->string()->minLength(3))
    ->else($p->int()->minimum(0))
;

$data = $schema->parse('test'); // Returns: 'test' (string, validated by then)
$data = $schema->parse(42);     // Returns: 42 (not a string, validated by else)
$data = $schema->parse('ab');   // Throws error (string, but then fails)
$data = $schema->parse(-1);     // Throws error (not a string, and else fails)

How It Works

  1. The input is checked against the if schema — as a pure condition: its coercions and transformations never leak, the chosen branch receives the original input
  2. If the if schema matches, the then schema is applied and its output returned, otherwise the else schema
  3. An absent branch means no constraint — the input is returned unchanged (JSON Schema: an absent then / else acts as true)
  4. When the applied branch fails, its errors propagate unchanged — IfThenElseSchema produces no errors of its own

Common Patterns

Conditional Object Shape

$schema = $p->if($p->assoc(['country' => $p->const('CH')])->additionalProperties($p->any()))
    ->then($p->assoc(['country' => $p->string(), 'postalCode' => $p->string()->pattern('/^\d{4}$/')]))
    ->else($p->assoc(['country' => $p->string(), 'postalCode' => $p->string()]))
;

Conditional Without Else

// only constrains strings, everything else passes unchanged
$schema = $p->if($p->string())->then($p->string()->minLength(3));

$schema->parse('test'); // Returns: 'test'
$schema->parse(42);     // Returns: 42 (untouched)

An else schema works without a then schema just as well: $p->if($ifSchema)->else($elseSchema).

Edge Cases

  • if is condition-only: $p->if($p->string()->toUpperCase())->then($p->const('test')) parses 'test' successfully — the then branch receives the original 'test', not 'TEST'.
  • null input: null is evaluated against the if schema like any other value; with nullable(), null short-circuits before the condition is checked.
  • if schemas that cannot fail: an if schema with catch() or default() may always succeed, which makes the else branch unreachable.
  • Error details: only the applied branch's errors are reported; the if schema's outcome is a decision, not an error.

Error Codes

IfThenElseSchema itself never produces an error — the applied branch schema's errors propagate unchanged.