Gathering all validation errors generated during AMP plugin unit tests

class-amp-base-sanitizer.php.diff

diff --git a/includes/sanitizers/class-amp-base-sanitizer.php b/includes/sanitizers/class-amp-base-sanitizer.php
index 32badf460..312fc2431 100644
--- a/includes/sanitizers/class-amp-base-sanitizer.php
+++ b/includes/sanitizers/class-amp-base-sanitizer.php
@@ -542,10 +542,12 @@ abstract class AMP_Base_Sanitizer {
 	 * @return bool Whether to sanitize.
 	 */
 	public function should_sanitize_validation_error( $validation_error, $data = [] ) {
+		$validation_error = $this->prepare_validation_error( $validation_error, $data );
+		file_put_contents( AMP__DIR__ . '/error-key-dump.txt', json_encode( $validation_error ) . PHP_EOL, FILE_APPEND );
+
 		if ( empty( $this->args['validation_error_callback'] ) || ! is_callable( $this->args['validation_error_callback'] ) ) {
 			return true;
 		}
-		$validation_error = $this->prepare_validation_error( $validation_error, $data );
 		return false !== call_user_func( $this->args['validation_error_callback'], $validation_error, $data );
 	}
 

collate-errors.php

<?php

$errors = [];
$all_keys = [];

foreach ( file( __DIR__ . '/error-key-dump.txt' ) as $line ) {
	$line = trim( $line );
	if ( empty( $line ) ) {
		continue;
	}
	$data = json_decode( $line, true );
	$errors[] = $data;
	foreach ( $data as $key => $value ) {
		if ( ! isset( $all_keys[ $key ] ) ) {
			$all_keys[ $key ] = 0;
		}
		$all_keys[ $key ] += 1;
	}
}

arsort( $all_keys );

foreach ( $all_keys as $property => $frequency ) {
	echo "$frequency\t$property\n";
}

file_put_contents( __DIR__ . '/all-unit-test-validation-errors.json', json_encode( $errors, JSON_UNESCAPED_SLASHES | JSON_PRETTY_PRINT ) );