bug #24874 [TwigBridge] Fixed the .form-check-input class in the bs4 templates (vudaltsov)

This PR was squashed before being merged into the 3.4 branch (closes #24874).

Discussion
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[TwigBridge] Fixed the .form-check-input class in the bs4 templates

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

If I am not mistaken, the `form-check-input` class should always be present in inputs of checkboxes and radios

Commits
-------

95a90e4231 [TwigBridge] Fixed the .form-check-input class in the bs4 templates

Author: fabpot

Resources/views/Form/bootstrap_4_layout.html.twig

@@ -71,7 +71,7 @@
 
 {% block checkbox_widget -%}
     {%- set parent_label_class = parent_label_class|default(label_attr.class|default('')) -%}
-    {%- set attr = attr|merge({class: attr.class|default('form-check-input')}) -%}
+    {%- set attr = attr|merge({class: (attr.class|default('') ~ ' form-check-input')|trim}) -%}
     {% if 'checkbox-inline' in parent_label_class %}
         {{- form_label(form, null, { widget: parent() }) -}}
     {% else -%}
@@ -83,7 +83,7 @@
 
 {% block radio_widget -%}
     {%- set parent_label_class = parent_label_class|default(label_attr.class|default('')) -%}
-    {%- set attr = attr|merge({class: attr.class|default('form-check-input')}) -%}
+    {%- set attr = attr|merge({class: (attr.class|default('') ~ ' form-check-input')|trim}) -%}
     {%- if 'radio-inline' in parent_label_class -%}
         {{- form_label(form, null, { widget: parent() }) -}}
     {%- else -%}

composer.json

@@ -24,7 +24,7 @@
         "symfony/asset": "~2.8|~3.0|~4.0",
         "symfony/dependency-injection": "~2.8|~3.0|~4.0",
         "symfony/finder": "~2.8|~3.0|~4.0",
-        "symfony/form": "~3.4-beta2|~4.0-beta2",
+        "symfony/form": "~3.4|~4.0",
         "symfony/http-foundation": "^3.3.11|~4.0",
         "symfony/http-kernel": "~3.2|~4.0",
         "symfony/polyfill-intl-icu": "~1.0",
@@ -41,7 +41,7 @@
         "symfony/web-link": "~3.3|~4.0"
     },
     "conflict": {
-        "symfony/form": "<3.4",
+        "symfony/form": "<3.4-beta4|~4.0,<4.0-beta4",
         "symfony/console": "<3.4"
     },
     "suggest": {