minor #21565 [Validator] Make public property requirement clearer for constraint options (kleinmann)

This PR was merged into the 6.4 branch.

Discussion
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[Validator] Make public property requirement clearer for constraint options

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The current language seems to allow for non-public properties, but in practice this fails, because the corresponding property remains uninitialized after deserialization.

An accidental private option can also be a bit of a headscratcher to pin down, since it may occur only once it is run in a production environment (due to different cache configurations).

Commits
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eeaf4cc Make public property requirement clearer for constraint options

Author: javiereguiluz

validation/custom_constraint.rst

@@ -266,7 +266,7 @@ You can use custom validators like the ones provided by Symfony itself:
             }
         }
 
-If your constraint contains options, then they should be public properties
+If your constraint contains options, then they must be public properties
 on the custom Constraint class you created earlier. These options can be
 configured like options on core Symfony constraints.