Suggest using quotes instead of Yaml::PARSE_KEYS_AS_STRINGS

Author: GuilhemN

CHANGELOG.md

@@ -9,16 +9,14 @@ CHANGELOG
 
  * Deprecated support for implicitly parsing non-string mapping keys as strings.
    Mapping keys that are no strings will lead to a `ParseException` in Symfony
-   4.0. Use the `PARSE_KEYS_AS_STRINGS` flag to opt-in for keys to be parsed as
-   strings.
+   4.0. Use quotes to opt-in for keys to be parsed as strings.
 
    Before:
 
    ```php
    $yaml = <<<YAML
    null: null key
    true: boolean true
-   1: integer key
    2.0: float key
    YAML;
 
@@ -30,13 +28,12 @@ CHANGELOG
    ```php
 
    $yaml = <<<YAML
-   null: null key
-   true: boolean true
-   1: integer key
-   2.0: float key
+   "null": null key
+   "true": boolean true
+   "2.0": float key
    YAML;
 
-   Yaml::parse($yaml, Yaml::PARSE_KEYS_AS_STRINGS);
+   Yaml::parse($yaml);
    ```
 
  * Omitted mapping values will be parsed as `null`.

Inline.php

@@ -494,7 +494,7 @@ private static function parseMapping($mapping, $flags, &$i = 0, $references = ar
                 $evaluatedKey = self::evaluateScalar($key, $flags, $references);
 
                 if ('' !== $key && $evaluatedKey !== $key && !is_string($evaluatedKey) && !is_int($evaluatedKey)) {
-                    @trigger_error('Implicit casting of incompatible mapping keys to strings is deprecated since version 3.3 and will throw \Symfony\Component\Yaml\Exception\ParseException in 4.0. Pass the PARSE_KEYS_AS_STRINGS flag to explicitly enable the type casts.', E_USER_DEPRECATED);
+                    @trigger_error('Implicit casting of incompatible mapping keys to strings is deprecated since version 3.3 and will throw \Symfony\Component\Yaml\Exception\ParseException in 4.0. Quote your evaluable mapping keys instead.', E_USER_DEPRECATED);
                 }
             }
 

Parser.php

@@ -238,7 +238,7 @@ private function doParse($value, $flags)
 
                 if (!(Yaml::PARSE_KEYS_AS_STRINGS & $flags) && !is_string($key) && !is_int($key)) {
                     $keyType = is_numeric($key) ? 'numeric key' : 'non-string key';
-                    @trigger_error(sprintf('Implicit casting of %s to string is deprecated since version 3.3 and will throw \Symfony\Component\Yaml\Exception\ParseException in 4.0. Pass the PARSE_KEYS_AS_STRINGS flag to explicitly enable the type casts.', $keyType), E_USER_DEPRECATED);
+                    @trigger_error(sprintf('Implicit casting of %s to string is deprecated since version 3.3 and will throw \Symfony\Component\Yaml\Exception\ParseException in 4.0. Quote your evaluable mapping keys instead.', $keyType), E_USER_DEPRECATED);
                 }
 
                 // Convert float keys to strings, to avoid being converted to integers by PHP

Tests/InlineTest.php

@@ -730,7 +730,7 @@ public function testTheEmptyStringIsAValidMappingKey()
 
     /**
      * @group legacy
-     * @expectedDeprecation Implicit casting of incompatible mapping keys to strings is deprecated since version 3.3 and will throw \Symfony\Component\Yaml\Exception\ParseException in 4.0. Pass the PARSE_KEYS_AS_STRINGS flag to explicitly enable the type casts.
+     * @expectedDeprecation Implicit casting of incompatible mapping keys to strings is deprecated since version 3.3 and will throw \Symfony\Component\Yaml\Exception\ParseException in 4.0. Quote your evaluable mapping keys instead.
      * @dataProvider getNotPhpCompatibleMappingKeyData
      */
     public function testImplicitStringCastingOfMappingKeysIsDeprecated($yaml, $expected)

Tests/ParserTest.php

@@ -1081,7 +1081,7 @@ public function testYamlDirective()
 
     /**
      * @group legacy
-     * @expectedDeprecation Implicit casting of numeric key to string is deprecated since version 3.3 and will throw \Symfony\Component\Yaml\Exception\ParseException in 4.0. Pass the PARSE_KEYS_AS_STRINGS flag to explicitly enable the type casts.
+     * @expectedDeprecation Implicit casting of numeric key to string is deprecated since version 3.3 and will throw \Symfony\Component\Yaml\Exception\ParseException in 4.0. Quote your evaluable mapping keys instead.
      */
     public function testFloatKeys()
     {
@@ -1103,7 +1103,7 @@ public function testFloatKeys()
 
     /**
      * @group legacy
-     * @expectedDeprecation Implicit casting of non-string key to string is deprecated since version 3.3 and will throw \Symfony\Component\Yaml\Exception\ParseException in 4.0. Pass the PARSE_KEYS_AS_STRINGS flag to explicitly enable the type casts.
+     * @expectedDeprecation Implicit casting of non-string key to string is deprecated since version 3.3 and will throw \Symfony\Component\Yaml\Exception\ParseException in 4.0. Quote your evaluable mapping keys instead.
      */
     public function testBooleanKeys()
     {