So for required fields, devs have to add the NotNull constraint, do they? I guess that's the common problem that people don't know how to validate optional/required fields. And using NotBlank seems more natural than NotNull.
And also the confusion whether an optional value is '' or null, see #11956. This then also influences whether NotNull actually works for required fields.

So for required fields, devs have to add the NotNull constraint, do they?

Exactly. As I said, they can use other means (such as Type and Length validation) to validate a value more specifically.

But I think there is an inconsistency in this idea: One the one hand you say, empty fields are represented as null, so we need to use the NotNull constraint to validate required fields. On the other hand constraints still allow empty strings '' as described in #11956 although the only purpose is to allow optional fields. So if NotNull is the correct approach, then the constraints should also stop ignoring empty strings. But you closed this issue.

@Tobion You are completely right. Obviously we can't do this without breaking BC, so this is postponed to 3.0.

Exactly. As I said, they can use other means (such as Type and Length validation) to validate a value more specifically.

This would first require to stop ignoring empty strings in other validators, considering only null as a valid value to allow optional one

@stof ;)

I just realize the nonsense of Blank vs NotBlank: false is invalid in both cases. lol
This means, false is "not blank" according to the BlankValidator and it is "blank" according to the NotBlankValidator.

@webmozart so when deprecating NotBlank, shouldn't Blank be deprecated as well?

Also the current issue description makes no sense. If we want to deprecate these constraints, then it must be done before 3.0. So the milestone is wrong.

The issue is that we cannot deprecate things without providing a replacement for the feature. and the new way cannot be built without BC break, so it cannot be built before 3.0. There is no way to deprecate it in 2.x for removal in 3.0

NotBlank should be deprecated. It's behavior is weird (as mentioned — false is invalid) and doesn't even conform to documentation where it is explicitly said that the value should be not equal to a blank string and also not equal to null.

This commit actually broke everything: 639513a

👍

3.0 is already here.
What's current state of this? What would be the suggested replacement?

@TomasVotruba The problem is, as @stof said, that we can only deprecate these constraints if we remove the '' !== $value checks from all other constraints validators. Otherwise empty strings will be ignored by all validators.

Any other solutions or can we only do this as part of the 4.0 release?

@webmozart Ok, that sound clear to me. Can prepare PR if this gets accepted.

I'm 👎 here in the way it is described, what we should do is:

• document that false is invalid with Blank as for empty string and null,
• better document difference between NotBlank and NotNull (the last one having to be used for boolean types)
• deprecated invalid behavior for invalid state of false with Blank and NotBlank,
• rename Blank and NotBlank to Empty and NotEmpty that would better reflect what it does mimicking PHP wording and behavior.

Let's close here in favour of #27876.