Throw ValidationFailedException with per-field codes for 422 responses

src/Id/Exceptions/ApiException.php

@@ -35,6 +35,11 @@ class ApiException extends ResourceException
             return PreconditionFailedException::fromResult($result);
         }
 
+        // refused input, with per-field codes on some endpoints
+        if ($status === 422 && static::class === self::class) {
+            return ValidationFailedException::fromResult($result);
+        }
+
         return new static(
             rtrim((string) ($body->message ?? $result->error()), '.'),
             $status,

src/Id/Exceptions/ValidationFailedException.php

@@ -0,0 +1,46 @@
+<?php
+
+namespace Anikeen\Id\Exceptions;
+
+/**
+ * Anikeen ID refused the input (422). `error` is the first code; endpoints with per-field codes
+ * (the profile API) send them as `codes`: `{field: code}`, e.g. `["username" => "username_taken"]`.
+ * Branch on the codes, the messages are for people and may change.
+ */
+class ValidationFailedException extends ApiException
+{
+    /**
+     * @return array<string, string> field => code; empty when the endpoint sends none
+     */
+    public function errorCodes(): array
+    {
+        $codes = $this->body()->codes ?? null;
+
+        return is_object($codes) || is_array($codes) ? array_map('strval', (array) $codes) : [];
+    }
+
+    public function errorCodeFor(string $field): ?string
+    {
+        return $this->errorCodes()[$field] ?? null;
+    }
+
+    /**
+     * Whether any field failed with $code, or the response's `error` is $code.
+     */
+    public function hasErrorCode(string $code): bool
+    {
+        return $this->error === $code || in_array($code, $this->errorCodes(), true);
+    }
+
+    /**
+     * The messages per field (`errors`), for showing them to people.
+     *
+     * @return array<string, list<string>>
+     */
+    public function errors(): array
+    {
+        $errors = $this->body()->errors ?? null;
+
+        return is_object($errors) || is_array($errors) ? array_map(fn ($messages) => array_values((array) $messages), (array) $errors) : [];
+    }
+}